JPH06216879A - Spread spectrum communication method - Google Patents

Abstract

PURPOSE:To attain communication with high accuracy even in a multiplex communication or a mobile body communication receiving much of external disturbance factors. CONSTITUTION:A synchronization BPSK demodulation circuit 45 of a receiver 40 executes binary phase shift keying demodulation in a form synchronously with a transmission wave from a transmitter. A digital PN code correlation signal generating circuit 46 outputs a correlation of a pseudo noise code with respect to part N-bits for each decoding bit. Then a correlation discrimination device 47 executes addition of correlation devices sequentially with respect to N bits of pseudo noise codes, regarding the correlation value as a probability against noise and executing majority decision depending whether the correlation value is positive or negative to decode transmission data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a transmitter for transmitting data modulated by a spread spectrum modulation system and a receiver for receiving data from this transmitter and demodulating received data by a spread spectrum demodulation system. Spread spectrum communication method in a data communication system.

[0002]

2. Description of the Related Art FIG. 11 shows the principle of a conventional general spread spectrum communication method, which is extracted from the document "Illustrated communication method (theory and practice), Engineering Book Co., Ltd., December 1985". 1 shows a block diagram of a data communication system according to this method. In FIG. 11, 1 is a carrier generator, 2 is a primary modulation signal, 3 is a primary modulation circuit for modulating the carrier from the carrier generator 1 with the primary modulation signal 1, and 5 is a PN
A spread signal generator 4 using a (pseudo noise) code spread-modulates the output signal of the primary modulation circuit 3 with the output signal of the spread signal generator 5, and outputs the spread signal from the antenna 6 as an SS (frequency spread) transmission wave. It is a modulation circuit. The state of each modulation is shown in FIG. In particular, it is shown that the spectrum in which the energy is concentrated at the specific frequency of the primary modulated wave is spread-modulated in accordance with the modulation speed of the spread signal. The above is the configuration of the transmitter.

In FIG. 11, reference numeral 7 is an antenna, 8 is a despreading modulation circuit, 10 is a spreading signal generator, 9 is a demodulation circuit for a primary modulated wave, and the above is the configuration of the receiver. FIG.
In the state where synchronization is established with the transmission wave by despread-modulating the spread-modulated input signal as shown in FIG. 5, the spread signal returns to the original modulated signal and energy of a specific frequency which is the primary modulated signal 2 is transferred. This means returning to the focused spectrum. Considering the state where the description is omitted but the synchronization is not established, SS communication is performed by performing phase control so that synchronization is established for the transmission wave so that the spread spectrum of the demodulated signal becomes a concentrated spectrum. It shows that it holds.

[0004]

A conventional spread spectrum communication method is an analog signal via a feedback loop including a despreading modulation circuit 8, a demodulation circuit 9 for a primary modulated wave, a demodulation signal 11 and a spread signal generator 10. This is a method of establishing synchronization in the form of correlation, and it is considered that the feedback loop becomes unstable due to noise and disturbance signals such as multiplex communication. In addition, it requires a delicate analog adjustment and is technically difficult. Therefore, in the conventional method, the technical accuracy is low and there are many problems in the multiplex communication and the mobile communication with many disturbance elements.

The present invention has been made to solve the above-mentioned problems, and realizes synchronization establishment and decoding without feedback loop by using digital processing that does not require adjustment, and also establishes synchronization. It is an object of the present invention to provide a spread spectrum communication method that makes it possible to perform sufficiently practical communication even in multiplex communication or mobile communication with many disturbance elements by adding a post despread signal.

[0006]

According to a first aspect of the present invention, the transmitter 20 causes the PN code generating circuit 26 to generate 1 bit of the transmission data as an N-bit pseudo noise code, and the transmission data of the transmission data is generated. According to the polarity, the pseudo noise code is divided into positive polarity and reverse polarity, and binary phase shift keying modulation is performed in synchronization with the pseudo noise code.
In addition to the SK modulation circuit 27, the bandpass filter 28 limits the unnecessary band transmission, and the transmission data is transmitted as a transmission wave. The receiver 40 synchronizes with the transmission wave from the transmitter 20 in a binary form. Phase shift keying demodulation is performed by the synchronous BPSK demodulation circuit 45, and the correlation value with the above pseudo noise code is output from the digital PN code correlation signal generation circuit 46 for each past N bits of the decoded bits. The correlation value is sequentially added to the N bits of the pseudo noise code, the correlation value is regarded as a probability phenomenon with respect to noise, and the correlation value determiner 47 performs a majority decision based on whether the correlation value is positive or negative. The above-mentioned transmission data is decoded.

According to the second aspect of the present invention, the transmitter 20 synchronizes with the reception timing in the state where the synchronization is established in the receiver 40, and the transmitter 20 transmits the transmission wave and its reverse polarity with the polarity of the transmission data fixed. Make a wave, above receiver 4
0 is a combination of the high frequency amplified wave after the reception of the transmission wave and the band of the reception wave, the transmission wave, the high frequency amplification wave and the reverse polarity transmission wave are separately combined by the combiners 61 and 62, The detectors 63 and 64 respectively detect the detected outputs, the comparator 65 compares the detected outputs with each other, and the analog switch 66 selects the detected output corresponding to the lower detected output level, and the phase inversion is performed with respect to the selected output. The inversion high frequency wave converted to the high frequency wave and the high frequency amplified wave are combined by the combiner 69.

In the invention of claim 3, the receiver 40
Indicates the threshold value of the correlation value as the synchronization determination setter 50.
It is controlled by the output of.

[0009]

In the invention of claim 1, in the transmitter 20, P
The N code generation circuit 26 sets 1 bit to N for transmission data.
The pseudo BPSK modulation circuit 27 generates a pseudo noise code of bits, divides the pseudo noise code into positive polarity and reverse polarity according to the polarity of the transmission data, and performs binary phase shift keying modulation in synchronization with the pseudo noise code. The band pass filter 28 limits the unnecessary band transmission of the binary phase shift keying modulation signal and transmits a transmission wave. In the receiver 40, the synchronous BPSK demodulation circuit 45 performs binary phase shift keying demodulation in synchronization with the transmission wave from the transmitter 20, and the digital PN code correlation signal generation circuit 46 outputs the past bit by bit for each decoded bit. A correlation value with the pseudo noise code is output for N bits, the correlation value determiner 47 sequentially adds the correlation value with respect to N bits of the pseudo noise code, and the signal quality determination circuit 54 outputs the correlation value with respect to noise. It is regarded as a stochastic phenomenon, the majority decision is made depending on whether the correlation value is positive or negative, and the transmitted data is decoded.

According to the second aspect of the invention, the transmitter 20 transmits the transmission wave and the transmission wave of the opposite polarity in a state where the synchronization is established in the receiver 40 and the polarity of the transmission data is fixed in synchronization with the reception timing. create. In the receiver 40,
Receiving the transmitted wave, the combiners 61 and 62 combine the high frequency amplified wave after passing through the band of the received wave, the transmitted wave, and the high frequency amplified wave and the opposite polarity transmitted wave, respectively, and the detectors 63 and 64 detect them. Respectively, the comparator 65 compares the respective detection outputs, the analog switch 66 selects the detection output corresponding to the one with the lower detection output level, and the combiner 69 selects the phase-inverted high frequency wave with respect to the selected output. The converted high frequency wave and the high frequency amplified wave are synthesized.

In the receiver 40 of the third aspect of the present invention, the output of the synchronization discrimination setting device controls the threshold value of the correlation value.

[0012]

Embodiment 1 Embodiment 1 (corresponding to claim 1). 1 is a block diagram showing the configuration of a transmitter in a data communication system according to a first embodiment of the present invention. FIG. 2 is a diagram showing the transmission spectrum characteristic of the transmitter. FIG. 3 is a block diagram showing the configuration of the receiver. 4 and 5 are flowcharts showing the operation of the first embodiment.

In FIG. 1, reference numeral 20 is a transmitter using a spread spectrum (SS) modulation method. In FIG.
Serial transmission data SD to be modulated, transmission request signal R
Based on S and the transmission timing signal ST, the transmission timing generation circuit 25 performs timing control, and the PN code generation circuit 26 performs P control with a code length of N bits.
Create and send N code. Synchronous BPSK modulation circuit 2
In 7, synchronous BPSK modulation is performed. The spectrum has a characteristic 30 as shown in FIG. The SS transmission wave is obtained by passing the bandpass filter 28 that passes only the necessary fundamental wave portion 31 of the characteristic 30. The transmission timing of the serial transmission data SD is output as a transmission timing signal ST when it is synchronized with the internal timing, and an external synchronization timing signal ST ′ is input when it is synchronized with the external timing. In addition, 21
Is a transmission request signal line for inputting a transmission request signal RS from the processing device on the transmission side shown in the figure, 22 is a transmission timing signal line for outputting the transmission timing signal ST to the processing device, and 23 is an external synchronization timing signal ST ′ For inputting an external synchronization timing signal line, 24 for inputting serial transmission data SD from the above processing device, and 29 for SS transmission for outputting SS transmission wave to a transmission path not shown. It is a wave output line.

On the other hand, in FIG. 3, the receiver 40 using the spread spectrum (SS) demodulation method inputs the SS transmission wave from the transmitter 20 as an SS reception wave via a transmission line (not shown). The carrier digital PLL circuit 44 is passed through the band pass filter 42 and the high frequency amplifier 43 to absorb the phase jitter due to the disturbance factor of the transmission path, and the synchronous BPSK demodulation circuit 45 decodes it into a pulse train in a form synchronized with the carrier. Then, in the digital PN code correlation signal generation circuit 46, the past code length N bits and the text code N bits are compared for each bit decoded, and if they are the same bit, they are added as "+1", and if they are different, they are added as "-1". Create a correlation value like this. At the time of synchronization detection, the correlation value is "+ N" for reception with no positive polarity error, "-N" for reverse polarity, and is distributed close to "0" in other cases. Even in the case where there is no signal and only noise is present, it is stochastically distributed to a value close to “0”. Separately, the correlation value determiner 47 outputs the correlation value of the received PN code as “1” when the correlation value is positive and “0” when the correlation value is negative and outputs it as the reception data RD from the signal line 55. That is, a majority decision is made.

On the other hand, the correlation value judging device 48 and the correlation value judging device 49 are for acquiring the synchronization in accordance with the PN code of the positive and reverse polarities of the PN code, and are set in the synchronization judgment setting device 50. The threshold value α is input and compared with the above correlation value. The correlation value determiner 48 outputs a pulse when the correlation value is larger than α, and the correlation value determiner 49 outputs a pulse when the correlation value is smaller than −α. From the self-synchronization generating circuit 53, which operates to operate the synchronization detection circuit 52 on the assumption that synchronization has been established, and operates at the internal timing, but to reset the timing counter when the synchronization detection circuit 52 outputs. The timing signal RT is output from the signal line 56. The timing signal RT operates as a reception determination timing by the correlation value determiner 47, and the majority determination of the reception is made effective by the timing. The signal quality judgment circuit 54 for outputting as the carrier detection signal CD monitors the output of the synchronization detection circuit 52 in a timer manner and judges that the line quality is secured when the output is obtained within a predetermined time, It outputs the carrier detection signal CD and serves to transmit the validity of the timing signal RT and the reception data RD to the outside.

Reference numeral 41 is an SS from a transmission line (not shown).
An SS reception wave input line for inputting a transmission wave as an SS reception wave, 55 a reception data line for outputting reception data RD to a reception side processing device (not shown), and 56 outputting a timing signal RT to the above processing device. Is a timing signal line 57 for outputting a carrier detection signal CD to the processing device.

Next, the operation of the first embodiment will be described with reference to the flow charts of FIGS. In the transmitter 20, for the serial transmission data SD and the transmission timing signal ST, 1 bit of the serial transmission data SD is generated as an N-bit pseudo noise code (PN code),
Depending on the polarities of "1" and "0" of the serial transmission data SD (step S1), the PN code has a positive polarity (step S).
2) The signal is transmitted separately from the reverse polarity of the inverted code (step S3), binary phase shift keying (BPSK) modulation is added in synchronization with the PN code (step S4), and unnecessary band transmission is limited. It is transmitted as an SS transmission wave synchronized to a high frequency level to be output to the outside through the band pass filter 28 to be added (step S5).

On the other hand, in the receiver 40, the SS transmission wave is input as the SS reception wave (step S6), passed through the band pass filter 42, and then amplified and decoded. Then, the BPSK demodulation is performed in synchronization with the transmission wave. (Step S
7) The correlation with the PN code is calculated for the past N bits for each one of the decoded bits (step S).
8). For example, "+1" when the polarities of "1" and "0" match the polarities of the original PN code, and "-1" when they do not match.
And the correlation values "N" to "-N" are regarded as a probability phenomenon with respect to noise and processed as follows.

In the correlation value judging device 47, a majority judgment is made depending on whether the correlation value is positive or negative.
Even if the S / N ratio of PSK demodulation has a poor S / N ratio (N is sufficiently larger than S), the code element error rate approaches 0.5 by using the probability N times. The S / N ratio is improved. For that purpose, it is a condition that the synchronization is established, but the correlation value determiners 48 and 49 are provided with a threshold value "α" of a constant correlation value and P
When the correlation values of the positive and negative polarities of the N code are detected to be "α" or more (step S9) and "-α" or less (step S10) respectively, and the detected values are obtained, the synchronization establishment condition is satisfied. And the self-synchronization creation timing signal RT is generated in synchronization with the timing (steps S12, S
13, S14, S17), the synchronization is maintained at the internal timing even when the synchronization probability condition is not obtained, and at the same time, the timer operation determines whether or not the synchronization establishment condition is valid (steps S15, S16). If valid, the carrier detection signal CD is output. In addition, the correlation value is "0"
In the above case, the determination output of decryption "1" is obtained (step S1
1, S18), if the correlation value is less than "0", decryption "0"
Is obtained (steps S11 and S19). As a result, the reception data RD is obtained. In the process of FIG. 4, the transmission rate of the transmission data is 128 Kb / s,
The processing speed of steps S2 and S3 is 16.256 Mb /
s, the frequency of the SS transmission wave is 2.4384 GHz, the frequency of the SS reception wave is 2.4384 GHz, and the BPSK demodulation speed is 16.256 Mb / s. In the process of FIG.
The output speed of the reception data RD is 128 Kb / s. These are reference values.

FIG. 6 shows the demodulation characteristics of the BPSK modem with S / N as the horizontal axis and the element error rate pe as the vertical axis.
In FIG. 6, with respect to the characteristic L1 of the original synchronous BPSK, 15 bits (about 12 dB improvement) and 31 bits (about 14 d)
B improvement), 63 bits (about 17 dB improvement), 127 bits (about 20 dB improvement), the element error rate as a result of majority decision by PN code is L2, L3, L4, L
As shown in Fig. 5, it is shown that -S / N can sufficiently make a practical line.

On the other hand, FIGS. 7 and 8 show the synchronization establishment rate using the threshold as a parameter. The horizontal axis represents S / N similarly to FIG. 6, and the vertical axis represents reception of a PN code block in which synchronization is obtained. The number of times is expressed as an average value, and En
N of (n is 0, 1, 2, ...) Represents the allowable number of errors, that is, the threshold value α = N−n. FIG. 7 shows the synchronization establishment rate of one of the PN code blocks, while FIG. 8 shows the synchronization establishment rate of two consecutive PN code blocks, and the threshold value α for the line quality S / N is shown. It is possible to adapt to a practical line by selecting the allowable time t.

In FIG. 7, the synchronization establishment rate E10,
E1, E5, E10, E15, E20, E25, E3
0, E35, E40, E45, E50, and E55 are (1 × 10 to the 30th power), (exceed 1 × 10 to the 30th power), (3.9 × 10 to the 29th power), (1.2 ×). 2 of 10
5th power), (1.58 × 10 19th power), (1.53 × 1)
0 to the 15th power), (6.65 × 10 to the 11th power), (1.0
1 × 10 9th power), (5.49 × 10 6th power), (6.
11 × 10 4), (1.64 × 10 3), (1
The average number of bits for establishing synchronization is (1.3 × 10), which is the code length of (1.3 × 10).

Further, in FIG. 8, the synchronization establishment rate E15,
E20, E25, E30, E35, E40, E45, E
50 and E55 are each (more than 1 × 10 to the 30th power),
(7.01 × 10 29th power), (4.42 × 10 23)
Squared), (1.02 × 10 19th power), (3.01 × 10
13), (3.73 × 10 9), (2.7 × 1)
It has an average number of bits for establishing synchronization for code lengths of 0 6), (1 × 10 4), and (1.69 × 10 2).

Embodiment 2 (corresponding to claim 2). FIG. 9 is a block diagram showing the configuration of the other station signal cancellation SS communication receiver according to the second embodiment. 9, 20 is the same as the transmitter shown in FIG. 1, and 40 is the same as the receiver shown in FIG.
The receiver of the second embodiment transmits the despread transmission signal based on the synchronization signal acquired at the time of receiving the SS transmission wave by applying the carrier synchronization method transmission / reception modulation method. The carrier transmission wave and its inverted phase ( (Reverse polarity) carrier and the original reception carrier are separately combined and detected, and by selecting the one with the lower detection level, only the disturbance signal with or without the local signal is extracted and the signal of that signal is extracted. This is an SS communication receiver for removing other-station signals, which makes it possible to take out only the original own-station signal by creating opposite-polarity signals of the same level and opposite phases and combining them with the original received wave.

In FIG. 9, reference numeral 41 is a receiving terminal from the SS communication antenna, 42 is a band pass filter, and 43.
Is a high frequency amplifier with AGC function. In the initial stage, the output of the amplifier 43 passes through the combiner 69 as it is and is input to the input line 41 of the receiver 40 and demodulated, and the received data RD, the demodulation timing signal RT and the carrier detection signal CD which are demodulation outputs are output. The detection signal CD is the transmitter 20
Is input to the transmitter 20 as a transmission request signal RS to activate, and similarly, the reception timing signal RT is input as a transmission timing signal ST, and the transmission data SD may be either positive or reverse polarity, but in the figure, "0". And starts transmission, and outputs the SS transmission wave from the SS transmission wave output line 29 in synchronization with the demodulation signal. Reference numeral 70 denotes a phase inverting amplifier which inverts only the phase at the same level as the input, but the output S of the high frequency amplifier 43 with AGC function.
The S reception amplified wave and the following two types of combined detection are performed. The first combined detection is the SS received amplified wave and the phase inverting amplifier 70.
The despread transmission wave of the output of the phase inversion amplifier is combined by the combiner 61 and detected by the detector 63. The second combined detection combines the SS received amplified wave and the despread transmitted wave into a combiner 62.
And is detected by the detector 64.

This system adopts a synchronous modulation / demodulation system up to a carrier signal. In the combination of the combiners 61 and 62, one of them has a signal phase matching that of the original SS received amplified wave, and the other has a reverse polarity. Becomes A slight phase shift is allowed.
Comparing the detection outputs of the detectors 63 and 64 in the comparator 65, the signal having the same signal phase has a higher level than the original SS received amplified wave, and the signal having the opposite polarity has the lower level.
The level difference is detected and output, but the analog switch 6
At 6, the selection is switched to the lower level. The lowering of the level occurs as a result of removing the SS received wave component of the own station by combining with the despread signal for all input signals. The output of the analog switch 66 is reversed in polarity by the phase inverting amplifier 67 and added by the combiner 69 to remove an unnecessary disturbance signal from the SS received amplified wave to extract the original SS signal of the own station, and the receiver 40 Thus, it is possible to realize a circuit that enables a reception code with high quality and high reliability.

Particularly in the case of performing multiplex communication, the signal of another station is likely to interfere with the signal of the same station as the external noise. However, after the synchronization signal of the own station is acquired, the despread signal is added to remove the signal of the other station. High quality and highly reliable reception code can be realized even in multiple communication channels.

As described above, in the second embodiment, the SS transmission wave is demodulated by the receiver 40.
In the state where the synchronization is established in the receiver 40, the SS transmission wave and the SS transmission wave of the opposite polarity are made in the state of being fixed to the polarity “1” or “0” in synchronization with the reception timing signal RT, and the SS transmission wave is transmitted. The high-frequency amplified wave after passing through the band-pass filter of the wave is separately combined with each SS transmission wave and the reverse polarity SS transmission wave, and the respective combined outputs are detected, and the respective detection outputs are compared to determine the level of the detection output. The lower one lowers the level due to synthesis because the required carrier level of the own station is in reverse phase, but the synthesized output of the lower level is switched and selected, and the selected output is converted to the phase inversion high frequency. When,
By combining the high-frequency amplified output of the SS received wave, unnecessary waves and noise of the SS received wave are removed, and only the desired wave of the own station is selected and multiplexed use for the same radio frequency of SS communication becomes possible. .

Embodiment 3 (corresponding to claim 3). In the first embodiment shown in FIG. 3, the receiver 40 sets the correlation value threshold value calculated in advance by the synchronization determination setting device 50, and obtains the correlation value exceeding the value to determine synchronization. In the third embodiment, as shown in FIG. 10, the output of the synchronization detection circuit 52 is input, and when the output cycle is short, the threshold level set value is increased and when it is long, it is decreased and balanced to the actual line. The optimum threshold calculator 58 is provided so as to control the synchronization determination setting device 50, and is also designed not to fall below a certain value. As a result, the synchronization acquisition adapted to the actual line is automatically controlled, and the evaluation value of the actual line can be obtained by knowing the threshold value.

In the second embodiment, the correlator threshold value α of the receiver 40 shown in FIG. 3 is variable. However, if there is an output from the synchronization detection circuit, the threshold value is lowered by "1" and there is no fixed time. In this case, an optimum threshold calculator 58 is provided which raises the value by "1" to bring it into a floating state and balance it according to the actual line, and controls the correlator threshold value α by the synchronization determination setting device 50.

In the spread spectrum communication method described in each of the above embodiments, the SS transmission wave is generated by applying the code modulation with the PN code to the transmission data and the synchronous binary phase shift keying modulation (BPSK modulation) with respect to the code modulation data. create. On the other hand, the code element error rate for S / N of the synchronous phase shift keying demodulation (BPSK demodulation) is regarded as an establishment phenomenon, and synchronization is acquired by digital correlation in the PN code process. This is a method that enables communication even if a slight signal is present in the noise by making a determination.

Therefore, according to each embodiment, the digital code modulation and the BPSK modulation are used as a synchronous system up to the transmission output, and the demodulation and decoding are also made a synchronous system, which greatly facilitates the digital circuit configuration and the characteristics of the BPSK modem. At the same time, it is easy to analyze the line characteristics, and at the same time, it is easy to add despreading as the next step, and since the evaluation of the line characteristics is reliable, it is possible to select the variable threshold for establishing the optimum synchronization according to the line. And

[0033]

As described above, according to the invention of claim 1,
Encoding / modulation / demodulation /
Since the coding of the decoding is the PN code, the digital circuit can be easily formed, the manufacturing cost can be reduced by the LSI, and no special adjustment is required. In addition, the line evaluation according to the line characteristics is easy, and the synchronization acquisition time and the bit error rate due to the decoding can be analyzed mathematically.
It is possible to improve the S / N, which is the purpose of communication, and facilitate the use of multiplex communication. Therefore, according to the present invention, there is an effect that it is possible to perform sufficiently practical communication even in multiplex communication and mobile communication with many disturbance elements.

According to the second aspect of the invention, in the transmitter, the transmission wave and the reverse polarity transmission wave are generated with the polarity of the transmission data fixed, and in the receiver, the high frequency amplified wave, the transmission wave, and the high frequency amplified wave are reversed. Polarity transmission wave is synthesized separately, each is detected, each detection output is compared, the detection output corresponding to the lower detection output level is selected, and the phase inversion high frequency is selected for this selection output. Since the converted inverted high frequency wave and the high frequency amplified wave are combined, unnecessary waves and noises of the received wave can be removed, only the desired wave of the own station can be selected, and the multiplex use for the same radio frequency of SS communication can be used. It has the effect of making it possible.

According to the invention of claim 3, since the threshold value of the correlation value is controlled by the synchronization discrimination output in the receiver, it is possible to know the threshold value adapted to the actual line. There is an effect that the evaluation value of the line can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a transmitter according to a first embodiment of the present invention.

FIG. 2 is a diagram showing the frequency spectrum and filter characteristics of the transmitter according to the first embodiment.

FIG. 3 is a block diagram of a receiver according to the first embodiment.

FIG. 4 is a flowchart for explaining the operation of the first embodiment.

FIG. 5 is a flowchart showing a continuation of FIG.

FIG. 6 is a diagram showing PN coded S / N improvement characteristics in the first embodiment.

FIG. 7 is a diagram showing a synchronization establishment rate for one code length in the first embodiment.

FIG. 8 is a diagram showing a synchronization establishment rate when the code length is twice in the first embodiment.

FIG. 9 is a block diagram of a receiver according to a second embodiment of the present invention.

FIG. 10 is a block diagram of a receiver according to Embodiment 3 of the present invention.

FIG. 11 is a block diagram of a conventional data communication system.

FIG. 12 is a signal waveform diagram showing an operation of a conventional transmitter.

FIG. 13 is a signal waveform diagram showing an operation of a conventional receiver.

[Explanation of symbols]

 20 transmitter 21 transmission request signal line 22 transmission timing signal line 23 external synchronization timing signal line 24 serial transmission data line 25 transmission timing creation circuit 26 PN code generation circuit 27 synchronous BPSK modulation circuit 28 band pass filter 29 SS transmission wave output line RS transmission request signal ST transmission timing signal ST 'External synchronization timing signal SD Serial transmission data 40 Receiver 41 SS Reception wave input line 42 Band pass filter 43 High frequency amplifier 44 Carrier digital PLL circuit 45 Synchronous BPSK demodulation circuit 46 Digital PN code correlation Signal generation circuit 47, 48, 49 Correlation value determination device 50 Synchronization determination setting device 51 OR circuit 52 Synchronization detection circuit 53 Self-synchronization creation circuit 54 Signal quality determination circuit 55 Received data line 56 Timing signal line 57 Carrier detection Signal line 58 Optimal threshold calculator RD Received data RT Timing signal CD Carrier detection signal 61,62 Combiner 63,64 Detector 65 Comparator 66 Analog switch 67 Phase inverting amplifier 68 Analog switch 69 Combiner 70 Phase inverting amplifier

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[Procedure amendment]

[Submission date] June 21, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

[0009]

In the invention of claim 1, in the transmitter 20, P
The N code generation circuit 26 sets 1 bit to N for transmission data.
The pseudo BPSK modulation circuit 27 generates a pseudo noise code of bits, divides the pseudo noise code into positive polarity and reverse polarity according to the polarity of the transmission data, and performs binary phase shift keying modulation in synchronization with the pseudo noise code. The band pass filter 28 limits the unnecessary band transmission of the binary phase shift keying modulation signal and transmits a transmission wave. In the receiver 40, the synchronous BPSK demodulation circuit 45 performs binary phase shift keying demodulation in synchronization with the transmission wave from the transmitter 20, and the digital PN code correlation signal generation circuit 46 outputs the past bit by bit for each decoded bit. The correlation value with the pseudo noise code is output for N bits, and the correlation value is used to detect synchronization.
And self-synchronization control to synchronize with synchronization timing / RT
Then, the correlation value judging device 47 decodes the transmission data by carrying out a majority judgment for N bits depending on whether the correlation value is positive or negative.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

[0010] In the invention of claim 2, the transmitter 20 is the rock in a state of fixing the polarity of the transmitted data in synchronization with the reception timing in a state where synchronization is established in the receiver 40 is established
A transmission wave for loose despreading and a transmission wave of its opposite polarity are created.
The receiver 40 receives the transmitted wave in which the unwanted wave is mixed, and the combiners 61 and 62 transmit the high frequency amplified wave after the band of the received wave, the despreading transmitted wave, and the high frequency amplified wave and the despreading inversed wave. Combining each with the polar transmission wave , one of the
Only the unnecessary waves remain, but the detectors 63 and 64 detect them respectively, the comparator 65 compares the respective detection outputs, and the analog switch 66 selects the detection output corresponding to the lower detection output level. The synthesizer 69 acts to remove unnecessary waves by synthesizing the inverted high frequency converted to the phase-inverted high frequency with the selected output and the high frequency amplified wave .
It

Claims (3)

[Claims] 1. A data communication system comprising: a transmitter for transmitting data modulated by a spread spectrum modulation method; and a receiver for receiving data from the transmitter and demodulating received data by the spread spectrum modulation method. The transmitter generates 1 bit as N-bit pseudo noise code for the transmission data, divides the pseudo noise code into positive polarity and reverse polarity according to the polarity of the transmission data, and generates the pseudo noise code as the pseudo noise code. Binary phase shift keying modulation is applied in a synchronous manner, unnecessary band transmission is further limited, and the transmission data is transmitted as a transmission wave, and the receiver is binary phase shift in synchronization with the transmission wave from the transmitter. Keying demodulation is performed, and the correlation value with the pseudo noise code is pasted to the past N bits for each bit of the decoded bit. N bits of the signal are sequentially added, the correlation value is regarded as a probability phenomenon with respect to noise, a majority decision is made depending on whether the correlation value is positive or negative, and the transmission data is decoded. Communication method. 2. The transmitter creates a transmission wave and a transmission wave of the opposite polarity in a state where the polarity of the transmission data is fixed and the transmission wave is synchronized with the reception timing when synchronization is established in the receiver. , The high frequency amplified wave after receiving the transmission wave and passing through the band of the reception wave, the transmission wave, the high frequency amplification wave and the reverse polarity transmission wave are separately synthesized, respectively detected, and each detection output And selecting the detection output corresponding to the lower detection output level, and synthesizing the inverted high frequency converted to the phase inversion high frequency with the selected output and the high frequency amplified wave. The spread spectrum communication method according to claim 1. 3. The spread spectrum communication method according to claim 1, wherein in the receiver, the threshold value of the correlation value is controlled by an output for discriminating the synchronization with the transmitted wave.