JP3346869B2 - SAW spread spectrum modulator / demodulator, communication apparatus and system using the same, and method of configuring SAW spread spectrum modulator / demodulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave (SAW).
The present invention relates to a SAW spread spectrum demodulator for demodulating a spread spectrum modulated signal using a matched filter, and more particularly to a SAW spread spectrum demodulator obtained by improving the spread spectrum modulated signal. The present invention further relates to a spread spectrum communication device configured using the SAW spread spectrum modulator / demodulator and a spread spectrum communication system configured using the spread spectrum communication device. The present invention also relates to a configuration method of the SAW spread spectrum modulator / demodulator of the present invention.

[0002]

2. Description of the Related Art A spread spectrum system is a radio communication system that has high signal confidentiality and is resistant to interference from other signal sources. Although several systems are known as spread spectrum systems, for example, in a direct modulation system, a transmission signal is phase-modulated by a code modulator mounted on a transmitter,
The received signal is demodulated by a code demodulator mounted on the receiver. The code used in the modulation / demodulation (spread spectrum modulation / demodulation) is called a pseudo-noise (PN) code, and the modulation of the code spreads the spectrum distribution of the transmission signal. Therefore, even if another party receives a transmission signal that has been subjected to spread spectrum modulation, the P
Demodulation cannot be performed without knowing the N code (signal confidentiality). Further, even if a radio signal in a close band is emitted from another signal source, the spectrum is spread and the interference is less likely to occur.

[0003] Of the characteristics of the spread spectrum system, confidentiality of a signal is particularly important in military related communication equipment in which concealment of information is important. Furthermore, in addition to the confidentiality, the characteristic of being resistant to interference is emphasized in various consumer devices. First, in recent years, the frequency of wireless systems has been increasing, and deterioration of received signal quality due to multipath interference has become a major problem. This problem can be mitigated or solved by a spread spectrum method that is strong against interference. Second, when trying to realize radio frequency sharing with another radio system in order to effectively use frequency resources, a spread spectrum method for spreading the spectrum of a transmission signal is effective.

In order to implement the spread spectrum method,
It is necessary to mount a code modulator (spread spectrum modulator) on the transmitter and a code demodulator (spread spectrum demodulator) on the receiver. Further, the modulation rate in the spread spectrum modulator must be higher than the transmission rate of the signal (data) to be transmitted. In addition, the demodulation rate of the receiver by the spread spectrum demodulator must be as high as the modulation rate of the transmitter. Since such high-speed processing is required, designers and the like are required to consider components related to spread spectrum modulation / demodulation more than components related to data modulation / demodulation.

Further, in a spread spectrum demodulator, it is necessary to obtain synchronization with a code used in a transmitter. As a method of acquiring synchronization, for example, there are a method of repeating demodulation until synchronization is achieved, and a method of performing synchronization acquisition and spread spectrum demodulation in parallel. However, these methods have a problem that time is required for acquiring synchronization and a problem that the configuration of a receiver is complicated.

As a spread spectrum demodulator that does not cause such a problem, there is a configuration using a SAW convolver. That is, the same code as the code used in the spread spectrum modulator is time-inverted and input to the SAW convolver, the correlation with the received signal is obtained, and the data is demodulated when the correlation value reaches a peak, Spread spectrum demodulation can be performed without causing the above-described problem. However, when such a configuration is used, a code obtained by time-inverting the code used in the spread spectrum modulator is required. Further, the efficiency of the SAW convolver is not so good, and the insertion loss is large.

As another configuration of the spread spectrum demodulator, there is a configuration using a SAW matched filter. That is, a filter (matched filter) having a complex conjugate frequency response with respect to the frequency spectrum of the spread spectrum modulated transmission signal is realized using the SAW delay line,
A received signal can be input to this filter to perform spread spectrum demodulation. When such a configuration is used, SA
There is no need for a time-reversed code like a W convolver,
Also, the insertion loss is relatively good.

[0008]

However, when performing spread spectrum demodulation using a SAW matched filter, this filter must be designed in accordance with the frequency spectrum of the spread spectrum modulated transmission signal. That is, the characteristics of the SAW matched filter must be designed according to the code used in the spread spectrum modulator.

The temperature characteristics of the SAW matched filter must be stable over the entire temperature range in which the system is used, and this stability must be absolutely obtained on the basis of the environmental temperature.

Further, when two-way communication is required as in a local area network (LAN) installed in an office, for example, when spread spectrum communication is to be performed between a server and a client, each device is spread spectrum. It is necessary to mount both the modulator and the spread spectrum demodulator, which results in an increase in the size and complexity of the device configuration, and a disadvantage in cost.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and firstly, a spread spectrum modulator mounted on a transmitter and a spread spectrum demodulator mounted on a receiver. It is an object of the present invention to make the characteristics of the spread spectrum demodulator easily compatible with the characteristics of the spread spectrum modulator. Second, a wider temperature range can be obtained by eliminating the need to absolutely secure the stability of the temperature characteristics on the basis of the environmental temperature and merely maintaining the stability based on the temperature difference (relative temperature) between the transmitter and the receiver. It is intended to be usable in. Third, by configuring the spread spectrum modulator and the spread spectrum demodulator as a single component, the spread spectrum modulator and the spread spectrum can be combined into a single device such as a system that performs two-way communication with spread spectrum. It is an object of the present invention to make it possible to reduce the size and weight of the device, even if the application requires a demodulator.

[0012]

In order to achieve the above object, a SAW spread spectrum modem according to the present invention comprises:
It has a piezoelectric substrate capable of transmitting SAW on its surface, an input electrode and an output electrode formed on the surface, and when a signal subjected to spread spectrum modulation is input to the input electrode, the signal is spread spectrum demodulated. A first SAW filter that outputs from the output electrode, and an input electrode and an output electrode that are formed on the surface, and when an impulse is input to the input electrode, this signal is spectrumd by the same sign as the first filter. The second output from the output electrode after diffusion modulation
A first SAW filter, and one of the input electrode and the output electrode of the first SAW filter and one of the input electrode and the output electrode of the second SAW filter are configured as a common electrode. The other of the input electrode and the output electrode of the SAW filter has a configuration in which the other of the input electrode and the output electrode of the first SAW filter is translated on the surface.

A SAW spread spectrum modulator / demodulator according to the present invention has a piezoelectric substrate capable of transmitting SAW on the surface thereof, and a SAW formed on the surface and responding to an input of an electric signal.
And transmitting the SAW in a predetermined direction on the piezoelectric substrate, while receiving a SAW from a direction opposite to the predetermined direction, converting the SAW into an electric signal and outputting the first electrode; A second electrode which is formed on the surface at a predetermined distance in the predetermined direction as viewed from the first electrode and receives a SAW transmitted by the first electrode, converts the SAW into an electric signal and outputs the electric signal; An electrode, and a third electrode formed on the surface at a predetermined distance in the opposite direction as viewed from the first electrode, generating a SAW in response to input of an electric signal, and transmitting the SAW to the first electrode. A first spread-spectrum-modulated signal is output from the second electrode or the first electrode when the spread-spectrum modulated signal is input to the first electrode or the second electrode. And second electrode pattern and second electrode pattern The interval is set, and the third electrode or the third electrode is configured to output a signal obtained by performing spread spectrum modulation on the impulse from the first electrode or the third electrode when the impulse is input to the third electrode or the first electrode. Is characterized by having substantially the same pattern as the second electrode.

When the spread spectrum communication apparatus according to the present invention is configured as a transmitter, the SAW spread spectrum modulator / demodulator according to the present invention and an impulse modulated by data to be transmitted are input to a third electrode or a first electrode. Means to
Means for transmitting and outputting a spread spectrum modulated signal output from the first electrode or the third electrode.

The spread spectrum communication apparatus of the present invention, when configured as a receiver, receives a SAW spread spectrum modulator / demodulator of the present invention, a signal carrying data and spread spectrum modulated, and a first electrode. Alternatively, it is characterized by comprising a means for inputting to the second electrode, and a means for reproducing data based on the spread spectrum demodulated signal output from the second electrode or the first electrode.

When the spread spectrum communication apparatus of the present invention is configured as a transceiver, the SAW spread spectrum modulator / demodulator of the present invention and an impulse modulated by data to be transmitted are input to a third electrode or a first electrode. Means for transmitting, transmitting and outputting a spread spectrum modulated signal output from the first electrode or the third electrode, and receiving a signal which carries data and is spread spectrum modulated, Means for inputting to the second electrode or the second electrode, and means for reproducing data based on the spread spectrum demodulated signal output from the second electrode or the first electrode.

A spread spectrum communication system according to the present invention comprises:
A spread spectrum communication apparatus according to the present invention for transmitting a spread spectrum modulated signal, and a spread spectrum communication apparatus for receiving a spread spectrum modulated signal according to the present invention.

The first configuration method of the SAW spread spectrum modulator / demodulator of the present invention excites the first electrode when the SAW transmitted from the first electrode is received by the second electrode. The pattern of the first electrode and the second electrode and the arrangement interval between them are determined so that the spread spectrum modulation applied to the obtained electric signal is demodulated and output as an electric signal from the second electrode. SAW transmitted from electrode
When the third electrode is received by the first electrode, a signal obtained by performing spread spectrum modulation on the electric signal that excites the third electrode is output from the first electrode as an electric signal. And an arrangement interval with respect to the first electrode is determined, and the first electrode is formed in a predetermined pattern on the surface of the piezoelectric substrate capable of transmitting SAW on the surface.
In each of the two directions in which the SAW transmitted from the first electrode propagates, the second electrode and the third electrode are spaced from the first electrode by a predetermined distance and in a predetermined pattern. By disposing, a spread spectrum modulator and a spread spectrum demodulator are formed on the surface of a single piezoelectric substrate, and an output electrode of the spread spectrum modulator and an input electrode of the spread spectrum demodulator are also used as a first electrode. It is characterized by having done.

The second configuration of the SAW spread spectrum modulator / demodulator according to the present invention is characterized in that, when the SAW transmitted from the first electrode is received by the second electrode, the electric power generated by exciting the first electrode is obtained. The pattern of the first electrode and the second electrode and the arrangement interval between them are determined so that the spread spectrum modulation applied to the signal is demodulated and output as an electric signal from the second electrode. The transmitted SAW is the third
When the signal is received by the first electrode, the third electrode pattern and the first electrode are output such that a signal obtained by performing spread spectrum modulation on the electric signal that excites the first electrode is output from the third electrode as an electric signal. When the first electrode is formed in a predetermined pattern on the surface of the piezoelectric substrate capable of transmitting the SAW on the surface, the SAW is transmitted from the first electrode. Is disposed in the two directions in which the second electrode and the third electrode are spaced from the first electrode by a predetermined arrangement interval and in a predetermined pattern, thereby forming a single piezoelectric substrate. A spread-spectrum modulator and a spread-spectrum demodulator are formed on the surface of the device, and an input electrode of the spread-spectrum modulator and an input electrode of the spread-spectrum demodulator are also configured as a first electrode. And it features.

A third configuration method of the SAW spread spectrum modulator / demodulator according to the present invention is characterized in that, when the SAW transmitted from the second electrode is received by the first electrode, the electric power generated by exciting the second electrode is obtained. The pattern of the first electrode and the second electrode and the arrangement interval between them are determined so that the spread spectrum modulation applied to the signal is demodulated and output as an electric signal from the first electrode. The transmitted SAW is the first
The third electrode pattern and the first electrode are output such that, when a signal is received by the first electrode, a signal obtained by performing spread spectrum modulation on the electric signal that excites the third electrode is output from the first electrode as an electric signal. When the first electrode is formed in a predetermined pattern on the surface of the piezoelectric substrate capable of transmitting the SAW on the surface, the SAW is transmitted from the first electrode. Is disposed in the two directions in which the second electrode and the third electrode are spaced from the first electrode by a predetermined arrangement interval and in a predetermined pattern, thereby forming a single piezoelectric substrate. A spread-spectrum modulator and a spread-spectrum demodulator on the surface of the device, and an output electrode of the spread-spectrum modulator and an output electrode of the spread-spectrum demodulator are also used as a first electrode. And it features.

According to a fourth configuration of the SAW spread spectrum modulator / demodulator of the present invention, when the SAW transmitted from the second electrode is received by the first electrode, the electric power generated by exciting the second electrode is obtained. The patterns of the first electrode and the second electrode and the arrangement interval between them are determined so that the spread spectrum modulation applied to the signal is demodulated and output as an electric signal from the first electrode. The transmitted SAW is the third
When the signal is received by the first electrode, the third electrode pattern and the first electrode are output such that a signal obtained by performing spread spectrum modulation on the electric signal that excites the first electrode is output from the third electrode as an electric signal. When the first electrode is formed in a predetermined pattern on the surface of the piezoelectric substrate capable of transmitting the SAW on the surface, the SAW is transmitted from the first electrode. Is disposed in the two directions in which the second electrode and the third electrode are spaced from the first electrode by a predetermined arrangement interval and in a predetermined pattern, thereby forming a single piezoelectric substrate. A spread-spectrum modulator and a spread-spectrum demodulator are configured on the surface of the device, and an input electrode of the spread-spectrum modulator and an output electrode of the spread-spectrum demodulator are also configured as a first electrode. And it features.

[0022]

In the SAW spread spectrum modulator / demodulator of the present invention, the first and second SAW filters are formed on a single piezoelectric substrate. The first SAW filter is a filter for spread spectrum demodulation (usually a matched filter), and the second SAW filter is a filter for spread spectrum modulation. That is, the first S
When a signal subjected to spread spectrum modulation (spread spectrum modulation signal) is input to the input electrode of the AW filter, a signal subjected to spread spectrum demodulation (spread spectrum demodulated signal) is output from the output electrode of this filter. When a spread spectrum demodulation signal is input to the input electrode of the second SAW filter, a spread spectrum modulation signal is output from the output electrode of this filter. The code related to the spread spectrum modulation performed by the second filter is the first code.
Is the same as the modulation code of the spread spectrum modulated signal demodulated by the filter.

In the present invention, one of the input electrode and the output electrode of the first SAW filter is connected to the second SAW filter.
One of the input electrode and the output electrode of the AW filter is configured as a common electrode. Here, an electrode configured as a common electrode is referred to as a first electrode, and the remaining two electrodes are referred to as a first electrode.
The electrodes constituting the first SAW filter and the electrodes constituting the second SAW filter among the types of electrodes are respectively referred to as second or third electrodes. In the present invention, the third electrode is configured as an electrode obtained by translating the second electrode on the surface of the piezoelectric substrate. As a result, the spread spectrum modulation function and the spread spectrum demodulation function can be formed compactly on a single piezoelectric substrate with the same characteristics, while also using a part of the structure.

As described above, in the present invention, a spread spectrum modulator and a spread spectrum demodulator are formed on a single piezoelectric substrate. Therefore, according to the spread spectrum communication apparatus equipped with the spread spectrum modulator / demodulator of the present invention, both the spread spectrum modulator and the spread spectrum demodulator must be mounted like a communication device for performing two-way communication with spread spectrum. The communication device becomes smaller and lighter.

Further, a case where both a spread spectrum modulator / demodulator mounted on a certain communication device (spread spectrum communication device) and a spread spectrum modulator / demodulator mounted on another spread spectrum communication device have the same configuration according to the present invention. However, since modulation and demodulation of the same principle and the same characteristics are performed in both of the spread spectrum communication devices, the design of determining the characteristics of the spread spectrum demodulator in consideration of the characteristics of the spread spectrum modulator has been conventionally used. The comparison does not have to be performed strictly.

In addition, since the modulation and demodulation of the same principle and the same characteristics are performed in any of a plurality of spread spectrum communication apparatuses that wirelessly communicate with each other, the temperature stability of the spread spectrum demodulator is absolutely determined based on the environmental temperature. There is no need to secure it. That is, the standard of the temperature stability of each spread spectrum communication apparatus may be determined for the difference between the operating temperatures. In general, the difference in operating temperature between communication devices in a communication system is smaller than the temperature range in which each communication device is used. Therefore, by using the present invention, the usable temperature range of a spread spectrum communication device is expanded.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

(1) Configuration of SAW spread spectrum modulator / demodulator FIG. 1 shows the configuration of a SAW spread spectrum modulator / demodulator 101 according to an embodiment of the present invention. The SAW spread spectrum modulator / demodulator 101 shown in FIG.
Has three types of electrodes 2 to 4 formed on the same surface.

Of these electrodes, the matched filter electrode 3 and the demodulation signal output electrode 4 constitute a SAW matched filter for demodulating a spread spectrum modulation signal. That is, when a signal is input to the electrode 3 via the terminal 6, the electrode 3 is excited by the signal, and a SAW is generated on the surface of the substrate 1. This SAW propagates rightward and leftward in FIG. The SAW propagating in the right direction is received by the electrode 4 and converted into an electric signal. Here, the electrode patterns of the electrodes 3 and 4 (for example, patterns such as electrode width, electrode pitch, and electrode length) and the electrode 3
Distance X ₀ of the electrode 4 and is such that the correlation between the signal and the electrode pattern has a peak when the spread spectrum modulated signals to the electrodes 3 (signal spread spectrum modulated is applied) is inputted, and is designed . Therefore, based on the signal output from the electrode 4 through the terminal 7 when the spread spectrum modulation signal is input to the electrode 3, the data carried by the spread spectrum modulation signal can be reproduced. Terminals 6 and 7 are therefore used as spread spectrum modulated signal input terminals or spread spectrum demodulated signal output terminals, respectively, when the device of this figure is mounted on a communication device.

The impulse input electrode 2 and the matched filter electrode 3 are configured as a SAW filter for generating a spread spectrum modulation signal. That is, when an impulse is input to the electrode 2 via the terminal 5, the impulse excites the electrode 2 and generates a SAW on the surface of the substrate 1. This SAW propagates rightward and leftward in FIG. The SAW propagating rightward is received by the electrode 3 and converted into an electric signal. Here, in addition to the electrode pattern of the electrode 3 being designed as described above, the electrode 2 has substantially the same electrode configuration (pattern) in which the electrode 4 is translated on the piezoelectric substrate 1. Therefore, when the impulse is input to the electrode 2, the signal output from the electrode 3 via the terminal 6 is the same code as the demodulation code of the matched filter composed of the electrodes 3 and 4, and the impulse is spread spectrum modulated. Signal. By inputting an impulse modulated by data as an impulse, a spread spectrum modulation signal carrying data is output from the terminal 6. Terminals 5 and 6 are therefore used as input terminals for an impulse modulated by data or output terminals for a spread spectrum modulation signal, respectively, when the device of this figure is mounted on a communication device.

The operation and effects As described above, according to this embodiment, since the matched filter is constituted by the electrode 3 and 4 of the three kinds of electrodes 2-4 formed on a single piezoelectric substrate 1, the spread spectrum The modulated signal can be demodulated by this filter.
Further, since the configuration of the electrode 2 is substantially the same as that of the electrode 4, by inputting an impulse to the electrode 2, it is possible to generate a spread spectrum modulation signal related to a code corresponding to the matched filter. That is, a spread spectrum modulator and a spread spectrum demodulator can be formed on a single piezoelectric substrate 1. In addition, the configuration is partially shared, so that the size and weight are reduced.

[0032] (2) spread spectrum communication apparatus configuration diagram 2, SAW spectrum modem 1 shown in FIG. 1
1 shows a configuration of a spread spectrum communication apparatus 201 configured by using No. 01. A spread spectrum communication apparatus 201 shown in this figure includes an impulse generator 102, a transmission / reception switch 10 in addition to a SAW spectrum modulator / demodulator 101.
3. Transmission mixer 104a, reception mixer 104b, local oscillator 105, high-frequency power amplifier 106, distributor 1
07, an antenna 108, a low noise amplifier 109, and a data regenerator 110.

The impulse generator 102 generates an impulse modulated by data to be transmitted,
The signal is input to the electrode 2 via the terminal 5 of the spectrum modulator / demodulator 101. The electrode 2 is excited by the impulse, and a SAW is generated on the surface of the piezoelectric substrate 1. The generated SAW is applied to the electrode 3 for a time T ₀ ′ = X ₀ ′ / v (where X
₀ ': interval between electrode 2 and electrode 3, v: propagation speed of SAW)
Received after the elapse. The electrode 3 converts the received SAW into an electric signal. The obtained signal is a signal obtained by performing spread spectrum modulation on the impulse. This spread spectrum modulated signal is input to the transmission / reception switch 103 via the terminal 6 and further input to the transmission mixer 104a. The transmission mixer 104a mixes a local oscillation signal generated by the local oscillator 105 and a spread spectrum modulation signal,
Convert to radio frequency (RF). High frequency power amplifier 1
06 power-amplifies the signal converted to RF, and
07 to the antenna 108. This allows
A signal carrying data and being spread spectrum modulated is transmitted wirelessly.

Conversely, when a spread spectrum modulated signal carrying data is received from another communication device, the signal is first supplied to a low noise amplifier 109 via a distributor 107, and the low noise amplifier 109 supplies a low noise amplifier. Is done. The low-noise amplified signal is supplied to the reception mixer 104b.
Is mixed with the local oscillation signal and converted from RF to an intermediate frequency (IF). The signal converted into the IF is input to the electrode 3 via the transmission / reception switch 103 and the terminal 6. The electrode 3 is excited by this signal, and a SAW is generated on the surface of the piezoelectric substrate 1. The generated SAW is received by the electrode 4 after a lapse of time T ₀ = X ₀ / v. Electrode 4
Converts the received SAW into an electric signal. When the code related to the spread spectrum modulation applied to the received signal matches the pattern of the electrodes 3 and 4, data can be reproduced based on the signal obtained from the electrode 4. This reproduction is performed by the data reproducer 110.

Operation and Effect Accordingly, by mounting the SAW spread spectrum modulator / demodulator 101 according to the present embodiment, the spread spectrum modem 201 for performing two-way communication with spread spectrum, such as a LAN in an office, can be made smaller and lighter. can do.

(3) Spread Spectrum Communication System FIG. 3 shows a spread spectrum communication apparatus 201 of FIG. 2 and a spread spectrum communication apparatus 201 having the same configuration.
And the configuration of the spread spectrum communication system having When the system is configured as shown in this diagram, the spread spectrum modulator / demodulator 101 mounted on each of the spread spectrum communication devices 201 and 201 'has the same principle,
Since it is possible to adopt a configuration relating to the same characteristic, modulation and demodulation with the same principle and the same characteristic can be performed by
01 and 201 '. At that time, electrode 2
Is substantially the same as the structure in which the fourth electrode is moved in parallel, so that it is not necessary to determine the characteristics of the spread spectrum demodulator in consideration of the characteristics of the spread spectrum modulator. Furthermore, since modulation and demodulation with the same principle and the same characteristics are performed in both of the spread spectrum communication apparatuses 201 and 201 ', it is not necessary to absolutely secure the temperature stability of the spread spectrum demodulator on the basis of the environmental temperature. In other words, the temperature characteristic may be stable with respect to the difference between the operating temperature of the spread spectrum communication apparatus 201 and the operating temperature of the spread spectrum communication apparatus 201 '. In general, when the operating temperature range of the spread spectrum communication devices 201 and 201 ′ is compared with the operating temperature difference between the two, the latter is smaller,
Thereby, spread spectrum communication apparatuses 201 and 201
The usable temperature range of 'expands.

(4) Configuration method of SAW spread spectrum modulator / demodulator Next, the SAW spread spectrum modulator / demodulator 1 shown in FIG.
01 will be described in more detail.

The construction method of the demodulation function First, the frequency spectrum of a spread spectrum modulated signal to be demodulated H (omega) (where, omega: angular frequency) and. The frequency response of a matched filter that performs spread spectrum demodulation of this signal is the complex conjugate H of the frequency spectrum H (ω).
^* (Ω). However, the frequency response H
^* (Ω) cannot be realized because it includes negative time. To avoid this, it is sufficient to provide a large delay T ₀ sufficiently as compared to the negative time. That is, a frequency response H ^* (ω) · exp (−jω) including a term exp (−jωT ₀ ) (where j is an imaginary unit) representing a delay.
T ₀ ), it can be realized. The SAW delay line using the SAW propagation delay on the piezoelectric substrate has a delay T
_This is effective in providing ₀ , and the SAW matched filter is configured using a SAW delay line. Specifically, the distance X ₀ of the two electrodes may be a value obtained by multiplying the SAW propagation velocity v in the delay T ₀ required.

In FIG. 1, such a matched filter is constituted by electrodes 3 and 4. First,
The frequency response of the electrode 3 for converting an electric signal to SAW is represented by S
_IN (ω), the frequency response of the electrode 4 for converting SAW to an electric signal is S _OUT (ω), and the interval between the electrode 3 and the electrode 4 is X _0.
= T ₀ · v, the frequency response S (ω) of the SAW filter constituted by the electrodes 3 and 4 can be expressed as follows.

[0040]

S (ω) = S _IN (ω) · S _OUT (ω) · exp (−jωT ₀ ) (1) In the present embodiment, the frequency response of the SAW filter constituted by the electrodes 3 and 4 S (ω) is the frequency response H ^* (ω) · exp (−jω) required for the matched filter.
The pattern of the electrodes 3 and 4 is designed to be T ₀ ). Therefore, in the present embodiment, equation (1) is modified as follows.

[0041]

[Number 2] _{^{H * (ω) = S IN}} (ω) · S OUT (ω) ... (2) That is, in the present embodiment, while dealing with negative time using the delay _{T 0,} the electrodes 3 and The frequency response S _IN (ω) and S _OUT (ω) determined by the pattern of FIG.
^* (Ω) is realized. It is common practice in a SAW spread spectrum demodulator to construct a matched filter and demodulate an original signal from a spread spectrum modulated signal in this way.

The most important feature of the present invention is the method of constructing the modulation function.
The point is that the spread spectrum modulation function is realized by adding an additional electrode on the piezoelectric substrate of the AW spread spectrum demodulator. In the embodiment, the impulse input electrode 2 is provided as an electrode for that purpose.

SAW Propagation Delay As described above, the SAW transmitted from the electrode 3 is received by the electrode 4. However, in general, SAWs propagate in two directions instead of one. Therefore, when an electric signal is input to the electrode 2 to excite the surface of the piezoelectric substrate 1, the generated SA
W propagates not only to the right but also to the left in FIG. The SAW propagating to the left is received by the electrode 2 in this embodiment. Assuming that the distance from the electrode 3 to the electrode 2 is X ₀ ′, the SAW propagating to the left in the drawing is
Is generated, the delay generated is T ₀ ′ = X ₀ ′ / v, and the frequency response representing this delay is exp (−jωT
₀ ').

SAW transmitted from electrode 3 to the left
The electrode 3 is configured to satisfy the expression (2). In other words, the response (impulse response) when an impulse is input to the electrode 3 is in the frequency domain.

S _IN (ω) = H ^* (ω) / S _OUT (ω) (3) In the time domain, its inverse Fourier transform s _IN (t) is obtained.
= S _IN (X / v). In addition, X is a position coordinate with the right direction in FIG. Therefore, when an impulse is input to the electrode 3, s _IN (X
/ V) = _sIN ^* (t) (where t: time) propagates, and _sIN ^{* in the} time domain in the left direction in FIG.
A SAW represented by (−X / v) = s _IN ^* (− t) propagates.

SAW transmitted from electrode 3 to the left
Furthermore, the general formula of the Fourier transform is

(Equation 4) Therefore, when an impulse is input to the electrode 3, FIG.
The frequency characteristic of the SAW propagating in the middle left direction is expressed as S _IN ^* (ω) as follows.

[0046]

(Equation 5) Therefore, the frequency characteristic of the SAW received by the electrode 2 from the electrode 3 is represented by the delay term exp (−jωT ₀ ) in S _IN ^* (ω).
′) Multiplied by the characteristic S _IN ^* (ω) exp (−jωT
₀ ').

The frequency response of the SAW filter composed of the electrodes 2 and 3 On the other hand, when the complex conjugate of both sides of the equation (3) is obtained,

S _IN ^* (ω) = H (ω) / S _OUT ^* (ω) (6) The frequency response of the SAW filter constituted by the electrodes 3 and 2 is, as in the case of the equation (1), as follows:

S ^* (ω) = S _IN ^* (ω) · S _OUT ^* (ω) · exp (−jωT ₀ ′) (7) By substituting equation (6) into this equation,

[Equation 8] ^{S * (ω) = {H} (ω) / S OUT * (ω)} · S OUT * (ω) · exp (-jωT 0 ') = H (ω) · exp (-jωT 0' ) (8)

This equation shows that when an impulse is input to the electrode 3, the frequency characteristic becomes H (ω) after the delay time T ₀ ′ has elapsed.
Is obtained from the electrode 2. S
Since the AW filter has the property that the same characteristic is obtained even if the input and output are switched, this equation is obtained by simultaneously inputting an impulse to the electrode 2 and changing the frequency characteristic to H after the delay time T ₀ ′. This shows that the electric signal of (ω) is obtained from the electrode 3. H (ω) is the frequency spectrum of the spread spectrum modulated signal that can be demodulated by the matched filter including the electrodes 3 and 4 as defined above. Therefore, in the embodiment of FIG.
An electrode having substantially the same configuration as that of the piezoelectric substrate 1 is moved in parallel along the surface of the piezoelectric substrate 1 to form an electrode 2, so that S
An AW spread spectrum modulator and a demodulator are obtained, and one of the electrodes constituting them is realized as the electrode 3.

(5) Others The characteristics of the filter composed of the electrodes 3 and 4 are as follows.
Neither the electrode 3 nor the electrode 4 is used as an input electrode. Similarly, the characteristics of the filter composed of the electrodes 2 and 3 are the same even if any of the electrodes 2 and 3 is used as the input electrode. Therefore, the configuration of the present invention is not limited to a configuration in which the electrodes 2 and 3 are used as input electrodes and the electrodes 3 and 4 are used as output electrodes.

[0050]

As described above, according to the present invention,
Of the three types of electrodes formed on a single piezoelectric substrate, a matched filter is formed by the first and second electrodes, and a signal subjected to spread spectrum modulation is demodulated by this filter. Since the configuration is substantially the same as that of the second electrode, the third electrode or the first
By inputting an impulse to each of the electrodes, it is possible to generate a signal subjected to spread spectrum modulation with a code corresponding to the above-mentioned matched filter, and the configuration is partially shared on a single piezoelectric substrate. And a spread spectrum demodulator.

Therefore, by mounting the SAW spread spectrum modulator / demodulator of the present invention, a spread spectrum modulator / demodulator for performing two-way communication with spread spectrum, such as a LAN in an office, can be made smaller and lighter.

Further, according to the present invention, since the SAW spread spectrum modulator / demodulator mounted on a plurality of spread spectrum communication apparatuses can have the same configuration according to the present invention, modulation / demodulation with the same principle and the same characteristics can be performed. This can be realized in each spread spectrum communication apparatus. That is, since the structure of the third electrode is substantially the same as the structure in which the second electrode is moved in parallel, it is not necessary to determine the characteristics of the spread spectrum demodulator in consideration of the characteristics of the spread spectrum modulator. become.

In addition, according to the present invention, modulation and demodulation with the same principle and the same characteristics are performed in any of a plurality of spread spectrum communication apparatuses that perform wireless communication with each other.
There is no need to absolutely secure the temperature stability of the W spread spectrum demodulator on the basis of the environmental temperature. Thereby, the usable temperature range of the spread spectrum communication device is widened.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a SAW spread spectrum modulator / demodulator according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a spread spectrum communication apparatus realized by applying this embodiment.

FIG. 3 is a block diagram showing a configuration of a spread spectrum communication system including the spread spectrum communication apparatus shown in FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Piezoelectric substrate 2 Impulse input electrode 3 Matched filter electrode 4 Demodulation signal output electrode 5 Impulse input terminal 6 Spread spectrum modulation signal output and spread spectrum modulation signal input terminal 7 Spread spectrum demodulation signal output terminal 101 SAW spread spectrum modulator / demodulator 102 Impulse generator 103 transmission / reception switch 104a transmission mixer 104b reception mixer 105 local oscillator 106 high frequency power amplifier 107 distributor 108 antenna 109 low noise amplifier 201, 201 'spread spectrum communication apparatus

────────────────────────────────────────────────── ─── Continued on the front page (58) Fields investigated (Int. Cl. ⁷ , DB name) H04J 13/00-13/06 H04B 1/69-1/713 H03H 9/42 H03H 9/72 JICST file ( JOIS)

Claims (10)

(57) [Claims] 1. A piezoelectric substrate having a surface capable of transmitting a surface acoustic wave, and an input electrode and an output electrode formed on the surface, wherein a signal subjected to spread spectrum modulation is input to the input electrode. A first SAW filter that spreads and demodulates a signal and outputs the signal from an output electrode; and an input electrode and an output electrode formed on the surface. When an impulse is input to the input electrode, the first SAW filter outputs the signal.
A second SAW filter that performs spread spectrum modulation using the same code as that of the first filter and outputs the same from an output electrode. One of the input electrode and the output electrode of the first SAW filter is input to the second SAW filter. The second SAW filter is configured as a common electrode with one of the electrode and the output electrode, and the other of the input electrode and the output electrode of the second SAW filter is in parallel with the other of the input electrode and the output electrode of the first SAW filter on the surface. A SAW spread spectrum modulator / demodulator having a shifted configuration. 2. A piezoelectric substrate capable of transmitting a surface acoustic wave on its surface; and a surface acoustic wave formed on the surface, in response to an input of an electric signal, and transmitting the surface acoustic wave in a predetermined direction on the piezoelectric substrate. A first electrode that converts a surface acoustic wave into an electric signal when receiving the surface acoustic wave from a direction opposite to the predetermined direction while outputting the wave, and the predetermined electrode as viewed from the first electrode on the surface. A second electrode formed at a predetermined distance in the direction and receiving the surface acoustic wave transmitted by the first electrode, converting the surface acoustic wave into an electric signal and outputting the electric signal; and a first electrode on the surface. A third electrode that is formed at a predetermined distance in the opposite direction as viewed from above, generates a surface acoustic wave in response to an input of an electric signal, and transmits the generated surface acoustic wave to the first electrode, and a spread spectrum modulated signal. Is input to the first electrode or the second electrode. In this case, the pattern of the first electrode and the second electrode and the interval between them are set so that a signal obtained by spread-spectrum demodulation of this signal is output from the second electrode or the first electrode. The third electrode is substantially the same as the second electrode so that a signal obtained by subjecting the impulse to spread-spectrum modulation is output from the first electrode or the third electrode when input to the third electrode or the first electrode. A SAW spread spectrum modulator / demodulator having the following pattern: 3. The SAW spread spectrum modulator / demodulator according to claim 2, further comprising:
Means for inputting to the first electrode or the first electrode, and means for transmitting and outputting the spread spectrum modulated signal output from the first electrode or the third electrode. apparatus. 4. A SAW spread spectrum modulator / demodulator according to claim 2, further comprising means for receiving a signal carrying data and being spread spectrum modulated, and inputting the received signal to a first electrode or a second electrode. Means for reproducing data on the basis of a signal subjected to spread spectrum demodulation output from the second electrode or the first electrode, and a means for reproducing data. 5. The spread spectrum communication apparatus according to claim 4, further comprising means for receiving a signal carrying data and being spread spectrum modulated and inputting the received signal to the first electrode or the second electrode. Means for reproducing data based on the spread spectrum demodulated signal output from the first electrode or the first electrode. 6. The spread spectrum communication apparatus according to claim 3 or 5, which transmits a spread spectrum modulated signal, and the spread spectrum communication apparatus according to claim 4 or 5, which receives a spread spectrum modulated signal. A spread spectrum communication system, comprising: 7. When the surface acoustic wave transmitted from the first electrode is received by the second electrode, the spread spectrum modulation applied to the electric signal that excites the first electrode is demodulated. The first electrode and the pattern of the second electrode and the interval between the two are determined so that the second electrode outputs an electric signal from the second electrode, and the surface acoustic wave transmitted from the third electrode is applied to the first electrode. And a third electrode pattern and a first electrode so that a signal obtained by performing spread spectrum modulation on an electric signal that excites the third electrode when the third electrode is received is output from the first electrode as an electric signal. When the first electrode is formed in a predetermined pattern on the surface of the piezoelectric substrate capable of transmitting the surface acoustic wave on the surface thereof, and the surface acoustic wave is transmitted from the first electrode, Two pieces that this surface acoustic wave propagates In each of the directions, the second electrode and the third electrode are arranged at a predetermined arrangement interval from the first electrode and in a predetermined pattern, so that the surface of the single piezoelectric substrate is spread. A SAW comprising a modulator and a spread spectrum demodulator, wherein an output electrode of the spread spectrum modulator and an input electrode of the spread spectrum demodulator are also used as a first electrode.
How to configure a spread spectrum modulator / demodulator. 8. When the surface acoustic wave transmitted from the first electrode is received by the second electrode, the spread spectrum modulation applied to the electric signal that excites the first electrode is demodulated. The first electrode and the pattern of the second electrode and the arrangement interval between them are determined so that the second electrode outputs an electric signal from the second electrode, and the surface acoustic wave transmitted from the first electrode is applied to the third electrode. And a third electrode pattern and a first electrode so that a signal obtained by performing spread spectrum modulation on an electric signal that excites the first electrode is output from the third electrode as an electric signal when received by the third electrode. When the first electrode is formed in a predetermined pattern on the surface of the piezoelectric substrate capable of transmitting the surface acoustic wave on the surface thereof, and the surface acoustic wave is transmitted from the first electrode, Two pieces that this surface acoustic wave propagates In each of the directions, the second electrode and the third electrode are arranged at a predetermined arrangement interval from the first electrode and in a predetermined pattern, so that the surface of the single piezoelectric substrate is spread. A SAW comprising a modulator and a spread spectrum demodulator, wherein an input electrode of the spread spectrum modulator and an input electrode of the spread spectrum demodulator are also used as a first electrode.
How to configure a spread spectrum modulator / demodulator. 9. When the surface acoustic wave transmitted from the second electrode is received by the first electrode, the spread spectrum modulation applied to the electric signal that excites the second electrode is demodulated. The pattern of the first electrode and the second electrode and the arrangement interval between the two are determined so that the first electrode outputs an electric signal from the first electrode, and the surface acoustic wave transmitted from the third electrode is applied to the first electrode. And a third electrode pattern and a first electrode so that a signal obtained by performing spread spectrum modulation on an electric signal that excites the third electrode when the third electrode is received is output from the first electrode as an electric signal. When the first electrode is formed in a predetermined pattern on the surface of the piezoelectric substrate capable of transmitting the surface acoustic wave on the surface thereof, and the surface acoustic wave is transmitted from the first electrode, Two pieces that this surface acoustic wave propagates In each of the directions, the second electrode and the third electrode are arranged at a predetermined arrangement interval from the first electrode and in a predetermined pattern, so that the surface of the single piezoelectric substrate is spread. A SAW comprising a modulator and a spread spectrum demodulator, wherein an output electrode of the spread spectrum modulator and an output electrode of the spread spectrum demodulator are also used as a first electrode.
How to configure a spread spectrum modulator / demodulator. 10. When a surface acoustic wave transmitted from a second electrode is received by a first electrode, spread spectrum modulation applied to an electric signal that excites the second electrode is demodulated. The first electrode and the pattern of the second electrode and the interval between them are determined so that the first electrode outputs an electric signal from the first electrode, and the surface acoustic wave transmitted from the first electrode is applied to the third electrode. And a third electrode pattern and a first electrode so that a signal obtained by performing spread spectrum modulation on an electric signal that excites the first electrode is output from the third electrode as an electric signal when received by the third electrode. When the first electrode is formed in a predetermined pattern on the surface of the piezoelectric substrate capable of transmitting the surface acoustic wave on the surface thereof, and the surface acoustic wave is transmitted from the first electrode, This surface acoustic wave propagates 2 By arranging the second electrode and the third electrode in a predetermined pattern at a distance from the first electrode and in a predetermined pattern in each of the three directions, the spectrum on the surface of the single piezoelectric substrate is obtained. A SAW comprising a spread modulator and a spread spectrum demodulator, wherein an input electrode of the spread spectrum modulator and an output electrode of the spread spectrum demodulator are also used as a first electrode.
How to configure a spread spectrum modulator / demodulator.