JPH09200083A - Receiver for spread spectrum communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily detect a peak position by using a waveform with higher sharpness in positive and negative waveforms with respect to a reference potential being outputs from a correlation means taking correlation between a reception signal and a reference signal. SOLUTION: A correlation output signal from a matched filter 11 is amplified by a high amplification factor amplifier 12. An output from a BPF 13 indicates that a positive side of a waveform looses sharpness as shown in Figure B due to distortion caused by the amplifier 12, but a negative waveform keeps a sufficient sharpness. The polarity of a diode being a component of an envelope detector 14 is decided for negative polarity detector and the negative waveform with high sharpness is detected. Thus, a sharper detection waveform than the case with detecting the positive waveform is obtained as shown in Figure D and then 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 spread spectrum communication receiver having a synchronizing circuit.

[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. 3 is a block diagram of a synchronizing circuit of a spread spectrum communication receiver using such a SAW matched filter. In the figure, 11 is a SAW for performing a correlation operation between a received signal and a fixed reference spreading code. A matched filter, 12 is an amplifier for amplifying an output signal, 13 is a bandpass filter for an output signal, 14a is a detector, and 15 is a peak position detector.

FIG. 4 is a diagram showing an example of the circuit configuration of the detector 14a, in which 21 is a diode and 22 is a diode.
Are capacitors for bypassing high frequency components, 23 and 24 are terminating resistors, and 25 is a buffer resistor.

The received signal is subjected to processing such as filtering, amplification and frequency conversion, and then SAW matched filter 1
1 is input. The SAW matched filter 11 performs a correlation operation between this received signal and a reference spreading code of a predetermined pattern that the SAW matched filter has, and outputs the operation result (correlation signal). here,
When the 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 causes the spreading code included in the received signal and the SAW
When the reference spreading codes of the matched filter match, a correlation peak output as indicated by A in the figure is obtained for each cycle of the spreading code. Here, as shown by A in the figure, an intermediate potential of the correlation peak output is defined as a reference potential, an upper side waveform with respect to the reference potential is referred to as a positive side waveform, and a lower side waveform is referred to as a negative side waveform. I will. The reference potential assumed here is 0 [V], but the reference potential is DC
Even if an offset is applied, the definition of the name for the waveform is not changed.

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 using the detector 14a, and the peak position detector 15 detects the peak. Detect the position.

[0008]

However, in the above-mentioned conventional example, the level of the correlation output signal (A in the figure) from the SAW matched filter 11 is usually as small as about -20 to -30 [dBm], so the output It is necessary for the signal amplification amplifier 12 to largely gain the level of the correlation output signal to a level that can be detected by the diode 21 of the detector 14a. Therefore, due to the gain distortion, the sharpness of the positive side of the waveform of the correlation output signal becomes dull as shown by B in the figure.
Since the detector 14a performs envelope detection on the positive side of the correlation output signal waveform B, the waveform after detection has a shape lacking sharpness as shown by C in the figure, and has no clear peak position. There is a problem that it becomes difficult to detect the peak position.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a spread spectrum communication receiver in which the peak position can be easily detected by using a sharp correlation output signal waveform.

The above-mentioned object is to provide a receiving device for spread spectrum communication having a correlating means for correlating a received signal with a reference code, and a peak position detecting means for detecting a peak position from the output of the correlating means. This is achieved by a configuration in which, of the waveforms on the positive electrode side or the negative electrode side of the output from the correlating means for correlating with the reference signal, the waveform on the higher sharpness side is used for peak position detection.

According to the above-mentioned means of the present invention, the sharpness of the waveform on the positive or negative side with respect to the reference potential of the waveform of the correlation output signal from the correlation means for correlating the received signal and the reference code By using the waveform on the higher side for the peak position detection, the waveform of the correlation output signal has a clear peak position, so that the peak position detection means can easily detect the peak position.

[0012]

Embodiments of the present invention will be described below.

FIG. 1 is a block diagram showing a first embodiment of a synchronizing circuit of a spread spectrum communication receiving apparatus according to the present invention. In the figure, 11 performs a correlation calculation between a received signal and a fixed reference spreading code. SAW matched filter, 12 is an amplifier for amplifying output signal, 13 is a band pass filter for output signal, 1
Reference numeral 4 is a detector, and 15 is a peak position detector.

FIG. 2 is a diagram showing an example of the circuit configuration of the detector 14, in which 21 is a diode, 22 is a high frequency component bypass capacitor, 23 and 24 are termination resistors, and 25 is a buffer resistor. Is.

In the present embodiment, as shown in FIGS. 1 and 2, of the waveforms on the positive side or the negative side with respect to the reference potential of the signal waveform B input to the detector 14, the side with the higher sharpness is selected. The direction of the diode 21 in the elements forming the detector 14 is determined and connected so that the waveform is envelope-detected.

The operation of this embodiment will be described below with reference to FIGS.

The received signal is subjected to processing such as filtering, amplification and frequency conversion, and the SAW matched filter 1
1 is input. The SAW matched filter 11 performs a correlation operation between this received signal and a reference spreading code of a predetermined pattern that the SAW matched filter has, and outputs the operation result (correlation signal). here,
When the 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 causes the spreading code included in the received signal and the SAW
When the reference spreading codes of the matched filter match, a correlation peak output as shown by A in the figure is obtained. The peak output is appropriately amplified and filtered by the amplifier 12 and the band pass filter 13, the envelope output of the correlation output signal is detected by the wave detector 14, and the peak position is detected by the peak position detector 15.

Since the level of the correlation output signal (A in the figure) from the SAW matched filter 11 is extremely small, the level of the correlation output signal is detected by the output signal amplifying amplifier 12 by the diode 21 of the detector 14. It is necessary to make a large gain up to. Therefore, due to the gain distortion, the positive side of the waveform of the correlation output signal has a waveform lacking sharpness as shown by B in the figure, but in the present embodiment, the waveform of the signal waveform B input to the detector 14 is Among the waveforms on the positive side or the negative side with respect to the reference potential, the diode 21 in the element constituting the detector 14 is determined and connected so as to perform envelope detection of the waveform on the higher sharpness side. Therefore, the negative side of the waveform of the correlation output signal, which is not rounded due to the gain distortion of the output amplifier 12 as compared with the positive side, is detected. Therefore, as the detection waveform output from the detector 14, a detection waveform (D in the figure) having a higher sharpness than the detection waveform when the positive pole side is detected is obtained, and as a result, the peak position can be easily detected. .

Since the output of the matched filter 11 is extremely small, when an amplifier having a high amplification factor is used, the sharpness on the positive electrode side is often blunt. In this embodiment, the detector 14
Among the elements configuring the above, the example in which the diode 21 is connected so as to be in the reverse bias direction when viewed from the input side of the detector 14 is shown. However, the connecting direction of the diode 21 is not limited to this example, and if the diode 21 is connected in the direction of detecting the waveform with high sharpness among the waveforms of the positive side or the negative side with respect to the reference potential of the correlation output waveform. Good.

In this embodiment, the SAW matched filter 11 is used as the correlating means, but other correlating means such as SAW convolver may be used.

The configuration of the output signal amplifying amplifier 12 is not particularly limited, but a one-chip IC (integrated circuit) amplifier may be used.

FIG. 5 is a block diagram showing an example of a communication system using the spread spectrum communication receiver as described in the first embodiment. 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 processor 412, a synchronizing circuit 413, a code generator 414 and a spread demodulation 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
Are the spread spectrum communication receiver 4131 and the spread spectrum communication receiver 4131 described in the first embodiment.
The signal processing circuit 4133 processes the signal output from the signal generator and outputs the spread code synchronization signal and the clock synchronization signal for the transmission signal to the code generator 414.

The output signal from the high frequency signal processing section 412 is input to the spread spectrum communication receiver 4131, and this signal and a matched filter (of the elements constituting the spread spectrum communication receiver 4131 shown in FIG. 1). Correlation calculation with a reference spreading code having a predetermined pattern of 11) is performed. Assuming that the reference spreading code is a code obtained by time-reversing the spreading code transmitted from the transmission side, from the matched filter in the spread spectrum communication receiving device 4131, the synchronization dedicated spreading code component included in the received signal is obtained. And the reference spreading code match, the correlation peak is output. The peak position detector 15 in the spread spectrum communication receiver 4131 detects the correlation peak position from the correlation peak output and sends the peak position detection signal to the signal processing circuit 4133 at the next stage. In the signal processing circuit 4133,
A code synchronization signal and a clock signal are created based on the peak position detection signal and output 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. Since the signal output from the spread demodulation circuit 415 is a signal modulated by a commonly used modulation method such as so-called frequency modulation or phase modulation, data demodulation is performed by a known demodulation circuit 416.

FIGS. 6 and 7 are block diagrams showing another example of a transmitter and a receiver of a communication system using the spread spectrum communication receiving apparatus as described above. In FIG. 6, 501 is a serial-parallel converter that converts serially input data into n parallel data, and 502-1 to n are parallelized data and n output data from a spread code generator. A multiplier group for multiplying with a spreading code, 503 is a spreading code generator for generating n different spreading codes and a spreading code dedicated to synchronization, and 504 is a multiplication with a spreading code dedicated to synchronization output from the spreading code generator 503. 502 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. 7, 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 configuration, on the transmission side, the input data is first converted by the serial-parallel converter 501 into n parallel data equal to the code division multiplex number. 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 synchronizing circuit 603 comprises the spread spectrum communication receiver 6031 and the signal processing circuit 6033 described in the first embodiment. Spread spectrum communication receiver 60
The output signal from the high-frequency signal processing unit 602 is input to 31 and this signal and the spread spectrum communication receiver 6031 are input.
Of the elements that make up the
Correlation calculation with a reference spreading code having a predetermined pattern of 1) is performed. Assuming that the reference spreading code is a code obtained by time-reversing the spreading code transmitted from the transmitting side, the synchronized dedicated spreading code component included in the received signal is output from the matched filter in the spread spectrum communication receiver 6031. And the reference spreading code match, the correlation peak is output. The peak position detector 15 in the spread spectrum communication receiver 6031 detects the correlation peak position from the correlation peak output and detects the next signal processing circuit 60.
Send the peak position detection signal to 33. 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 spreading code generator 604 generates a spreading code group having the same clock and spreading code phase as the transmitting spreading code group. 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. As the configuration of the carrier regenerating circuit 605, for example, a circuit using a phase locked loop is used. 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.

Although the present embodiment is a case of binary modulation, other modulation methods such as quadrature modulation may be used.

[0033]

As described above, according to the present invention, the spread spectrum having the correlating means for correlating the received signal and the reference code and the peak position detecting means for detecting the peak position from the output of the correlating means. In the communication receiver,
Among the waveforms on the positive electrode side or the negative electrode side of the output from the correlating means for correlating the received signal and the reference signal, the waveform on the higher sharpness side is used for peak position detection. Thus, since the waveform of the correlation output signal has a clear peak position, the peak position detecting means can easily detect the peak position.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a circuit configuration of a wave detector in the first embodiment.

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

FIG. 4 is a diagram showing a circuit configuration of a detector in a conventional example.

FIG. 5 is a block diagram showing an example of a communication system using the spread spectrum communication device according to the first exemplary embodiment of the present invention.

FIG. 6 is a block diagram showing a transmitter of another example of a communication system using the spread spectrum communication device according to the first exemplary embodiment of the present invention.

FIG. 7 is a block diagram showing a receiver of another example of a communication system using the spread spectrum communication device according to the first exemplary embodiment of the present invention.

[Explanation of symbols]

 11 SAW Matched Filter 12 Amplifier for Output Signal Amplification 13 Bandpass Filter for Output Signal 14 Detector 15 Peak Position Detector 21 Diode 22 High Frequency Component Bypass Capacitor 23, 24 Termination Resistor 25 Buffer Resistor 41 Receiver 413 Synchronous Circuit 603 Synchronous Circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Egara 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Akane Yokota 3-30-2 Shimomaruko, Ota-ku, Tokyo Kyano Within the corporation

Claims (11)

[Claims] 1. A spread spectrum communication receiver comprising a correlating means for correlating a received signal and a reference code, and a peak position detecting means for detecting a peak position from an output of the correlating means. Among the waveforms of the positive side or the negative side of the reference potential of the output from the correlating means for correlating with Receiving device for spread communication. 2. The receiving apparatus for spread spectrum communication according to claim 1, further comprising detection means for detecting an output of a correlating means for correlating the received signal and the reference signal. 3. The spread spectrum communication reception according to claim 2, wherein the detection method of the detection means for detecting the output of the correlation means for correlating the received signal and the reference signal is envelope detection. apparatus. 4. A diode is used as one of the circuit elements constituting the detection means for detecting the output of the correlation means for correlating the received signal and the reference signal. A receiver for spread spectrum communication as described above. 5. The spread spectrum communication receiving apparatus according to claim 1, further comprising an amplifying unit that amplifies an output from a correlating unit that correlates the received signal with a reference code. 6. The spread spectrum communication receiver according to claim 5, wherein the characteristic of the amplifying means for amplifying the output from the correlating means for correlating the received signal with the reference code includes a non-linear amplifying characteristic. apparatus. 7. An amplifying means for amplifying an output from a correlating means for correlating the received signal with a reference code is a one-chip IC.
The receiver for spread spectrum communication according to claim 5, wherein the receiver is an amplifier. 8. The spread spectrum communication receiver according to claim 1, wherein the correlating means for correlating the received signal and the reference signal is a surface acoustic wave matched filter. 9. The spread spectrum communication receiver according to claim 1, wherein the correlating means for correlating the received signal and the reference signal is a surface acoustic wave convolver. 10. The negative-side waveform of the output from the correlating means for correlating the received signal and the reference signal with respect to the highly sharp reference potential is used for peak position detection. 10. A receiver for spread spectrum communication according to any one of 9 to 10. 11. Correlation between a received signal and a reference code,
In the spread spectrum signal reception method that detects the peak position from the correlation output for synchronization, it was used to detect the peak of the waveform with the higher sharpness of the positive or negative waveform with respect to the reference potential of the correlation output. A method for receiving a spread spectrum signal, which is characterized in that