JPH09214399A - Demodulator for spread spectrum communication and surface acoustic wave element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the cost and to make the equipment small in the SS communication use demodulator demodulating transmission data based on a correlation peak signal. SOLUTION: The surface acoustic wave element 1 is made up of a 1st correlation peak signal detection means 15 consisting of an input electrode 3, a 1st intermediate output electrode 4 and a 1st delay output electrode 6 and up of a 2nd correlation peak signal detection means 16 consisting of the input electrode 3, a 2nd intermediate output electrode 5 and a 2nd delay output electrode 7. When transmission data being an SS signal given to the input electrode 3 have the same phase continuously, the 1st correlation peak detection means 15 provides an output of a correlation peak signal and when the transmission data have different phases continuously, the 2nd correlation peak detection means 16 provides an output of the correlation peak signal and an identification circuit 19 identifies the correlation peak signal to demodulate and output the received data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a demodulation device for spread spectrum communication, which demodulates transmission data based on a correlation peak signal obtained each time the spread spectrum signal matches a bit pattern signal of a PN code, and this spread spectrum communication. The present invention relates to a surface acoustic wave device used as a correlation peak signal detecting means of a demodulator.

[0002]

In recent years, spread spectrum (hereinafter referred to as S) which is resistant to noise and excellent in confidentiality has been developed.
Communication systems have started to attract attention, and along with this, development of transmission / reception devices has been advanced.

Generally, in the SS communication system, an SS signal which is a transmission signal is a predetermined code sequence having a predetermined high bit rate, for example, pseudo noise (Pseudo Ran).
domNoise (hereinafter abbreviated as PN) sequence is first-modulated with an information signal, and then the carrier is secondarily modulated with the modulated signal to generate an SS signal in a wide frequency band.

Phase shift keying (Phase Shift Keyin) is one of the methods for transmitting and receiving the SS signal.
g, hereinafter abbreviated as PSK) A differential encoding PSK (Differentially PSK) that can simplify the configuration of the receiver by a method designed to eliminate the disadvantages of the modulation method.
Encoded PSK, hereinafter abbreviated as DPSK) modulation method. In the PSK modulation method, data to be transmitted is modulated by modulating it as phase information and then transmitted, but in this DPSK modulation method, the data to be transmitted is not converted as it is as the absolute value of the phase,
It is a method of performing relative conversion that sets the phase from the relationship of the data before and after.

FIG. 4 shows an example of conversion of transmission data by the DPSK modulation method. At the transmitter,
When the transmission data is converted, either data “0” or “1” is set as the initial value. For example, if the data “1” is set in advance as the initial value, the transmission data is given. Then, the exclusive-OR operation of the first bit data of the transmission data and the initial value data “1” is performed, and the result of the operation is output as post-conversion data. . Then, the obtained converted data and the data of the next bit of the transmission data are subjected to an exclusive OR operation, and the exclusive OR operation is sequentially repeated to obtain the bits of the converted data. You can get the pattern.

Then, the carrier wave is transmitted as an SS signal by phase-modulating the carrier wave with a phase difference of 0 ° or 180 ° corresponding to the data value "1" or "0" of the converted data. There is.

Therefore, for example, the transmission data is "11
.. ”(see FIG. 4A), the second bit data“ 1 ”that is substantially the conversion target is exclusive of the preset initial value data“ 1 ”. When the logical sum is calculated, it becomes "0",
The data "0" of the third bit becomes "0" when the exclusive OR operation with the data "0" after the exclusive OR operation of the data of the second bit is performed. Thereafter, in the same manner, the above-mentioned exclusive OR operation is sequentially performed to obtain a bit pattern of “1001110010111 ...” (see FIG. 11B) as the converted data.

Then, the transmitter phase-modulates the carrier by correlating the data "1" of the converted data with a phase difference of 0 ° and the data "0" with a phase difference of 180 °. , And transmits the carrier wave to the receiver as an SS signal (see (c) in the figure).

Upon receiving the SS signal, the receiver converts it into a bit pattern and uses it as pre-demodulation data (see FIG. 3D). Then, by performing a calculation process opposite to the above-described sum conversion process on this pre-demodulation data,
The original transmission data can be obtained as the reception data. That is, the pre-demodulation data “1001110010111 ...”, which has the same bit pattern as the converted data, is subjected to the exclusive OR operation of consecutive bits to obtain the reception data “101001011100 ...” () having the same bit pattern as the transmission data. (See (e) in the figure)
Can be obtained.

In this case, the data "1" of the first bit of the transmission data is missing in the reception data because it is not transmitted. For example, by providing a virtual bit in advance in the transmission data, the first bit of the transmission data is It is possible to transmit the data “1” of 1 without missing.

By the way, as a circuit configuration for performing the demodulation processing of the SS signal as described above, generally, a matched filter for detecting the correlation peak signal of the SS signal,
A delay line for delaying the correlation peak signal obtained by this matched filter by one cycle, an amplifier circuit for amplifying the correlation peak signal output from both of them to a certain level, and each amplified signal Based on this, an arithmetic circuit for calculating these products is required.

In this case, as a configuration of the arithmetic circuit, it is general to use a double balanced mixer (hereinafter referred to as DBM) circuit composed of a transformer and a diode connected in a bridge. The use of such a DBM circuit causes a large insertion loss, and also becomes expensive and large in size as a whole, which is a factor to be constrained in reducing the cost and the size of the communication device. ing.

The present invention has been made in view of the above circumstances, and an object thereof is a demodulator for SS communication that demodulates transmission data based on a correlation peak signal, and a DBM for an input SS signal. It is an object of the present invention to provide a demodulation device for spread spectrum communication, which can obtain a demodulation output without using a circuit and can reduce the cost and downsize the device.

[0014]

A demodulator for spread spectrum communication of the present invention detects a correlation peak signal when a spread spectrum signal is input, and demodulates transmission data based on the detected peak signal to obtain a spectrum. In a demodulator for spread spectrum communication, when a spread spectrum signal is input, a first surface acoustic wave element having electrodes arranged so as to output a correlation peak signal when the transmission data has the same phase continuously. A second device comprising a correlation peak signal detecting means and a surface acoustic wave element in which electrodes are arranged so as to output the correlation peak signal when the spread spectrum signal is continuously input and transmission data having different phases. Correlation peak signal detection means and identification means for identifying and outputting transmission data based on the outputs of the first and second correlation peak signal detection means are provided. Having the features the time.

According to the demodulator for spread spectrum communication configured as described above, when the spread spectrum signal is input, the correlation peak signal is output from the first correlation peak signal detecting means when the transmission data are continuously in the same phase. The second correlation peak signal detecting means outputs a correlation peak signal when the transmission data is continuously output and has different phases.
The identification data identifies the transmission data based on these correlation peak signals. Therefore, the conventional DBM
The transmission data can be identified without using an arithmetic circuit having a circuit, which can reduce the cost and downsize the device.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The first demodulator for spread spectrum communication of the present invention, which includes a surface acoustic wave element, will be described below.
Examples will be described with reference to FIGS. 1 and 2. Surface acoustic wave element (hereinafter abbreviated as SAW element) 1
Is the input electrode 3, the first and second intermediate output electrodes 4 and 5, and the first and second intermediate output electrodes 4 and 5 on the upper surface of a long piezoelectric substrate 2 made of, for example, a single crystal of quartz or a ceramic material capable of propagating surface acoustic waves. The first and second delayed output electrodes 6 and 7 are formed.

The input electrode 3 is arranged on one end side of the piezoelectric substrate 2, and is composed of a plurality of pairs of interdigitated electrode electrodes facing each other, and the pattern of the interdigitated electrode electrodes is S.
It is formed so as to match the bit pattern of the PN code at the time of S modulation.

The first and second intermediate output electrodes 4 and 5 are
The input electrodes 3 are arranged side by side at predetermined intervals along the traveling direction of the surface acoustic wave, and each has two pairs of crossing finger electrodes formed in a normal shape. ing. Then, the first and second intermediate output electrodes 4 and 5 together with the input electrode 3 are matched filter 8
When an SS signal matching the interdigital electrode pattern of the input electrode 3 is input, a signal converted from the surface acoustic wave propagating in the piezoelectric substrate 2 is output as a correlation peak signal.

The first and second delayed output electrodes 6 and 7 are
The first and second intermediate output electrodes 4 and 5 are arranged side by side at predetermined intervals along the traveling direction of the surface acoustic wave with respect to the first and second intermediate output electrodes 4 and 5, respectively. Similar to 4 and 5, each has a structure having two pairs of cross finger electrodes formed in a normal shape. The first delay output electrode 6 constitutes the first delay line 9 together with the first intermediate output electrode 4, and the second delay output electrode 7 together with the first intermediate output electrode 5 constitutes the second delay line 9. The line 10 is configured to output the correlation peak signal after being delayed by one cycle from the timing at which the correlation peak signal is output from the first and second intermediate output electrodes 4 and 5, respectively. There is.

Here, the crossing order of the first and second intermediate output electrodes 4 and 5 and the crossing finger electrode of the first delay output electrode 6 is the same as each other. With respect to these three output electrodes, only the second delay output electrode 7 is formed in the order in which the crossing fingers of the crossing finger electrodes are in the reverse order. That is, the first and second intermediate output electrodes 4 and 5 and the first delay output electrode 6 have the same phase output, and the second delay output electrode 7 has the opposite phase output. is there.

Further, one electrode 4a of the first intermediate output electrode 4 and one electrode 6a of the first delay output electrode 6 are electrically connected by a bonding wire 11, and an envelope detector as a detecting means. Similarly, one electrode 5a of the second intermediate output electrode 5 and one electrode 7a of the second delay output electrode 7 are electrically connected to each other by a bonding wire 13. Similarly, it is connected to the input terminal of the envelope detector 14 which is also a detecting means. And
The other electrodes 4b, 5b, 6b and 7b of the first intermediate output electrode 4, the second intermediate output electrode 5, the first delay output electrode 6 and the second delay output electrode 7 are connected in common. It is grounded.

The input electrode 3, the first intermediate output electrode 4 and the first delayed output electrode 6 described above make it possible to use the first electrode in the present invention.
And the second intermediate output electrode 5 and the second delayed output electrode 7 constitute the second correlation peak signal detection means 16 in the present invention. That is, these first and second correlation peak signal detecting means 15 and 16 are provided so as to share the input electrode 3.

The envelope detector 12 detects the frequency component of the signal supplied from the first correlation peak signal detecting means 15 from a high frequency and wide band to a low frequency and narrow band and serves as an amplifying means. Output to the amplifier 17. The envelope detector 14 detects the frequency component of the signal given from the second correlation peak signal detecting means 16 from a high frequency and wide band to a low frequency and narrow band and outputs it to the amplifier 18 which is an amplifying means. .

The amplifier 17 amplifies the signal given from the envelope detector 12 and outputs the amplified signal to the discrimination circuit 19, and the amplifier 1
8 amplifies the signal given from the envelope detector 14 and outputs it to the discrimination circuit 19. Then, the identification circuit 19 as identification means identifies the signals given from the amplifiers 17 and 18 and outputs them as reception data.

Next, the operation of the above configuration will be described with reference to FIG. The SS signal described here is
The transmission data “1101001011100 ...” shown in FIG. 4 (a) described in the section of the above-mentioned conventional example is subjected to a sum conversion process with the initial value data being “1”, and thus FIG.
The converted data "1001110010111 ..."
And 0 ° for the converted data “1”.
It is generated by phase-modulating a carrier wave with a phase difference of 180 ° with respect to the data “0”.

In the SAW element 1, when the above SS signal is applied to the input electrode 3, when the SS signal matches the pattern of the interdigital electrode of the input electrode 3, a large S signal is generated.
It propagates as an AW signal toward the first and second intermediate output electrodes 4 and 5. When this SAW signal reaches the first and second intermediate output electrodes 4 and 5, a part of the SAW signal is converted into an electrical signal, and the SAW signal is converted from the first and second intermediate output electrodes 4 and 5 at the same time. The correlation peak signal is output with a bit pattern of "100111 ..." Equal to the bit pattern of the subsequent data (see FIG. 2A). Further, the SAW signal component that does not contribute to the conversion propagates toward the first and second delayed output electrodes 6 and 7.

When the SAW signal reaches the first and second delayed output electrodes 6 and 7, a part of the SAW signal is converted into an electric signal and the first and second intermediate output electrodes 4 and 5 are converted. A correlation peak signal delayed by one period from the correlation peak signal output from is output.

At this time, as described above, the first intermediate output electrode 4 and the first delay output electrode 6 are formed in the same order as the intersecting order of the electrodes of the intersecting finger electrode pattern. For example, when the correlation peak signal output from the first intermediate output electrode 4 is output with the correlation peak of data “1” being positive and the correlation peak of data “0” being negative, the first delay output electrode 6 The output correlation peak signal is also output with the correlation peak of data "1" as positive and the correlation peak of data "0" as negative (see (b) in the same figure).

On the other hand, the second intermediate output electrode 5 and the second delay output electrode 7 are formed, for example, in the second order because the electrodes of the crossing finger electrode pattern intersect in the opposite order.
When the correlation peak signal output from the intermediate output electrode 5 is output with the correlation peak of the data “1” being positive and the correlation peak of the data “0” being negative, it is output from the second delay output electrode 7. The correlation peak signal is output with the correlation peak of the data “1” being negative and the correlation peak of the data “0” being positive (see FIG. 7C).

Therefore, when the first correlation peak signal detecting means 15 simultaneously outputs the correlation peak signals of the same data from the first intermediate output electrode 4 and the first delay output electrode 6, that is, the input When data of the same phase is continuously input to the electrode 3, a correlation peak signal output from the first intermediate output electrode 4 and a correlation peak signal output from the first delayed output electrode 6 Have the same phase, so that a large correlation peak signal that is the sum of them is output (see (d) in the same figure).

In this case, when the correlation peak signals of different data are simultaneously output from the first intermediate output electrode 4 and the first delay output electrode 6, that is, the correlation peak signals are continuously different with respect to the input electrode 3. When phase data is input,
Since the correlation peak signal output from the first intermediate output electrode 4 and the correlation peak signal output from the first delay output electrode 6 have opposite phases to each other and cancel each other, the first correlation is generated at that timing. Peak signal detecting means 15
Does not output a correlation peak signal.

On the other hand, the second correlation peak signal detecting means 16
From the second intermediate output electrode 5 and the second delayed output electrode 7
When the correlation peak signals of different data are simultaneously output from and, that is, when the data of different phases are continuously input to the input electrode 3, the second intermediate output electrode 5
The correlation peak signal output from the second delay output electrode 7 and the correlation peak signal output from the second delay output electrode 7 have the same phase, and a large correlation peak signal that is the sum of them is output (see FIG. (See (e)).

In this case, when the correlation peak signals of the same data are simultaneously output from the second intermediate output electrode 5 and the second delay output electrode 7, that is, the same is continuously input to the input electrode 3. When phase data is input, the second
Since the correlation peak signal output from the intermediate output electrode 5 and the correlation peak signal output from the second delay output electrode 7 have mutually opposite phases and cancel each other, the second correlation peak signal at that timing No correlation peak signal is output from the detection means 16.

In the envelope detector 12, when the correlation peak signal is given from the first correlation peak signal detecting means 15, the frequency component of the correlation peak signal is changed from high frequency and wide band to low frequency and narrow band. The signal is detected (see (f) in the figure) and the detected signal is output to the amplifier 17. Similarly, in the envelope detector 14,
When the correlation peak signal is given from the second correlation peak signal detecting means 16, the frequency component of the correlation peak signal is detected from a high frequency and wide band to a low frequency and narrow band (see FIG. 9 (g)). ), The detected signal is amplified by the amplifier 18
Output to

In the amplifiers 17 and 18, when the detection signals are given from the envelope detectors 12 and 14, respectively,
The detected signal is amplified and output to the discrimination circuit 19. Then, in the identification circuit 19, when the detection signals are given from the amplifiers 17 and 18, the detection signal given from the amplifier 17 is identified as data “0”, and the detection signal given from the amplifier 18 is identified as data “1”, The reception data “10100 ...” Is generated and output (see FIG. 11H).

As described above, according to the demodulator for spread spectrum communication of the present embodiment, the first correlation peak signal detecting means 1
5, the correlation peak signal is output when the transmission data of the same phase is continuously input, and the second correlation peak signal detecting means 16 continuously outputs a different phase (in this case, a phase difference of 180 °). And a discrimination circuit 19 which outputs a correlation peak signal when the transmission data of
Thus, the received data is demodulated and output based on the correlation peak signals output from the first and second correlation peak signal detecting means 15 and 16, and thus the DBM circuit is used as in the conventional one. Without this, demodulation output can be obtained, and along with this, cost reduction and device miniaturization can be achieved.

Further, in the present embodiment, the first correlation peak signal detecting means 15 and the second correlation peak signal detecting means 16 are provided.
With the configuration including and, it becomes possible to demodulate the received data by detecting which of these outputs the correlation peak signal. Can be treated as a signal of. And thereby the amplifiers 17 and 1
It is not necessary to make 8 correspond to a high frequency and wide band frequency component, that is, it can be made inexpensive and the noise resistance can be improved.

Further, in this embodiment, the first correlation peak signal detecting means 15 and the second correlation peak signal detecting means 1
Since 6 is integrally provided, the input electrode 3 can be shared in a compact structure, and the overall size of the device can be reduced.

FIG. 3 shows a second embodiment of the present invention, and only the parts different from the first embodiment will be described below. That is, in this second embodiment, three output electrodes 22, 23 and 24 are provided on the upper surface of the piezoelectric substrate 21.
And two pairs of normal-form crossing finger electrodes are formed at both ends of the output electrodes 22 and 23, and they are used as a first intermediate output electrode 25 and a first delay output electrode 26. At the same time, two pairs of normal-form crossing finger electrodes are formed at both ends of the output electrodes 23 and 24, and they are used as a second intermediate output electrode 27 and a second delay output electrode 28. That is, the first intermediate output electrode 25 and the first delayed output electrode 26 are integrally formed, and together with the input electrode 3, the first correlation peak signal detecting means 29 is configured, and the second intermediate output electrode 27. And the second delayed output electrode 28 are integrally formed, and together with the input electrode 3, the second correlation peak signal detection means 30 is configured.

The output electrode 22 is the bonding pad 22.
The output electrode 24 is connected to the input terminal of the envelope detector 12 via a, and the output electrode 24 is connected to the input terminal of the envelope detector 14 via a bonding pad 24a. The output electrode 23 is grounded. In the second embodiment as well, as in the first embodiment, the order in which the first and second intermediate output electrodes 25 and 27 and the crossing finger electrodes of the first delay output electrode 26 intersect is the same. However, only the second delay output electrode 28 is formed in the reverse order of the intersecting finger electrodes.

Therefore, also in the above-mentioned second embodiment, when the first correlation peak signal detecting means 29 continuously inputs the transmission data of the same phase as in the first embodiment. Outputs the correlation peak signal to the second
The correlation peak signal detection means 30 outputs the correlation peak signal when the transmission data of different phases are continuously input, and the discrimination circuit 19 further causes the first and second correlation peak signal detection means. Since the received data is demodulated and output based on the correlation peak signals output from 29 and 30, the demodulated output can be obtained without using the DBM circuit, and cost reduction and downsizing of the device can be achieved. You can

The present invention is not limited to the above embodiment, but can be modified or expanded as follows. Of the four output electrodes of the first and second intermediate output electrodes 4 and 5 and the first and second delay output electrodes 6 and 7, the electrodes of the cross finger electrode pattern of the second delay output electrode 7 The order of crossing was formed in the order opposite to that of the other three output electrodes, but the present invention is not limited to this, and any one of the four output electrodes crosses the electrode of the finger electrode pattern of any one of the four output electrodes. It suffices if the order is opposite to that of the other three output electrodes.

First and second intermediate output electrodes 4 and 5, and
The number of electrode pairs of the four output electrodes of the first and second delayed output electrodes 6 and 7 may be one pair or three or more pairs as required. The input electrode 3 may be provided corresponding to each of the first and second intermediate output electrodes 4 and 5.

Further, the present invention is not limited to the two-phase DPSK modulation method, but can be applied to the four-phase DPSK modulation method.

[0045]

As is apparent from the above description, according to the demodulator for spread spectrum communication of claim 1,
With respect to the input spread spectrum signal, the first correlation peak signal detection means continuously outputs the correlation peak signal when the transmission data has the same phase, and the second correlation peak signal detection means continuously outputs the correlation peak signal. Since the correlation peak signal is output when the transmission data has different phases and the transmission data is identified and output based on the correlation peak signals by the identifying means, the conventional DBM circuit is not used. A demodulation output can be obtained, and cost reduction and device miniaturization can be achieved.

According to the demodulator for spread spectrum communication of the second aspect, since the correlation peak signal is inputted by the detecting means to carry out the envelope detection, the output of the envelope detected by the amplifying means is amplified. By detecting the signal of the high frequency and wide band frequency component applied to the amplifier in the detecting means to the signal of the low frequency and narrow band frequency component, the amplifying means can be made inexpensive and the noise resistance is improved. Can be achieved.

According to the surface acoustic wave element of claim 3,
Since the first correlation peak signal detecting means and the second correlation peak signal detecting means share the input electrode, the size of the first correlation peak signal detecting means and the second correlation peak signal detecting means can be reduced. Can be planned.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an electrical configuration of a first embodiment of the present invention.

FIG. 2 is a diagram showing a waveform of an output signal.

FIG. 3 is a view corresponding to FIG. 1, showing a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of the DPSK method.

[Explanation of symbols]

In the drawing, 1 is a surface acoustic wave element, 3 is an input electrode, 4 is a first
Intermediate output electrode, 5 is a second intermediate output electrode, 6 is a first delay output electrode, 7 is a second delay output electrode, 12 is an envelope detector (detection means), and 14 is an envelope detector ( (Detection means), 15 is a first correlation peak signal detection means, 16 is a second correlation peak signal detection means, 17 is an amplifier (amplification means), 18 is an amplifier (amplification means), 19 is an identification circuit (identification means) , 25 is a first intermediate output electrode, 26 is a first delayed output electrode, 27 is a second intermediate output electrode, 28 is a second delayed output electrode, 29 is a first correlation peak signal detection means,
30 is a second correlation peak signal detecting means.

Claims (3)

[Claims] 1. A demodulator for spread spectrum communication, which detects a correlation peak signal when a spread spectrum signal is input and demodulates transmission data based on this to obtain the spread spectrum signal. And a first correlation peak signal detecting means composed of a surface acoustic wave element in which electrodes are arranged so as to output a correlation peak signal when the transmission data has the same phase as the above, and the spread spectrum signal is input. And a second surface acoustic wave device in which electrodes are arranged so as to output a correlation peak signal when the transmission data has different phases continuously.
Demodulation apparatus for spread spectrum communication, characterized in that: the correlation peak signal detection means and the identification means for identifying and outputting transmission data based on the outputs of the first and second correlation peak signal detection means. . 2. A detector for envelope-detecting the correlation peak signals detected by the first and second correlation peak signal detectors, and an amplifier for amplifying the output of the envelope-detected envelopes by the detectors. The demodulator for spread spectrum communication according to claim 1, wherein the identifying means is configured to identify the transmission data based on an amplified output of the amplifying means. 3. The spread spectrum communication demodulator according to claim 1 or 2, which is used as first and second correlation peak signal detecting means, wherein the spread spectrum signal PN is formed on a piezoelectric substrate. An input electrode having an interdigitated electrode corresponding to the reference numeral, and a first electrode provided at a predetermined interval from the input electrode so as to constitute the first correlation peak signal detecting means.
Second intermediate output electrode and first delayed output electrode, and a second electrode provided at a predetermined distance from the input electrode so as to configure the second correlation peak signal detection means.
A surface acoustic wave device for detecting a correlation peak signal, comprising: the intermediate output electrode and the second delayed output electrode.