JP2006081052A - Transmitter, receiver, radio communication system, and radio communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication device that is small and thin and can transmit or receive radio waves of a plurality of frequency bands with a single transmitter or receiver.
A transmitter for solving the above-described problem is a transmitter including at least an oscillator that outputs a transmission signal and an antenna that emits a transmission signal from the oscillator as a radio wave. The oscillator is on a piezoelectric substrate. A SAW resonator having a pair of reflectors arranged in parallel with each other and a pair of IDTs composed of comb-like electrodes provided in parallel between the pair of reflectors; and a pair of SAW resonators arranged on the SAW resonator An amplifier connected in parallel with the IDT, and an output control unit that is provided on the output side of the SAW resonator and that performs amplitude modulation based on the input output control signal, enables communication at two frequencies in ASK communication. In addition, FSK communication is also possible. In addition, the receiver is configured to include an oscillator capable of outputting signals of two frequencies in the local oscillator.
[Selection] Figure 1

Description

  The present invention relates to a transmitter, a receiver, a wireless communication system using the transmitter and the receiver, and a wireless communication method, and more particularly, a transmitter, a receiver, and a wireless communication that define a plurality of communication frequency bands. The present invention relates to a system and a wireless communication method.

  In the conventional wireless communication device, the transmission frequency band and the reception frequency band are determined as one frequency band, and cannot be changed. Therefore, in a wireless communication device that defines two frequency bands, a transmitter that uses a high frequency band is a receiver that uses a high frequency band, and a transmitter that uses a low frequency band is a receiver that uses a low frequency band. You can only communicate with the machine. For this reason, in order to perform wireless communication, it is necessary to select a communication device that matches the frequency band between the transmission side and the reception side.

  In view of such circumstances, a wireless communication device as in Patent Document 1 has been proposed. A wireless communication device described in Patent Document 1 includes a band filter for receiving / transmitting a signal in a high frequency band and a band filter for receiving / transmitting a signal in a low frequency band, and transmits or receives a signal This is a wireless communication device configured to be able to switch a band-pass filter to be used according to the frequency.

According to the wireless communication device having such a configuration, the frequency band of the other party (communication device) can be switched according to the frequency band of the signal to be transmitted or received, and the use frequency band between the transmission side and the reception side is necessary. Accordingly, it is possible to switch between them, and it is possible to deal with signals in two frequency bands with one wireless communication device.
JP-A-6-132847

According to the wireless communication device described in Patent Document 1, it is possible to certainly carry out communication in two frequency bands with one wireless communication device.
However, in recent years, there is a strong tendency for communication devices to be reduced in size and thickness, and this tendency is particularly strong for portable wireless communication devices. On the other hand, the wireless communication device described in Patent Document 1 has a larger number of parts than the conventional wireless communication device by the amount of provision of band filters corresponding to a plurality of frequency bands and peripheral components. This means that it becomes larger than the conventional wireless communication device, which is contrary to the market trend. Of course, it is certain that the volume of the wireless communication device is greatly reduced as compared with the case of having a plurality of conventional wireless communication devices, but it is not desired that the communication device itself be enlarged.

  The present invention provides a transmitter and a receiver that can transmit or receive radio waves in a plurality of frequency bands with a single transmitter or receiver, and that are not different from conventional ones or that are smaller and thinner than conventional ones. And a wireless communication system including a transmitter and a receiver thereof, and a pair of communication devices (wireless communication systems) that can perform favorable communication while suppressing the influence of interference waves An object is to provide a communication method.

  First, in a transmitter, a high-frequency signal (carrier wave) output from an oscillator and a data signal input from a transmission data signal input terminal are modulated by a modulator using a predetermined modulation method to obtain a transmission signal.

  In the receiver, the received signal and the output signal from the local oscillator are mixed to obtain an intermediate frequency signal. Based on this, the low frequency signal is demodulated to obtain the data signal transmitted from the transmitter.

  For this reason, if a transmitter, an oscillator provided in a receiver, and a local oscillator can generate signals in a plurality of frequency bands, it is not necessary to provide a plurality of band filters and oscillators, and a small and thin transmitter, and It is considered that a receiver can be realized.

Therefore, a transmitter according to the present invention is a transmitter including at least an oscillator that outputs a transmission signal and an antenna that emits a transmission signal from the oscillator as a radio wave. The oscillator includes a pair of piezoelectric elements disposed on a piezoelectric substrate. A SAW resonator having a reflector and a pair of IDTs composed of comb-like electrodes provided in parallel between the pair of reflectors, and a pair of IDTs arranged in the SAW resonator are connected in parallel. An amplifier;
An output control unit that is provided on the output side of the SAW resonator and performs amplitude modulation based on an input output control signal, and a pair of comb-like electrodes that constitute one of the pair of IDTs And a pair of frequency switching circuits and the frequency switching circuit based on the input frequency selection signal or the output control signal are switched synchronously, and one of the pair of comb electrodes Is connected to the input side or output side of the amplifier, and the other of the pair of comb-like electrodes is connected to the output side or input side of the amplifier, and the output control unit and the frequency control unit And a modulation switching circuit for switching the input of the output control signal between them.

  According to the transmitter having the above configuration, the connection of the input / output signal to one IDT of the SAW resonator provided in the oscillator is fixed, and the connection of the input / output signal to the other IDT can be switched by the switching circuit. Thus, a plurality of (two) oscillation modes having different modes, for example, the S0 mode (same phase) and the A0 mode (antiphase) can be realized by one SAW resonator. For this reason, it becomes possible to produce a plurality of oscillations having different frequency bands with one SAW resonator. Since the frequency band can be switched by one SAW resonator, it is not necessary to tune the frequency accuracy or the frequency shift accuracy. For this reason, it becomes easy to adjust the frequency accuracy and the frequency shift accuracy, and both the frequency accuracy and the frequency shift accuracy can be kept good. In addition, by always oscillating any one of the pair of IDTs as an oscillating unit that performs oscillating as a reference, a reference oscillating unit can be provided in one oscillator. For this reason, even if the input / output signal is switched to the other IDT, the phase can be immediately matched to the oscillation of the one IDT, and the discontinuity of the output phase can be eliminated.

Furthermore, amplitude modulation (ASK: Amplitude Shift Keying) is performed by the output control unit, and frequency modulation (FSK: Frequency Shift Keying) is performed by the frequency control unit, so that only the switching of the communication frequency band causes interference waves ( When it is possible to avoid interference signals), energy saving communication is performed using the ASK communication method, and when it is difficult to avoid interference signals only by switching frequency bands, good (high quality) communication can be performed using the FSK communication method. It becomes.
In the transmitter configured as described above, the pair of IDTs disposed in the SAW resonator may be configured to have the same cross width of the comb-like electrodes.

  With the above configuration, it is possible to synchronize oscillations by mutual IDTs and improve frequency accuracy and frequency shift accuracy. This is because the IDT in the SAW resonator causes a slight change in the output frequency by changing its crossing width. For this reason, a desired frequency system can be realized by adjusting (controlling) the crossing width of the comb-like electrodes constituting the IDT.

  The receiver according to the present invention includes at least an antenna that receives a signal transmitted as a radio wave, a local oscillator that oscillates a signal in the apparatus, a signal that is received by the antenna, and a signal that is oscillated by the local oscillator And a detector for demodulating the intermediate-frequency signal into a low-frequency signal, the local oscillator is a pair arranged on a piezoelectric substrate. A SAW resonator having a pair of IDTs composed of comb-like electrodes provided in parallel between the pair of reflectors, and a pair of IDTs arranged in the SAW resonator are connected in parallel. The detector includes an amplitude modulation signal detector that demodulates an amplitude modulation signal and a frequency modulation signal detector that demodulates a frequency modulation signal, and the pair of IDTs Between each of the pair of comb-like electrodes constituting the IDT and the amplifier, a pair of frequency switching circuits and the frequency switching circuit are synchronized based on the input frequency selection signal. Switching, connecting one of the pair of comb-shaped electrodes to the input side or output side of the amplifier, and connecting the other of the pair of comb-shaped electrodes to the output side or input side of the amplifier; The both detectors include a detection switching circuit for switching a detector to be used, a signal for the amplitude modulation signal detector and the frequency modulation signal detector based on the input demodulation selection signal. And a demodulation control unit that switches the input / output paths of the first and second channels.

  According to the receiver having the above configuration, the connection of the input / output signal to one IDT of the SAW resonator provided in the local oscillator is fixed, and the connection of the input / output signal to the other IDT can be switched by the switching circuit. Thus, a plurality of oscillation modes having different modes, for example, the S0 mode (in-phase) and the A0 mode (antiphase) can be realized by one SAW resonator. For this reason, it becomes possible to oscillate signals in two frequency bands from one local oscillator, and it is possible to obtain two received signal frequencies that can be converted to the same intermediate frequency. Therefore, the receiver can receive signals of a plurality of frequency bands, but can be small and thin.

  In addition, since it is possible to switch the frequency band with one SAW resonator, it is not necessary to tune the frequency accuracy or the frequency shift accuracy. For this reason, it becomes easy to adjust the frequency accuracy and the frequency shift accuracy, and both the frequency accuracy and the frequency shift accuracy can be kept good. In addition, by always oscillating any one of the pair of IDTs as an oscillating unit that performs oscillating as a reference, a reference oscillating unit can be provided in one oscillator. For this reason, even if the input / output signal is switched to the other IDT, the phase can be immediately matched to the oscillation of the one IDT, and the discontinuity of the output phase can be eliminated.

  Further, as a detector (demodulator), a detector for demodulating the ASK communication signal and a detector for demodulating the FSK communication signal are provided, and both detectors can be switched and selected. Thus, when the interference wave (interference signal) can be avoided only by switching the communication frequency band, energy saving communication is performed by the ASK communication method, and when it is difficult to avoid the interference wave only by switching the frequency band, FSK. Good (high quality) communication can be performed by the communication method.

  In the receiver having the above-described configuration, a second mixer and a second local oscillator connected to the second mixer may be provided between the mixer and the detector. .

  With such a configuration, a receiver of a double superheterodyne system can be obtained, and communication with a wide reception frequency band in which a plurality of reception frequency settings can be performed is possible. In addition, since the local oscillator provided in the preceding stage can oscillate signals in a plurality of frequency bands, the width of the reception frequency band can be expanded as compared with a conventional double superheterodyne receiver. Furthermore, compared with a conventional receiver having an equivalent function, it is possible to realize a reduction in size and thickness.

  The second local oscillator includes a pair of reflectors disposed on a piezoelectric substrate, and a pair of IDTs formed of comb-like electrodes provided in parallel between the pair of reflectors. And an amplifier connected in parallel to a pair of IDTs disposed in the SAW resonator, each of the pair of comb-like electrodes constituting one IDT of the pair of IDTs, and the amplifier A pair of frequency switching circuits provided between the two and the frequency switching circuit are switched synchronously based on the input frequency selection signal, and one of the pair of comb-like electrodes is connected to the input side or the output side of the amplifier And it is good to set it as the structure which has a frequency control part which connects the other side of a pair of said comb-tooth shaped electrode to the output side or input side of the said amplifier.

With the receiver having such a configuration, the combination of the local oscillator, the second local oscillator, and the frequency band of the oscillation signal has four patterns, and the width of the reception frequency band can be further widened and stabilized. Communication is also possible.
Furthermore, in the receiver configured as described above, the pair of IDTs arranged in the SAW resonator may be configured to have the same cross width of the comb-like electrodes.

  With the above configuration, it is possible to synchronize oscillations by mutual IDTs and improve frequency accuracy and frequency shift accuracy. This is because the IDT in the SAW resonator causes a slight change in the output frequency by changing its crossing width. For this reason, a desired frequency system can be realized by adjusting (controlling) the crossing width of the comb-like electrodes constituting the IDT.

  In order to achieve the above object, a wireless communication system according to the present invention comprises a transmitter having the above configuration and a receiver having the above configuration. According to the wireless communication system including the transmitter and the receiver configured as described above, an optimal communication pattern can be selected according to the state of the interference signal with respect to the transmission signal.

  In addition, a wireless communication method according to the present invention for achieving the above object is to switch between a frequency band to be used, a modulation scheme in a transmitter, and a demodulation scheme in a receiver in a pair of transmitter and receiver, It is characterized by suppressing the influence of interference signals on communication signals.

  With the wireless communication method as described above, it is possible to select an optimal communication method according to the state of the interference wave (interference signal), and it is possible to realize good (good quality) wireless communication. The wireless communication method as described above can naturally be realized by the transmitter and the receiver described above, but the wireless communication device has the same functions as the receiver and the transmitter. Can also be implemented.

  Hereinafter, embodiments of a transmitter, a receiver, and a wireless communication method according to the present invention will be described with reference to the drawings. Note that the embodiments disclosed below are a part of the embodiments of the transmitter, the receiver, and the wireless communication method of the present invention, and the present invention includes various forms as long as the main part is not changed. To do.

  First, an embodiment according to the transmitter of the present invention will be described with reference to FIG. The transmitter 200 of the present embodiment includes an oscillator 50 that outputs a transmission signal, an output control signal input terminal 46a that inputs a data signal (output control signal) to be transmitted, and a transmission signal that is output from the oscillator 50 as a radio wave. The output antenna 52 has a basic configuration.

  First, the configuration of the oscillator 50 will be described with reference to FIG. The oscillator 50 used in the transmitter 200 of this embodiment is connected to the SAW resonator 10, an inverting amplifier (hereinafter referred to as an inverter) 20 as an amplifier circuit that transmits a signal to the SAW resonator 10, and the inverter 20. The oscillation circuit 50 a including the power supply terminal 42 is a basic configuration, and the SAW resonator 10 is provided in the positive feedback circuit of the inverter 20.

  As shown in FIG. 3, the SAW resonator 10 includes a piezoelectric substrate 12, a pair of reflectors 14a and 14b disposed on one main surface of the piezoelectric substrate 12, and the pair of reflectors 14 (14a and 14b). ) Between the plurality of comb-like electrodes 18 (18a, 18b, 18c, 18d).

The piezoelectric substrate 12 is made of a piezoelectric single crystal such as quartz, lithium tantalate (LiTaO ₃ ), lithium tetraborate (Li ₂ B ₄ O ₇ ), lithium niobate (LiNbO ₃ ), or a ZnO thin film. What is necessary is just to comprise with the provided sapphire substrate etc.

  The conductive pattern for forming the reflector 14 and the comb-like electrode 18 disposed on the piezoelectric substrate 12 is formed by forming a thin film of conductive metal such as gold, copper, or aluminum by vapor deposition or sputtering, and etching (eg, photo The pattern may be formed by a lithography technique.

  The reflector 14 disposed on the piezoelectric substrate 12 of the SAW resonator 10 as described above is a conductive pattern formed in a ladder shape, and the ladder is formed on the piezoelectric substrate 12 with respect to the propagation direction of the surface acoustic wave. The electrode portions 15 are arranged so as to be orthogonal to each other. A pair of reflectors 14 are disposed on the piezoelectric substrate 12. The arrangement of the pair of reflectors 14a and 14b on the piezoelectric substrate is made in a direction along the propagation direction of the surface acoustic wave.

  The comb-like electrode 18 constitutes one IDT (interdigital transducer) 16 by meshing two of the comb-like electrode on the signal input side and the comb-like electrode on the signal output side. .

  A pair of IDTs 16 are arranged in parallel on the piezoelectric substrate 12 between the reflectors 14a and 14b. Specifically, on the piezoelectric substrate 12, the direction in which the pair of reflectors 14 a and 14 b are arranged, and the direction along the propagation direction of the surface acoustic wave between the reflectors 14 a and 14 b is used as an axis. A pair of IDTs 16a and 16b are arranged line-symmetrically. When the IDT 16 is disposed, an insulating portion along the propagation direction of the surface acoustic wave is provided between the IDT 16a and the IDT 16b. By disposing the IDT as described above, the comb-shaped electrode portion of the comb-shaped electrode 18 is disposed so as to be orthogonal to the propagation direction of the surface acoustic wave.

  In the SAW resonator 10 having the above-described configuration, the signals input to the comb-shaped electrodes 18a to 18c constituting the IDTs 16a and 16b and the signals to be output are reversed so that the IDT 16a and the IDT 16b are identical. Oscillations in different modes such as phase and antiphase can be realized (S0 mode and A0 mode in this embodiment). For this reason, it is possible to produce vibrations in a plurality of frequency bands (two in this embodiment) by one SAW resonator 10. In addition, since the frequency band can be switched by one SAW resonator 10, it is not necessary to oscillate by tuning the frequency accuracy and frequency shift accuracy of the plurality of SAW resonators. For this reason, it becomes easy to adjust the frequency accuracy and the frequency shift accuracy, and both the frequency accuracy and the shift accuracy can be kept good.

  Further, by always oscillating any one IDT 16 of the pair of IDTs 16 (16a, 16b) as an oscillating unit that performs the reference oscillation, the reference oscillating unit is included in one SAW resonator 10. Will have. For this reason, even if the input / output signal of the other IDT 16 is switched, the phase can be immediately matched with one IDT 16 serving as the reference oscillation unit, and the output phase is not discontinuous.

  In the present embodiment, the S0 mode and the A0 mode refer to oscillation modes as shown in FIG. That is, the S0 mode is a line target mode that is a basic mode, and the A0 mode is a point-symmetric mode that is a higher-order mode.

The configuration of the oscillation circuit 50a on which the SAW resonator having the above configuration is mounted is as follows (see FIG. 2).
That is, the IDT 16 a and the IDT 16 b that constitute the SAW resonator 10 are connected in parallel to the inverter 20, and a frequency switching circuit (frequency switching means) 22 is provided between the IDT 16 b and the inverter 20. An input / output signal to the comb-like electrode 18 constituting the IDT 16 can be reversed. The frequency switching unit 22 is connected with a frequency control unit 44 that receives the frequency selection signal described above and switches the frequency switching units 22a and 22b in synchronization by inputting the frequency selection signal. The frequency control unit 44 includes a frequency selection signal input terminal 44a for inputting a frequency selection signal.

  Specifically, the configuration is as follows. When the comb-like electrode 18a of the IDT 16a is an input electrode and the comb-like electrode 18b is an output electrode, an input signal path 30 for inputting an input signal to the IDT 16a, which is an output signal from the inverter 20, is used as the comb-teeth. An output signal path 40 that is an input signal to the inverter 20 and outputs an output signal from the IDT 16a is connected to the comb-like electrode 18b.

  Further, the input signal path 30 and the output signal path 40 are branched to form an input signal path 30a and an output signal path 40a. In the input / output signal paths 30a and 40a, frequency switching means 22 (22a) that enables switching between α and β for selecting one of the two systems of the S0 mode signal transmission path and the A0 mode signal transmission path. 22b).

The S0 mode signal transmission path and the A0 mode signal transmission path that can be switched by the frequency switching means 22 are connected to the IDT 16b. In the IDT 16b, the output-side and input-side signal paths are respectively connected to both the comb-like electrode 18c and the comb-like electrode 18d. That is, when the input side S0 mode signal transmission path (input signal path) 32 when α is selected is connected to the comb-shaped electrode 18c, the output side S0 mode signal transmission path (output signal path) 36 when α is selected is a comb tooth. To the electrode 18d. In this case, the input side A0 mode signal transmission path (input signal path) 34 when β is selected is connected to the comb-shaped electrode 18d, and the output side A0 mode signal transmission path (output signal path) 38 when β is selected is a comb tooth. Connected to the electrode 18c.
With such a circuit configuration, it is possible to reverse the input / output of signals to / from the IDT 16b by switching between α and β by the frequency switching means 22.

  In the oscillation circuit 50a configured as described above, the IDT 16a to which the input / output signal paths 30 and 40 are connected always has the comb-like electrode 18a to which signals are input and the comb-like electrode 18b to which signals are output. Since it is connected, there is no change in the phase of the surface acoustic wave.

  On the other hand, in the IDT 16b to which the input / output signal paths 30a and 40a are connected, by switching the α / β of the input / output path by the control of the frequency switching means 22, the comb-like electrode on the input side and the output side The phase of the oscillating surface acoustic wave is shifted by 180 ° due to the reverse rotation of the comb-like electrode.

  For this reason, when the frequency switching means 22 is set to α, the comb-shaped electrode 18a and the comb-shaped electrode 18c serve as signal input-side electrodes, and surface acoustic waves oscillated by the IDT 16a and the IDT 16b are in phase. Thus, the oscillation of the S0 mode is performed as the oscillation circuit. On the other hand, when the frequency switching means 22 is set to β, the comb-teeth electrode 18a and the comb-teeth electrode 18d are electrodes on the signal input side, and the surface acoustic waves oscillated by the IDT 16a and the IDT 16b have opposite phases. As an oscillation circuit, A0 mode oscillation is performed.

  As described above, the SAW resonator having the above-described configuration can realize two modes of oscillation with one SAW resonator by controlling the input and output of signals to the comb-shaped electrodes 18a to 18d.

  In the oscillation circuit of the present embodiment, since the input / output of signals to the comb-shaped electrodes 18a, 18b constituting the IDT 16a of the SAW resonator is continuously performed, the signal input / output to / from the IDT 16b is reversed. Even in the case of switching (switching), there is no fear that the oscillation of the SAW resonator is momentarily interrupted, and there is no output phase shift caused by it. For this reason, it can be used for high-speed communication or the like.

  In general, it is known that a set of comb-like electrodes constituting a SAW resonator causes a change in oscillation frequency by changing the crossing width. Therefore, in the SAW resonator 10 mounted on the oscillator 50 having the above-described configuration, the cross width of each comb-like electrode 18 constituting the IDT 16 is adjusted (controlled) according to desired frequency accuracy. As a result, the frequency difference (frequency deviation) can be adjusted as shown in FIG. As can be seen from FIG. 5, the frequency difference can be adjusted to a practical level by setting the crossing width. Note that the crossing width of the comb-like electrode 18 between the IDT 16a and the IDT 16b is configured to be the same. Thereby, the oscillation of the mutual IDT can be tuned, and the oscillation in the S0 mode and the A0 mode is possible.

  In the oscillator according to the present embodiment, the output control unit 46 that performs modulation for ASK communication is provided on the output side of the oscillation circuit 50a described above. An output control signal input path for inputting transmission data (output control signal) is connected to the output control section 46, and an output control signal input terminal 46a is provided in the output signal input path (see FIG. 1). With such a configuration, the above-described oscillator 50 can output a transmission signal for ASK communication.

  The output control signal input path includes a path branched by a modulation switching circuit (modulation switching means) 48, and the branch path is connected to the frequency control unit 44 described above. For this reason, the frequency control unit 44 switches the connection of the frequency switching means 22a and 22b by an input signal from the frequency selection signal input terminal 44a or an input signal from the output control signal input terminal 46a. Therefore, when the connection of the frequency switching means 22a, 22b is switched by an input signal from the output control signal input terminal 46a, the output signal from the oscillation circuit 50a is a signal that is frequency-modulated according to the output control signal. Become. For this reason, the transmission signal output from the oscillator 50 is for FSK communication.

  The modulation switching means 48 is provided with a modulation switching terminal 48a, and when the modulation switching signal is input to the modulation switching terminal 48a, the input path of the output control signal is switched and the modulation format of the transmission signal is switched. To do. When the input path of the output control signal is connected to the frequency control unit 44, the signal input to the output control unit 46 is only the output signal from the oscillation circuit 50a. The output signal (in this case, the transmission signal for FSK communication) is output to the antenna 52 as it is.

In the transmitter 200 according to the present embodiment, two types of modulation can be performed by one transmitter, and thus the following effects can be obtained.
First, when performing ASK communication, power consumption during communication is small, which is suitable for long-time communication or communication with a long standby time. In addition, when performing FSK communication, it is possible to perform good (good quality) communication even when there are many interference waves.

  In the transmitter 200 configured as described above, when the signal transmission path is connected to the SAW resonator 10, the input / output signal paths 30 and 40 are connected to the IDT 16a, and the input / output signal paths 30a and 40a are connected to the IDT 16b. The input / output signal paths 30 and 40 may be connected to the IDT 16b, and the input / output signal paths 30a and 40a may be connected to the IDT 16a.

  A channel having a high frequency band as shown in FIG. 6 by adopting a configuration capable of switching the frequency band of radio waves to be transmitted (switching of channels) as required, like the transmitter 200 having the above configuration. Even in the case where an interference wave is applied to 1, the frequency band to be used can be switched to the channel 2 which is a low frequency band. For this reason, it is possible to perform communication by selecting a frequency band with less interference wave for communication. Therefore, it is possible to perform good communication even with ASK communication that is susceptible to interference. ASK communication is suitable for long-time wireless communication because power consumption can be suppressed compared to FSK communication.

  Also, even if the frequency band of the carrier used for communication in ASK communication is changed, if it is affected by an interference wave (interference signal), the modulation method is switched to perform FSK communication. Can be. In general, FSK communication is not easily affected by jamming waves, and high-quality communications can be performed even when there are many jamming waves.

  Next, a first embodiment according to the receiver of the present invention will be described with reference to FIG. The receiver 210 of this embodiment is a receiver for receiving a transmission signal from the transmitter 200 described above.

  The basic configuration of the receiver 210 of the present embodiment includes an antenna 72 for receiving a radio wave (transmission signal) transmitted from the transmitter, and a high-frequency signal in a frequency band different from the transmission signal is output inside the receiver. A local oscillator 70, a mixer 78 that mixes the received signal received by the antenna 72 and the output signal output by the local oscillator 70 to obtain an intermediate frequency signal, and the mixer 78 And a detector for demodulating the intermediate frequency signal output via the low frequency signal. That is, the basic configuration of the receiver 210 of the present invention can be said to be a general receiver that employs a super heterodyne system (Super Heterodyne System).

  The receiver 210 including such basic components is configured such that a mixer 78 is disposed between the antenna 72 and the local oscillator 70 and a detector is provided after the mixer 78.

  Between the antenna 72 and the mixer 78, a radio frequency filter (RF filter) 74 for obtaining a signal in a frequency band within a set range from the received high frequency signal, and the RF filter 74 are provided. A high-frequency amplifier (RF amplifier) 76 that amplifies the filtered high-frequency signal (received signal) is provided.

  As described above, the reception signal amplified by the RF amplifier 76 is mixed with the output signal from the local oscillator 70 by the mixer 78, converted into an intermediate frequency signal, and output to the detector side. Here, the intermediate frequency is a frequency difference between the frequency of the received signal and the frequency of the output signal from the local oscillator, and is also referred to as an internal frequency.

Between the mixer 78 and the detector, an intermediate frequency filter (IF filter) 80 for removing a signal other than a set frequency band from the intermediate frequency signal is filtered by the IF filter 80. And an intermediate frequency amplifier (IF amplifier) 82 for amplifying the intermediate frequency signal.
The detector demodulates the intermediate frequency signal output from the IF amplifier 82 into a low frequency signal and outputs the demodulated signal to the output terminal 92.

  Since the local oscillator 70 used in the receiver 210 of the present embodiment can switch and output signals in two frequency bands, the detailed configuration thereof is the oscillation circuit used in the transmitter 200 described above. It is substantially the same as 50a. In FIG. 7, the frequency controller and the frequency selection signal input terminal are omitted.

In order for the receiver 210 of this embodiment to receive all the transmission signals of the transmitter 200 described above, the receiver 210 must be configured to receive not only the ASK communication signal but also the FSK communication signal. Since the ASK communication signal and the FSK communication signal have different signal modulation schemes, the demodulation schemes are also different. For this reason, the receiver 210 of this embodiment is provided with a detector 84 for ASK communication and a detector 86 for FSK communication. The input signal path to each of the detectors 84 and 86, and the output signal Detection switching circuits (detection switching means) 90a and 90b are connected to the path. The detection switching means 90a, 90b is connected to a detection control unit 88 having a demodulation (detection) selection signal input terminal 88a. Based on the signal input to the demodulation selection signal input terminal 88a, detection is performed. The detection switching means 90a and 90b provided on the input side and the output side of the detectors 84 and 86 are configured to switch in synchronization.
The ASK detector 84 performs demodulation in a process of rectifying by a diode and smoothing (removing a carrier wave) by a capacitor.

  On the other hand, the FSK detector 86 has a more complicated configuration than the ASK detector 84 because the FSK communication signal is demodulated after being converted into an ASK communication signal. That is, two ASK signals are generated from the amplitude limiting unit 86a that removes noise components mixed in the transmission signal and the FSK signal that is an output signal from the amplitude limiting unit 86a, and the signal components included in the two ASK signals are synthesized. Thus, a frequency discriminating unit 86b that obtains an output signal and a deferresis circuit unit 86c for improving the SN ratio (signal-to-noise ratio) of the output signal from the frequency discriminating unit 86b. Since the data signal transmitted from the received signal by the FSK communication is demodulated with such a configuration, the communication quality of the FSK communication is higher than that of the ASK communication.

  As in the receiver 210 having the above-described configuration, the frequency band of the signal output from the local oscillator 70 can be switched (switching the channel) as necessary, so that it can be converted to the same intermediate frequency. The frequency of one received signal can be obtained. For this reason, it is possible to perform communication by selecting a frequency band with less interference wave for communication. Therefore, it is possible to perform good communication even with ASK communication that is susceptible to interference. ASK communication is suitable for long-time wireless communication because power consumption can be suppressed compared to FSK communication.

  Further, as described above, when the local oscillator 70 is switched and an interference wave is present even when the use frequency band is switched, the detector is switched from ASK to FSK. Therefore, it is possible to enable high-quality communication that is not easily affected by interference.

  Next, a second embodiment according to the receiver of the present invention will be described with reference to FIG. The receiver 210a of this embodiment has the same basic configuration as the receiver 210 according to the first embodiment. However, the receiver 210 according to the first embodiment employs a single superheterodyne system, whereas the receiver 210a according to the present embodiment employs a double superheterodyne system. Accordingly, the same components as those in the first embodiment are denoted by the same reference numerals and detailed description thereof is omitted.

  The receiver 210a of the present embodiment is configured to generate an intermediate frequency signal once more on the output side of the IF amplifier (referred to as the first IF amplifier in this embodiment) 82. More specifically, a high frequency signal received from the antenna 72 and a high frequency signal oscillated from a local oscillator (referred to as a first local oscillator in this embodiment) 70 are mixed by a mixer (referred to as a first mixer in this embodiment) 78. The intermediate frequency signal obtained in this embodiment (referred to as the primary intermediate frequency signal in this embodiment) is further mixed with a high frequency signal to obtain a secondary intermediate frequency signal, which is demodulated.

As a specific configuration of the receiver 210a, the second mixer 102 is provided at the subsequent stage of the first IF amplifier 82, and the output terminal of the second local oscillator 100 is connected to the second mixer 102. The output signals from both sides are mixed to output a secondary intermediate frequency signal. Further, a second IF filter 104 for filtering the secondary intermediate frequency signal and a second IF amplifier 106 for amplifying the filtered secondary intermediate frequency signal are provided at the subsequent stage of the second mixer 102. The detectors 84 and 86 are connected to the output side of the second IF amplifier 106.
Note that the second local oscillator 100 in the present embodiment may be a high frequency oscillator using a general SAW resonator or the like.

  With the receiver 210a having such a configuration, image interference (reception) can be eliminated, and stable communication can be performed while receiving signals in a wider frequency band.

Next, a third embodiment according to the receiver of the present invention will be described.
The receiver according to the present embodiment is almost the same as the structure of the receiver 210a according to the second embodiment, and the configuration of the second local oscillator 100 is the same as the configuration of the first local oscillator 70. The point is different.

  In the receiver according to the present embodiment having such a feature, since the combinations of signals for obtaining the secondary intermediate frequency signal are four patterns, the generated secondary intermediate frequency signals are also in four frequency bands. It will be possible to obtain. Therefore, the number of frequency bands that can be selected to avoid interference waves in communication increases. For this reason, even if the reception frequency band is expanded, stable communication is possible.

  According to the above-described wireless communication system including the transmitter and the receiver, the frequency band used for communication between the paired communication devices (transmitter or receiver), the modulation method in the transmitter, and the reception Wireless communication can be performed by switching the demodulation method in the machine. Therefore, since it becomes possible to perform communication while suppressing the influence of the interference signal on the communication signal, it is possible to realize high-quality communication according to each condition.

It is a block diagram which shows the structure of the transmitter of this invention. It is a block diagram which shows the structure of the oscillator with which the transmitter of this invention and a receiver are equipped. It is a block diagram which shows the structure of the SAW resonator in an oscillator. It is a figure which shows the oscillation mode of a SAW resonator. It is a figure which shows the change of the frequency difference at the time of changing the cross width of the comb-tooth shaped electrode of a SAW resonator. It is a figure which shows an example effective when switching a transmission radio wave. It is a block diagram which shows the structure of 1st Embodiment which concerns on the receiver of this invention. It is a block diagram which shows the structure of 2nd, 3rd embodiment which concerns on the receiver of this invention.

Explanation of symbols

  10 ... SAW resonator, 12 ... Piezoelectric substrate, 14 (14a, 14b) ... Reflector, 16 (16a, 16b) ... IDT, 18 (18a, 18b, 18c, 18d) ... ... Comb-shaped electrode, 20 ......... Inverter (inverting amplifier), 22 (22a, 22b) ......... Frequency switching means, 42 ......... Power supply terminal, 44 ......... Frequency control unit, 46 ......... Output control 48 ......... Modulation switching means (modulation switching circuit), 50 ......... oscillator, 52 ......... antenna, 70 ......... local oscillator, 72 ......... antenna, 78 ......... mixer (mixer), 84 ......... Detector (for ASK), 86 ......... Detector (for FSK), 90 (90a, 90b) ......... Detection switching means (detection switching circuit), 200 ......... Transmitter, 210, 210a ………Receiving machine.

Claims (8)

In a transmitter comprising at least an oscillator that outputs a transmission signal and an antenna that emits a transmission signal from the oscillator as a radio wave,
The oscillator includes a SAW resonator having a pair of reflectors disposed on a piezoelectric substrate, and a pair of IDTs formed of comb-like electrodes provided in parallel between the pair of reflectors;
An amplifier connected in parallel to a pair of IDTs disposed in the SAW resonator;
An output control unit that is provided on the output side of the SAW resonator and performs amplitude modulation based on an input output control signal;
Between each of the pair of comb-like electrodes constituting the IDT of one of the pair of IDTs and the amplifier, a pair of frequency switching circuits,
The frequency switching circuit is switched synchronously based on the input frequency selection signal or the output control signal, one of the pair of comb-like electrodes is connected to the input side or output side of the amplifier, and the pair of combs A frequency control unit for connecting the other of the toothed electrodes to the output side or the input side of the amplifier;
A modulation switching circuit for switching input of the output control signal between the output control unit and the frequency control unit;
A transmitter characterized by comprising:   2. The transmitter according to claim 1, wherein the pair of IDTs arranged in the SAW resonator have the same cross width of the comb-like electrodes. At least an antenna that receives a signal transmitted as a radio wave, a local oscillator that oscillates the signal in the aircraft, and a signal that is received by the antenna and a signal that is oscillated by the local oscillator are mixed into an intermediate frequency signal In a receiver comprising a mixer for conversion and a detector for demodulating the intermediate frequency signal into a low frequency signal,
The local oscillator includes a SAW resonator including a pair of reflectors disposed on a piezoelectric substrate, and a pair of IDTs including comb-like electrodes provided in parallel between the pair of reflectors, and the SAW resonance. An amplifier connected in parallel to a pair of IDTs arranged in the child,
The detector comprises an amplitude modulation signal detector that demodulates an amplitude modulation signal and a frequency modulation signal detector that demodulates a frequency modulation signal,
Between each of the pair of comb-like electrodes constituting the IDT of one of the pair of IDTs and the amplifier, a pair of frequency switching circuits,
The frequency switching circuit is switched synchronously based on the input frequency selection signal, one of the pair of comb-like electrodes is connected to the input side or the output side of the amplifier, and the other of the pair of comb-like electrodes is connected A frequency control unit connected to the output side or the input side of the amplifier,
In both the detectors, a detection switching circuit for switching the detector to be used, and
A demodulation control unit that switches an input / output path of a signal to the amplitude modulation signal detector and the frequency modulation signal detector based on the input demodulation selection signal;
A receiver comprising:   The reception according to claim 3, wherein a second mixer and a second local oscillator connected to the second mixer are provided between the mixer and the detector. Machine. The second local oscillator includes a SAW resonator having a pair of reflectors disposed on a piezoelectric substrate, and a pair of IDTs composed of comb-like electrodes provided in parallel between the pair of reflectors; An amplifier connected in parallel to a pair of IDTs disposed in the SAW resonator;
A pair of frequency switching circuits provided between each of the pair of comb-like electrodes constituting the IDT of one of the pair of IDTs and the amplifier;
Based on the input frequency selection signal, the switching circuit is switched synchronously, one of the pair of comb electrodes is connected to the input side or the output side of the amplifier, and the other of the pair of comb electrodes is connected to the input side. A frequency controller connected to the output side or input side of the amplifier;
The receiver according to claim 4, comprising:   The receiver according to any one of claims 3 to 5, wherein the pair of IDTs arranged in the SAW resonator have the same crossing width of the comb-like electrodes.   A wireless communication system comprising the transmitter according to claim 1 or 2 and the receiver according to any one of claims 3 to 6.   A radio communication method characterized in that, in a pair of transmitter and receiver, a frequency band to be used, a modulation scheme in the transmitter, and a demodulation scheme in the receiver are switched to suppress the influence of an interference signal on the communication signal. .

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