JPH10126198A - Surface acoustic wave element matching circuit, spectrum diffusion demodulation circuit and its control method, and spectrum diffusion communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a demodulation signal of a proper integrated waveform by connecting a circuit element of variable inductance in series to the output comb-line electrode of a surface acoustic wave element and suppressing the variance of the delay value. SOLUTION: An example of a surface acoustic wave matched filter is shown in the diagram. A circuit element 3 of fixed inductance which resonates by the capacitance and carrier frequency of a signal input encoding electrode 5 is connected as a matching circuit of the electrode 5. A circuit element 1 of variable inductance is connected to an output comb-line electrode 6. In such a constitution, the variance of matching points caused by the variance of capacity of the electrode 6, the variance of accuracy of inductance, the variance due to the assembly, etc., can all be suppressed. Furthermore, the reactance component can be set at zero at the matching points. As a result, the reflection coefficient is reduced, and the output voltage is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matching circuit for a surface acoustic wave device, a spread spectrum demodulation circuit using the matching circuit, a method of adjusting the spread spectrum demodulation circuit, and a spread spectrum communication using the spread spectrum demodulation circuit. Related to the device.

[0002]

2. Description of the Related Art In recent years, a spread spectrum communication system which is resistant to noise and excellent in confidentiality and confidentiality has attracted attention as a communication system for consumer use. In the spread spectrum communication system, a carrier signal obtained by modulating information to be transmitted with a carrier signal is subjected to spread spectrum modulation with a predetermined code sequence having a predetermined high chip rate, so that a spread spectrum signal to be a transmission signal is obtained. can get. In this case, there are a pseudo-noise code sequence (PN code sequence) and a Barker code sequence as the above-mentioned code sequences, and a direct spread system (DS system) and a frequency hopping system as the spread spectrum modulation systems.

In such a spread spectrum communication system, a demodulation circuit for demodulating a transmitted spread spectrum signal is required on the receiver side. For example, PN
When spread spectrum modulation is performed by the DS method using a code sequence, the receiver performs demodulation using the same PN code sequence as the transmitter. The demodulation circuit used at this time is roughly classified into a demodulation circuit using an IC and a demodulation circuit using a surface acoustic wave element. A surface acoustic wave element used for a demodulation circuit has attracted attention because a photolithography technique can be used to form the demodulation circuit at a low cost and with a simple configuration.

[0004] The surface acoustic wave element is classified into a surface acoustic wave matched filter and a surface acoustic wave convolver according to its configuration. Since the surface acoustic wave convolver can select a PN code sequence for demodulation, it is particularly suitable for applications requiring secrecy or confidentiality. The surface acoustic wave matched filter has a fixed PN code sequence used for demodulation. However, the peripheral circuit can be simply configured and the system as a whole can be inexpensive. Attention has been paid to surface acoustic wave devices used for such applications.

Here, the spread spectrum modulation method is DS
FIG. 7 shows a demodulation circuit of a delay detection system using a conventional surface acoustic wave matched filter in the system. FIG. 7A is a block diagram showing a demodulation circuit corresponding to the two-phase modulation, and FIG. 7B is a circuit diagram showing a fixed inductance circuit element as a matching circuit. In FIG. 7A,
61 is a surface acoustic wave matched filter, 62 is a surface acoustic wave delay line having a delay amount of one cycle T of a signal to be received and demodulated, 63 is an output signal from the surface acoustic wave matched filter 61 and a surface acoustic wave delay line 62 Integration circuit for integrating
4, 65, 66 and 67 are matching circuits. Generally, as the matching circuits 64, 65, 66, and 67, circuit elements having a fixed inductance that resonate with the electrode capacitance of the electrodes and the carrier frequency are used as shown in FIG. 7B.

The operation of the demodulation circuit shown in FIG. 7A will be briefly described. The spread spectrum signal s input to the surface acoustic wave matched filter 61 is converted into a correlation signal by the surface acoustic wave matched filter 61 and then divided into two systems of correlation signals m and n. One correlation signal m is directly input to the integrating circuit 63. The other correlation signal n is input to the surface acoustic wave delay line 62, delayed by one cycle T, and then input to the integrating circuit 63. In the integrating circuit 63, the correlation signal m
And a correlation signal n delayed by one cycle T is obtained, and a demodulated signal is obtained. This is shown in FIG. FIG.
(G) is a data diagram for explaining data processing in the demodulation circuit of FIG. 7. Considering "1011101110" as the input data D1 as shown in FIG. 8A, first, the input data D1 is differentially encoded on the transmission side, and the transmission data D2 "110100101" as shown in FIG.
Next, the transmitting side performs two-phase modulation, and transmits "0" and "1" of the transmission data in correspondence with the phases "0" and "π". The correlation signal m from the matched filter 61 is as shown in FIG. 8C while maintaining the phase state on the transmission side, and the surface acoustic wave delay line 62
Is delayed by one period T, as shown in FIG. The integrating circuit 63 integrates the correlation signals m and n to obtain an integrated waveform S1 as shown in FIG. 8 (e). The input data is obtained by associating the + side with “1” and the − side with “0”. Can be demodulated.

In the delay detection system using such an integrating circuit, the amount of delay between the correlation signal m and the correlation signal n is very important. For example, the data transmission speed is 1 Mbps,
When 200 MHz is used as the carrier frequency, the correlation signal n needs to be delayed by 1 μs from the correlation signal m.

[0008]

However, in the delay detection system using such an integrating circuit, for example, the data transmission speed is 1 Mbps and the carrier frequency is 2 Mbps.
When 00 MHz is used, the correlation signal n needs to be delayed by 1 μs with respect to the correlation signal m. If the correlation signal n is shifted by 1.25 ns (１ ／ cycle of the carrier frequency) with respect to 1 μs, FIG. If the waveform is shifted by 2.5 ns (１ ／ cycle of the carrier frequency) as shown in the integrated waveform S2 shown in FIG. 8F, the waveform becomes completely opposite to the integrated waveform S3 shown in FIG. There was a problem that.

Here, the surface acoustic wave matched filter 61
A fixed inductance, which is a conventional matching circuit, is connected to the output electrode of the surface acoustic wave delay line 62 and the output electrode of the surface acoustic wave delay line 62, and the surface acoustic wave matched filter 61 and the surface acoustic wave delay line 62 at the matching point on the Smith chart are connected. FIG. 9 shows the relationship between the difference in reactance and the difference in delay amount. FIG. 9 is a graph showing the difference of the reactance on the horizontal axis and the shift of the delay amount on the vertical axis. It can be seen that the delay amount changes in proportion to the difference of the reactance. In each electrode, variations in reactance are caused by variations in capacitance components due to variations in the width of the comb-shaped electrodes, variations due to inductance accuracy, variations in inductance assembly status, and the like. The amount of delay will vary.

In particular, the accuracy of the fixed inductance is only ± 5% at the maximum in the range of 500 to 600 nH to be used, resulting in a variation of ± 25 to 30 nH. When converted to reactance, the variation becomes ± 31 to 37Ω, and the maximum becomes 62 to 74Ω, and the delay amount becomes 0.7 n
There is a problem that a shift of about s to 0.9 ns occurs, and a demodulated signal having a proper integrated waveform cannot be obtained as described above.

In the matching circuit for a surface acoustic wave device, a spread spectrum demodulation circuit using the same, a method of adjusting the spread spectrum demodulation circuit, and a spread spectrum communication apparatus using the spread spectrum demodulation circuit, a shift in delay amount is suppressed. To generate a demodulated signal having a proper integrated waveform.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems. A matching circuit for a surface acoustic wave element for generating a demodulated signal having an appropriate integrated waveform while suppressing a shift in the delay amount, and a shift circuit for the delay amount. A spread spectrum demodulation circuit capable of generating a demodulated signal of a proper integrated waveform by suppressing the spread spectrum demodulation circuit capable of generating a demodulated signal of a proper integrated waveform by suppressing a shift in the delay amount; It is another object of the present invention to provide a spread spectrum communication apparatus capable of generating a demodulated signal having an appropriate integrated waveform while suppressing a shift in a delay amount.

[0013]

SUMMARY OF THE INVENTION In order to solve this problem, a matching circuit for a surface acoustic wave device according to the present invention includes a variable inductance circuit device connected in series to an output electrode of the surface acoustic wave device. Configured.

Thus, a matching circuit for a surface acoustic wave element for generating a demodulated signal having an appropriate integrated waveform while suppressing a shift in the amount of delay can be obtained.

In order to solve this problem, a spread spectrum demodulation circuit according to the present invention comprises a surface acoustic wave matched filter, a surface acoustic wave delay line, an output signal of the surface acoustic wave matched filter, and an output of the surface acoustic wave delay line. An integrating circuit that integrates the signal, and a spread spectrum demodulation circuit that demodulates the signal using the signal, wherein the output electrode of a surface acoustic wave matched filter or the output electrode of a surface acoustic wave delay line or A matching circuit for a surface acoustic wave element, which is connected in series and includes a variable inductance circuit element or a variable inductance circuit element including an inductance value that resonates at the carrier frequency with the electrode capacitance of the output electrode, is provided.

As a result, a spread spectrum demodulation circuit that can generate a demodulated signal having an appropriate integrated waveform while suppressing a shift in the amount of delay can be obtained.

To solve this problem, a method for adjusting a spread spectrum demodulation circuit according to the present invention comprises a surface acoustic wave matched filter, a surface acoustic wave delay line, an output signal of the surface acoustic wave matched filter, and a surface acoustic wave delay line. And an integrating circuit for integrating the output signal of the output signal, a method of adjusting a spread spectrum demodulation circuit that demodulates the signal using the output signal of the output electrode of the surface acoustic wave matched filter or the output electrode of the surface acoustic wave delay line. A circuit element having a variable inductance is connected in series to one or the other, and the output signal of the integrating circuit is set so that the delay amount of the output signal of the surface acoustic wave delay line with respect to the output signal of the surface acoustic wave matched filter becomes a predetermined delay amount. It was configured to monitor and adjust the inductance of the circuit element.

As a result, a method of adjusting a spread spectrum demodulation circuit that can generate a demodulated signal having an appropriate integrated waveform while suppressing a shift in the amount of delay can be obtained.

A spread spectrum communication apparatus according to the present invention for solving this problem is configured to include the above spread spectrum demodulation circuit according to the present invention.

Thus, it is possible to obtain a spread spectrum communication apparatus capable of generating a demodulated signal having an appropriate integrated waveform while suppressing a shift in the amount of delay.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention comprises a variable inductance circuit element connected in series to an output electrode of a surface acoustic wave element. Also, it has the effect of suppressing variations in the accuracy of the inductance and variations in the matching points of the electrodes due to variations in the inductance due to the assembly.

According to a second aspect of the present invention, in the first aspect, the circuit element includes an inductance value which resonates at a carrier frequency and an electrode capacitance of the output electrode. , Variations in the accuracy of inductance, and variations in the matching points of the electrodes due to variations in inductance due to the assembly, and has the effect of reducing the reactance at the matching points to zero.

According to a third aspect of the present invention, there is provided an integrated circuit for integrating a surface acoustic wave matched filter, a surface acoustic wave delay line, an output signal of the surface acoustic wave matched filter, and an output signal of the surface acoustic wave delay line. And a spread spectrum demodulation circuit that demodulates a signal by using the output electrode of the surface acoustic wave matched filter or the output electrode of the surface acoustic wave delay line, or a serially connected to each of them, and a variable inductance. And a matching circuit for a surface acoustic wave element including a variable inductance circuit element including an inductance value that resonates at the carrier frequency with an electrode capacitance of the output electrode and an inductance value. Variations in electrode matching points due to variations in inductance due to Has the effect of Kiga is suppressed.

According to a fourth aspect of the present invention, there is provided a surface acoustic wave matched filter, a surface acoustic wave delay line, an integrating circuit for integrating an output signal of the surface acoustic wave matched filter and an output signal of the surface acoustic wave delay line. , A method of adjusting a spread spectrum demodulation circuit for demodulating a signal by using a circuit element having a variable inductance in one or each of an output electrode of a surface acoustic wave matched filter and an output electrode of a surface acoustic wave delay line. Are connected in series, and the output signal of the integrating circuit is monitored and the inductance of the circuit element is adjusted so that the delay amount of the output signal of the surface acoustic wave delay line with respect to the output signal of the surface acoustic wave matched filter becomes a predetermined delay amount. This has the effect that the variation in the amount of delay is easily suppressed.

According to a fifth aspect of the present invention, there is provided the spread spectrum demodulation circuit according to the third aspect, wherein variations in accuracy of inductance and variations in electrode matching points due to variations in inductance due to assembly are reduced. This has the effect of suppressing the variation of the delay amount.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 is a schematic plan view showing a matching circuit for a surface acoustic wave device according to Embodiment 1 of the present invention. FIG.
, 1 is a variable inductance circuit element, 2 is a surface acoustic wave element, 3 is a fixed inductance circuit element, 4
Is a piezoelectric substrate made of quartz, LiNbO _3, etc., and 5 is A
A signal input encoding electrode made of a metal having a small electric resistance such as 1 or Au; 6 is an output comb electrode made of a metal having a small electric resistance such as Al or Au; Is a sound absorbing material for absorbing unnecessary surface acoustic waves. In the present embodiment, an example of a surface acoustic wave matched filter has been described as a surface acoustic wave element. As the matching circuit for the signal input encoding electrode 5, the electrode capacitance of the signal input encoding electrode 5 and the fixed inductance circuit element 3 which resonates at the carrier frequency are connected as in the conventional matching circuit. The electrode 6 is connected to the circuit element 1 having a variable inductance. With such a configuration, it is possible to suppress variations in electrode capacitance of the output comb-shaped electrode 6, variations in accuracy of inductance, and variations in matching points due to variations in inductance due to assembly, and it is possible to make the matching points a certain point. (Matching is possible at a specific frequency).

In particular, by connecting a variable inductance circuit element including an electrode value of the output comb-shaped electrode 6 and an inductance value that resonates at a carrier frequency as the variable inductance circuit element 1 in series, variations in the electrode capacity, With all the variations in the accuracy of the inductance and the variations in the matching points due to the variations in the inductance due to the assembly, the reactance at the matching points can be reduced to zero, so the reflection coefficient can be reduced and the output voltage can be reduced. There is an effect that it can be increased.

It is needless to say that the same effect can be obtained by using a variable inductance circuit element as a matching circuit for the signal input encoding electrode 5.

As described above, according to the present embodiment, the variable inductance circuit element 1 is connected in series to the output comb electrode 6, so that the reactance at the matching point can be made zero. Thus, it is possible to generate a demodulated signal having an appropriate integrated waveform by suppressing the shift of the delay amount. Further, by using a variable inductance circuit element including an inductance value that resonates at the carrier frequency with the electrode capacitance of the output comb-shaped electrode 6 as the variable inductance circuit element 1, the reactance component at the matching point is reliably reduced to zero. Therefore, the reflection coefficient can be reduced, and the output voltage can be increased.

(Embodiment 2) FIG. 2 is a configuration diagram showing a spread spectrum demodulation circuit according to Embodiment 2 of the present invention. In FIG. 2, reference numeral 11 denotes a surface acoustic wave matched filter, 12 denotes a fixed inductance circuit element serving as a matching circuit for an input electrode of the surface acoustic wave matched filter 11, 1
Reference numeral 3 denotes a fixed inductance circuit element serving as a matching circuit for the output electrode of the surface acoustic wave matched filter 11, reference numeral 14 denotes a surface acoustic wave delay line, and reference numeral 15 denotes a fixed inductance serving as a matching circuit for the input electrode of the surface acoustic wave delay line 14. Circuit elements,
Reference numeral 16 denotes a circuit element having a variable inductance serving as a matching circuit for an output electrode of the surface acoustic wave delay line 14, reference numeral 17 denotes an amplifier,
8 is an integrating circuit, 21 is a piezoelectric substrate made of quartz, LiNbO ₃ or the like, 22 is a signal input encoding electrode made of a metal having a small electric resistance such as Al or Au, and 23 is a small electric resistance such as Al or Au. An output comb-shaped electrode made of a metal, 24 is an earth pattern made of a metal having a small electric resistance such as Al or Au, 25 is a sound absorbing material for absorbing unnecessary surface acoustic waves, 26 is a piezoelectric material made of quartz, LiNbO ₃ or the like. substrate,
27 is a signal input comb-shaped electrode made of a metal having a small electric resistance such as Al or Au, 28 is an output comb-shaped electrode made of a metal having a small electric resistance such as Al or Au, and 29 is a small comb-shaped electrode such as Al or Au. Metal ground pattern, 30
Is a sound absorbing material for absorbing unnecessary surface acoustic waves.

Next, the surface acoustic wave matched filter 11,
The configuration of the surface acoustic wave delay line 14 will be described. In FIG. 2, a piezoelectric substrate 21 made of quartz, LiNbO ₃ or the like is used.
A signal input encoding electrode 22 for converting an electric signal into a surface acoustic wave, and an output comb electrode 23 for converting a surface acoustic wave into an electric signal at a predetermined distance from the signal input encoding electrode 22 are provided on the upper side. A ground pattern 24 is provided around the input / output electrodes 22 and 23 for the purpose of reducing electromagnetic induction noise, and a sound absorbing material 25 is provided outside the input / output electrodes 22 and 23 for the purpose of absorbing unnecessary surface acoustic waves. Are formed, and the surface acoustic wave matched filter 11 is configured. At this time, when an n-bit PN code sequence is used as the code sequence, the signal input encoding electrode 22 has n comb electrode pairs corresponding to the PN code sequence, and each comb electrode pair corresponds to the chip rate. Formed at predetermined intervals. At this time, the number of electrode fingers of the comb-shaped electrode pair corresponding to each bit of the signal input encoding electrode 22 is set to a number larger than one pair and equal to or less than the ratio of carrier frequency to chip rate (carrier frequency / chip rate). You have set. In the case of the present embodiment, since the carrier frequency is 200 MHz and the chip rate is 11 MHz,
It becomes 2 or more and 18 or less. With such a configuration, the efficiency of converting an electric signal into a surface acoustic wave can be increased.

In FIG. 2, a signal input comb-shaped electrode 27 for converting an electric signal into a surface acoustic wave and a period T corresponding to one cycle of a signal to be received / demodulated are provided on a piezoelectric substrate 26 made of quartz, LiNbO ₃ or the like. An output comb electrode 28 for converting a surface acoustic wave into an electric signal is provided at an interval, and an earth pattern 29 is provided so as to reduce electromagnetic induction noise so as to surround the input / output electrodes 27 and 28. A sound absorbing material 30 is formed outside the output electrodes 27 and 28 for the purpose of absorbing unnecessary surface acoustic waves, and the surface acoustic wave delay line 14 is formed.

The operation of the demodulation circuit is the same as that of the conventional circuit shown in FIG. However, the present embodiment is different from the first embodiment in that a variable inductance circuit element 16 is used as a matching circuit for the output comb-shaped electrode 28 of the surface acoustic wave delay line 14. As described above, in the delay detection using the surface acoustic wave matched filter and the surface acoustic wave delay line, the amount of delay of the output signal of the surface acoustic wave delay line with respect to the output signal of the surface acoustic wave matched filter becomes very important. In the present embodiment, variations in the electrode capacitance of the output comb electrode 23 of the surface acoustic wave matched filter 11, variations in the electrode capacitance of the output comb electrode 28 of the surface acoustic wave delay line 14, and variations in the accuracy of the fixed inductance 13, The variation in the delay amount due to the variation in inductance due to the actual assembly and the variation in the delay amount due to the amplifier 17 are adjusted by adjusting the variable inductance circuit element 16 which is a matching circuit for the comb electrode 28 for output of the surface acoustic wave delay line 14. Therefore, an appropriate integrated waveform can be obtained.

As described above, according to the present embodiment, the variable inductance circuit element 16 is connected in series to the output comb-shaped electrode 28, so that the variation in the delay amount due to the variation in the electrode capacitance and inductance and the amplifier 17 can be suppressed, and a demodulated signal having an appropriate integrated waveform can be generated. Also, by using a variable inductance circuit element including an inductance value that resonates at the carrier frequency with the electrode capacity of the output comb-shaped electrode 28 as the variable inductance circuit element 16, the reactance at the matching point is reliably reduced to zero. Therefore, it is possible to generate a demodulated signal having an optimal integrated waveform by suppressing a shift in the delay amount.

(Embodiment 3) FIG. 3 is a block diagram showing a spread spectrum demodulation circuit according to Embodiment 3 of the present invention. In FIG. 3, reference numeral 31 denotes a composite surface acoustic wave element in which a surface acoustic wave matched filter and a surface acoustic wave delay line are integrated, 32 denotes a piezoelectric substrate made of quartz, LiNbO ₃ or the like, 33a and 33b denote Al, Signal input encoding electrodes 34a, 34b made of a metal having a small electric resistance such as Au;
Is a fixed inductance circuit element that becomes a matching circuit for the signal input encoding electrodes 33a and 33b, and 35a and 35b are A
Output electrodes of a surface acoustic wave matched filter made of a metal having a small electric resistance such as l, Au, etc., 36a and 36b are fixed inductance circuit elements which are matching circuits for the surface acoustic wave matched filter output electrodes, and 37a and 37b are Al and A
u, etc., output electrodes of a surface acoustic wave delay line made of a metal having a small electric resistance, 38a, 38b are circuit elements of variable inductance which are matching circuits for output electrodes of the surface acoustic wave delay line, 39 is Al, Au, etc. An earth pattern for reducing noise made of a metal having a small electric resistance, 40 is a sound absorbing material for absorbing unnecessary surface acoustic waves, 41a is an output signal of the output electrode 35a of the surface acoustic wave matched filter and a surface acoustic wave delay line. The integration circuit 41b integrates the output signal of the output electrode 37a with the output signal of the output electrode 35b of the surface acoustic wave matched filter and the output electrode 3 of the surface acoustic wave delay line.
7b is an integrating circuit for integrating the output signal of FIG.

Next, the pattern of FIG. 3 will be described.
On the piezoelectric substrate 32, the signal input encoding electrodes 33a, 33b for converting an electric signal into surface acoustic waves, and the surface acoustic waves are converted into electric signals at predetermined intervals from the signal input encoding electrodes 33a, 33b. Output electrodes 35a and 35b of a comb-shaped surface acoustic wave matched filter are provided to constitute a surface acoustic wave matched filter, and furthermore, a distance corresponding to a predetermined delay amount from the output electrodes 35a and 35b of the surface acoustic wave matched filter. Output electrodes 37a and 37b of a comb-shaped surface acoustic wave delay line for converting surface acoustic waves into electric signals at a distance
Are provided to form a surface acoustic wave delay line. At this time, when an n-bit PN code sequence is used as the code sequence, the signal input encoding electrodes 33a and 33b have n comb electrode pairs corresponding to the PN code sequence, and each comb electrode pair has a chip rate. Are formed at intervals corresponding to. Also, the input / output electrodes 33a, 33b, 35a, 35b, 37
Ground patterns 39 for reducing noise are formed around a and 37b. In the present embodiment, the ground pattern is inclined from the traveling direction of the surface acoustic wave so that the phases of the reflected waves by the ground pattern of the surface acoustic wave are not aligned. Further, the input / output electrodes 33a, 33b, 37a, 37
b, a sound absorbing material 4 for absorbing unnecessary surface acoustic waves
0 is formed as needed. In addition, the size of the element can be reduced by configuring each of the encoding electrodes and the ground-side terminals of the comb-shaped electrodes formed on the same substrate and the ground pattern provided as necessary as one common pattern.

In FIG. 3, when fc is the carrier frequency, the interval between the output electrodes 35a and 37a is (T + 1 /
8 / fc) and the interval between the output electrodes 35b and 37b is (T-1 / 8 / fc), whereby the spread spectrum demodulation circuit of the present embodiment can support the four-phase modulation method. Thus, a transmission rate twice as high as that of the two-phase modulation method described in the related art and the second embodiment can be obtained.

As in the second embodiment, in the present embodiment, variations in the electrode capacitance of the output electrodes 35a, 35b, 37a, 37b and the fixed inductance of the circuit elements 36a, 36
b, the variation in the amount of delay due to the variation in inductance due to the actual assembly.
By adjusting the variable inductance circuit elements 38a and 38b, which are the matching circuits a and 37b, this can be suppressed, and a proper integrated waveform can be obtained. Moreover,
In the case of the four-phase modulation method, the tolerance for the variation in the delay amount is smaller than that of the two-phase modulation method.
The effect of suppressing the variation in the delay amount becomes greater.

The signal input encoding electrodes 33a, 33
b, the number of electrode finger pairs of the comb-shaped electrode pair corresponding to each bit is 1
By making the number more than the pair and being equal to or less than the ratio of the carrier frequency and the chip rate to be used (carrier frequency / chip rate), an electric signal can be efficiently converted into a surface acoustic wave, and a highly efficient surface acoustic wave device can get.

Next, a method of adjusting the spread spectrum demodulation circuit in the configuration of the present embodiment will be described with reference to FIGS.
This will be described with reference to FIG. FIGS. 4A to 4J are data diagrams for explaining data processing in the demodulation circuit of FIG. Four-phase modulation is like two-phase modulation. "
0 "and" 1 "do not correspond to" 0 "and" π ", but" 00 "," 01 "," 1 "as shown in FIG.
0 "and" 11 "correspond to the four phase states A, B, C, and D. The input signal D1 is set to""as shown in FIG.
10011111100 ", because of four-phase modulation," 10 "," 01 "," 11 ",""as shown in FIG.
A signal D3 that is serially / parallel-converted to 11 ″, “00” (D2) and then differentially encoded and transmitted is shown in FIG.
“00”, “10”, “00”, “1” as shown in FIG.
On the transmitting side, the signal D3 is subjected to four-phase phase modulation and spread spectrum modulation, and transmitted.The output electrode 35a of the surface acoustic wave matched filter in the spread spectrum demodulation circuit on the receiving side is transmitted. , 3
The outputs S1a and S1b of 5b are as shown in FIG. 4E while maintaining the transmitted phase information of D3. At this time, the output S2a of the output electrode 37a of the surface acoustic wave delay line is delayed by (T + ／/ fc) for the output S1 of the output electrode 35a of the surface acoustic wave matched filter. Ideally, A'D'A'C'A 'as shown in FIG. The phase states A ', B', C ',
D ′ lags A, B, C, and D by 45 degrees (an angle corresponding to ８ / fc) as shown in FIG.
By inputting such outputs S1a and S2a to the integrating circuit 41a, it is possible to obtain an integrated waveform S3a as shown in FIG. 4 (g), where the plus side is "1" and the minus side is "0". Thus, S3a becomes "1011". In addition, the output S2b of the output electrode 37b of the surface acoustic wave delay line is different from the output S1b of the output electrode 35b of the surface acoustic wave matched filter by (T−
Ideally, it is delayed by 1/8 / fc) and becomes A "D" A "C" A "as shown in FIG.
The phase states A ", B", C ", D" at this time are shown in FIG.
45 degrees to A, B, C, and D (1/8
/ Fc) (the angle corresponding to / fc). Similarly, output S1
By inputting b and S2b to the integrating circuit 41b, FIG.
An integrated waveform S3b as shown in (i) can be obtained,
Like S3a, S3b becomes “0111”, and S3a,
A demodulated signal D4 "10011111" is obtained from the two signals of S3b as shown in FIG.

However, even if the delay amount is defined by the surface acoustic wave delay line as described above, the output electrodes 35a, 35b,
Variations in the amount of delay occur due to variations in the electrode capacitances of the 37a and 37b, variations in the accuracy of the fixed inductance circuit elements 36a and 36b, and variations in the inductance due to actual assembly. It fluctuates.

Referring to FIGS. 4E, 4H and 4I, ideally, the phase difference between the phase state A in FIG. 4E and the phase state D ″ in FIG. At 135 degrees, the phase difference between the phase state A in (e) and the phase state C "in (h) is +135 degrees, and both are positively integrated outputs of the same magnitude. However, if the delay amount varies for the reason described above, for example, if the delay amount increases, the phase difference between A and D "becomes smaller than -135 degrees, and the integrated output becomes smaller.
And C ″ becomes larger than +135 degrees and the integrated output becomes larger. The method of adjusting the spread spectrum demodulation circuit according to the present embodiment focuses on this point.
By selecting appropriate input data such as D ″ and A ″ and A ″ and C ″ having different phase differences to form the same integrated waveform on the + side, the inductance of the variable inductance circuit element can be monitored while monitoring the integrated waveform. By adjusting the value, it is possible to set an optimal delay amount.

FIGS. 5A to 5C are waveform diagrams showing integrated waveforms of the integrating circuit 41b. FIG. 5A shows an integrated waveform when a circuit element having a fixed inductance is used.
FIG. 5B shows an integrated waveform when the delay amount at the time of input to the integrating circuit is adjusted to be (T-1 / 8 / fc) by a variable inductance circuit element, and FIG. 5C shows the integrated waveform. The integrated waveform after adjusting the circuit element of the variable inductance so that the magnitudes of the integrated waveform on the + side and the integrated waveform on the-side are the same while monitoring. Variations in the magnitude of the integrated waveform can be suppressed by using a circuit element having a variable inductance. However, by monitoring the integrated waveform and adjusting the variable inductance as in the present embodiment, the integration circuits 41a, It is possible to obtain a proper integrated waveform by suppressing the variation of the delay amount due to the amplifier in 41b.

As described above, according to the present embodiment, the variation in the delay amount due to the variation in the electrode capacitance, the fixed inductance and the like is adjusted by adjusting the variable inductance circuit elements 38a and 38b which are the matching circuits of the output electrodes 37a and 37b. Thus, a demodulated signal having an appropriate integrated waveform can be obtained. In addition, in the case of the four-phase modulation method, the tolerance for the variation of the delay amount is two.
Since the phase difference is smaller than that in the phase phase modulation system, the effect of suppressing the variation in the amount of delay is greater. Further, since the variable inductance circuit elements 38a and 38b are adjusted and the variable inductance circuit elements 38a and 38b are adjusted by monitoring the integrated waveforms of the integration circuits 41a and 41b, the amplifiers in the integration circuits 41a and 41b are used. It is possible to obtain a demodulated signal having an appropriate integrated waveform by suppressing the variation in the delay amount.

(Embodiment 4) FIG. 6 is a block diagram showing a spread spectrum communication apparatus according to Embodiment 4 of the present invention. In FIG. 6, reference numeral 51 denotes a spread spectrum modulation unit for converting information to be transmitted into a spread spectrum signal by a predetermined code sequence, 52 denotes a transmission / reception frequency conversion unit for converting the frequency of a transmission / reception signal, and 53 denotes the second embodiment or A spread spectrum demodulation unit 54 equipped with a spread spectrum demodulation circuit 3 is an antenna for transmitting and receiving radio signals.

The operation of the spread spectrum communication apparatus configured as described above will be described. Spread spectrum modulation section 51 converts a carrier signal obtained by modulating information to be transmitted with a carrier signal into a spread spectrum signal using a predetermined code sequence. This spread spectrum signal is converted to the frequency of the radio signal by the transmission / reception frequency conversion section 52 and transmitted from the antenna 54. The radio signal received by the antenna 54 is frequency-converted by the transmission / reception frequency converter 52 and demodulated by the spread spectrum demodulator 53. The spread spectrum demodulation unit 53 has the demodulation circuit described in the second or third embodiment as described above, and performs the same demodulation operation as in the second or third embodiment.

As described above, in the spread spectrum communication apparatus of FIG. 6, since the spread spectrum demodulation circuit according to the second or third embodiment is used, the variation of the integrated waveform from the integrating circuit can be suppressed to a small value. Of the error rate can be suppressed. In the above description, the configuration of one transceiver using one frequency converter for transmission and reception has been described. However, the configuration is not limited to the circuit configuration. Alternatively, a configuration in which the transmitter and the receiver are separated may be used, and various types of spread spectrum communication apparatuses including the spread spectrum demodulation unit 53 having the spread spectrum demodulation circuit according to the second or third embodiment are possible.

As described above, according to the present embodiment, since the spread spectrum demodulation section 53 has the spread spectrum demodulation circuit of the second or third embodiment, the amount of delay due to variations in electrode capacitance, fixed inductance, etc. Can be suppressed by adjusting the circuit element having a variable inductance, and a demodulated signal having an appropriate integrated waveform can be obtained.

[0049]

As described above, according to the matching circuit for a surface acoustic wave device of the present invention, variations in electrode capacitance of the surface acoustic wave device, variations in accuracy of inductance, and variations in electrode matching points due to variations in inductance due to assembly. Since the variation can be suppressed, there is an advantageous effect that a demodulated signal having a proper integrated waveform can be obtained.

Further, since the circuit element includes an inductance value which resonates at the carrier frequency with the electrode capacitance of the output electrode, a variation in the electrode capacitance of the surface acoustic wave element, a variation in the accuracy of the inductance, and a variation in the inductance due to the assembly are caused. It is possible to obtain the advantageous effects that the variation of the matching points of the electrodes can be suppressed, the reactance at the matching points can be reduced to zero, the reflection coefficient can be reduced, and the output voltage can be increased.

Further, the output electrode of the surface acoustic wave matched filter and / or the output electrode of the surface acoustic wave delay line are connected in series to each other, and a circuit element having a variable inductance or an electrode capacitance of the output electrode and a carrier frequency. By providing a matching circuit for a surface acoustic wave element consisting of a circuit element with a variable inductance that includes an inductance value that resonates with the electrode, variations in electrode capacitance of the surface acoustic wave element, variations in accuracy of inductance, and variations in inductance due to assembly Since the variation of the matching point can be suppressed, it is possible to obtain a demodulated signal of an appropriate integrated waveform, or to reduce the reactance component of the matching point to zero,
An advantageous effect is obtained that a spread spectrum demodulation circuit capable of reducing the reflection coefficient and increasing the output voltage can be realized.

Further, a circuit element having a variable inductance is connected in series to one or each of the output electrode of the surface acoustic wave matched filter and the output electrode of the surface acoustic wave delay line, and the output signal of the surface acoustic wave delay line is connected. By monitoring the output signal of the integrating circuit and adjusting the inductance of the circuit element so that the delay amount with respect to the output signal of the surface acoustic wave matched filter becomes a predetermined delay amount, it is possible to easily adjust to a demodulated signal having an appropriate integrated waveform. The advantageous effect described above can be obtained.

Further, the output electrode of the surface acoustic wave matched filter and / or the output electrode of the surface acoustic wave delay line are connected in series to each other, and a circuit element of variable inductance or an electrode capacitance of the output electrode and a carrier frequency By having a spread spectrum demodulation circuit equipped with a matching circuit for a surface acoustic wave element comprising a variable inductance circuit element including an inductance value that resonates at An advantageous effect is obtained that a signal can be generated and a spread spectrum communication apparatus that can reduce an error rate can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing a matching circuit for a surface acoustic wave device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating a spread spectrum demodulation circuit according to a second embodiment of the present invention;

FIG. 3 is a configuration diagram showing a spread spectrum demodulation circuit according to a third embodiment of the present invention;

4A is a data diagram for explaining data processing in the demodulation circuit of FIG. 3; FIG. 4B is a data diagram for explaining data processing in the demodulation circuit of FIG. 3; (D) Data diagram for explaining data processing in the demodulation circuit of FIG. 3 (e) Data diagram for explaining data processing in the demodulation circuit of FIG. 3 (f) FIG. (G) Data diagram for explaining data processing in the demodulation circuit in FIG. 3 (h) Data diagram for explaining data processing in the demodulation circuit in FIG. 3 (i) 3) Data diagram for explaining data processing in the demodulation circuit in FIG. 3 (j) Data diagram for explaining data processing in the demodulation circuit in FIG.

5A is a waveform diagram showing an integrated waveform of the integrating circuit. FIG. 5B is a waveform diagram showing an integrated waveform of the integrating circuit. FIG. 5C is a waveform diagram showing an integrated waveform of the integrating circuit.

FIG. 6 is a block diagram showing a spread spectrum communication apparatus according to a fourth embodiment of the present invention.

FIG. 7A is a block diagram showing a demodulation circuit corresponding to a two-phase modulation method. FIG. 7B is a circuit diagram showing a fixed inductance circuit element as a matching circuit.

8A is a data diagram for explaining data processing in the demodulation circuit of FIG. 7; FIG. 8B is a data diagram for explaining data processing in the demodulation circuit of FIG. 7; (D) Data diagram for explaining data processing in the demodulation circuit in FIG. 7 (e) Data diagram for explaining data processing in the demodulation circuit in FIG. 7 (f) FIG. Data diagram for explaining data processing in demodulation circuit (g) Data diagram for explaining data processing in demodulation circuit in FIG.

FIG. 9 is a graph showing a difference in reactance on the horizontal axis and a shift in delay amount on the vertical axis.

[Explanation of symbols]

1, 16, 38a, 38b Variable inductance circuit element 2, 31 Surface acoustic wave element 11 Surface acoustic wave matched filter 14 Surface acoustic wave delay line 3, 12, 13, 15, 34a, 34b, 36a, 36
b Circuit element with fixed inductance 4, 21, 26, 32 Piezoelectric substrate 5, 22, 27, 33a, 33b Coding electrode for signal input 6, 23, 28 Comb electrode for output 35a, 35b, 37a, 37b Output electrode 7 , 24, 29, 39 Earth pattern 8, 25, 30, 40 Sound absorbing material 17 Amplifier 18, 41a, 41b Integration circuit 51 Spread spectrum modulation section 52 Transmission / reception frequency conversion section 53 Spread spectrum demodulation section 54 Antenna

Claims (5)

[Claims] 1. A matching circuit for a surface acoustic wave device comprising a variable inductance circuit device connected in series to an output electrode of the surface acoustic wave device. 2. The matching circuit for a surface acoustic wave device according to claim 1, wherein the circuit element includes an inductance value resonating at a carrier frequency with an electrode capacitance of the output electrode. 3. A signal using a surface acoustic wave matched filter, a surface acoustic wave delay line, and an integration circuit that integrates an output signal of the surface acoustic wave matched filter and an output signal of the surface acoustic wave delay line. A spread-spectrum demodulation circuit that performs demodulation, and is connected in series to one or each of the output electrode of the surface acoustic wave matched filter or the output electrode of the surface acoustic wave delay line, and a circuit element of variable inductance or A spread spectrum demodulation circuit comprising a matching circuit for a surface acoustic wave element including a circuit element having a variable inductance including an inductance value resonating at a carrier frequency with an electrode capacitance of the output electrode. 4. A signal using a surface acoustic wave matched filter, a surface acoustic wave delay line, and an integrating circuit that integrates an output signal of the surface acoustic wave matched filter and an output signal of the surface acoustic wave delay line. A method of adjusting a spread spectrum demodulation circuit that performs demodulation of: a circuit element having a variable inductance connected in series to one or each of an output electrode of the surface acoustic wave matched filter and an output electrode of the surface acoustic wave delay line. Monitor the output signal of the integrating circuit to adjust the inductance of the circuit element so that the delay amount of the output signal of the surface acoustic wave delay line with respect to the output signal of the surface acoustic wave matched filter becomes a predetermined delay amount. A method of adjusting a spread spectrum demodulation circuit. 5. A spread spectrum communication apparatus comprising the spread spectrum demodulation circuit according to claim 3.