JPH0437340A - Spread spectrum receiver - Google Patents

Abstract

PURPOSE:To discriminate an adjacent channel from an object channel and to make the synchronization acquisition and synchronization tracking efficient by providing a timer dividing a calculation period of a correlation calculation device and providing an adder adding outputs of the correlation calculation devices to the receiver. CONSTITUTION:A correlation calculation device 11 uses an output signal Y(n) of an adaptive filter 20 and a reference signal d(b) and calculates a correlation C'(gamma) according to equation I for each period divided by a timer 18. An adder 19 adds the correlation C'(gamma) outputted for each period from the calculation device 11 for m-times and outputs the result as the correlation C(n). A change in frequency fluctuation of a desired signal included in reception signals X1(n)- XN(n) with respect to the correlation C(n) is plotted by taking a frequency fluctuation (Hz) of the desired signal as the X axis and taking a relative correlation normalized by a maximum value of the correlation C(n) as the Y axis. The output of the adder 11 is inputted to a synchronization acquisition tracking means 21, in which the synchronization acquisition and synchronization tracking are implemented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a spread spectrum receiving device, and in particular, to an improvement of a signal processing device installed in a spread spectrum receiving device to ensure synchronization of communication between transmission and reception in spread spectrum. It is related to.

[Prior art] Figure 5 is a Technical Research Report [Spread Spectrum Communication] by the Institute of Electronics, Information and Communication Engineers, Type 2 Study Group, IEICE Technology V.

1.2NαI 5S88-11, Tetsube Kirimoto's paper ``Addabuti and rBu antenna for rss-FH communication''
1 shows a conventional spread spectrum receiver shown in FIG.

In the figure, 1 receives a frequency hopping signal, N
2 is an array antenna consisting of N element antennas; 2 is an N amplifier that amplifies the signal received by each antenna element 1; 3 is a signal amplified by the amplifier 2 and a frequency signal generated by a frequency synthesizer 17; N mixers for mixing; 4 is a hand-pass filter that filters the output signal of the mixer; 5 is N A/D converters that converts the output signal of the band-pass filter 4 into a digital signal; 7 is an A/D converter. N mixers that mix the output of the converter 5 and the output signal of the load calculator 6; 8 an adder that adds the outputs of the N mixers; 10 a reference signal generator that generates a reference signal; 9 the adder 6 is a load calculator that calculates a load value from the outputs of the N A/D converters 5 and the output of the subtracter 9; 20 is the above-mentioned load calculator; An adaptive filter consisting of circuits 6 to 9, 11 a cross-correlation value calculator that calculates the cross-correlation value of the creative force from the output of the adaptive filter 20 and the output of the reference signal generator, and 13 a cross-correlation value calculator that calculates the cross-correlation value of the creative force from the output of the adaptive filter 20 and the output of the reference signal generator; A register 12 stores the output of the value calculator 11, and compares the output of the cross-correlation value calculator 11 with the stored contents of the register 13. If the output of the cross-correlation calculator 11 is larger, the cross-correlation value calculator 11 14 is a first code generator that repeatedly slides and generates a code, and 15 is a comparator. a second code generator that generates the same code as the code generation pattern of the first code generator 14 with the signal from 12; 16 is a frequency synthesizer 1;
a switch for switching the code sent to 7 to the code of either the first code generator 14 or the second code generator 15;
A frequency synthesizer 17 generates a frequency signal corresponding to the code sent from the switch 16.

Reference numeral 21 denotes a synchronous acquisition and tracking means composed of the circuits 13 to 17.

Next, the operation will be explained.

Frequency hopping signals SL (t) to SN (t) received by N antenna elements 1 are amplified by N amplifiers 2 connected to each, and the output signal is the output signal u(t) of frequency synthesizer 17. ) and are mixed by each mixer 3. This mixed signal passes through a bandpass filter 4 and is converted by an A/D converter 5 into digital signals Xi (n) to XN (n). The digital signals Xi (n) to XN (n) are the load values Wl (n −1) to WN (n −
1) and mixer 7. The signals mixed by each mixer 7 are summed by an adder 8 and become an output signal Y (n) of the adaptive filter 20. The output signal Y (n) is branched in the adaptive filter 20 and subtracted from the reference signal d (n), which is the output signal of the reference signal generator 10, in the subtracter 9.

The output of the subtracter 9 is input to the load calculator 6 as an error signal e (n). The load values Wl(n) to WN(n) are, for example, L M S (Least-gate-ean-
In S(1)2, μ is a parameter that controls the stability of convergence.

The cross-correlation value calculator 11 calculates the output Y(n) of the adaptive filter 20 and the reference signal d (
n) is input, and its cross-correlation value C(n) is calculated using equation (2).

Σ d(k)°y(k) The value of this cross-correlation value C(n) is as shown in FIG.
It varies depending on the frequency variation of the desired signal included in the received signal.

In FIG. 6, the horizontal axis represents the amount of frequency variation (H2) of the desired signal, and the vertical axis represents the relative correlation coefficient normalized by the maximum value of the cross-correlation value C(n). According to the figure, if, for example, adjacent channels due to frequency hopping are 25KH2M apart, the difference based on the cross-correlation value is that the frequency fluctuation of the desired wave is about 1. Up to 9KHz is possible. This cross-correlation value C(n) is input to the comparator 12.

This comparator 12 compares the output of the cross-correlation value calculator 11 with the cross-correlation value stored in the register 13, and the output of the cross-correlation calculator 11 is compared with the cross-correlation value stored in the register 13.
If the value is larger than the value, the memory of the register 13 is changed by the output of the cross-correlation value calculator 11, and the information about the changed memory contents of the register 3 is sent to the first code generator 1.
Send to 4. The first code generator 14 sends L code sequences to a frequency synthesizer 17 via a switch 16 at regular intervals.
The code sequence generated at that time is output to the second one by sliding it for a certain period of time every - period until the code sequence starts with the same code again. It is output to the code generator 15. The second code generator 15 repeatedly outputs the code finally inputted from the first code generator 14 to the frequency synthesizer 17 via the switch 16 . The switch 16 outputs the output of the first code generator 14 to the frequency synthesizer 17 during code generation by the first code generator 14, and then switches to the code output of the second code generator 15. Frequency synthesizer 17 generates a frequency signal corresponding to the code sent from switch 16 and sends it to mixer 3.

Through the above operations, synchronization acquisition is performed as a code transferred from the second code generator 15 to the frequency synthesizer 17 at a synchronization timing that matches both the transmitter and the receiver.

[Problem to be solved by the invention]

Since the conventional spread spectrum receiver is configured as described above, when a change occurs in the frequency of the received signal due to factors such as the Doppler effect, the cross-correlation value C(n) obtained by equation (2) is Due to the changes shown in FIG. 6, it becomes difficult to judge based on the strength of correlation values with adjacent frequency hopping channels, resulting in failure in synchronization acquisition.

This invention was made to solve the above problems. Even if the frequency of the received signal changes, adjacent channels can be distinguished based on the strength of the correlation value, and synchronized acquisition and tracking can be performed efficiently. The purpose of the present invention is to obtain a spread spectrum receiving device that can perform a spread spectrum reception.

[Means to solve the problem]

The spread spectrum receiver according to the present invention is provided with a timer that divides the calculation period of the cross-correlation value calculator, and an adder that adds the outputs of the cross-correlation value calculator.

[Effect]

The correlation value calculation method in this invention reduces the attenuation of the correlation value even if the frequency of the received signal changes.
It is possible to distinguish between adjacent channels and perform synchronized acquisition and tracking efficiently.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a spread spectrum receiver according to an embodiment of the present invention.

In the figure, 1 is an array antenna composed of N element antennas that receive frequency hopping signals, 2 is N amplifiers that amplify the signal received by each antenna element 1, and 3 is an array antenna that is amplified by amplifier 2. N mixers that mix the signal and the frequency signal generated by the frequency synthesizer 16, 4 a bandpass filter that filters the output signal of the mixer, and 5 N that converts the output signal of the bandpass filter 4 into a digital signal. 7 is a mixer that mixes the output of the A/D converter 5 and the output signal of the load calculator 6, 8 is an adder that adds the outputs of the N mixers, 10 is a reference. a reference signal generator that generates a signal; 9 a subtracter that eliminates the outputs of the adder 8 and the reference signal generator; 6 a load value from the N A/D converter 5 outputs and the output of the subtracter 9; 20 is an adaptive filter consisting of each of the circuits 6 to 9; 11 is a cross-correlation value calculator that calculates the cross-correlation value of both outputs from the output of the adaptive filter 20 and the output of the reference signal generator; 18 is a timer that divides the calculation period of the cross-correlation value calculator 11; 19 is an adder that adds the cross-correlation value for each calculation interval of the cross-correlation value calculator 11; and 13 is the timer that divides the calculation period of the cross-correlation value calculator 11; A register 12 stores the output, and compares the output of the adder 19 with the contents stored in the register 13.
If the output of adder 19 is larger, the output of adder 19 is transferred to register 1.
3 is a comparator to be stored; 14 is a first code generator that generates a code by repeatedly sliding it; 15 is a comparator 12;
A second code generator 16 generates the same code as the code generation pattern of the first code generator 14 using a signal from the first code generator 14 or the second code generator 16 which generates a code to be sent to the frequency synthesizer 17. A switch 17 is a frequency synthesizer that generates a frequency signal corresponding to the code sent from the switch 16. Reference numeral 21 denotes a synchronous acquisition and tracking means constituted by the above-mentioned elements 13 to 17.

Next, the operation will be explained.

The frequency hopping signal is received by an array antenna consisting of N antenna elements 1 and amplified by an amplifier 2 connected to each antenna element 1. The amplified received signal is mixed by the mixer 3 with the signal u (n) output from the frequency synthesizer 17 . At this time, if the received signal is synchronized with the receiving device, it will be demodulated into a signal of the desired band, and if not, it will hop to a completely different band. The signals mixed by N mixers 3 pass through N bandpass filters 4. Here, signals that are not demodulated into the desired band are removed, but if the signal power to be removed is large, it may leak or bandpass
Unnecessary waves within the passband of filter 4 are not removed.

The signal that has passed through these N bandpass filters 4 is A
/D converter 5 converts digital signals Xi (n) to XN
(n) and input to the adaptive filter 20. The adaptive filter 20 has an input signal X1
(n) to XN (n), remove unnecessary waves that have no correlation with the reference signal d (n). adaptive filter 20
The operation is the same as the conventional method. The correlation value calculator 11 uses the output signal Y (n) of the adaptive filter 2o and the reference signal d (n) to calculate the cross-correlation MC'' (γ) for each section divided by the timer 8 according to equation (3). .

γ=n/m Note that the calculation interval is the interval of equation (2) divided into m equal parts.

The adder 19 adds the section cross-correlation values C'' (T) outputted for each section from the cross-correlation value calculator 11 m times, and outputs the result as a cross-correlation value C(n).

FIG. 2 shows changes in the desired signals contained in the received signals Xi (n) to XN (n) due to frequency fluctuations in the case of the cross-correlation value C(n) calculated in this way. In FIG. 2, the horizontal axis represents the amount of frequency variation (H2) of the desired signal, and the vertical axis represents the relative correlation coefficient normalized by the maximum value of the cross-correlation value C(n). According to the figure, for example, if adjacent channels due to frequency hopping are separated by 25KH2, discrimination based on the cross-correlation value C(n) can be performed up to a frequency fluctuation of about 7KH2. The output of this adder 11 is input to the synchronization acquisition and tracking means 21 to perform synchronization acquisition and tracking. The operation of the synchronous acquisition and tracking means 21 is the same as in the conventional system.

Next, another embodiment of the present invention will be explained.

In the above embodiment, a cross-correlation value calculator and an adder are used to calculate the cross-correlation value C(n), and a timer is used to specify the calculation interval.
ignal Processor).

In the figure, the DSP calculates the cross-correlation value C(n) according to the flowchart shown in FIG.

First, as shown in 22, the section cross-correlation value C' (γ) is calculated using equation (3) of the above example. Add value. Here, the initial value of α is zero. 24
Then, it is determined whether or not the process in step 23 has been performed m times, and m
If it is less than m times, the process returns to step 22, and if it is m times, it executes step 25. In step 25, α is output as a cross-correlation value C(n).

By employing the DSP as described above, cross-correlation value calculation can be performed using all software, and the number of processing times m can be easily changed.

〔Effect of the invention〕

As described above, according to the spread spectrum receiver according to the present invention, a timer is provided for dividing the calculation period of the cross-correlation value calculator, and an adder is provided for adding up the outputs of the cross-correlation value calculator. Therefore, even if a change occurs in the received signal, it is possible to distinguish between adjacent channels based on the strength of the correlation value, and there is an effect that synchronization acquisition and synchronization tracking can be performed efficiently.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a spread spectrum receiver according to an embodiment of the present invention, and FIG. 2 is for explaining the influence of frequency fluctuation of a desired signal on cross-correlation value calculation shown in the embodiment of FIG. , FIG. 3 is a block diagram showing another embodiment of the present invention, FIG. 4 is a diagram showing the processing flow of the DSP used in the other embodiment of FIG. 3, and FIG. 5 is a diagram showing the conventional spread spectrum reception. FIG. 6, a block diagram showing the apparatus, is a diagram for explaining the influence of frequency fluctuation of a desired signal due to conventional cross-correlation value calculation. In the figure, 1 is an antenna element, 2 is an amplifier, 3 is a mixer, 4 is a bandpass filter, 5 is an A/D converter, 1
0 is a reference signal generator, 11 is a cross-correlation value calculator, 18 is a timer, 19 is an adder, 20 is an adaptive filter,
21 is a synchronous acquisition tracking means. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A device that receives one or more frequency hopping signals transmitted from each user at a distance by spreading the frequency using a code, and receiving the outputs of N A/D converters. It has an adaptive filter that inputs and removes unnecessary waves, a cross-correlation value calculator that calculates a cross-correlation value from the output of the adaptive filter and the output signal of the reference signal generator, and also has code synchronization with the received signal. A spread spectrum receiving apparatus having a synchronization acquisition means, means for dividing calculation periods of the cross-correlation value calculator, and addition means for adding the output cross-correlation values of the cross-correlation value calculator for each output calculation period. A spread spectrum receiving device characterized by comprising: