DE2120673A1 - Method and device for signal acquisition - Google Patents

Description

DR. ING. E. HOFFMANN · DIPL. ING. W. EITLE DR. RER. NAT. K. HOFFMANN

PATENT LAWYERS

D.8000 MÖNCHEN 81ARABELLASTRASSE 4 TELEPHONE (0811) 911087

Dynell Electronics Corporation, Melville, N.Y./USA

Method and device for signal acquisition

The invention relates to a method and device for signal detection, in particular to a method and device for detecting sequentially transmitted signals of known but different durations.

As the transportation industry continues to grow, the need for improved navigation systems is increasing became clear. Such systems must provide the navigator with a reliable position determination. Next should the Systems preferably be operational regardless of the time of day, weather conditions, or geographic location. The modern navigator has turned to electronics to solve the fundamental problems of reliability, and one of the youngest earth-spanning systems is the omega-navi-

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gation system. This system uses a plurality of transmitters which transmit low-frequency signals in discrete time intervals. The transmitters are strategically placed around ensure that the signals from several transmitters are always available at any point on earth. By identification the signals and comparison of the phase relationship, it is possible for the navigator to determine his position with great accuracy to determine.

The omega navigation system on which the invention is built uses detection and relative evaluation of signals transmitted from a plurality of stations strategically located on the earth. Every station transmits a signal of a certain duration, and so the transmitting stations can determine the duration of a received Signal can be identified. In addition to using discrete signal durations for each station, this system specifies set a specific sequence of transmissions for all stations. The sequence ensures that the stations in a predetermined Transfer order within a recurring period of 10 seconds. The receiver equipment that comes with If the Omega navigation system is to work, it must be able to detect the transmitted signals and should preferably be able to capture the signals identify as of a certain duration. With this information in relation to two transmitted signals one can determine where these signals appear in the transmission sequence.

Known receivers generate local signals which the transmitted signals both in duration and in consequence of the Occurrence. These local signals are then used in an acoustic detection arrangement to the Synchronize receivers with acoustic indications of the received signals. In general, the known detection arrangements make this possible neither an equilateral operation with

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all received signals, nor do they provide a simple or satisfactory alignment process.

There is a need for an improved method and apparatus for signal detection which is based on digital Technology based. There is also a need for an improved method and apparatus for signal detection, which comprise a visual display simultaneously with a plurality of sequentially received signals with known properties in terms of duration can work. Signals of the intended type are subject to a prior to being received Deterioration, and accordingly it is beneficial to digi-. tale facilities to restore these signals at Receiving location and for adjusting the phase of the locally generated signals in accordance with the restored signals to be provided.

The object of the invention is provided by a method for signal detection in response to sequentially transmitted signals known but different duration, which are transmitted with a recurring period solved, which according to the invention by sequentially generating a plurality of signals corresponding to each of the transmitted signals, optical Displaying the generated signals in a time-related manner, optically displaying the transmitted signals in a corresponding manner time-related manner and in a position next to the display of the corresponding generated signals, and setting the Phase the generated signals to a coincidence of the indications to effect the generated and transmitted signals.

The object of the invention is also achieved by a signal acquisition system, which responds to sequentially received signals of known but different duration, those with a recurring Period are received, which according to the invention by a device for sequentially generating a plurality of signals with known but different durations, a first device for generating an optical display

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corresponding to the occurrence of each of the generated signals, and a second means for generating a visual display corresponding to the reception of each of the received signals in a position adjacent to the display of the generated signals.

The object of the invention is also achieved by a receiver that responds to a plurality of received signals a predetermined frequency, each of which is transmitted from a different location during a discrete period of time is, and which has a device for generating a signal, which according to the invention is a detection device, which in response to the generated signal and each of the received signals show the phase difference between generated two representative output, and a register device, which is controlled by the output, to a Store display according to the magnitude of the phase difference of each of the plurality of signals relative to the generated signals, includes.

A more complete understanding of the invention and a better understanding of its features can be found in the following, detailed description of a preferred embodiment in connection with the drawing. In the Drawing show:

Fig. 1 is a perspective view of an omega receiver, which embodies the features of the invention,

Figure 2 is a schematic representation of a small portion of an omega navigation map useful for understanding of the Omega long-range navigation system and its features that are important for the invention,

Fig. 3 is a timing diagram showing the duration of four typical Represents signals generated by Omega broadcasting stations,

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Pig. 4 is a general block diagram of a receiver embodying the features of the invention;

Figure 5 is a detailed block diagram of the synchronizing section a receiver using the features of the invention,

Figure 6 is a detailed block diagram of the display and control section a recipient using the features of the invention,

Figure 7 is a detailed block diagram of the receive and signal acquisition section a receiver using the features of the invention,

Figure 8 is a detailed block diagram of the phase tracking section a receiver using the features of the invention,

Fig. 8a is a schematic representation of the type, as Fig. 5 to can be ordered to provide a complete, detailed block diagram of a receiver to which the Embodies features of the invention,

9 is a timing diagram to illustrate the "on-time" control signals; which is generated by the synchronizing section shown in Fig. 5 and in connection with the display and control section are used,

Fig. 10 is a timing diagram showing the phases of the "early" and "late" control signals generated by the in 5 are generated and used in the display and control section,

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Fig. ₉ HB and HC are a graph and waveforms for explaining the operation of the binary coded decimal adder used in the receiving and signal detecting section.

Figs. 12A and 12B illustrate a plurality of waveforms for use in Figs Explanation of the mode of operation of the phase detector «which appears in the reception and signal acquisition section *

Fig. Ij5 is a schematic block diagram of the integrator and Quantizing circuit, which in the reception and signal detection section is used »and

14 is a block diagram illustrating the generation of a binary speed multiplier pulse for use in the phase tracking section shows.

General explanation of the Omega navigation system

The Omega navigation system in which the recipient is after of the invention is a very low-frequency system, in which each transmitter signals with a range of 8047 to 12875 km generated. These signals make it possible «an overlapping or to provide redundant navigation all over the world with only eight broadcasting stations. There are currently four stations or transmitters A * B, C and D in operation in the operating system in Bratland »Norway, Trinidad« West India, Haika, Hawaii and Forestport, New York, are · Yier additional stations are planned.

The transmissions from the individual stations are synchronized relative to one another according to a predetermined red program. As shown in Fig. JJ, bars, which represent the transmission time of four stations or transmitters A, B * C and D, are arranged in separate horizontal rows. The abscissa in this figure represents time. Each station -ar * - *;

a continuous wave on two specific frequencies. 10.2 kHz transmissions, which are used for basic measurements are used as hatched bars and 13.6 kHz transmissions, which are used for stripe resolution, are shown as unhatched bars. Although only four stations are shown in detail, it goes without saying that the transmissions from the remaining four stations or transmitters, E.g. E, P, G and H can be represented in a similar way and it can be assumed that these send 1.1, 0.9, 1.2 or 1.0 seconds in the sequence. The entire in Fig. 3 darger Asked cycle repeats itself every 10 seconds. During this interval there are eight transmission periods more variable Length and intervals of 0.2 seconds between adjacent transmission periods. Only sends during one of the periods a station on a certain frequency. In this way, the transmissions from each station are unique and distinctive. On the other hand, since two stations transmit during the same period of time, even if not at the same time, Precautions are taken to determine what time within a complete transmission cycle of 10 Seconds be ". ^ mmte transmission has occurred.

Looking at the ratio of the wavelengths to the distance, it can be seen that the relative phase between two transmitters will recur at intervals of 12.87 k * n. These Intervals called "stripes" are defined by half a wavelength of 10.2 kHz. It occurs like that an ambiguity of the phase and therefore the position, which repeats every 12.87 km. If the position is not is known within 6.44 km, additional facilities must be provided in order to obtain a position determination. Operations can also be performed at the frequency of 13.6 kHz, which is 4/3 times the base frequency of 10.2 kHz. This additional frequency results in a separate set of phase contours whose position is along the

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Earth is different. By working on both frequencies, the effective strip separation can be increased to around 38 * 6 km which corresponds to a strip separation which is achieved when using a difference frequency of 3.4 kHz would. The more transmitter pairs are used for the measurements, the more precisely the information about the position can be designed.

Fig. 2 shows a small section from an Omega navigation map and shows the position P of a receiver. The map shows different stripes which go through the signals are defined by three transmitters A, B and C. The stripes T, -T " are through the signals from transmitters A and C, the strips

Th-Tt ₃ are through the signals from transmitters A and B, and the A a

Strips T _n -T ,, are through the signals from transmitters B and C

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certainly.

In order to obtain a position determination, one first selects a pair of transmitters, e.g. A and C, and measures the phase difference between the signals received by them of the continuous 10.2 kHz wave. This gives a hyperbolic position line LOP-I for the observer, similar to what is obtained from the measurement the time delay between LORAN-C transmissions is obtained from two transmitters. The same procedure is then followed for one or more additional transmitter pairs, e.g. B and C and A and B repeated to add additional position lines LOP-2 resp. Create LOP-3. The position of the recipient will be exactly dirch determines the intersection of two position lines. Obviously, the accuracy of the determination is greater when the crossing angle at the point of intersection is large. It is therefore very important select the appropriate transmitter pairs for the most accurate position determination to be determined.

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The position itself is set on maps which are the hyperbolic position lines for time of day omega readings of all working transmitter pairs included. In addition, tables are provided showing the annual and daily changes the velocity of propagation, which enables a navigator to reduce the observed readings to the equivalent Time of day reading before plague to reduce its position on the map.

Although the signals transmitted by each station are synchro-; are nized, they contain neither synchronization nor phase reference information. So must the phase shift between each pair of transmitters can be measured relative to the phase of a local source. To see the relative phase between To define two received signals and to use this information, the desired signals must be identified, separated from each other and "connected" in a way that the continuous pursuit of their Phase enables and the subsequent measurement of the phase difference is facilitated.

It is desirable and necessary to provide a receiver that can operate at least three stations at the same time 10.2 kHz and can receive at least three transmissions at 13.6 kHz at the same time. Naturally improves the ability To receive more than three stations, the navigation capacity is essential. The receiver described below is actually capable of Signals can be received simultaneously on both frequencies and from all eight transmitters at the same time *

General reception operation

Using digital and multiplexing techniques, developed the compact, lightweight and very reliable unit shown in FIG.

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On the front panel of the receiver shown in FIG there is the unique signal detection system, which is represented by two rows of lights 10 to the left of the center. Two Pairs of dials 11 and 12 for transmitter selection enable the cautious man to select the particular transmitter from each pair, which he would like to watch. A voter 13 places for reading determines which position line should be displayed and an indicator 14 makes the stripe count visible. This is achieved in the effect that the phase relationship between the observed signals, as selected by the scales 11 and 12, is compared. A card 15 also becomes continuous made from the observed line of position ^. Test controls, Synchronization settings and other less frequently used controls are behind door 16 in the front panel envisaged.

In the following description and in the accompanying drawings, the various elements and connecting lines are denoted by two-part reference numerals, the first part of the reference numeral is a number corresponding to the figure in which the line or element is first seen and the the second part of the reference designates separately the specific element in this figure. So appears sB, the element 5-10 in Fig. 5 and is a crystal oscillator in the upper left ψ quadrant, of Fig. 5 ·

Fig. 4 is a general block diagram showing the main parts of a receiver incorporating the features of the invention. For the sake of clarity, this figure shows me the elements used in connection with the processing of a 10.2 IiEm signal. The IJ.6 kHz signal is processed in a mustard analog manner, and the slight differences are mentioned below.

The signals received by the antenna 4-10 are only fed to a receiving section 4-11, where they are recognized and for

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the forwarding to the following circuits of the receiver can be processed. Obviously, all signals are simultaneous received in their transmitted sequence, and the only reason for ambiguity relative to the received signals is based on the fact that two transmitters always work for the same period of time, even if not at the same time. In general, this does not lead to difficulties, since the transmitters with the same "on" time are deliberately at great distances are arranged to each other on earth. The result is the next station and therefore the one with the strongest signal dominate.

As shown in Figure 4, a single phase tracker 4-21 is used in the receiver. This is made possible by a multiplex operation in the process of phase tracking, which takes place on each of the eight received signals or can be done. It will be understood that many of the advantageous features of the invention are used in modifications to the receiver and in particular eight separate phase tracking systems can be used. The related however, digital technology used with the invention makes it convenient and very desirable to use multiplexing.

The received signals are processed under the timing control by a synchronizer 4-12, which contains the master clock of the receiver. The synchronizer 4-12 generates the internal reference signals from which all Timer and control operations are derived. Under the control of the synchronizer and a display and control section 4-13 means are provided for synchronizing the internal clock generator with the transmitted signals. The recipient then stays in the we- * mostly phase locked, mainly as a result of the stability of the internal clock. On the other hand are

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further facilities are provided to regain synchronization if it should be lost. Among other things there the synchronizer 4-12 output "on-time" control signals which have a duration corresponding to the duration of the received signals. These control signals are provided to the display and control section 4-15 fed, where they are compared with the received signals and control over the internal clock to effect the facilitate actual synchronization.

The signal detector 4-14 operates to determine the presence or absence of a signal in the phase tracker 4-21. When a signal is present it is used for a number of specific purposes. First, it is used as an input on a pulse width meter 4-15 to enable synchronization of the internal clock. Second, it gets connected with "early-late" control signals generated by synchronizer 4-12 used, which stretch the detected signal and enable pin synchronization of the internal clock.

The individual elements from which the synchronizer 4-12, the receiving section 4-11, the signal detector 4-14, the Pulse Width Meter 4-15, the Display and Control Section 4-13 and the Phase Follower 4-21 Confess are detailed in Pig. 5 to 8 shown. Pur a complete representation of the Receiver, these figures can be assembled as shown in Fig. 8A.

The sync part of the receiver as it is in Pig. 5 includes a master oscillator, digital divider circuitry and control circuitry for laying the necessary Timing sequence and signals for controlling receiver operation. The main oscillator is a crystal oscillator 5-10, which works at 4.8 MHz. Such oscillators can have a stability of approximately one in a hundred million getting produced. Of course, it goes without saying that the basic

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frequency of 4.08 MHz was chosen because the transmission signals with 10.2 and 13 * 6 kHz in the Omega navigation system are given. These fundamental frequencies for the transmission signals are used in the following description. Pure in the event that other frequencies are related to either the omega navigation system or other systems similar Only the specific frequencies used need to be used in accordance with the technique set out here and teaching are discontinued.

To get the fundamental frequency for the internal signals of 10.2 kHz, the output of the crystal oscillator is in Divisors 5-13 and 5-14 divided by 400. The divisor 5-14 for 1/100 is a binary coded decimal unit and provides output on lines 5-30 and 5-31. Note that the width for line 5-30 from the corresponding exit The channel shown indicates a cable which carries binary coded decimal data, which is shown in the shown in FIGS automatic distance tracking circle can be used. One that recurs at a frequency of 10.2 kHz The signal is fed to the following divider circuits via the line 5-31 in order to produce further control pulses and signals.

The output of the crystal oscillator 5-10 is also divided by 300 by dividers 5-11 and 5-12 to get one Frequency of 13 * 6 kHz. This frequency is both available in binary coded decimal form as well as a 13.6 kHz signal and is used as required.

If you look further at the 10.2 kHz output on line 5-31 * you can see that this is only used to generate a 3.4 kHz signal on a line 5-41 through three and to generate a 85O Hz signal on a line 5-32 through twelve is shared. The signal on line 5-41 is in

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a further divided Expensive 5-19 by 85 to provide a ¹ K) Hz signal on a line 5-33, which in a control signal generator 5-22 for generating in Pig. "Early" and "late" control signals shown in IO is used. The output of a divider 5-15 is further fed to a variable divider 5-16 which is nominally divided by 85 to produce a 10 Hz output on line 5-3 ^. The divider 5-16 responds to a tracking control 5-26 in a known manner in order to modify the dividing process during the synchronization of the receiver with the individual received signals. This capability is sufficient to achieve the required functioning in connection with the display and control section shown in FIG. A convenient set of factors for the subprocess may include I / 8I and I / 89.

The output of divider 5-16 on line 5-3 ^ is further divided by 100 in a divider 5-I7, vm a 0.1 Hz signal, ie a signal with a period of 10 seconds, on line 5-35 and to provide a binary coded decimal output on a line 5-36. The signal on line 5-35 is further divided by 16 in a divider 5-18 in order to obtain signals with only 0.006 Hz on line 5-37. The binary coded decimal signals at 0.1 Hz on line 5-36 are fed to a decoder 5-20 for subsequent processing and distribution via cables or lines 5-38 and 5-39 to the phase follower section or the display and control section. The slowly repeating signals on the line 5-37 are passed on via a pulse generator 5-21 as binary speed multiplier pulses to the gates appearing in the phase follower in FIG.

It should be noted that the 0.1 Hz signal is a basic sync signal for the decoder 5-20 which generates various control signals used in the receiver. The input speed of 0.1 Hz for the decoder-sets the period of

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10 seconds, which is the repetition period of the Omega navigation system is equivalent to. Since the system does not transmit any synchronization, the internally generated Period of 10 seconds and all control signals generated by it initially in time coincident with the transmitted Period of 10 seconds. This is achieved by changing the nominal dividing factor 85 which is used for basic triggering of the decoder's pulse train is used. By increasing the division factor of 85 on 89 the decoder 5-20 will work e.g. with a lower repetition frequency and the control signals it generates will therefore be delayed relative to the received signals. This phase adjustment continues until phase synchronization is reached, at which point the divisor is reset to its normal size of 85 will.

Four output pulses are selected from the divider 5-18 by 1/16 and made available on the cable or line 5-37: One pulse every 20 seconds, one pulse every 40 seconds, one pulse every 80 seconds and one pulse every I60 Seconds. The person skilled in the art is familiar with the manner in which repetitive pulses can be extracted from a binary divider with four binary levels at these intervals.

Signal acquisition .

In Fig. 6 the display and control section of the receiver is shown. This figure shows two indicators 6-0 and 6-11, which are referred to as "coarse indicator" and "fine indicator", respectively. The coarse indicator 16 has two '■ rows arranged lights on. There are eight columns with two lights each. The columns are from left to right

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denoted by 0.9, 1.0, 1.1, 1.2, 1.1, 0.9, 1.2 and 1.0. Purely selected lighting of each light in response to appropriate devices are provided for a control pulse. These lights correspond to the arrangement of lights 10, which on the front plate of the Pig. I appear at the recipient shown.

It should be repeated that the transmitting stations of the Omega navigation system during periods corresponding to the Transfer the column names of the coarse indicator. So shows the timing diagram in Pig. 3 * that the stations or transmitters A through D successively during periods of 0.9 * 1 * 0, 1.1 or 1.2 seconds. The remaining four stations of a proposed eight station system would be the Successive transmissions during the remainder of the 10 second period with periods of 1.1, 0.9, 1.2 and 1.0 second, respectively. to continue.

The decoder 5-20 in the synchronizing section generates a series of "on-time" control signals which correspond to the received signals. These control signals are in Pig. 9 shown as the puncture of time. Like in Pig. 9, the plurality of control signals A ¹ to H ¹ correspond to idealized signals which could be received by each transmitting station of the navigation system. These signals are laid out in accordance with the transmitter which would be generating a coincident signal at that time. It can be seen that the entire group of signals is generated sequentially over an interval of 10 seconds. There is an interval of 0.2 seconds between the signals, during which a "control signal to end" pulse of approximately 0.1 seconds is provided. The "control signal end" pulses begin at the end of each "on-time" control signal.

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The process of aligning the receiver with the transmitted signals of the system consists in aligning the "on-time" control signals with those actually received Signals from the various transmitters. Since all signals are coordinated relative to each other, each signal, which is of sufficient strength to be received, in its proper timing within the interval of Occur for 10 seconds.

Looking further at the coarse indicator 6-10, it should be noted that the internally generated "on-time" and "control signals to the end "signals from the decoder 5-20 via the cable or line 5-59 and a suitable control logic 6-12 to the Means for illuminating the upper row of lights are supplied. Signals similar to those from the transmitters The signals received correspond to the signal detector on a line 7-42 via a pulse width measuring circuit 6-14 and appropriate control logic 6-15 applied to the lower row of lights.

Assuming that no signals are initially received, the operator will observe illumination of the top row in the appropriate time sequence under the control of the signals from decoder 5-20. If the sequence is initiated at the start of generating the "on-time" control signal A * in Figure 9, it will consist of illuminating the first light for approximately 0.1 seconds when the "control end" pulse is received will. Then about 1.1 seconds later the 1.0 second light will light up for 0.1 seconds: about 1.2 seconds later the 1.1 second light will light up; and about 1.3 seconds later the 1.2 second light will come on. This continues with the remaining 1.1, 0.9, 1.2 and finally 1.0 second lights, which light up when the "control signal to 'end" pulses occur, which at the end of the signals E', F ¹ , G ¹ and H ¹ , respectively.

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When signals from the transmitters of the Omega navigation system are actually received and these signals are of sufficient strength to pass through the signal detector and the to activate the circuits described below « these signals to illuminate the corresponding lights in the bottom row. It is assumed that a signal is received with a duration of 1.0 seconds. Viewing Fig. 3 shows that a signal of this duration comes from both station or dsm transmitter B and from the station or transmitter H is generated and that it will occur as either the second or eighth signal within the 10 second interval can. This 1.0 second signal is processed by the signal detector and fed to the pulse width measuring circuit 6-14. The pulse width measuring circle 6-14 can take the form of a simple one Have counting circuitry that starts operating when a signal from the signal detector on the Leidig 7-42 occurs and upon termination of this signal a pulse on a separate one Line generated depending on whether the input from the signal detector has a duration of 0.9, 1.0, 1.1 or 1.2 seconds exhibited. The output of the pulse width measuring circuit 6-14 has a duration of approximately 0.1 seconds and is controlled by the control logic 6-15 with the corresponding lights, in this case the second and eighth, in the lower row of the coarse indicator 6-10 fed. So when the signal comes from station B, when it ends, the second and eighth lights will be in the lower row can be illuminated for 0.1 seconds. The operator can now determine the relative time that the Observe upper and lower 1.0 second lights.

To match the receiver with the received signal, it is only necessary to activate the tracking control 5-26 temporarily in order to influence the division factor of the divider 5-16. If the operator wants to increase the speed at which the internal front panel lamps come on,

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the divisor of the divider 5-16 is reduced to 81, for example. This will advance the phase of the internal control signals and effectively causing them to occur earlier. The use of the tracking control 5-26 becomes make it possible to synchronize the illumination of the 1.0 second lights. When the top and bottom If lights illuminate synchronously, the associated signals are essentially in phase.

Since two transmitters operate during an interval of 1.0 seconds, namely transmitters B and H, there is no way determine which broadcast is being received when the signals from both transmitters are strong. This is why it is important that a second signal of different duration be received and processed to resolve the ambiguity. In reality the stations or transmitters B and H will be far apart and consequently only a very small one real possibility of the signals from the transmitters B and H at the same time or with a comparable signal strength.

Assuming that the stations or transmitters A, B and C are all in range of the receiver, the 0.9, 1.0, and 1.1 second lights in the bottom row will all become »corresponding ones Light up time. If an incorrect sequence is noticed, the tracking controller 5-26 will correct it be used. This means that there is no possibility of an ambiguous comparison if a second signal is a different one Duration is received.

Experience with the operation of this circuit arrangement and the recognition of the applied principles have shown that the coarse adjustment in many cases for an exact synchronization of the recipient will be sufficient. Nevertheless, the fine indicator 6-11 is provided to monitor the internal time

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switching arrangement with the received signal with an accuracy of approximately 0.075 seconds. In conjunction with the fine indicator, the control signal generator generates 5-22 "early" and "late" control signals in the intervals between the "on-time" control signals.

In Fig. 10, waveform 10-10 represents a composite signal obtained by adding all of the "on-time" control signals. The intervals 10-11, 10-12 and 10-13 between the pulses have a duration of 0.2 seconds. The pulse durations 10-14 and 10-15 correspond to the signals which the stations or transmitters A and B represent. It will be seen that an "early" control signal is generated 0.075 seconds prior to the start of each internal "on-time" control window. A "late" control signal is generated 0.075 seconds after the end of each "on-time" control signal. The duration of the "early" and "late" control signals is 0.025 seconds. In the interval of 0.2 seconds between the generated "on-time" control signals, a "late" and an "early" control signal are generated. These control signals are used in AND gates 6-16 and 6-17, respectively, in order to pass the signals from the signal detector on line 7- ^ 2 either to the upper or lower light of the fine indicator 6-11. If these two lights are extinguished at the same time, it is ensured that the alignment is better than a Is 0.075 seconds. Obviously, if the actual received signal falls within the "late" control signal, it will not fall within the "early" control signal. By noting that neither the "late" and "early" control signals are in time with the signal, the operator is assured that the signal will begin no later than 0.075 seconds before the indicated internal control signal time and no later than 0.075 seconds after the end of the internally generated control signal ends.

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Although the synchronization and adjustment described have no particular effect on the measurement of the phase of the 10.2 kHz signal from any two Omega transmitters, it can be seen that they allow a maximum time for the Apply phase measurements, and that a better and more positive station identification is ensured.

As a result of the stability of the crystal controlled clock in the receiver, it has been found to last over time At the moment only minor adjustments have to be made due to the operation of the torment indicator. With just a little experience it is it is possible to set the synchronization of the internal and external control signals to within 0.025 seconds.

Once the internal time system with the external Omega navigation transmission system has been adjusted, the receiver is ready to start taking the phase measurements on the various received signals to determine the actual location of the receiver itself. The measurements are made in the Receive and phase tracking sections of the receiver performed .

The receiving section

The receiving section of this Omega receiver system is the only part that works in analog mode. this section provides the necessary amplification, bandwidth and processing of signals, which can be slightly below the noise level.

As shown in Fig. 7, the signals are received by an antenna 7-10 and passed through a band-pass filter 7-11 for 10-14 kHz. After being processed by a limiter 7-12, the signal follows two separate paths on lines "J-13 and 7-14. These paths separate the two signals with the fundamental frequencies of 10.2 and 13 * 6 kHz. Here only the 10 , 2 kHz channel. It goes without saying that a similar circuit

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arrangement with the necessary changes as required for the treatment of the 13.6 kHz signal is provided.

The 15.6 kHz signal is only used for phase tracking is used and consequently would not be fed into the signal acquisition part of the equipment.

The signal on line 7-1 is first passed through a very simple bandpass filter 7-15. After filtering, the signal is again limited by a limiter 7-16 and appears as an essentially pure signal with the carrier frequency of 10 , 2 kHz off. in order to determine the reception position, it is necessary to determine the phase of this signal. Correspondingly, the signal from the limiter 7-16 is fed to the automatic phase tracking circuit shown in Pig, 8. In addition, this signal is fed via a line 7-21 d ~ - ■ signal detection circuit, in which it is used to generate a well-shaped output for use in trimming and the operations described above.

Signal acquisition

The 10.2 kHz signal on line 7-21 is fed to the two sides 7-32 and 7-32 · of a right angle phase detector. In connection with a merging low-pass filter 7-33, the right-angle phase detector generates the envelope of the received signal on a line 7-26. The envelope is compared in a comparator 7-36 with an automatically controlled threshold value in order to generate a binary signal which the presence or absence of the received signal. indicates.

In the receiver, the received signals are processed in such a way that they are used further in the digital circuits can be. So the signal detector quantizes the

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received signals in time and results in an output on line 7-42, which is representative of the presence of a Signal during each of the 400 0.025 second intervals making up the 10 second period of the omega transmission pattern can be viewed as constructed.

The period of 10 seconds is determined by quantizing the Time base in 0.025 second intervals (the period of a 40 Hz signal) divided into 400 units or time units. A shift register 7-4o works in combination with a logical Circuit 7-39, a query circuit 7-37 and a comparator 7-36 to store and generate the desired discrete signal information relative to each unit of time. The shift register may actually consist of 400 suitably connected binary levels, each of which in turn is a four-level Binary counter or register which can register a maximum count of 15 and a minimum count of zero able.

A 40 Hz signal is sent from the synchronization circuit via the Line 5-33 before &. shen. This signal triggers the interrogation circuit 7-37 every 0.025 seconds. The interrogation circuit 7-37 can have the form of a controlled flip-flop, which has a binary output generated according to the presence or absence of a signal from the comparator 7-36 at the time of triggering. Of the The output of the interrogation circuit 7-37 is via the logic circuit 7-39 for adding or subtracting a digit to the Number in the stage of the shift register which corresponds to the requested time unit is used. Following one of these Entering data into this stage becomes the following stage for ready to enter data.

A control 7-4l for a constant "false alarm amount" (CFAR) is provided to control the threshold voltage on a line 7-38 to such a level that the output

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of the! Comparator 7-36 has a fixed "false alarm amount" due to the noise when no signals are received. The binary number in the shift register 7- ^ 0 is queried for four equally spaced time accesses within the period of 10 seconds, which represents a time separation of 2.5 seconds. The lowest number occurring on these four time accesses has a very high probability of being the sample from an area of the omega time frame of 10 seconds in which no signal is received. Since a receiver is not received from all eight channels signals, the timings of Ubertrageungen which f for reception to be far away, simply contain noise. This number is compared with a level which corresponds to the middle number at which the noise in the shift register should be integrated. If the smallest sample is greater than this level, the CFAR loop operates and increases the threshold voltage on line 7-38 slightly, thereby reducing the "false alarm amount ^11" at the output of comparator 7-36. The opposite effect is achieved if the least sample is less than the reference level, thus realizing a closed loop system which sets the threshold voltage at a desired level.

In the following, the work sequence during the recording of a 1.0 second signal will be considered, which all Repeated 10 seconds. An ideal signal of this type will be present for 40 time units of 0.025 seconds. Indeed, atmospheric and other attenuations can cause a received signal to occur much less frequently. The comparator 7-36 is activated during the presence of the 1.0 second Signal produce an output and the interrogation circuit 7-37 will correspondingly provide a discrete binary output, e.g. binary one every time the 40 Hz trigger signal is on the

t ι

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.25. 2120633

Line 5-33 occurs. The shift register 7-40 is incremented at the rate of 40 Hz and is therefore present a separate stage to logic circuit 7-39 during each unit of time. If the binary signal is one at the output of the interrogation circuit 7-37 is present, the count stored in the associated stage of the shift register increases by one be enlarged. If the binary signal one is not present, the count will be decremented by one. Under the assumption After two minutes, i.e. 12 intervals of 10 seconds, 40 consecutive Shift register stages 7-40 store a count of twelve and all other stages store a count close to zero.

For the purposes of the present recipient, it is assumed that a signal is present when the detector registers a count of eight in any unit of time. So will a pulse is generated in the output on line 7-42 when the stage corresponding to any unit of time has a count of contains eight or more. In the case under consideration, line 7-42 becomes 1.0 after picking up an ideal signal Seconds duration for one minute and twenty seconds a pulse train of 40 pulses with a repetition frequency at 40 Hz and at intervals of 10 seconds. In actual working conditions, the on a line 7-42 occurring pulse series a synthesis of all represent received signals. The eight stages of the shift register, which are the intervals of 0.2 seconds between received signals will be significantly below eight, and so there will be a clear separation between the signals from occur at every broadcaster.

The pulse width measuring circuit 6-14 counts the pulses generated on the line 7-42. So he registers a value immediately the number of time units during which the associated stages of the shift register re-count eight and more

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register. The four possible omega signals, which are 0.9 / 1.0, 1.1 and 1.2 seconds are ideal counts of 36, 40, 44 and 48 respectively. Because of possible pulse stretching however, if the receiver is set to read every count between 35 and 38 as an indication of a 0.9 second signal, each count from 39 to 42 as an indication for a 1.0 second Signal, every count from 43 to 46 indicating a 1.1 Second signal and each count from 47 to 50 as an indication for identified a 1.2 second signal. The control logic 6-I5 recognizes the various counting limits and sets them the illumination of the corresponding light in the lower row of the coarse indicator 6-10 is in operation.

Phase tracker

Since there are eight potential transmitters in the Omega navigation system, it is desirable that the receiver be at the same time which can receive 10.2 and 13.6 kHz signals from all eight stations® This reception capacity requires facilities for tracking the phasre of 16 signals simultaneously are provided. This can be achieved either with sixteen separate phase trackers or by one Multiplex arrangement in which a single phase tracking circuit is used for all signals on the two received frequencies. In practice only the 10.2 kHz signal is for the primary position determination required. For the sake of simpler explanation, the following description is only used in with respect to a single phase tracking operation at 10.2 kHz. The additional for the single multiplex processing of all 10.2 kHz signals required elements are described.

Looking at FIGS. 7 and 8 together, there is an upper one Detect loop part, which works as the only integrating tracker, and a lower loop partj, wsloher

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Compensates for tracking errors that may occur as a result of the movement of the receiving stations. That lower loop is analogous to a stabilization loop of the second order, as can be found in analog servo technology. It's closed note that the entire phase tracking process is done using digital elements and techniques, what making multiplexing both possible and useful.

In the upper middle part of Pig. 7 is initially a bi- ' När coded decimal adder 7-29 to recognize. That adder can be a two-decade unit, each decade having four multiple interconnected levels, around one decimal To give a count of 10. It can be in response to pulses on the line 5-30 from the divider 5-14, which with 1.02 MHz occur, count continuously from 0 to 99. The actual one registered in the adder 7-29 at any one time Number can be modified by an input via a cable or line 8-20, which gives the adder a "predetermined" Phase number "is imprinted to ensure phase synchronization at the frequency of 10.2 kHz between the internal clock and the received signal.

The predetermined number of phases which the return of the is closed loop aes phase tracking circuit is fed into the adder 7-29 from a phase number register 8-39 and changes during the interpulse period. As far as the adder is modified at a speed of 3jO2 MHz it is subject to change at a rate of approximately one number per microsecond. Since 100 Counts are required, the complete cycle takes the time exactly equal to the period of the 10.2 kHz signal, * or approximately 100 microseconds.

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Pig. HA shows a graph in which the abscissa is time and the ordinate represents the number of phases. The illustration will be useful in considering the operation of adder 7-29 relative For the rest of the circuit, this illustration shows that the output trigger pulse on line 5-30 is normally acts on adder 7-29 to produce solid line 11-11 which increases over time with a fixed slope. If at any point in the cycle of operation a predetermined number of phases, e.g., 15, is introduced, the output will be along the dashed line 11-12 run. In this case the adder starts with a bias of plus 15 at the beginning of the 10.2 kHz period. In effect, the adder 7-29 works as an adjustable phase shifter.

When the count reaches 50, an exit is made on a Line 7- ^ 0 pulled out of adder 7-29. This exit ends when the count reaches 99. Appropriate logic circuitry is provided to pull this output out and use it with a binary value of one. A waveform corresponding to this condition is in Pig. HB. The curve is over the same timescale as in Pig. HA applied and represents the waveform when the predetermined phase number is zero.

The one in Pig. The waveform shown in HC corresponds to the one which occurs as the output of the adder 7-29 when the vorbes timmte number of phases is equal to 15 and the count accordingly the dashed line 11-12 in Pig. HA progresses. It can be seen immediately that the waveform in Pig. HC in the Phase relative to the waveform in Pig. HB is advanced by the value 15. In terms of the frequencies used this is approximately 15 microseconds or more precisely 15/100 or 10.2 kHz period. So a phase shifter is provided in which by changing the predetermined number of phases

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Control signal is generated, which in steps of one microsecond can be moved into any desired time slot.

The control signal which has just been described is applied as an input to a phase detector 7-17. A The second input comes via a line 7-22 and corresponds to the 10.2 kHz input signal.

One function of the phase detector 7-17 is to to provide an output, which enables a precise adjustment of the incoming signal relative to the internal clock pulses. In Pig. Figures 12A and 12B are representations of three waveforms designated 12-A, 12-B and 12-C. In of each of these figures, the abscissa represents time and the ordinate represents amplitude. The time scales for each of the waveforms on the left and on the right are aligned with each other so that a vertical line represents the same cell pulse would represent for each waveform.

If the receiver is properly tracking the received signals, the control signal will be waveform 12-B relative to of the incoming waveform 12-A as shown in Fig. 12A. The control signal is present under this condition the line 7-30 in the middle of the incoming waveform on the line 7-22 and the output from the phase end detector 7-17 Signal has equal positive and negative parts. Incorrect alignment is shown in the waveforms of Figure 12B where shown is that the control signal with waveform 12-B occurs in an advanced position and the phase detector 7-17 correspond to a larger positive part of the incoming waveform A than the corresponding negative part gives away. The output of the phase detector appears at 10.2 kHz and will have a mean value which is either positive or negative, depending on whether the control signal is advanced or delayed relative to the received signal.

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It is clear that when the control signal is properly balanced, an output of zero (equal positive and negative Parts of waveform 12-C) to output to the following integrator 7-18, the predetermined number of phases required to achieve this Condition has been introduced into the adder 7-29, discretely the phase of the incoming signal relative to the internal clock signal The certain value of the predetermined number of phases has none real meaning; however, similar phase numbers developed for each received signal can be used for determination of the difference between these can be compared. A circuit, not shown, is provided for the subtraction of the Phase number, which represent selected pairs of stations, and the difference is usually on the indicator 14 in Fig.l. displayed. This difference is a true value and determines the geographic location of the recipient. It should be noted that the actual phase detection and phase comparison are carried out on a digital basis, and that any errors caused by introduced the previous analog part of the receiving section can be added to each of the received signals and subtracted out in the comparison process so that they have no meaning for the phase comparison process.

Integration circuit

The output of the phase detector is as shown by waveforms 12-C in FIG. 12A and 12B. It is necessary, evaluate this output to determine whether the mean is plus or minus. This is done with the aid of a threshold quantizer 7-19 connected integrator 7-18 · A schematic circuit diagram in detail of these parts is shown in FIG. In general, the output of the phase detector is integrated by the integrator 7-18 during the entire time which the signal is received, which would be 0.9 seconds for the station or the transmitter A, for example. At the end of this period the integrator is reset to zero so that it

109848/1224 -31-

integration ready for the next received signal is. The output of the integrator is fed to the threshold value quantizer 7-19, which generates an output which is either positive or negative depending on the sign of the phase error and either as a logical one or a logical zero appears. In accordance with whether the output is one or zero, an AND gate becomes 8-10 or an AND gate 8-11 on receipt of a "control signal to the end" signal from the decoder 5-20 effective and leave an adder gate 8-12 or 8-15 a pulse to the input "to" up "or" down "of the phase number register 8-39.

The phase number register 8-59 is a binary coded decimal Adder, which counts up or down, as the case may be whether or not signals are fed on lines 8-50 or 8-31. It is envisaged that this adder will last two decades with four levels each. So shows the cable or line 8-20 in the output of the phase number register 8-39 for the suitable direct input to each stage of the adder 7-29 Partial lines on.

Recapitulating, it should be noted that a control loop has been established in such a way that the phase number register will preset the adder 7-29, depending on whether the control signal from the adder 7-29 äae received signal leads or not. The time constant of the loop is quite large, as the pulses from the threshold quantizer 7-19 are fed to the phase number register at the end of each signal period for each particular station for control. This occurs once every 10 seconds. So the predetermined number of phases is changed by a single count only every 10 seconds.

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The lower loop of the phase tracker, which has an adder 8-18, logic gates 8-24 and a switch 8-27 is provided to take account of the fact that in most cases the receiver is relative to the transmitter be in motion and consequently produce a speed error. The adder 8-18 is a binary counter. He under- • differs from the phase number register 8-59 in that it only has Includes 5 bits. Thus, the counter 8-18 is supplied with inputs which enable it to either go up or down below counts, depending on whether these inputs are on a line

^ device 8-16 or a line 8-17 are fed. Since he is a has a single decade and is not arranged as a decimal counter, this binary counter can be any number between +15 and -15 to register. It is repeated that AND gates 8-10 and 8-11 produce a single output upon termination of the signal, which is quantized by a particular transmitter. So the adder 8-18 goes up or down every 10 seconds adjusted. When the receiver has a speed relative to the transmitting station, e.g. when the receiver is from If the sending station moved more than a constant radius arc, the receiving station would normally use a relatively constant speed out of phase with the transmitting station drift. The lower loop compensates for this movement

) supply by adding additional pulses to the phase number register 8-39 fed with the correct polarity and the correct amount in order to reduce the speed error caused by this movement of the receiver to essentially zero to decrease.

The adder 8-18 is in a count in a point between -I5 and + I5 according to the speed · Ability of the recipient. The polarity of the stored number is fed to the switch 8-27 via a line 8-22 and is determined, whether the switch is in an "up" or "down" position.

1 09848/1224

It will be understood that switch 8-27 is shown in mechanical form. In fact, it's in an electronic way realized. The adder 8-18 controls the logic gates 8- ^ 24 via lines or a line 8-23 * around the binary speed multiplier pulses from the pulse generator 5-21 into the upper and lower terminals of the phase number register 8-39 respectively. As noted above, the pulse generator 5-21 has four discrete outputs. These outputs all add up to 20, 40, 80 or 16O seconds a single pulse.

Fig. 14 shows the structure in more detail of adder 8-18 and logic gates 8-24 are shown. The logical ones Gates 8-24 may comprise four AND gates 14-1 to 14-4, each of which has inputs from the pulse generator 5-21 and likewise from a counter 14-10 which makes up the adder 8-18. The output of every AND gate is via an OR gate 14-5 directed at switch 8-27. Thus, when the counter 14-10 registers a count of two, the AND gate 14-2 can every 160 Allow two pulses for seconds or one pulse every 80 seconds. Depending on whether the polarity of the number is positive or negative is, these pulses are through the adding gate 8-12 or 8-I3 to the count input "up" or "down" of the phase number register 8-39 forwarded.

The particular strip in which the receiver is located relative to a transmitter can be monitored by following the change in the predetermined number of phases. One full cycle, or 360 ^{degrees, of} the 10.2 kHz signal represents one stripe width. To cross a full cycle, the phase number will go through a full count of 100. An adder 8-49, which is a three-decade binary coded decimal counter, responds to phase number changes by either adding or subtracting a number as the phase number register passes

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goes a full cycle. The adder 8-49 has one Stripe counting capacity of 999, and the count can be monitored at its output via a line 8-50 for each the way you want.

Multiple station tracking (multiplex operation)

In the immediately preceding section, the mode of operation of the receiver is in the context of a single transmitting station received signals has been described. In fact, under optimal conditions, signals from each of the transmitting) Stations received. Under other conditions, the receiver can respond to at least several of the transmitting stations. So the possibility of phase tracking must be provided for each received signal, and with these signals in can be continued in the manner already described. The recipient described here is in view of the fact that the signals are received sequentially, particularly well suited for processing the signals on a time division multiplex basis.

Looking at the phase tracking circuit in FIG. 8, it will be remembered that the adder 8-18 is storing a number. chert, which represents the receiver movement relative to a first "transmitting station. This number is at most every 10 Seconds changed when the signal is received and processed by the receiver. During the remainder of this interval from 10 seconds it is possible, and indeed desirable, to use the adder in conjunction with other transmitted signals to use. Storage devices are provided which are associated with each of the various registers of the phase tracker work together.

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A shift register 8-21 is used in conjunction with the adder 8-18. This shift register can be words record with 5 bits. Each word of 5 bits corresponds to the complete registration of the adder 8-18, where 4 Bits register the counted number from zero to 15 and the fifth bit the polarity of the count. A signal from the decoder is used in conjunction with a suitable control circuit to keep the information synchronized with reception of the various signals from the transmitters to and from the shift register.

A shift register 8-38 is associated with the Phase number register 8-39 provided. This register is an eight-level unit with 8-bit words in each level. Thus, each stage can store the full count in the phase number register at any time. Signals from the decoder are synchronized to shift information into and out of shift register 8-38 on lines 8-41 and 8-40, respectively used with the particular signals received.

Next is a shift register 8-44 related to the adder 8-49 provided with three decades, which for the fringe count is used. This shift register comprises eight stages, each of which has 8-bit words as required for operation in conjunction with adder 8-49. It should be noted that the shift register 8-44 is also controlled for shifting the input and output of the decoder, and that it is closed is kept in synchronism with the specific signals that are being used at all times.

In summary, a receiver has been described, wfelcher uses the characteristic features of the invention. Of the ,

-36-1098-48 / 1224

Receiver used to. to be able to operate with the omega navigation system, a number of active circles for acquiring, aligning and generating information which make it possible for the operator of the receiver to determine its exact position. The equipment described above is all digital with the exception of a limited number of analog input circuits from the receiving antenna. All phase comparisons are made digitally with a guaranteed accuracy of at least 3.6 °.

A detailed explanation of the treatment of the secondary signals received by each transmitter, i.e. the 13.6 kHz Signals was not carried out. As shown at the beginning of the description, the main functions of the receiver performed with the 10.2 kHz signal. Nevertheless, an automatic phase tracking takes place at the frequency of 13.6 kHz. This is done in exactly the same way as described for the 10.2 kHz signal.

It will be recognized that various particular arrangements have been described in the illustrative description are to show the person skilled in the art in which way the invention System can be implemented advantageously. However, the invention is not intended to address the specific frequencies or the elements suggested above. The invention and its scope emerges in particular from the range of claims. All modifications which are obvious to one skilled in the art and from the teaching of the invention as encompassed by the claims are intended to be covered thereby.

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Claims (1)

Claims l.) Method for signal detection in response to sequentially transmitted signals of known but different duration, which transferred with a recurring period by sequentially generating a plurality of signals corresponding to each of the transmitted signals, optical Displaying the generated signals in a time-related manner, optically displaying the transmitted signals in a corresponding manner time-related manner and in a position next to the display of the corresponding generated signals, and setting the Phase of the generated signals to cause the displays of the generated and transmitted signals to coincide. 2. A method for signal detection according to claim 1, in which the transmitted signals are temporally spaced by a known interval are separated, characterized by generating pulses synchronized with the generated signals, which precede and follow the generated signals by a predetermined interval, providing a first signal if the previous pulse coincides with a transmitted signal, and providing a second signal when the subsequent pulse coincides with a transmitted signal, and visual display of the occurring ΖμΒαπκηβηίaliens. 5. A method for signal detection according to claim 1 or 2, including Receiving the transmitted signals and generating an electrical signal corresponding thereto, characterized by generating a plurality of time units within the recurring period, interrogating the electrical signal for a plurality of times within this known Duration and generating a binary display, if any, storing and counting the times during each tent session occurring binary displays, and generating a signal -38- 109848/1224 known duration if a suitable plurality of time units register the occurrence of a predetermined number of binary indications. 4. A method for 3 signal detection according to claim 3 * thereby gekennzei chnet that the transmitted signals in Following their reception, prior to generating the electrical signals are compared with a threshold level, wherein the threshold level from an analysis of the time units that register a minimum number of binary displays, is being developed. 5. Signal acquisition system, which is based on sequentially received Responds to signals of known but different duration, which are received with a recurring period, characterized by a device (4-12) for sequential Generating a plurality of signals with known but different durations, a first device for generating a ο ptical display according to the occurrence of each of the generated Signals, and second means for producing a visual indication in response to receipt of each of the received Signals in a position next to the display of the generated signals. 6. Signal detection system according to claim 5 * characterized, by means (5-26) for adjusting the phase of the generated signals to achieve collapse of ads. 7. Signal detection system according to claim 5 or 6, characterized in that the optical displays each signal associated indicators (6-10) which are actuated for a predetermined time interval following the end of each signal will. -39-109848 / 1224 8. Signal detection system according to one of claims 5 to 7 * characterized by a first plurality of each of the generated signals associated with and in a first A series of lights (10) arranged in the order of the sequentially generated signals, and a second plurality of each of the received signals and arranged in a second row in the order of the sequentially received signals Lights (10), the lights in one of the rows in one layer next to the lights in the other row the signals of the corresponding duration are arranged. ' 9. signal detection system according to any one of claims 5 to 8, characterized in that said second means comprises for generating a discrete output responsive to the received signals during the presence of which means (7-37) * a detector (7- ² K)) for retrieving the discrete output during a plurality of times within the duration of each of the received signals registering the number of times the output is present during the duration and comprising means (6-14) generated by the detection means a display control signal having the duration of each of the received signals is controlled in accordance with the number registered in the detecting means. 10. Signal detection system according to claim 9 *, characterized in that the discrete output only generates when the received signals exceed a threshold level and that one which is responsive to the detection means Means (7-41) is provided, which the threshold level in accordance with that registered in it Number during the time periods when no signal is received. -40- 1 09848/1224 11. Signal detection system according to claim 5 * by digital means (4-12) for sequentially generating a plurality of generated signals and means (5-26) for phasing the generated signals with the received signals. 12. Signal detection system according to claim 11, characterized by a receiving device (7-32 * 7-33) which is responsive to the received signals for generating this corresponding electrical signals, means (7-36) for generating a discrete output when the electrical Signal exceeds a predetermined threshold value, an interrogator (7-37) for interrogating the discrete output during a plurality of times within the duration of each of the received signals and providing a binary display, if the electrical signal is present, register means (7-40) for storing the binary indications in time units which represent discrete time intervals within the recurring time period, the register device records the number of binary displays present in each unit of time, and a facility (6-14) for generating outputs to control the second display device when the number is a predetermined value exceeds. 13. Signal detection system according to claim 12, characterized in that the means for generating of outputs a counter (6-I5) for generating a signal of known duration corresponding to a received one Signal includes when the number in a plurality of time units exceeds the predetermined value, this being the same Signal controls the second display device. -41- 109848/1224 - 4i - 14. Signal detection system according to one of claims 5 to 13, in which the received signals are separated in time by a known interval, characterized by a device (5-22) for generating pulses synchronized with the generated signals and so spaced apart in time, that these precede and follow each of the received signals by a predetermined interval, and means (6-16, 6-17, 6-11) for comparing the generated pulses with the received signals to effect a phase alignment of the generated signals and the received signals. 15. Signal detection system according to claim 14, characterized in that that the means for comparing a logic means (6-I6, 6-I7) for providing a first signal when the previous pulse and the received signal appear to be coincident and to provide one second signal when the subsequent pulse and the received signal appear to be coincident, and a visual display device (6-10) responsive to the first and second signals. 16. Signal detection system according to one of claims 11 to 15, characterized in that the received Signals are separated in time by a known interval, and that digital means (5-22) for generating pulses synchronized in time with the generated signals to precede and follow each of the received signals by a predetermined interval and logic circuitry (6-16, 6-I7) for comparing the generated pulses with the received ones Signals are provided to effect a phase alignment of the generated signals and the received signals. 109848/1224 17 · Signal acquisition system according to Claim 16, characterized in that the logic circuits have a Means (6-16, 6-17) for providing a first signal when the preceding pulse and the received signal coincide appear, and to provide a second signal when the subsequent pulse and the received one Signal appear coincident, and comprise a visual display device (6-11), which on the first and responds to the second signals. 18. Receiver that responds to a plurality of received sig- " each of a predetermined frequency, each from a different location during a discrete period of time is transmitted, and which has a device for generating a signal, characterized by a detector (7-17) * which in response to the generated signal and each of the received signals a the phase difference between the two representative output is generated, and a register device (8-39) * which through the output is controlled to provide an indication according to the magnitude of the phase difference of each of the plurality of signals relative to save the generated signals. 19. Receiver according to claim 18, characterized in that that the register means (8-39) operates on a time-sharing basis and a particular display only during the reception of the relevant signal of the plurality of received signals is registered. 20. Receiver according to claim 18 or I9, characterized by a storage device (8-38) which is coupled to the register device (8-39) and which stores the displays according to the size stores the phase difference of the plurality of received signals relative to the generated signals during the period during which the received signals cannot be received. -43-1Q9848 / 1224 21. Receiver according to claim 18 to 20, characterized by a further register device (8-18), which on the output for storing a display according to the speed with which the receiver moves relative to the location from which each of the plurality of signals is transmitted. 22. Receiver according to claim 21, characterized by a memory device (8-21) coupled to the further register device, which stores the displays according to the speeds, with which the receiver moves relative to the locations from which each of the plurality of received signals is transmitted, stores during the period when the received signals are not received. 23. Receiver according to claim 18, characterized by means (818) responsive to the output for modifying the Displaying by an amount according to the movement of the receiver relative to the locations from which the received signals are being transmitted, appeals to. 24. Receiver according to one of claims 18 to 23, characterized by a device (6-10) for displaying Data corresponding to indications developed in response to selected ones of the received signals. 25. Receiver according to one of claims 18 to 24, characterized in that that the detection means (7-17) includes a generating means (7-29) for control signals, which responsive to 'the generated signals for generating a control pulse repeating at a predetermined frequency, the Device for generating control signals by the register device (8-39) for setting the phase of the control pulse accordingly the display stored in the register device is controlled. -44-109848 / 1224 26. Receiver according to claim 25, characterized in that et that the detection device (7-17) is a digital one Comprises generating means (7-29) for control signals and generating one of three discrete signals which indicate that a received signal leads, is in phase or lags the control pulse, and that the register device (8-39) - show digital circuits storing in numerical form and in response to the discrete signals, enlarging the displays when the discrete signals are in an advanced condition display, the displays zoom out when the discrete signals indicate a lagging condition, and the displays unchanged * lets, if the discrete signals indicate a state in phase, wherein the generating means (7-29) for control signals from the register means (8-39) for changing the phase of the control pulse is controlled in steps according to the numerical changes in the displays. 27. Receiver according to claim 26, characterized by a digital storage device (8-38) coupled to the register device, which stores the displays according to the phase difference of each of the plurality of received signals during the period in which the signals are not received. 28. Receiver according to claim 26, characterized by a further digital device (8-I8) which is directed to the output the detection means (7-17) responds and stores the indications in numerical form according to the speeds at which the receiver moves relative to the locations from which each of the plurality of received signals is transmitted. 29. Receiver according to claim 28, characterized by .. means for modifying the displays in the register means (8-39) in accordance with those in the further digital Setup (8-18) saved displays. 109848/1224 _ 45 - 30. Receiver according to one of claims 26 to 29 *, characterized in that the generating device (7-29) for Control signals is a digital adder. 31. Receiver according to claim 30, characterized in that that the generated signal has a frequency greater than the predetermined frequency and fed to the digital adder (7-29) is to increase the count in this cyclically with a period corresponding to the period of the predetermined frequency. 32. Receiver according to claim 3I, characterized in that the register device (8-39) is a digital adder, "the output of which is switched so that the counting of the generating device (7-29) for control signals is in a discrete ratio to that in the Register device appearing count modified 109848/1774 Blank page