JP2502634B2 - Spread spectrum communication device - Google Patents

Description

The present invention relates to a spread spectrum communication device, and more particularly to a reference signal generator for generating a predetermined reference signal modulated by a pseudo noise signal generated by a code generator, and The present invention relates to a spread spectrum communication device including a convolver that performs despread demodulation of a received signal by performing convolutional integration of the received signal and a reference signal output from a reference signal generator.

[Prior Art] Spread spectrum communication (hereinafter referred to as SS communication) is a PN with a sufficiently wide bandwidth for information signals to be transmitted.
(Pseudo noise) A communication system that modulates and transmits with a code, and features such as code division multiplexing, resistance to interference, and high confidentiality. In the reception processing in this SS communication, the transmitted information signal is demodulated by performing so-called despreading processing in which the PN code assigned to each communication channel is used to obtain the autocorrelation with the received signal.

[Problems to be Solved by the Invention] FIG. 4 shows the structure of a conventional SS communication receiver.

In FIG. 4, reference numeral 1 is an antenna, reference numeral 16 is a correlator,
Reference numeral 4 is a modulator, reference numeral 6 is a local oscillator, reference numeral 7 is a PN code generator, reference numeral 10 is a data demodulation circuit, and reference numeral 13 is a received and demodulated information signal.

The correlator 16 despreads the received signal and takes out a modulated signal modulated by a predetermined method. Modulation signal is data demodulation circuit
Demodulated by 10, the information signal 13 is restored. The despread signal is transmitted to the local oscillator 6 by the modulator 4 including a multiplier.
Is generated by modulating the local oscillation signal output by the PN code generator 7 with pseudo noise output by the PN code generator 7.

Conventionally, there is a convolver as one of the devices used as the correlator 16. The convolver is a device that performs convolutional integration, but if the reference PN code has a time-reversed relationship with the received signal, it is a device that performs correlation calculation.

One of the convolvers is the SAW (surface acoustic wave) convolver. SAW convolver uses non-linear characteristics to
The signals are multiplied and the result is integrated by the electrodes provided on the interaction area. The SAW convolver is an elastic convolver that uses the nonlinearity of materials,
AE using nonlinearity between SAW and carrier in semiconductor
There is a (acoustic / electric) convolver.

Figure 5 shows the structure of the SAW convolver. Reference numeral 1 in FIG.
7, 18 are input transducers, reference numeral 19 is a piezoelectric substrate,
Reference numeral 20 indicates an output electrode. The signal F (t) e ^jwt input from the input transducer 17 is to the right in the figure, and the signal G (t) e ^jwt input from the input transducer 18 is mechanical vibration (surface acoustic wave) and left on the substrate 19. Propagate as SAW in the direction. On the propagation path, a product operation of two signals is performed by the non-linear effect, and the result is integrated by the output electrode 20.

The electric signal H (t) output from the output electrode 20 is expressed by the following equation.

Here, k is a constant, L is the length of the output electrode 20, v is the propagation velocity of the surface acoustic wave, and z is the distance taken in the propagation direction of the signal F (t) e ^jwt .

In general, the output electrode length L can be arbitrarily selected with respect to the data length, but here, the case where the output electrode length is equal to the length of one data hit on the propagation path is taken as an example. Further, here, consider the case where one cycle of the PN code and the length of one bit of data are equal. In the SAW convolver, when the reference PN code and the received signal match in the interaction area, a waveform with a relatively large amplitude (hereinafter referred to as spike waveform) is obtained as shown in FIG. Normally, in SS communication, the carrier wave is two-phase modulated by data, so if the output H1 (t) from the output electrode 20 corresponding to the data “1” is H1 (t) = A (t) e ^j2wt , The output H0 (t) corresponding to the data “0” is Hφ (t) = A (t) e ^{j (2wt + π)} , and H1 (t) and H0 (t) have the same envelope A (t) and the phase The signals differ by 180 °. Data demodulation is performed by comparing the phase of this signal with a signal delayed by one data bit, for example.

However, in the above-mentioned conventional example, it is impossible to determine whether the data is "1" or "0" by the envelope of the convolver output, and there is a drawback that the phase comparison must be performed in the high frequency stage.

[Means for Solving Problems] In order to solve the above problems, in the present invention,
A reference signal generator that generates a predetermined reference signal that is modulated by the pseudo noise signal that is generated by the code generator, and the received signal is reversed by performing the convolution integration of the reference signal output by this reference signal generator and the received signal. In a spread spectrum communication device having a convolver for spread demodulation, two convolvers for inputting the received signal and a polarity inverting circuit for inverting the polarity of the pseudo noise signal output by the code generator for each 1-bit data are provided. , A reference signal modulated by a pseudo noise signal generated by the code generator is used as a reference signal of one of the two convolvers, and a reference signal generated by the polarity inversion circuit is used as a reference signal of the other convolver. The configuration using the reference signal is adopted.

[Operation] According to the above configuration, when continuous 2-bit data in the received signal has the same value, a spike waveform appears in the output of one convolver, and when different, a spike waveform appears in the other convolver. Will appear. Therefore, the data demodulation can be easily performed only by detecting the envelope peaks of the outputs of these two convolvers.

[Examples] Hereinafter, the present invention will be described in detail based on examples shown in the drawings. In the following, the same or corresponding members as those in the conventional example will be designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 shows an SS communication receiver adopting the present invention.
In FIG. 1, unlike the conventional example, in addition to the convolver 2 for despreading, another convolver 3 is provided. The local oscillator 6 provides a reference local oscillator signal to the exchanges 4 and 5 connected to the convolvers 2 and 3, respectively. The PN code is input to the modulator 4 by the PN code generator 7 as in the conventional case. On the other hand, the signal input to the modulator 5 is the original PN signal and the PN logically inverted by the data inversion circuit 12.
It is an exclusive OR signal by the exclusive OR circuit 11 of the code clock signal.

The outputs of the convolvers 2 and 3 are input to envelope detection circuits 8 and 9, respectively, and after being detected, they are input to the data demodulation circuit 10 to form an information signal 13.

In the above configuration, the reception signal received by the antenna 1 is input to the two convolvers 2 and 3. In the convolver 2, the signal generated by the local oscillator 6 is modulated by the modulator 4 by the PN code generated by the PN code generator 7, and the convolution integral of the reference signal and the received signal is performed.

On the other hand, in the convolver 3, a PN code and a clock signal that repeats data "1" and data "0" for each bit of data generated using the signal indicating the beginning of the data generated from the PN code generator 7 are generated. The signal generated by the local oscillator 6 is modulated by the modulator 5 by the signal obtained by the exclusive OR operation, and the convolution integration is performed between the reference signal and the received signal.

FIG. 2 schematically shows the structures and functions of the convolvers 2 and 3. In the figure, symbol A is a received signal input terminal, symbol B is a reference signal input terminal, and symbol C is an output terminal.

Reference numerals 31 and 41 in FIG. 2 both represent received signals, reference numeral 32 is the reference signal of the convolver 2, and reference numeral 42 is the convolver 3.
The reference signal of is shown. The numbers 1, 2, ... N-1 and N in the block of FIG. 2 represent each bit of the PN code, and the horizontal line on the numbers represents the polarity inversion signal of the same bit data.

In the convolvers 2 and 3, when the received signal and the reference signal are synchronized so that the data delimiter is located at the center of the convolver, the convolver 2 determines that the received signals are adjacent to each other as indicated by reference numerals 31 and 32 in FIG. When the two bits of the data to be processed have the same value, the received signal and the reference signal match and an output having a relatively large amplitude is generated.

On the other hand, in the convolver 3, as shown by reference numerals 41 and 42, when two adjacent data bits of the received signal have different values, the received signal and the reference signal match, and an output having a relatively large amplitude is generated.

Therefore, the outputs of the convolvers 2 and 3 are envelope-detected by the envelope detectors 8 and 9, and data demodulation can be performed by detecting the points where the respective outputs exceed the predetermined threshold.

According to the above embodiment, two convolvers are provided, and the received signal and the reference signal are convolved and integrated in each convolver.
A reference signal modulated by a code is given, and to the other convolver, a reference signal modulated by a code obtained by inverting the polarity of the same PN code for each bit of data is given for each bit.
Therefore, when the continuous 2-bit data in the received signal has the same value, a spike waveform appears at the output of one convolver, and when different, a spike waveform appears at the other convolver. Therefore, the data demodulation can be easily performed only by detecting the peaks of the envelopes of the outputs of these two convolvers, and there is no need to perform the phase comparison in the high frequency stage as in the conventional case, and the configuration of the device can be simple and inexpensive.

 FIG. 3 shows a second embodiment of the present invention.

3 is different from FIG. 1 in that the reference signal supplied to the exclusive OR circuit 11 is a pulse generator 14 and a frequency divider 15.
Is a point formed by.

The pulse generator 14 outputs a clock pulse for driving the PN code generator 7, and its output is frequency-divided by the frequency divider 15 and input to the exclusive OR circuit 11.

In the configuration of FIG. 3, the convolver 2 performs the convolutional integration of the output of the modulator 4 and the received signal as in FIG.

On the other hand, the convolver 3 divides the clock pulse generated by the pulse generator 14 that drives the PN code generator 7 to form a pulse in which data "1" and data "0" are repeated for each 1-bit data, A signal obtained by an exclusive OR of the pulse and the PN code and the received signal are input, and convolution integration of these two signals is performed.

Even in such a configuration, the convolver 2 and the second
The same operation as shown in the drawing can be performed, and the same effect as described above can be obtained.

In addition to the configurations shown in FIGS. 1 and 3, a bandpass filter for filtering a reception signal received by the antenna 1 may be provided. With this configuration, signals and noise outside the required band can be removed, which leads to an improvement in the SN ratio, so that communication reliability can be improved in any of the above embodiments.

It is also conceivable to insert an amplifier at the input end and the output end of the convolver. According to this structure, there is an effect of compensating for the insertion loss of the convolver, and it is effective in any of the above embodiments.

[Effects of the Invention] As is apparent from the above, according to the present invention, a reference signal generator for generating a predetermined reference signal modulated by the pseudo noise signal generated by the code generator, and the reference signal generator are provided. In a spread spectrum communication device equipped with a convolver for despreading and demodulating a received signal by performing convolution integration of an output reference signal and the received signal, two convolvers for inputting the received signal and the pseudo output by a code generator are provided. A polarity inverting circuit for inverting the polarity of a noise signal for each bit of data is provided, and a reference signal modulated by a pseudo noise signal generated by the code generator is used as a reference signal of one of the two convolvers, Configuration in which a reference signal modulated by a code generated by the polarity inverting circuit is used as the reference signal of the other convolver Therefore, when continuous 2-bit data in the received signal has the same value, a spike waveform appears in the output of one convolver, and when different, a spike waveform appears in the other convolver. Therefore, the data demodulation can be easily performed without performing the phase comparison in the high frequency stage only by detecting the envelope peaks of the outputs of these two convolvers, which has an excellent effect that the device can be configured easily and inexpensively. .

[Brief description of drawings]

FIG. 1 is a block diagram of a spread spectrum communication device adopting the present invention, FIG. 2 is an explanatory diagram showing the operation of a convolver, and FIG. 3 is a block diagram showing another embodiment of the present invention,
FIG. 4 is a block diagram of a conventional spread spectrum communication device, FIG. 5 is an explanatory diagram showing the configuration of a SAW convolver, and FIG. 6 is a waveform diagram showing the output waveform from the convolver. 1 ... Antenna 2, 3 ... Convolver 4, 5 ... Modulator, 6 ... Local oscillator 7 ... PN code generator 8, 9 ... Envelope detector 10 ... Data demodulation circuit 11 ... Exclusive Logical OR circuit 12 …… data inversion circuit, 13 …… information signal 14 …… pulse generator, 15 …… divider 16 …… correlator 17,18 …… input transducer 19 …… piezoelectric substrate, 20… ... Output electrode

Claims (1)

(57) [Claims] 1. A reference signal generator for generating a predetermined reference signal modulated by a pseudo noise signal generated by a code generator, and convolution integration of a reference signal output from this reference signal generator and a received signal. In a spread spectrum communication device equipped with a convolver for despreading and demodulating a received signal by means of two convolvers for inputting the received signal and a polarity for inverting the polarity of the pseudo noise signal output by the code generator for each 1-bit data. An inversion circuit, wherein a reference signal modulated by a pseudo noise signal generated by the code generator is used as a reference signal for one of the two convolvers, and a reference signal generated by the polarity inversion circuit is used as a reference signal for the other convolver. Spread spectrum communication device characterized by using a reference signal modulated by a code.