JPH0497631A - Spread spectrum communication equipment - Google Patents

Abstract

PURPOSE:To allow one correlation device to attain similar correlation processing to that when two correlation devices or over are in use by dividing a correlation processing enable band of the correlation device into two or over, applying different correlation of the signal to each band and separating correlation signals. CONSTITUTION:A reception signal is inputted to a reception side of a correlation device (convolver) 14 via a band pass filter 10 and an amplifier 15 and the correlation device 14 takes correlation between the reception signal and a modulated signal. A correlation processing band (signal input band) is divided on a frequency axis and the divided bands are used to take correlation of a correlation signal of independent spread signals and the correlation output signal is extracted separately at a frequency set to each band. Thus, the similar correlation processing is implemented to the case with two correlation devices or over by having only to use one correlation device 14 and occurrence of an error of a demodulation data due to noise or disturbance or the like is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spread spectrum communication device, and more particularly to an improvement in a spread signal correlation processing method using one correlator.

[Summary of the Invention] A spread spectrum communication device is provided with one correlator, whose correlation processing band (signal input band) is divided on the frequency axis, and the divided band is used to calculate the correlation between correlation signals of independent spread signals. The correlation output signal is separated and extracted at a frequency set for each band.

[Prior Art] In a spread spectrum receiver, when data demodulation is performed using correlation spikes obtained by correlating a received signal and a reference signal using a correlator, conventional methods include, for example, the method of the present invention. Patent application No. 1-2 related to the earlier application
There is No. 9538 "Spread Spectrum Communication Device".

The correlator in this system performs convolution integration of the received signal and the reference signal on the time axis.

Assuming that the received signal is f, (t) and the reference signal is f, (t), the convolution integral on the time axis is generally expressed by equation (1).

f(t)=f, (t) book f, (t)=ff, (τ)f,
(t-τ)dτ...(1) However, the integration interval of a correlator, such as a matched filter or convolver, is finite due to the shape of the element used as the correlator, so the gate delay time (
τG).

Here, the fact that convolution of two functions in the time domain is equivalent to multiplication in the frequency domain is based on the important properties of symmetry and dependence between time and frequency of Fourier transform, as shown in equation (2). it is obvious.

F [f, (t)*f, (t)] = f f, (r)e
−JωtF, ((11) dr=F, (ω)F, (ω
)...(2) In other words, the correlator multiplies each spectrum of the received signal and the reference signal, and the frequency characteristics that can be calculated by multiplying each spectrum of each input are determined by the gate delay time. Reciprocal number (1/τG)
determined by

Therefore, the correlation result between the received signal SS-modulated equal to the center frequency f of the correlator and the reference signal is determined by the pseudo-renton code (PN code) used, as shown in FIG. 6(a) of the above-mentioned earlier application.
If they match, a sharp spike waveform will appear on the time axis.

As for the correlation result on the frequency axis, it is easy to see from equation (2) that spectral components in a symmetrical relationship with the center frequency 2f are obtained, and also as shown in FIG. 6(a) of the above-mentioned earlier application.
It is a well-known fact that only the envelope is shown, and the spike waveform or spurious (side lobe of autocorrelation) actually contains a 2f component.

In the spread spectrum communication (SSC) method using a convolver, as shown in Figure 8, different carrier waves (f,, f,) are assigned to binary data (1, O), and these carrier waves are modulated with a spreading code. , FSK transmits one of the spread signals according to 1.0 of the data.
(Eying on Frequency 5hift)
There is a method.

FIG. 8 shows such an FSK method transmission system, 1 and 2.
are first and second carrier wave sources; 3 is a switch that selectively outputs the first or second carrier wave f atf according to the type of transmission data; 4 is a PN code generator; 5 is a PN code based 6 is an amplifier, 7 is a band pass filter, and 8 is an antenna.

In the above transmission system, 2
two carrier waves apart. Additionally, the spreading bandwidth is equal to the convolver input band at the receiver in order to effectively transmit the spread signal energy.

As a result of the above, when attempting to demodulate the data 1 and O spread signals, two correlators having carrier waves corresponding to the respective signals are required.

However, a relatively large amplitude autocorrelation waveform (correlation peak) appears when the spread signals corresponding to either data match or when both codes match.
According to the method of identifying data 1.0 by presence or absence, only one correlator is required. Figure 10 shows a reception system using such a method, where 9 is an antenna, 10 is a bandpass filter, and 11 is a correlator. A carrier signal source that generates a carrier signal having the same frequency as the second carrier wave f, 12 a PN code generator that generates a reference 1 nonce PN code that is time-reversed with respect to the transmitting side PN code, and 13 this time-reversed PN code. P did
a modulator for modulating the carrier signal with an N code; 14;
16 is an amplifier for amplifying the correlation output; 17 is an envelope detector; 18 is a waveform processing circuit.

FIG. 11 shows the spectrum of the received signal, reference signal, and correlation output in the receiving system.

Note that when data is identified using only one correlator, as in the above receiving system, the risk of data errors due to noise, interference, etc. is greater than when two correlators are used. .

Also, CS K (Code 5hift Keyin
In communication using the g) method, data can be similarly demodulated with one correlator, but it is possible to demodulate data using two correlators,
It is better to demodulate each 1.0 of the data and compare them.
Data becomes more reliable.

The 12th VM is an example of a receiving system using the C3K method, where %20 is an antenna, 21 is a bandpass filter, and 2
2 and 23 are first and second convolvers, 24 and 25
are first and second carrier signal sources, 26 is a PN code generator that generates a time-reversed reference PN code with respect to the transmitting side PN code, 27 and 28 are first and second modulators, and 29 and 30 are amplifiers 31 and 32 are first and second amplifiers;
33 and 34 are first and second waveform processing circuits, 35 is a level comparator, and 35 is a third waveform processing circuit. FIG. 13 shows the spectrum of each signal in the above receiving system.

[Problem M to be solved by the invention] As mentioned above, in the conventional SSC system, in the demodulation method using only one correlator, one type of spreading is used in the frequency band (input signal band) in which the correlator can perform correlation processing. This only correlates signals, and as mentioned above, there is a risk that errors may occur in the demodulated data due to noise, interference, etc.

Therefore, as described above, there is a method to improve the reliability of demodulated data, but it requires the use of two correlators.

[Objective of the Invention Therefore, the object of the present invention is to use one correlator, and to connect the correlator to 211
It is an object of the present invention to provide a spread spectrum communication device using a method equivalent to the spread signal correlation processing method used above.

[Means for Solving the Problems] In order to achieve the above object, the first invention provides first and second carrier wave sources having different frequencies, and the first and second carrier wave sources having different frequencies, and a switching means for selectively outputting the first or second carrier wave source; and based on the PN code,
a transmitter comprising: a first modulating means for modulating the output of the switching means; and a transmitter comprising: a first modulating means for modulating the output of the switching means; 3rd and 4th carrier signal sources respectively corresponding to the second carrier wave source; a first combining means for combining carrier signals from a fourth carrier signal source; a second modulating means for modulating the combined carrier signal with a reference PN code time-reversed with respect to the PN code; a correlator that correlates the signal with the signal modulated by the second modulation means; a first signal extraction means that extracts a signal corresponding to the first band from the output of the correlator; a second signal extraction means for extracting a signal corresponding to a second band different from the first band from the output of the correlator; The first to extract the second envelope component
and a second envelope detection means, and a level comparator that compares the levels of the extracted first and second envelope components,
The present invention further comprises a threshold detector that compares the output of the level comparator with a predetermined threshold and outputs a pulse when the output is greater than the threshold.

Further, the second invention includes first and second PN code generators that generate a first PN code and a second PN code that are different from each other, and the first and second PN code generators that generate a first PN code and a second PN code that are different from each other. a transmitter including a switching means for selectively outputting a second PN code; and a first modulation means for modulating the output of the switching means with a predetermined carrier wave; a second modulating means for modulating with a first reference PN code having a mirror image relationship with the code;
a third modulation means that modulates the carrier signal of the carrier signal with a second reference PN code that is in a mirror image relationship with the second PN code, and combines the modulation signals modulated by the second and third modulation means. a fourth modulating means for modulating the received signal with a third carrier signal having a frequency that is half the difference between the first carrier signal and the second carrier signal; a correlator for correlating the output of the modulating means No. 4 with the output of the synthesizing means; a first signal extracting means for extracting a signal corresponding to the first band from the output of the correlator; and the correlator. a second signal extracting means for extracting a signal corresponding to a second band different from the first band from the output of the first band; The first to extract the second envelope component
and a second envelope detection means, a level comparator for comparing the extracted first and second envelope components by one novel, and comparing the output of the level comparator with a predetermined threshold;
The gist of the present invention is to include a threshold detector that outputs a pulse when the pulse is larger than the threshold.

Furthermore, a third invention includes first and second PN code generating means each including first and second PN code generators that generate a first PN code and a second PN code that are different from each other; first and second switching means for selectively outputting the first and second PN codes in the first and second PN code generation means according to the type of data; a transmitter comprising first and second modulating means for modulating the outputs of the first and second switching means; and a first combining means for combining the outputs of the respective modulating means;
a third modulating means for modulating the carrier signal of the seventh carrier signal with a first reference PN code having a mirror image relationship with the first PN code;
a fourth modulating means for modulating with a second reference PN code having a mirror image relationship with the N code; a second combining means for combining the modulated signals modulated by the third and fourth modulating means; a correlator for correlating the signal with the output of the second modulation means; a first signal extraction means for extracting a signal corresponding to the first band from the output of the correlator; a second signal extraction means for extracting a signal corresponding to a second band different from the first band from the output; and a second signal extracting means for extracting a signal corresponding to a second band different from the first band from the output; first and second envelope detection means for extracting a second envelope component, and comparing the extracted first and second envelope components with predetermined thresholds, respectively, and The gist of the present invention is to include first and second threshold value detectors that output a pulse when the value is larger than the threshold value.

[Operation] With the above configuration, the correlation processing band of the correlator is divided into two or more, different signals are correlated in each band, and the obtained correlation signals can be separated using a filter. .

[Example] The present invention will be described in detail below with reference to the drawings.

As shown in Fig. 1(a), by overlapping two spread signals whose spread bands are spread over a frequency band in which correlation processing can be performed to some extent as shown in Fig. 1(b), frequency band B in which correlation processing is possible is achieved.
input to the receiving side of the correlator.

On the reference side of the convolver, two spread signals corresponding to the receiving side are similarly applied to the correlation processing frequency band for demodulation.
! Input like I (C).

The correlator performs convolution integration of the spread signals input from the receiving side and the reference side. Here, the convolution integral is
Multiplying the frequency axis is a calculation, and the calculation range is the reciprocal of the gate time of the correlator, so the two reception side input spread signals are the corresponding reference side input spread signals in a mirror relationship. , the center frequencies of the two correlation output signals are calculated in an independent manner, and an output signal as shown in FIG. 1(d) is output. - By separating the output signals using a bypass filter and a low-pass filter that are turned off, each correlation signal can be extracted as shown in FIGS. 1(e) and (f).

In this way, it is possible to divide the correlation processing band of the correlator into two or more, correlate different signals in each band, and separate the correlated signals using a filter.

In the above example, we explained the case where the spreading band is equal to the processing band, but by using a code that is less than half of the spread band processable band, it is possible to prevent two or more spread signals from overlapping within the spreading band. Completely independent correlation outputs can be provided.

FIG. 2(a) shows a transmission system of an embodiment of the FSK type spread spectrum communication device according to the present invention, and FIG.
2(a) and (b), the same reference numerals as in FIGS. 8 and 10 indicate the same or similar circuits, and in particular, the transmitting system is the same as in FIG. 8. The configuration is such that the spectrum of the transmitted signal is set as shown in FIG. 3, and in the receiving system, 41 and 42 are third and fourth carrier signal sources corresponding to the first and second carrier waves, 43 is an adder that combines the third and fourth carrier signals, 44 is a modulator that modulates the combined carrier signal with a reference P'N code, 45 is a low-pass filter, 46 is a bypass filter, and 47 and 48 are the third and fourth carrier signals. 1
and a second envelope detector, 49 and 50 are the first and second envelope detectors.
51 is a level comparator, 52 is a threshold value detector, and 53 is a third waveform processing circuit.

In the transmission system of FIG. 2('a), data 1.
The two carrier waves corresponding to 0 are set to fall within the input band of the convolver 14 on the receiving side.

For example, data 1 is set to fl, and data 0 is set to f.

The two carrier waves are transmitted to the switch 3 in response to the transmitted data.
One of the frequencies is selected, and then modulated by the modulator 5 using a PN code and transmitted from the transmitting side.

In the receiving system shown in FIG. 2(b), the received signal passes through a bandpass filter 1o and an amplifier 11, and then passes through a correlator (
convolver) 14 on the receiving side. An adder 43 on the reference side of the correlator 14 adds carrier signals corresponding to data 1 and 0 of the received signal. The added signal is modulated by a modulator 44 using a reference PN code having a mirror image relationship with the PN signal on the transmitting side, and a reference signal is input to the reference side of the correlator 14.

Then, the correlator 14 performs convolution integration. Convolution integration on the time axis is equivalent to multiplication in the frequency domain, so from the correlator 14, one spread signal F,
The phase-to-phase output is not output.

Therefore, the correlator 14 outputs a despread signal centered on F, zero F3, or F, *F, due to the correlation between the received signal and the reference signal.

From this correlation output, cut frequency (F *F, +F.

A bypass filter 46 having an IF, )/2 and a low-pass filter 45 separate despread signals centering on carriers F*F and F,*F. After each of the separated signals is amplified, envelope detectors 47 and 48 extract the envelope components. The extracted waveforms of the respective envelope components are subjected to waveform processing by waveform processing circuits 49 and 50, and then compared by a level comparator 51, and data as a result of the comparison is output. Further, the output is compared with a threshold value set by a threshold value detector 52, and if it is larger than the threshold value, a pulse is outputted from the threshold value detector 51. The waveform processing circuit 53 shapes the pulse into a pulse having a constant width and uses it as demodulated data.

FIG. 4 shows the waveforms of each signal on the frequency axis in the receiving system.

Next, FIGS. 5(a) and 5(b) respectively show transmission and reception systems of an embodiment of a CSK type spread spectrum communication device according to the present invention.

In (b), the same reference numerals as in FIGS. 2(a) and (b) refer to the same or similar circuits. In particular, in the transmission system, the mutual signals output from the first and second PN code generators 1160°61 Different first and second PN codes are selectively outputted by a switch 3 in accordance with the type of transmission data, and tuned to a first modulator 5. The first and second carrier signals f,, f, from the two carrier signal sources 62.63 are transmitted to the first and second carrier signals f, f, in the second and third modulators 64.65.
The modulated signals are modulated by the first and second reference PN codes from the reference side PN code generator 12 and 12' which have a mirror image relationship with the PN code of the adder 6.
6 and input to the reference side of the correlator 14, and the received signal is combined by the third carrier signal source 67 and input to the reference side of the correlator 14.
carrier signal.

Note that FIG. 6 shows the transmission signal spectrum.

As is clear from the above, on the transmitting side, the PN code is switched depending on the data, and the PN code corresponding to the data is changed.
Modulate the carrier wave with N code and transmit.

On the receiving side, as in the FSK method described above, the carrier signals that fall within the correlation processable band have two carrier signals, and each carrier signal is converted into a spreading code corresponding to data 1.0 on the transmitting side and a mirror image. No. 1 in a relationship. A signal spread with the second PN code is input to the correlator 14 as a reference signal.

Correlate the received signal with each PN signal of the reference signal (f, −
In order to obtain f, ), the received signal is modulated with a sine wave.

As a result, as in the FSK method, when one of the codes matches the transmitted data, a despread signal is output.

Thereafter, the correlation output is processed in the same manner as in the FSK method.

FIGS. 7(a) and 7(b) show a transmitting system and a receiving system of an embodiment of a C3K type high-speed transmission type SSC device according to the present invention, and the same reference numerals as in FIGS. 5(a) and 5(b) are the same. −
Or a similar circuit.

In FIG. 7(a), the first and second blocks of blocks A and B
The PN code generating means includes first and second PN code generators 7.
It consists of 0 to 73. 74 and 75 are first and second switches, which switch the first and second PNs according to the type of data to be sent.
The first . Selectively output the second PN code. 76°77 are the first and second modulators, 78.7
Reference numeral 9 indicates mutually different carrier wave sources fa and fb, and 80 indicates an adder.

Moreover, in FIG. 7(b), the difference from FIG. 5(b) is the first and second carrier signals fa.

fb is the reference PN from the third and fourth PN code generators 83.84 by the third and fourth modulators 81.82.
The signal (PN on the transmitting side, which has a mirror image relationship with PN) is modulated by the lower and lower τ, and the respective modulated outputs are combined by an adder 43 and the result is input to the reference side of the convolver 14. In this configuration, the above device divides the convolver input band into two, and each
This correlator is used as if there were two correlators. Since the input signals of these two divided bands can be subjected to correlation processing independently, the conventional data identification method with or without autocorrelation output can be used as is.

That is, in the transmitting section, in block A, a PN signal 1) n + or pns for performing C3K modulation is selected based on data, and the carrier wave (fa) is spread-modulated. Furthermore, in block B, the PN code PN or PN is similarly selected based on the data, and the carrier wave (fb) is spread-modulated.

Then, the spread signals from block A and block B are added by adder 80 and transmitted. (pn may be PN) In the receiving section, in order to correlate the spread signals of block A and block B, spread signals corresponding to the respective spread signals are inputted to the reference side of the correlator 14 as reference signals. In the correlator 14, the spread signals from each block are independently despread and output as a correlation output. The output correlation output signal is separated into two by low pass and bypass filters 45, 46 as previously described. Each separated signal passes through envelope detectors 47 and 48 and is input to threshold detection circuits 81 and 82 to determine whether a correlated spike exists, and the data is demodulated via waveform processing circuits 83 and 84. Ru.

[Effects of the Invention] As explained above, according to the present invention, by using only one correlator, it is possible to perform correlation processing equivalent to that using two correlators, and it is possible to perform correlation processing equivalent to that using two correlators. It is possible to suppress the occurrence of errors in demodulated data.

[Brief explanation of drawings]

FIG. 1 is an explanation of the principle of the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, FIG. 3 is a transmission signal spectrum diagram of the embodiment, and FIG. FIG. 5 is a block diagram showing another embodiment of the present invention, FIG. 6 is a transmission signal spectrum diagram of the embodiment, and FIG. M7 is a diagram showing still another embodiment of the present invention. 8 is a block diagram of a conventional FSK method SSC transmission system, and FIG. 9 is a spectrum diagram of its transmission signal,
Fig. 10 is a block diagram of a conventional FSK system SSC reception system, Fig. 11 is a spectrum diagram of each signal in the system, Fig. 12 is a block diagram of a conventional C3K system SSC reception system, and Fig. 13 is a block diagram of this system. It is a spectrum diagram of each signal of a system. 1.2...Carrier source, 3...
...Switch, 4...PN code generator,
5...Modulator, 12......
Reference PN code generator, 14...
Convolver, 41.42...Carrier signal source, 47.48...Envelope detector. Patent Applicant Glarion Co., Ltd. Agent Patent Attorney Nagai 1) Takeshi Part 2 Figure 1 #7fm (b) Chikara Ueshi Kaze'#B Figure 3 Magi/! 4 meeting-1#nuheOkutonoP Figure 6 fO book/fo+ ft */fl Fig. 8 Transmission unddem Fig. 9 A71 signal - Numakutno V Fig. 10 Evening signal Sude A → f Fig. 11 Thai warehouse 1 sinu V Kutno V Takashi H skinade ÷ Zuhe Kutno V fig.
No.VA''A 4481R:r, Procedural Amendment Form) December 26, 1990 2゜3゜1990 Patent Application No. 215278 Title of Invention Spread Spectrum Communication Device Person Who Amends 1 Relationship to Case Patent applicant address name (148) Clarion Co., Ltd. 5゜6゜ name (7238) Date of patent attorney amendment order (dispatch) September 25, 1990 Target of amendment Takeshi Nagata, Part 3, Figure 4 I/ '11

Claims (3)

[Claims] (1) First and second carrier wave sources having different frequencies, and the first or second carrier wave sources having different frequencies;
a transmitter comprising: switching means for selectively outputting the carrier wave source; and first modulation means for modulating the output of the switching means based on a PN code; third and fourth carrier signal sources corresponding to each other, a first combining means for combining carrier signals from the third and fourth carrier signal sources, and converting the combined carrier signal into the PN code. a second modulating means that modulates the signal using a time-reversed reference PN code; a correlator that correlates the received signal with the signal modulated by the second modulating means; a first signal extracting means for extracting a signal corresponding to a band; and a second signal extracting means for extracting a signal corresponding to a second band different from the first band from the output of the correlator; The first and second band signals are extracted from the first and second band signals, respectively.
first and second envelope detection means for extracting a second envelope component; a level comparator for comparing levels of the extracted first and second envelope components; and an output of the level comparator. 1. A spread spectrum communication device comprising: a threshold detector that compares the current value with a predetermined threshold value and outputs a pulse when the threshold value is greater than the threshold value. (2) first and second PN code generators that generate a first PN code and a second PN code that are different from each other;
a transmitter including a switching means for selectively outputting a PN code; and a first modulation means for modulating the output of the switching means with a predetermined carrier wave; a second modulating means that modulates the second carrier signal with a first reference PN code that has a mirror image relationship; and a third modulator that modulates the second carrier signal with a second reference PN code that has a mirror image relationship with the second PN code. a modulating means for combining the modulated signals modulated by the second and third modulating means, and a combining means for combining the modulated signals modulated by the second and third modulating means; a fourth modulating means that modulates with a third carrier signal having a frequency of 2; a correlator that correlates the output of the fourth modulating means with the output of the combining means; and from the output of the correlator, a first signal extracting means for extracting a signal corresponding to a first band; and a second signal extracting means for extracting a signal corresponding to a second band different from the first band from the output of the correlator. and, from the extracted first and second band signals, respectively.
first and second envelope detection means for extracting a second envelope component; a level comparator for comparing levels of the extracted first and second envelope components; and an output of the level comparator. 1. A spread spectrum communication device comprising: a threshold detector that compares the current value with a predetermined threshold value and outputs a pulse when the value is larger than the threshold value. (3) A first PN code generator comprising first and second PN code generators that generate a first PN code and a second PN code that are different from each other.
and a second PN code generating means, and first and second PN code generating means for selectively outputting the first and second PN codes in the first and second PN code generating means in accordance with the type of input data. a second switching means; first and second modulation means that modulate the outputs of the first and second switching means using mutually different predetermined carrier waves; and a first combination that combines the outputs of the respective modulation means. and third modulating means for modulating the sixth carrier signal with a first reference PN code having a mirror image relationship with the first PN code, and modulating the seventh carrier signal as described above. a fourth modulating means for modulating with a second reference PN code having a mirror image relationship with the second PN code; and a second combining means for combining the modulated signals modulated by the third and fourth modulating means. a correlator that correlates the received signal with the output of the second modulation means; a first signal extraction means that extracts a signal corresponding to the first band from the output of the correlator; a second signal extraction means for extracting a signal corresponding to a second band different from the first band from the output of the correlator;
first and second envelope detection means for extracting a second envelope component; and comparing the extracted first and second envelope components with predetermined threshold values, respectively; A spread spectrum communication device comprising: first and second threshold detectors that output a pulse when the pulse is larger.