JP2005172760A - Direction finder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem in a conventional device that an increase in number of receiving antennas is needed in case of a wide frequency band to be received or in order to raise the precision of measured direction, and the numbers of receivers, A/D converters and cross spectrum calculating circuits are also increased according to it, resulting in an enlarged device scale. <P>SOLUTION: In this direction finder, the arrival direction is calculated by three receiving antennas 1 for receiving radio waves; a selector 2 for selecting the receiving antennas 1; a receiver 4 for amplifying and IF-converting a received signal; an A/D converter 5 for converting IF signal; an antenna switch part 3 for comparing digital data with a threshold to detect the presence/absence of input signal, and switching the receiving antennas 1; a waveform memory 6 for recording switching-by-switching digital data; a cross spectrum arithmetic part 7 for determining a cross spectrum from the switching-by-switching digital data in the waveform memory and recording the result; a time difference detection part 8 for determining an arrival time difference based on the switching-by-switching cross spectrum; and a direction calculation part 9 for determining the direction of the arrived signal from the switching-by-switching arrival time difference. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to an azimuth detection apparatus, and more particularly to an apparatus for detecting an azimuth using a difference in arrival time of radio waves.

As an apparatus for calculating an azimuth based on a difference in arrival time of radio waves, Japanese Patent Application Laid-Open No. 9-257902 discloses an azimuth detecting apparatus using one set of two receiving antennas and two sets of three receiving antennas, respectively. Has been. In FIG. 1, a receiver and an A / D converter are arranged for each receiving antenna, and a set of two receiving antennas for determining the arrival direction based on the average value of the arrival time differences is used. An azimuth finding device has been disclosed.

12 and 13 of the present specification are a configuration diagram and a processing content explanatory diagram in which the conventional azimuth detecting device described in Japanese Patent Laid-Open No. 9-257902 is transferred for explanation. In FIG. 12, 1-1 to 1-3 are receiving antennas that receive incoming signals, 4-1 to 4-3 are receivers that amplify the received signals and perform frequency conversion to IF signals, and 5-1 to 5-3. Is an A / D converter that converts IF signals into digital data, 7-1 and 7-2 are cross spectrum calculation circuits that calculate the cross spectrum of the digital data, and 8 is a time difference detection circuit that obtains the arrival time difference of radio waves from the cross spectrum. , 9 is an azimuth calculating circuit for obtaining the arrival azimuth of the radio wave from the arrival time difference.

The cross spectrum calculation circuit 7-1 includes FFT (Fast Fourier Transform) circuits 101-1 and 101-2 that perform fast Fourier transform on each input received signal, and a complex multiplication circuit 102− that calculates a cross spectrum of the Fourier-transformed signal. 1 is comprised. The cross spectrum calculation circuit 7-2 includes FFT circuits 101-2 and 101-3 that perform fast Fourier transform on each input received signal, and a complex multiplication circuit 102-2 that calculates a cross spectrum of the Fourier-transformed signal. Yes.

Next, the operation will be described. When a radio wave arrives at the azimuth detecting device of FIG. 12, it is received by the receiving antennas 1-1 to 1-3 and output to the receivers 4-1 to 4-3. The receivers 4-1 to 4-3 amplify the input received signal, further convert it to a predetermined frequency, and output it to the A / D converters 5-1 to 5-3. The A / D converters 5-1 to 5-3 convert the received signal input at a predetermined sampling timing into digital data and output the digital data to the cross spectrum calculation circuit 7-1 and the cross spectrum calculation circuit 7-2.

In the cross spectrum calculation circuit 7-1, first, the input digital signal is subjected to fast Fourier transform, and the amplitude and phase are calculated. Assuming that the signals obtained by the fast Fourier transform are XA and XB, respectively, XA and XB are input to a multiplication circuit, and a cross spectrum is calculated by multiplying the complex conjugate XB * of XA and XB. The cross spectrum calculation circuit 7-2 performs fast Fourier transform on the input digital signal, and calculates the amplitude and phase. Assuming that the signals obtained by the fast Fourier transform are XB and XC, respectively, XB and XC are input to a multiplication circuit, and a cross spectrum is calculated by multiplying the complex conjugate XC * of XB and XC.

FIG. 13 shows the processing contents of the cross spectrum calculation circuits 7-1 and 7-2. FIGS. 13A, 13B, and 13C are processes of the cross spectrum calculation circuit 7-1. The fast Fourier transform process of the received signal waveform A, the fast Fourier transform process of the received signal waveform B, and the cross between them, respectively. It is a result of a spectrum. FIGS. 13B, 13D, and 13E show the processing of the cross spectrum calculation circuit 7-2. The fast Fourier transform processing of the received signal waveform B, the fast Fourier transform processing of the received signal waveform C, both It is a result of a cross spectrum. The coherence and phase shown in FIG. 13C and the coherence and phase shown in FIG. 13E are both output to the time difference detection circuit 8.

In the time difference detection circuit 8, the frequency band f (f1) having a high coherence level output from the cross spectrum calculation circuit 7-1 and the phase gradient a (a1) at that time, and the output from the cross spectrum calculation circuit 7-2. A frequency band f (f2) having a high coherence level and a phase gradient a (a2) at that time are obtained. And, n = 0, 1, 2,... Δt = a / 2π + n / f (1)
A plurality of possible time differences .DELTA.t1 and .DELTA.t2 are obtained from the above. The obtained arrival time difference candidates are output to the bearing calculation circuit 9. In the azimuth calculation circuit 9, the arrival time differences Δt1 and Δt2 output from the time difference detection circuit 8, the interval between the reception antenna 1-1 and the reception antenna 1-2, and the interval between the reception antenna 1-2 and the reception antenna 1-3. Based on the above, each of the azimuth candidates having the possibility of arrival is obtained using the following equation (2).
sin θ = cΔt / d (2)
d is the distance between the receiving antennas, θ is the arrival azimuth, Δt is the arrival time difference, c is the propagation speed of the radio wave, and the azimuth included in the candidate azimuth calculated in each of these two systems is extracted, and the arrival of the original radio wave Get the bearing.

Japanese Patent Laid-Open No. 9-257902 Japanese Patent Laid-Open No. 2003-35761

Since the conventional azimuth detection apparatus is configured as described above, it is necessary to increase the number of reception antennas when the frequency band to be received is wide, or to increase the accuracy of the measurement azimuth. There is a problem that the device scale becomes large because the number of / D converters and cross spectrum calculation circuits need to be increased.

An azimuth detection apparatus according to the present invention includes three reception antennas that receive incoming radio waves at a predetermined distance, a selector that selects two reception antennas from the three reception antennas, and a reception signal from the selected reception antenna A receiver that performs amplification and frequency conversion to an IF signal, an A / D converter that converts the IF signal into digital data, a signal detection circuit that compares the digital data with a threshold value to detect the presence of an input signal, A simulator pulse generating circuit for generating a simulator pulse based on the pulse width and pulse interval of the detected signal, an antenna switch for switching the antenna for each simulator pulse, a waveform memory for recording digital data for each switching, A cross spectrum calculation unit that obtains the cross spectrum from the digital data of the waveform memory at each switching and records the result; And time difference detection unit for determining the arrival time difference based on the cross-spectrum for each switch, in which a bearing calculation unit to obtain the arrival direction of the incoming signal on the basis of the arrival time differences for each switch.

The azimuth detecting apparatus according to the present invention includes a CW detection circuit for detecting a CW signal (continuous wave), and a simulator pulse generation circuit for invalidating a simulator pulse once every predetermined time when receiving the CW signal. It is provided.

In addition, an azimuth detection apparatus according to the present invention includes a pulse separation circuit that separates incoming radio waves from a plurality of radio wave sources by PW (pulse width), PRI (pulse repetition interval), and the like, and a predetermined target that performs pulse separation. A simulator pulse circuit for generating a simulator pulse only for a signal is provided.

The azimuth detecting apparatus according to the present invention also includes a simulator pulse circuit that generates simulator pulses of a plurality of target signals that have undergone pulse separation, and an antenna switch that switches a receiving antenna according to priority when the simulator pulses overlap. It is a thing.

The azimuth detecting apparatus according to the present invention includes n receiving antennas that receive incoming radio waves at a predetermined distance and an antenna switch that selects two receiving antennas from the n receiving antennas. It is.

The azimuth detecting apparatus according to the present invention further includes an antenna switch for selecting and switching an optimum set of receiving antennas based on the frequency obtained by performing FFT processing for each incoming radio wave from a plurality of radio wave sources. It is.

An azimuth detection apparatus according to the present invention includes an azimuth estimation circuit that predicts an azimuth for each switching with respect to an incoming radio wave from a moving radio wave source, and an antenna switch that switches a receiving antenna based on the predicted azimuth. It is a thing.

In Embodiment 1 of the present invention, three receiving antennas that receive incoming radio waves at a predetermined distance, a selector that selects two receiving antennas from the three receiving antennas, and a received signal from the selected receiving antenna A signal that amplifies and converts the frequency of the IF signal into an IF signal, an A / D converter that converts the IF signal into digital data, and a signal that compares the digital data with a predetermined threshold to detect the presence of an input signal A detection circuit, a simulator pulse generation circuit for generating a simulator pulse based on the pulse width and pulse interval of the detected signal, an antenna switch for switching an antenna for each simulator pulse, and digital data for each switching are recorded. Cross that obtains the cross spectrum from the waveform memory and the digital data of the waveform memory for each switching and records the result It comprises a spectrum calculation unit, a time difference detection unit for obtaining an arrival time difference based on the cross spectrum for each switching, and an azimuth calculation unit for obtaining the arrival direction of the incoming signal based on the arrival time difference for each switching, particularly a receiver, An A / D converter or the like can be configured in two systems by using a selector, so that the scale of the apparatus can be made compact and a simple azimuth detecting apparatus can be obtained.

In the second embodiment of the present invention, a CW detection circuit for detecting a CW signal (continuous wave) and a simulator pulse generation circuit for invalidating the simulator pulse once every predetermined time and detecting the CW signal are provided. Thus, it is possible to obtain an azimuth detecting device that can cope with a signal having a long input period.

In Embodiment 3 of the present invention, a pulse separation circuit that separates incoming radio waves from a plurality of radio wave sources by PW (pulse width) and PRI (pulse repetition interval), and a simulator for only a predetermined target signal that has undergone pulse separation A simulator pulse generation circuit that generates a pulse is provided, and it is possible to obtain an azimuth detecting device that can detect an azimuth by separating predetermined signals from a plurality of radio wave sources.

The fourth embodiment of the present invention includes a simulator pulse generation circuit that generates simulator pulses of a plurality of target signals that have undergone pulse separation, and an antenna switch that switches reception antennas according to priority when the simulator pulses overlap. Therefore, it is possible to accurately detect the direction of a plurality of radio wave sources.

The fifth embodiment of the present invention includes n receiving antennas that receive incoming radio waves at a predetermined distance and an antenna switch that selects two receiving antennas from the n receiving antennas. It is possible to obtain an azimuth detecting device capable of widening the frequency and increasing the accuracy of the measurement azimuth. Even when the number of receiving antenna groups is relatively large, the receiver and the A / D converter are completely two systems, and a simple configuration can be achieved.

In the sixth embodiment of the present invention, an antenna switch for selecting and switching an optimum set of receiving antennas based on the frequency obtained by performing the FFT process for each incoming radio wave from a plurality of radio wave sources is provided. There is an advantage that it is possible to shorten the period of sequential switching and to reduce the number of switching antenna groups, and as a result, it is possible to shorten the direction calculation time.

The seventh embodiment of the present invention includes an azimuth estimation circuit that predicts an azimuth for each switching with respect to an incoming radio wave from a moving radio wave source, and an antenna switch that switches a receiving antenna based on the predicted azimuth. Therefore, it is possible to obtain an azimuth detecting device that can follow a moving radio wave source with high accuracy.

Example 1.
FIG. 1 is a block diagram showing an azimuth detection apparatus according to Embodiment 1 of the present invention. In the figure, the same reference numerals as those in FIG. 12 denote the same or corresponding parts. 2 is a selector (receiving antenna selector) that selects two receiving antennas from three receiving antennas 1, 201 is a signal detection circuit that compares the digital data with a preset threshold value and detects the presence or absence of an input signal, and 202 is a signal A simulator pulse generating circuit for generating a simulator pulse based on the pulse width and pulse interval of the detected signal, 203 an antenna switch for switching antennas for each simulator pulse, and 6-1 and 6-2 for digital data for each switching 7 is a cross spectrum calculation unit (cross spectrum calculation circuit) that obtains the cross spectrum from the digital data of the waveform memory 6 for each switching and records the result. In addition to the FFT circuit 101 and the complex multiplication circuit 102, The operation result memory 103 for temporarily storing these operation results It is. 8 is a time difference detection unit (time difference detection circuit) for obtaining the arrival time difference based on the cross spectrum for each switching, and 9 is an orientation calculation unit (azimuth calculation circuit) for obtaining the arrival direction of the incoming signal based on the arrival time difference for each switching. .

Reference numeral 3 is a generic name for the signal detection circuit 201, the simulator pulse generation circuit 202, the antenna switch 203, and the like, and is referred to as an antenna switching unit.

Next, the operation will be described. First, the receiving antenna 1-1 and the receiver 4-1 are selected by the antenna switching unit 3, and the presence or absence of an input signal (arrival radio wave) is binarized by the signal detection circuit 201 with reference to a threshold value. If there is an input signal, the PW (pulse width) and PRI (pulse arrival time interval) of the detected signal are measured by the simulator pulse generation circuit 202, and the simulator pulse is output as the simulator pulse generation circuit 202 based on the PW and PRI. Is generated. When a time lag between the simulator pulse and the input signal is expected to occur due to problems such as rise time and delay time, the simulator pulse generator 202 corrects the simulator pulse width in consideration of the expected lag. deep. The antenna switch 203 switches the reception antenna 1 for each simulator pulse as shown in the timing chart of FIG. That is, since there are three antennas in two systems, the combination of the receiving antenna 1-1 and the receiving antenna 1-2, the receiving antenna 1-1 and the receiving antenna 1-3, and the combination of the receiving antenna 1-2 and the receiving antenna 1-3 is performed. Then, a switching signal is sequentially sent to the selector 2. On the other hand, the A / D converted digital data is recorded in parallel as digital data for each switching in the waveform memory 6-1 and the waveform memory 6-2. The cross spectrum calculation unit 7 reads the digital data for each switching from the waveform memory 6-1 and the waveform memory 6-2, obtains the cross spectrum, and records the result for each switching in the calculation result memory 103. The time difference detection unit 8 obtains the arrival time difference from the cross spectrum result for each switching. Finally, the direction calculation unit 9 calculates the arrival direction of the incoming signal.

From the above, in this embodiment, it is possible to detect the direction with two receivers and A / D converters with respect to the three receiving antennas 1, and the apparatus scale can be made compact.

A case where direction detection is performed on the CW signal in the first embodiment will be described in the second embodiment.

Example 2
FIG. 3 is a block diagram showing an azimuth detection apparatus according to Embodiment 2 of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same or corresponding parts. Reference numeral 204 denotes a CW detection circuit that detects a CW signal. Reference numeral 202 denotes a simulator pulse generation circuit that disables the simulator pulse once every predetermined time and makes it valid when the CW signal continues.

Next, the operation will be described. The branch output of the signal detection circuit 201 is input to the CW detection circuit 204. When the signal detection continues for a certain period or longer, the CW detection circuit 204 sends the CW detection signal to the simulator pulse generation circuit 202. In the simulator pulse generation circuit 202, when there is a CW detection signal, the simulator pulse is once invalidated and validated at regular intervals in synchronization with the CW detection signal. That is, the continuing simulator pulse is once reset and then automatically restored to its original state. The antenna switch 203 switches the receiving antenna 1 for each simulator pulse as shown in the timing chart of FIG.

That is, since there are 3 antennas in 2 systems, the receiving antenna 1-1 and the receiving antenna 1-2, the receiving antenna 1-1 and the receiving antenna 1-3, and the receiving antenna 1-2 and the receiving antenna 1-3 in the order of combination. A switching signal for switching is sent to the selector 2. In parallel, the waveform memory 6-1 and the waveform memory 6-2 record digital data for each switching. The cross spectrum calculation unit 7 reads the digital data for each switching from the waveform memory 6-1 and the waveform memory 6-2, obtains the cross spectrum, and records the result for each switching. The time difference detection unit 8 obtains the arrival time difference from the cross spectrum result for each switching. Finally, the arrival direction of the incoming signal is calculated by the direction calculation circuit 9.

In the present embodiment, it is possible to detect a direction even for a signal having a long input signal period such as a CW signal by two receivers and three A / D converters for the three receiving antennas 1.

A case where the direction detection is performed for one target by separating the incoming radio waves from a plurality of radio wave sources in the first embodiment will be described in the third embodiment.

Example 3
FIG. 5 is a block diagram showing an azimuth detection apparatus according to Embodiment 3 of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same or corresponding parts. 205 is a pulse separation circuit that separates incoming radio waves from a plurality of radio wave sources by PW (pulse width) and PRI (pulse repetition interval), and 202 is a simulator pulse that generates a simulator pulse only for a predetermined target signal that has been pulse-separated. It is a generation circuit.

Next, the operation will be described. For a plurality of different types of detection signals detected from the signal detection circuit 201, the pulse separation circuit 205 converts detection signals corresponding to incoming radio waves from a plurality of radio wave sources into respective PW (pulse width) and PRI (pulse repetition intervals). ), And outputs one of the detection signals satisfying the preset PW and PRI conditions to the simulator pulse generation circuit 202. The simulator pulse generation circuit 202 generates a simulator pulse of only a predetermined target signal. The antenna switch 203 switches the antenna for each simulator pulse as shown in the timing chart of FIG.

In this embodiment, since there are three reception antennas, the combination order of the reception antenna 1-1 and the reception antenna 1-2, the reception antenna 1-1 and the reception antenna 1-3, and the reception antenna 1-2 and the reception antenna 1-3. Switch with. In parallel, the waveform memory 6-1 and the waveform memory 6-2 record digital data for each switching. The cross spectrum calculation unit 7 reads the digital data for each switching from the waveform memory 6-1 and the waveform memory 6-2, obtains the cross spectrum, and records the result for each switching. The time difference detection unit 8 obtains the arrival time difference from the cross spectrum result for each switching. Finally, the arrival direction of the incoming signal is calculated by the direction calculation circuit 9.

In this embodiment, two receivers and three A / D converters for three receiving antennas 1 separate incoming radio waves from a plurality of radio wave sources, specify a desired target, and detect a direction. it can.

In the third embodiment, a case where direction detection is performed for a plurality of targets by separating incoming radio waves from a plurality of radio wave sources will be described in a fourth embodiment.

Example 4
FIG. 7 is a block diagram showing an azimuth detection apparatus according to Embodiment 4 of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same or corresponding parts. Reference numeral 205 denotes a pulse separation circuit which outputs individual signals subjected to pulse separation to the simulator pulse generation circuits 202-1 to 202-N. 202-1 to 202-N are simulator pulse generating circuits that generate simulator pulses corresponding to a plurality of pulse-separated target signals, and 203 is an antenna switching that switches the receiving antenna 1 according to priority when the simulator pulses overlap. It is a vessel.

Next, the operation will be described. For a plurality of target radio wave sources separated by the pulse separation circuit 205, simulator pulse generation circuits 202-1 to 202-N generate simulator pulses corresponding to the radio wave sources from the respective targets. The antenna switch 203 switches the receiving antenna 1 for each simulator pulse as shown in the timing chart of FIG. In this embodiment, since there are three reception antennas, the combination order of the reception antenna 1-1 and the reception antenna 1-2, the reception antenna 1-1 and the reception antenna 1-3, and the reception antenna 1-2 and the reception antenna 1-3. Switch with.

By the way, when the simulator pulse overlaps, the receiving antenna 1 is switched according to the priority order set in advance. In FIG. 8, since the input signal 2 which is one of the radio wave sources from the target is prioritized over the input signal 1, the input signal 2 is continued and the antenna switch 203 is a combination of the receiving antenna 1-2 and the receiving antenna 1-3. Is sent to the selector 2. In parallel, the waveform memory 6-1 and the waveform memory 6-2 record digital data for each switching. The cross spectrum calculation unit 7 reads the digital data for each switching from the waveform memory 6-1 and the waveform memory 6-2, obtains the cross spectrum, and records the result for each switching. The time difference detection unit 8 obtains the arrival time difference from the cross spectrum result for each switching. Finally, the arrival direction of the incoming signal is calculated by the direction calculation circuit 9.

In the present embodiment, it is possible to detect azimuths for a plurality of targets by separating incoming radio waves from a plurality of radio wave sources with two receivers and A / D converters for the three receiving antennas 1.

In the first to fourth embodiments, the direction detection for the three reception antennas 1 has been described. However, the case where the direction detection is performed for n reception antennas will be described in the fifth embodiment.

Embodiment 5 FIG.
FIG. 9 is a block diagram showing an azimuth detection apparatus according to Embodiment 5 of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same or corresponding parts. Reference numeral 2 denotes a selector that switches and selects n reception antennas 1, and reference numeral 3 denotes an antenna switching unit that switches n reception antennas 1.

Next, the operation will be described. The antenna switching unit 3 selects the receiving antenna 1-1 and the receiver 4-1, and the signal detection circuit 201 detects the presence or absence of an input signal. When there is an input signal, the PW and PRI of the detection signal are measured by the simulator pulse generation circuit 202, and a simulator pulse is generated as an output of the simulator pulse generation circuit 202 based on the PW and PRI. As described in the first embodiment, when the simulator pulse and the input signal are shifted in time, the simulator pulse generation circuit 202 corrects the shift. The antenna switching unit 3 switches the antenna for each simulator pulse. In this embodiment, since there are n receiving antennas, the receiving antenna 1-1 and the receiving antenna 1-2, the receiving antenna 1-1 and the receiving antenna 1-3,..., The (n-1) th receiving antenna and the nth receiving antenna are used. Switch in order of all combinations up to the receiving antenna.

In parallel, the waveform memory 6-1 and the waveform memory 6-2 record digital data for each switching. The cross spectrum calculation unit 7 reads the digital data for each switching from the waveform memory 6-1 and the waveform memory 6-2, obtains the cross spectrum, and records the result for each switching. The time difference detection unit 8 obtains the arrival time difference from the cross spectrum result for each switching. Finally, the arrival direction of the incoming signal is calculated by the direction calculation circuit 9. Although the antenna switching unit 3 in the present embodiment has the same configuration as that of the first embodiment, in the case of multi-target azimuth detection, the antenna switching unit 3 having the configuration of the third or fourth embodiment is used. In this embodiment, two receivers and A / D converters are set for n receiving antennas. However, the number of receivers and A / D converters may be less than n.

In this embodiment, since n receiver antennas 1 are constituted by two receivers and A / D converters, a large number of receive antennas 1 can be used for widening the reception frequency and increasing the measurement accuracy. However, the use of the antenna switching unit 3 and the selector 2 makes it possible to keep the device scale compact. In addition, since the incoming radio waves from a plurality of radio wave sources are separated to detect a plurality of targets, high-performance direction detection is possible.

In the fifth embodiment, all combinations are sequentially switched for the n receiving antennas 1 to detect the direction. However, the antenna switching unit 3 selects the optimum receiving antenna based on the received frequency information from the target. A case where direction detection is performed by selecting 1 will be described in a sixth embodiment.

Example 6
FIG. 10 is a block diagram showing an azimuth detection apparatus according to Embodiment 6 of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same or corresponding parts. In this figure, 3 identifies a signal obtained by branching and outputting the frequency of the received signal obtained in the FFT circuit 101-1, and the interval between the receive antennas 1 is less than a half wavelength of the receive frequency wavelength (λ). This is an antenna switching unit that switches the reception antenna 1 by selecting a combination.

Next, the operation will be described. As a function of the antenna switching unit 3, a combination of the receiving antennas 1 is set in advance so that the interval of the receiving antennas 1 corresponding to the reception frequency wavelength is λ / 2 or less, and the antenna switching unit 3 switches the order. That is, when the receiving antenna 1 is an array antenna, a large number of array antennas are arranged in two rows in a staggered manner, the antenna spacing of each column is λ / 2, and only combinations of adjacent array antennas are set in advance. Other combinations are thinned out by the antenna switch 203. This is a measure for the case where phase ambiguity occurs depending on the arrival direction of radio waves when the interval between the reception antennas 1 is one wavelength or more of the radio waves to be received. In the present embodiment, the branch signal of the FFT circuit 101-1 is coded in advance in the frequency band, and the antenna switch 203 identifies the frequency code signal.

In this embodiment, the ambiguity is reduced and the azimuth is reduced by selecting and switching the optimum set of the receiving antennas 1 based on the frequency of the received signal by the two receivers and the A / D converter for the n receiving antennas 1. Direction detection with reduced calculation time is possible.

The case where the receiving antenna 1 is switched by predicting the azimuth for each switching with respect to the incoming radio wave from the moving radio wave source in the first to sixth embodiments will be described in the seventh embodiment.

Example 7
FIG. 11 is a block diagram showing an azimuth detection apparatus according to Embodiment 7 of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same or corresponding parts. Reference numeral 10 denotes an azimuth estimation circuit that predicts the azimuth for each switching, and 3 an antenna switching unit that switches the receiving antenna 1 based on the predicted azimuth.

Next, the operation will be described. The time difference detection unit 8 obtains the arrival time difference for each switching, and the direction calculation circuit 9 calculates the arrival direction. The arrival direction information is branched and output, and the branch output is processed by the direction estimation circuit 10. In the case of a large number of array antennas installed in all directions, reception information from unnecessary directions is removed in consideration of the installation environment (geographic environment), the dead angle with respect to the arrival direction, and the like. That is, the azimuth estimation circuit 10 estimates the specific target east-west north-south and elevation angle (decline) from the arrival time difference and angle information obtained by the azimuth calculation circuit 9.

Next, this azimuth estimation signal is sent to the antenna switching unit 203 of the antenna switching unit 3. The antenna switch 203 collates the azimuth estimation signal with the azimuth antenna group list (memory circuit data) in order to select the east, west, north, and west azimuth antenna groups set in advance, and receives the other azimuth antenna groups and the receiving antenna 1 that switches in order. Thin out the combination. That is, the antenna switching unit 3 sends an optimal selection switch signal of n receiving antennas to the selector 2 from the direction prediction signal from the direction estimation circuit 10 based on the time difference of incoming radio waves and angle information.

In the present embodiment, two receiving systems for n receiving antennas, and receiving antennas that are optimal for reception by predicting the azimuth for each switching with respect to incoming radio waves from a radio wave source that is moved by an A / D converter Since the receiving antenna 1 is operated by the antenna switching unit 3 so as to follow the target with 1, the direction detection with high accuracy becomes possible.

It is a block diagram which shows the azimuth | direction detection apparatus by Example 1 of this invention. It is a switching timing chart of the receiving antenna by Example 1 of this invention. It is a block diagram which shows the azimuth | direction detection apparatus by Example 2 of this invention. It is a switching timing chart of the receiving antenna by Example 2 of this invention. It is a block diagram which shows the azimuth | direction detection apparatus by Example 3 of this invention. It is a switching timing chart of the receiving antenna by Example 3 of this invention. It is a block diagram which shows the azimuth | direction detection apparatus by Example 4 of this invention. It is a switching timing chart of the receiving antenna by Example 4 of this invention. It is a block diagram which shows the azimuth | direction detection apparatus by Example 5 of this invention. It is a block diagram which shows the azimuth | direction detection apparatus by Example 6 of this invention. It is a block diagram which shows the azimuth | direction detection apparatus by Example 7 of this invention. It is a block diagram which shows the conventional azimuth | direction detection apparatus. It is explanatory drawing which shows the processing content of the conventional azimuth | direction detection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reception antenna, 2 Reception antenna selector, 3 Antenna switching part, 4 Receiver, 5 A / D converter, 6 Waveform memory, 7 Cross spectrum calculation part (cross spectrum calculation circuit), 8 Time difference detection circuit, 9 Direction calculation circuit , 10 azimuth estimation circuit, 101 FFT circuit, 102 complex multiplication circuit, 103 operation result memory, 201 signal detection circuit, 202 simulator pulse generation circuit, 203 antenna switch, 204 CW detection circuit, 205 pulse separation circuit.

Claims (6)

N + 2 (n is a natural number) receiving antennas that receive incoming radio waves at a predetermined distance, a selector that selects n + 1 or less receiving antennas from n + 2 receiving antennas, and n + 1 selected receiving antennas A receiver that converts the frequency of each received signal, an A / D converter that converts the signal frequency-converted by the receiver into digital data, and a digital data signal branched from the output of the A / D converter A signal detection circuit that compares and binarizes the value, a simulator pulse generation circuit that generates a simulator pulse based on a pulse width and a pulse interval of the signal detected by the signal detection circuit, and a signal received by the selector for each simulator pulse An antenna switch for transmitting an antenna switching signal and a digital data signal output from the A / D converter; A waveform memory that records digital data for each switching of the receiving antenna, a cross spectrum calculation unit that obtains a cross spectrum from the digital data in the waveform memory for each switching of the receiving antenna and records the result, and a cross for each switching of the receiving antenna A time difference detection unit that obtains an arrival time difference from spectrum coherence and its phase inclination, and an azimuth calculation unit that obtains an azimuth of an arrival signal from the arrival time difference at each reception antenna switching and the interval between the reception antennas. Direction finding device. CW detection circuit for detecting presence / absence of continuous wave by branch signal from signal detection circuit, and simulator pulse generation circuit for invalidating and validating simulator pulse once every predetermined time by continuous wave signal information of the CW detection circuit The azimuth detecting device according to claim 1, further comprising: It is characterized in that, for a plurality of incoming radio waves, a signal that has been subjected to pulse separation is sent to a simulator generation circuit via a pulse separation circuit that separates different types of signals detected based on the respective pulse widths and pulse intervals. The azimuth detecting device according to claim 1. 4. An azimuth detecting device according to claim 3, further comprising an antenna switch for sending a signal for switching one of the simulator pulse signals with priority to a simulator pulse signal having mutually overlapping pulse generation periods. apparatus. 2. An antenna switch that selectively switches a set of receiving antennas installed within a half wavelength interval of the frequency of the incoming radio wave from the frequency of the incoming radio wave obtained by the cross spectrum calculation unit. The azimuth | direction detection apparatus of any one of thru | or 3. For an incoming radio wave from a moving radio wave source, select an azimuth antenna group list based on the predicted azimuth signal, an azimuth estimation circuit that predicts the azimuth for each reception antenna switching by a branch signal from the azimuth calculation unit, and The azimuth detection apparatus according to claim 1, further comprising an antenna switch that selectively switches the reception antenna in the azimuth antenna group list.

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