JPH09247046A - Receiver for spread spectrum communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the spread spectrum communication receiver in which detection of a peak position is easy even on the occurrence of time fluctuation in a reception signal level or superimposed noise by providing means in addition to adjust a gain of an output from a detection means. SOLUTION: An output of a detection circuit 14 is branched into two, the one is fed to a peak level hold circuit 16, and the other is fed to an automatic gain adjustment device 18 via a delay circuit 17. An output of the automatic gain adjustment device 18 is connected to an input of a peak position detection section 15, and an output of a peak level hold circuit 16 is connected to a gain adjustment input terminal of the automatic gain adjustment device 18. Through the constitution above, on the occurrence of time fluctuation in a reception signal, a level of a correlation output signal from an SAW matched filter 11 has different peak level and the level of the signal received by a peak position detection section 15 is made constant. As a result, the peak position is easily detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronizing circuit for a spread spectrum communication receiver.

[0002]

2. Description of the Related Art A spread spectrum communication system uses a spread code sequence such as a pseudo noise code (PN code) from a normally transmitted digital signal to generate a signal having an extremely wider bandwidth than the original data. It is converted into an RF (radio frequency) signal and transmitted. At the receiving side, the same demodulation spreading code (reference spreading code) as that at the transmitting side is used to perform despreading (despreading demodulation) that correlates with the received signal, and the received signal has a bandwidth corresponding to the original data. Convert to narrow band signal. Subsequently, normal data demodulation is performed to reproduce the original data.

Here, as the means for obtaining the correlation, there are a surface acoustic wave (SAW) matched filter, a SAW convolver, a digital matched filter and the like. Among them, the SAW matched filter is: -Simplified circuit configuration compared to a device using a surface acoustic wave convolver or a device using a digital matched filter-No power consumption because it is a passive element-Simple structure and manufacturing There are various advantages such as ease.

FIG. 3A is a block diagram of a synchronizing circuit of a spread spectrum communication receiver using such a SAW matched filter. In FIG. 3, 11 is a correlation calculation between a received signal and a fixed reference spread code. SAW matched filter that performs 1
Reference numeral 2 is an output signal amplifying amplifier, 13 is an output signal band pass filter, 14 is a detection circuit, and 15 is a peak position detection unit.

The received signal is subjected to processing such as filtering, amplification, frequency conversion, etc., and SAW matched filter 1
1 is input. The SAW matched filter 11 performs a correlation operation between this received signal and the reference spreading code of the predetermined pattern of the SAW matched filter, and outputs the operation result (correlation signal). , If a spreading code that is temporally inverted with respect to the spreading code included in the received signal is used as the reference spreading code, the SAW matched filter 11 determines that the spreading code included in the received signal is
When the reference spread codes of the SAW matched filter match, a correlation peak output as shown by A in FIG. 3B is obtained every cycle of the spread code.

After the correlation peak output is appropriately amplified and filtered by the amplifier 12 and the bandpass filter 13, the positive side of the correlation output signal waveform is envelope-detected by the detection circuit 14 (B in FIG. 3B). ), And the peak position detector 15 detects the peak position.

[0007]

However, in the above conventional example, when the level of the received signal fluctuates with time, the level of the correlation output signal from the SAW matched filter 11 is shown by A'in FIG. 3 (c). Thus, the peak level fluctuates. Further, since the level of the correlation output signal is usually as small as about -20 to -30 (dBm), it is easily affected by noise from the outside, and even if the level of the received signal is constant in time, the received signal is The level of the correlation output signal fluctuates similarly to the case where the level f changes with time. The detection circuit 14 performs envelope detection on the positive side of the correlation output signal waveform A ', and the waveform after detection is also shown in FIG.
There is a problem that false detection of peaks and loss of peaks occur because the level fluctuates as in medium B ', making peak detection difficult. In particular, since the output of the amplifier 12 for high frequencies varies, the problem of the output of the matched filter 11 for period is larger than that of the circuit for spread demodulation.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a spread spectrum communication receiving apparatus in which the peak position can be easily detected even when the received signal level fluctuates over time or noise is superimposed. .

The above object has a correlating means for correlating the received signal and the reference code, a detecting means for detecting the output of the correlating means, and a peak position detecting means for detecting a peak position from the output of the detecting means. This is achieved by a configuration in which the spread spectrum communication receiver further includes means for adjusting the gain of the output from the detection means.

According to the above-mentioned means of the present invention, the level of the output from the detecting means for detecting the output of the correlating means for correlating the received signal with the reference signal is adjusted by the gain adjusting means to keep the level constant. False detection of false peaks and peak loss due to temporal fluctuation of signal level and superposition of noise are suppressed,
As a result, it becomes easy for the peak position detecting means to detect the peak position.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A is a block diagram showing a first synchronizing circuit of a spread spectrum communication receiver according to the present invention, in which reference numeral 11 denotes a received signal and a fixed reference spread code. SAW matched filter for performing correlation calculation, 12 is an output signal amplification amplifier, 13 is an output signal band pass filter, 14 is a detection circuit, 15 is a peak position detector, 16 is a peak level hold circuit, 17 is a delay circuit, 18 Is an automatic gain adjuster.

As shown in FIG. 1A, the output of the detection circuit 14 is branched into two, one of which is input to the peak level hold circuit 16 and the other of which is input to the automatic gain adjuster 18 through the delay circuit 17. The output of the automatic gain adjuster 18 is connected to the input of the peak position detector 15, and
The output from the peak level hold circuit 16 is connected to the gain adjusting input terminal of the automatic gain adjuster 18.

The received signal is subjected to processing such as filtering, amplification, frequency conversion, etc., and SAW matched filter 1
1 is input. The SAW matched filter 11 performs a correlation operation between this received signal and the reference spreading code of the predetermined pattern of the SAW matched filter, and outputs the operation result (correlation signal). , If a spreading code that is temporally inverted with respect to the spreading code included in the received signal is used as the reference spreading code, the SAW matched filter 11 determines that the spreading code included in the received signal is
When the reference spreading codes of the SAW matched filter match, a correlation peak output as shown by A in FIG. 1B is obtained. The peak output is appropriately amplified and filtered by the amplifier 12 and the bandpass filter 13, and then the correlation output signal is envelope-detected by the detection circuit 14 (B in FIG. 3B).

The output of the detection circuit 14 is branched into two, one of which is connected to the peak level hold circuit 16 and the other of which is connected to the automatic gain adjuster 18 via the delay circuit 17. The peak level hold circuit 16 holds the peak value of the output from the detection circuit 14 until the next peak is observed, and outputs it to the automatic gain adjuster 18 as a control signal for gain adjustment (FIG. 3). (B) Middle C). The automatic gain adjuster 18 uses the gain adjustment control signal output from the peak level hold circuit 16 to detect the detection circuit 1.
Adjust the amplitude of the signal output from 4 (see Fig. 3 (b)
D), and output to the peak position detection unit 15 connected to the next stage. In the automatic gain adjuster 18, a delay circuit 17 is provided between the detection circuit 14 and the automatic gain adjuster 18 so that the output signal from the detection circuit 14 is input after receiving the gain adjustment control signal. Is provided. In the peak position detector 15, the automatic gain adjustment circuit 17
The peak position is detected based on the signal output from.

Here, when the received signal varies with time or when noise is superimposed on the correlation output signal, SA
The level of the correlation output signal from the W matched filter 11 is different at each peak level as indicated by A in the figure, and the detection waveform obtained by envelope detection of this signal by the detection circuit 14 is also shown in the figure.
Although the level of each peak is different as in B, the level of the signal input to the peak position detection unit 15 is constant as indicated by D in the figure as described above, so false detection of false peaks and loss of peaks occur. Is suppressed, and as a result, the peak position detection unit 15 can easily detect the peak position.

FIG. 2A is a block diagram showing a second synchronizing circuit of the spread spectrum communication receiver according to the present invention. In this figure, the members in FIG. 1 (a) are designated by the same reference numerals, and a duplicate description will be omitted.

As shown in FIG. 2A, the output of the detection circuit 14 is branched into two, one of which is input to the peak level hold circuit 16 and the other of which is input to the automatic gain adjusting means 18 via the delay circuit 17. The automatic gain adjustment circuit 1
The output of 8 is connected to the input of the peak position detector 15, the output from the peak level hold circuit 16 is connected to the gain adjustment input terminal of the automatic gain adjuster 18, and the peak position detector 15 The control signal line is connected to the peak hold circuit 16.

Also in the spread spectrum receiver having such a configuration, the level of the signal input to the peak position detecting section 15 is constant as shown by D in the figure, as in FIG. Is suppressed and the peak loss is suppressed, and as a result, the peak position detecting section 15 can easily detect the peak position.

After observing the peak in the peak position detecting section 15, a reset signal is transmitted to the peak level hold circuit 16 (E in FIG. 2B), and the peak level hold circuit 16 receives the reset signal until then. The peak value that was held is reset to zero and the automatic gain adjuster 18
2 (C in FIG. 2B), the gain of the automatic gain adjuster 18 is kept at the lowest level until the next peak, and during that time, it is not affected by noise or the like.

In FIGS. 1 and 2, part of the output from the detection circuit 14 is used as the peak level hold circuit 1.
The output of the SAW matched filter 11 is used as the input of the peak level hold circuit 16
May be used as the input of.

In addition, in FIGS. 1 and 2, the delay circuit 1 inserted between the detection circuit 14 and the automatic gain adjuster 18 is shown.
7 is not always necessary.

In FIGS. 1 and 2, the SAW matched filter is used to obtain the correlation between the received signal and the reference spread code, but a SAW convolver or the like may be used.

FIG. 4 is a block diagram showing an example of a communication system using the spread spectrum communication receiver as described with reference to FIGS. In the figure, 40 indicates a transmitter. This transmitter spread-spectrum-modulates a signal to be transmitted using a spread code, and transmits it from an antenna 401. The transmitted signal is received by the receiver 41 and demodulated.

The receiver 41 includes an antenna 411, a high frequency signal processing section 412, a synchronizing circuit 413, a code generator 414 and a spread demodulating circuit 4.
15 and demodulation circuit 416. The reception signal received by the antenna 411 is appropriately filtered and amplified by the high frequency signal processing unit 412, and is output as it is as a transmission frequency band signal or as an appropriate intermediate frequency band signal. The signal is input to the synchronizing circuit 413. Synchronous circuit 413
Is a spread spectrum communication receiver 4131 shown in FIGS. 1 and 2 and the spread spectrum communication receiver.
A code generator 414 processes the signal output from the 4131 and outputs a spread code synchronization signal and a clock synchronization signal for the transmission signal.
And a signal processing circuit 4133 for outputting to.

The output signal from the high frequency signal processing unit 412 is input to the spread spectrum communication receiver 4131, and the peak positions shown in FIGS. 1 and 2 are provided in the spread spectrum communication receiver 4131 based on this signal. In the detection unit 15,
The correlation peak position is detected from this correlation peak output, and a peak position detection signal is sent to the signal processing circuit 4133 at the next stage. The signal processing circuit 4133 creates a code synchronization signal and a clock signal based on the peak position detection signal and outputs the code synchronization signal and the clock signal to the code generator 414.

After the synchronization is established, the code generator 414 generates a spread code having the same clock and spread code phase as the spread code on the transmitting side. This spread code is input to the spread demodulation circuit 415, and the signal before spread modulation is restored. The signal output from the spread modulation / demodulation circuit 415 is a signal that has been modulated by a commonly used modulation method such as so-called frequency modulation or phase modulation, and therefore a demodulation circuit well known to those skilled in the art.
Data demodulation is performed by 416.

FIGS. 5 and 6 are block diagrams showing an example of a transmitter and a receiver of a communication system using the spread spectrum communication receiver as described with reference to FIGS. In FIG. 5, 501 is a serial-parallel converter that converts serially input data into n parallel data, and 502-1 to n are n parallel data and n output from the spread code generator 503. , 503 is a spreading code generator for generating n different spreading codes and a spreading code dedicated to synchronization, and 504 is a spreading code dedicated to synchronization output from the spreading code generator 503. An adder for adding n outputs of the multiplier groups 502-1 to 502-1 is a high frequency stage for converting the output of the adder 504 into a transmission frequency signal, and 506 is a transmission antenna.

Further, in FIG. 6, 601 is a receiving antenna, 602 is a high frequency signal processing section, 603 is a synchronizing circuit for capturing and maintaining synchronization with the spread code and clock on the transmitting side, 604.
Is a spreading code generator that generates the same n + 1 spreading codes as the spreading code group on the transmission side by the code synchronizing signal and the clock signal input from the synchronizing circuit 603, and 605 is a carrier output from the spreading code generator 604. A carrier reproduction circuit that reproduces a carrier signal from the reproduction spread code and the output of the high frequency signal processing unit 602, and 606 is the output of the carrier reproduction circuit 605, the output of the high frequency signal processing unit 602, and the output of the spread code generator 604.
A baseband demodulation circuit that performs demodulation in the baseband using n spread codes, and 607 is a parallel-serial converter that performs parallel-serial conversion on the n parallel demodulated data output from the baseband demodulation circuit 606.

In the above structure, the input data is first converted by the serial-parallel converter 501 into n pieces of parallel data equal to the number of code division multiplexes on the transmission side. On the other hand, the spread code generator 503 generates spread codes PN0 to PNn having n + 1 identical code periods but different from each other. Of these, PN0 is dedicated to synchronization and carrier reproduction and is directly input to the adder 504 without being modulated by the parallel data. The remaining n spreading codes are modulated by n parallel data in the multiplier groups 502-1 to 502-1 and input to the adder 504. The adder 504 has been input
The n + 1 signals are linearly added and the added baseband signal is output to the high frequency stage 505. The baseband signal is subsequently converted into a high frequency signal having an appropriate center frequency in the high frequency stage 505 and transmitted from the transmitting antenna 506.

On the receiving side, the signal received by the receiving antenna 601 is appropriately filtered and amplified by the high frequency signal processing unit 602, and is output as it is as a transmission frequency band signal or as an appropriate intermediate frequency band signal. The signal is input to the synchronizing circuit 603. The synchronization circuit 603 is shown in FIGS.
And a signal processing circuit 6033.

The output signal from the high frequency signal processing unit 602 is input to the spread spectrum communication receiver 6031, and based on this signal, the spread spectrum communication receiver 603.
1 provided in FIG. 1, the peak position detection unit 1 shown in FIG.
At 5, the correlation peak position is detected from this correlation peak output and a peak position detection signal is sent to the signal processing circuit 6033 at the next stage. The signal processing circuit 6033 creates a code synchronization signal and a clock signal based on the peak position detection signal and outputs the code synchronization signal and the clock signal to the code generator 604.

After the synchronization is established, the spread code generator 604 generates a spread code group having the same clock and spread code phase as the spread code group on the transmission side. Of these code groups, the spread code PN0 dedicated to synchronization is input to the carrier reproduction circuit 605.
The carrier reproduction circuit 605 despreads the received signal converted to the transmission frequency band or the intermediate frequency band, which is the output of the high frequency signal processing unit 602, by the synchronization-dedicated spreading code PN0 and reproduces the carrier wave in the transmission frequency band or the intermediate frequency band.

The carrier reproducing circuit 605 has a circuit using a phase locked loop, for example. The received signal and the spread code for synchronization PN0 are multiplied by the multiplier. After synchronization is established, the clock and code phase of the synchronization-dedicated spreading code in the received signal and the reference synchronization-dedicated spreading code match, and the synchronization-dedicated spreading code on the transmitting side is not modulated with data. It is despread and a carrier component appears at its output. The output is then input to a bandpass filter, and only the carrier component is extracted and output. The output is then input to a well-known phase-locked loop consisting of a phase detector, a loop filter, and a voltage-controlled oscillator, which locks the phase to the carrier component output from the band-pass filter from the voltage-controlled oscillator. The signal is output as a reproduced carrier. The reproduced carrier wave is input to the baseband demodulation circuit 606.

The baseband demodulation circuit 606 generates a baseband signal from the reproduced carrier wave and the output of the high frequency signal processing section 602. The baseband signal is divided into n pieces and is despread for each code division channel by the spreading code groups PN1 to PNn which are the outputs of the spreading code generator 604, and then data demodulation is performed. The parallel demodulated n demodulated data are converted into serial data by the parallel-serial converter 607 and output.

The modulation method is not limited to binary modulation, and other modulation methods such as quadrature modulation may be used.

[0036]

As described above, according to the present invention, the correlating means for correlating the received signal and the reference code, the detecting means for detecting the output of the correlating means, and the peak from the output of the detecting means. In the spread spectrum communication receiving device having the peak position detecting means for detecting the position, by further comprising a means for adjusting the gain of the output from the detecting means, the reception signal and the reference signal The level of the output from the detector that detects the output of the correlator that correlates is adjusted and kept constant by the gain adjuster, so false detection of false peaks and peak loss due to temporal fluctuations in the received signal level and noise superposition are suppressed. As a result, it becomes easy for the peak position detecting means to detect the peak position.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first spread spectrum communication receiver according to the present invention.

FIG. 2 is a block diagram showing a second spread spectrum communication receiver according to the present invention.

FIG. 3 is a block diagram showing a conventional spread spectrum communication device.

FIG. 4 is a block diagram showing an example of a communication system using the spread spectrum communication device of the present invention.

FIG. 5 is a block diagram showing a transmitter of a communication system using spread spectrum communication.

FIG. 6 is a block diagram showing a receiver of a communication system using the spread spectrum communication device of the present invention.

[Explanation of symbols]

 11 SAW Matched Filter 12 Amplifier for Output Signal Amplification 14 Detection Circuit 15 Peak Position Detection Section 16 Peak Level Hold Circuit 18 Automatic Gain Adjuster 413 Synchronization Circuit 414 Code Generator 415 Spreading Demodulation Circuit 603 Synchronization Circuit 604 Spreading Code Generator 606 Baseband Demodulation circuit

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Koichi Egara 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tadashi Eguchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canono Within the corporation

Claims (8)

[Claims] 1. A spectrum spreader having a correlating means for correlating a received signal and a reference code, a detecting means for detecting an output of the correlating means, and a peak position detecting means for detecting a peak position from the output of the detecting means. A receiver for spread spectrum communication, characterized in that the receiver for communication further comprises means for adjusting the gain of the output from the detection means. 2. The receiving apparatus for spread spectrum communication according to claim 1, wherein the output of the detecting means is used to control the means for adjusting the gain of the output of the detecting means. 3. The receiving apparatus for spread spectrum communication according to claim 1, wherein the means for adjusting the gain of the output from the detection means is controlled by using the output from the correlation means. 4. An automatic gain control amplifier and a peak level hold circuit are used as means for adjusting the gain of the output from the detecting means.
A receiver for spread spectrum communication according to item 1. 5. The spread spectrum communication device according to claim 1, wherein the correlating means is a surface acoustic wave matched filter. 6. The spread spectrum communication device according to claim 1, wherein the correlating means is a surface acoustic wave convolver. 7. A spread spectrum signal receiving method, wherein a correlation signal is output by obtaining a correlation between a received signal and a reference code, the correlation signal is detected, and a peak position of the detected correlation signal is detected. A spread spectrum signal receiving method characterized by adjusting the gain of a detected correlation signal. 8. A communication device comprising the spread spectrum communication receiving device according to any one of claims 1 to 6.