JPH0570347B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an intermittent transmission system, and more particularly to an intermittent transmission system using a surface acoustic wave (SAW) device.

(Background Art) Time division multiple access (TDMA) using short burst waves is attracting attention as a digital wireless communication system. This method utilizes the intermittency between bursts, has high utilization efficiency, and allows for flexibility in system configuration.
Used in ALOHA systems, etc.

However, technical improvements were required in the secondary modulation of the transmitting system and the synchronization of the receiving system in the above system.

(Problems to be solved by the invention) In order to solve these problems, the present invention provides a comb-shaped transducer, that is, a comb-shaped electrode in which comb-like electrode fingers are alternately arranged interdigitally on one surface of a piezoelectric substrate. The purpose of this invention is to provide a new intermittent transmission method that can easily obtain phase modulation and synchronization by using surface acoustic wave (SAW) devices with

Hereinafter, the present invention will be explained in detail based on the drawings.

(Structure and operation of the invention) FIG. 1a is a block diagram showing the structure of a transmission system in an embodiment of the invention. In the same figure, 1
1 is a polarity separator which inputs a bipolar DC pulse A constituting digital information, separates the input signal according to the polarity of this DC pulse, and outputs a positive DC pulse B to a monostable multivibrator 12; A negative DC pulse C is output to the monostable multivibrator 13. 12 and 13 are monostable multivibrators. The monostable multivibrator 12 outputs two types of impulse signals D and E each time the positive DC pulse B output from the polarity separator 11 is input. Similarly, monostable multivibrator 13
outputs two types of impulse signals F and G each time the negative DC pulse C output from the polarity separator 11 is input. Reference numerals 14 and 15 denote SAW devices, which are transducers having three sets of interdigitated electrodes in which comb-like electrode fingers are alternately arranged interdigitally on one surface of a piezoelectric substrate. The SAW devices 14, 15 output a burst signal H or I by adding two impulse signals D, E or F, G. Further, 16 is a differential amplifier, which amplifies only the difference component between the signals from the SAW devices 14 and 15. The amplified burst signal J is transmitted via an antenna. The operation will be described later.

FIG. 1b is a circuit diagram of a transmission system in an embodiment of the present invention, and is a diagram specifically showing FIG. 1a. Although the diagram corresponds to the blocks of FIG. 1a, it goes without saying that the circuits and blocks shown in the diagram are not limited.

FIG. 2a is a block diagram showing the configuration of a receiving system in an embodiment of the present invention. In the same figure, 1
Reference numeral 7 denotes an amplifier that amplifies the received signal in order to drive the SAW device 21. A full-wave rectifier 18 performs full-wave rectification of the received signal.
A monostable multivibrator 19 outputs a single rectangular pulse every time the output signal of the full-wave rectifier 18 is input. This rectangular pulse is used as an impulse signal for synchronization. Full wave rectifier 18
Synchronous circuit 2 with monostable multivibrator 19
0 is configured. 21 is the SAW device, SAW
It has the same configuration as devices 8 and 9.
An amplifier 17 is installed in the two sets of interdigital transducers.
The output of the amplifier 17 and the output of the monostable multivibrator are respectively given, and burst signals of different levels are outputted depending on the phase of the burst signal which is the output signal of the amplifier 17. A detector 22 detects the output signal of the SAW device 21. The operation will be described later.

FIG. 2b is a circuit diagram of the amplifier 17 of FIG. 2a. FIG. 2c shows a synchronous circuit 20 consisting of the full-wave rectifier 18 and monostable multivibrator 19 shown in FIG. 2a.
FIG. Further, FIG. 2d is a circuit diagram of the detector 22 of FIG. 2a. FIGS. 2b to 2d are examples, and the present invention is not limited thereto.

FIG. 3 is a schematic diagram showing the structure of a SAW device in one embodiment of the present invention. In the same figure,
23 and 24 are input transducers, and 25 is an output transducer. The SAW device consists of the three sets described above, with an output interdigital transducer 25 provided in the center on the same surface of the piezoelectric substrate, and input interdigital transducers 23 and 2 sandwiching it from both sides.
4 is located. The comb-shaped electrode fingers of the input interdigital transducers 23 and 24 are symmetrical, and one of the electrodes of the three sets of interdigital transducers is grounded. Furthermore, the signals shown in the figure show the case where this SAW device is used in a transmission system, and by applying two impulse signals to the input interdigital transducers 24 and 25 as shown in the figure,
A burst wave as shown in the figure is obtained from the output interdigital transducer 25. Further, in this SAW device, when an impulse signal is applied to one of the two input interdigital transducers and a burst signal is applied to the other, the level of the resulting output signal changes depending on the phase of the burst signal. In the experiments described below, the SAW device used LiNbO ₃ with Z-axis cut and Y-axis propagation as the material of the piezoelectric substrate. In addition, the electrode period of the interdigital electrode is 170 μm, and the SAW
The number of electrode pairs of devices 14, 15, and 21 is 3,
The center frequency is 20MHz. The SAW device 21 also has a filter function.

Next, the operation of an embodiment of the present invention will be explained using FIG. 4, which shows signal waveforms corresponding to points A to P shown in FIGS. 1 and 2a. Note that the horizontal axis in FIG. 4 indicates time.

First, in the transmission system, the input signal has a signal waveform A
The positive and negative impulse signals are as follows. Signal waveform A
is separated into two signals according to the polarity via the polarity separator 11. A positive impulse signal has a signal waveform B, and a negative impulse signal has a signal waveform C. The signal waveform B is passed through the monostable multivibrator 12, so that a single square pulse (DC pulse) is divided into positive and negative polarities each time a trigger pulse of the signal waveform B is applied. The output signals of the monostable multivibrator 12 have signal waveforms D and E. Similarly, signal waveform C passes through monostable multivibrator 13 to output DC pulses like signal waveforms F and G. Signal waveforms D and E are input to two input transducers of the SAW device 14, and a burst signal like signal waveform H is outputted via the output transducer. Similarly, signal waveforms F and G are input to two input transducers of the SAW device 15, and a burst signal such as signal waveform I is outputted via the output transducer. The signal waveform H is input to the non-inverting terminal of the differential amplifier 16, and the signal waveform I is input to the inverting terminal of the differential amplifier 16 and amplified, and the differential amplifier 16 outputs a phase-modulated waveform J. , transmit.

In the receiving system, the signal waveform K transmitted from the transmitting system is input to an amplifier 17 and a full-wave rectifier 18. The signal waveform K is amplified via an amplifier 17,
The signal waveform becomes L. Further, the signal waveform K is full-wave rectified by the full-wave rectifier 18 to become a signal waveform M. This signal waveform M becomes a synchronizing impulse signal like signal waveform N via the monostable multivibrator 19. The burst signal of the signal waveform L and the synchronization impulse signal of the signal waveform N are input to the input transducer of the SAW device 21, respectively. The two signals are processed by the SAW device 21 to become a burst signal having a signal waveform O. Here, the rightmost waveform of the signal waveform O, that is, the burst signal corresponding to the negative impulse signal of the input signal in the transmission system, has an amplitude due to the rightmost waveform of the signal waveform L and the rightmost waveform of the signal waveform N canceling each other out. is a small waveform. The signal waveform O passes through the detector 22 and becomes a signal waveform P having a potential difference, which is a signal corresponding to the polarity of the input signal (signal waveform A) in the transmission system. Moreover, the input signal (signal waveform A) in the transmitting system and the detection output signal (signal waveform P) at the final stage of the receiving system are in a synchronized state.

FIGS. 5 and 6 show the results of an experiment of the present invention. The SAW device used in this experiment was the one described above, and the other parts used the circuit described above. Figure 5 shows the transmitted wave (signal waveform J) at the bottom.
and the impulse signal for synchronization (signal waveform N) on the upper side.
This waveform corresponds to the negative impulse signal of the input signal in the transmission system. Figure 6 shows the relationship between the positive and negative impulse signals (signal waveform A) of the input signal in the transmitting system on the upper side and the detection output signal (signal waveform P) at the final stage of the receiving system on the lower side. It is clear that the two signals are phase modulated and transmitted in a synchronized manner. Therefore, it is necessary for the demodulation of the phase modulated and demodulated waves to be synchronized, and as shown in the experimental results, the phase modulation is carried out in a synchronized state and is transmitted, and the modulation and demodulation are performed using a similar structure. Since this can be done in a device, the effects of transmission line conditions and differences in attenuation between the modulation and demodulation sides can be greatly reduced. In addition, when transmitting audio in the above experimental system, the transmission speed was 64Kbit/sec.
It was confirmed that it was possible to transmit data over 10 lines, and 5 lines for telephone lines.

(Effects of the Invention) As explained above, according to the present invention, a new SAW device having three sets of interdigital transducers in the transmitting system and receiving system is used to easily obtain synchronization and phase modulation. Can provide intermittent transmission method.

[Brief explanation of the drawing]

Figure 1a is a block diagram showing the configuration of a transmission system in an embodiment of the present invention, Figure 1b is a circuit diagram of a transmission system in an embodiment of the invention, and Figure 2a is an embodiment of the invention. Fig. 2b is a block diagram showing the configuration of the receiving system in Fig. 2a;
Figure c is a circuit diagram of the synchronous circuit of Figure 2a, Figure 2d is a circuit diagram of the detector of Figure 2a, and Figure 3 is a schematic diagram showing the structure of a SAW device in an embodiment of the present invention. FIG. 4 is a diagram showing signal waveforms corresponding to the points shown in FIGS. 1a and 2a, and FIGS. 5 and 6 are measurement diagrams of the signal waveforms. 11...Polar separator, 12,13,19...Monostable multivibrator, 14,15,21...SAW
Device, 16...Differential amplifier, 17...Amplifier, 1
8... Full-wave rectifier, 20... Synchronous circuit, 22... Detector, 23, 24... Interdigital transducer for input, 25... Interdigital transducer for output.

Claims (1)

[Claims] 1. In a digital wireless communication system for transmitting digital information, the transmission system includes three sets of interdigital transducers in which electrode fingers are interdigitally arranged in a comb shape on one surface of a piezoelectric substrate. It has two surface acoustic wave devices each having a transducer, and two sets of interdigital transducers of one surface acoustic wave device have two sets of interdigital transducers that receive two sets of transducers based on positive pulse signals among the DC pulse signals that constitute digital information. A burst signal corresponding to the positive pulse wave of the input signal is obtained from the remaining one set of interdigital transducers, and a burst signal corresponding to the positive pulse wave of the input signal is applied to the other two sets of interdigital transducers of the surface acoustic wave device. gives two types of impulse signals obtained based on the negative pulse signal of the DC pulse signal, obtains a burst signal corresponding to the negative pulse wave of the input signal from the remaining set of interdigital transducers, and Each burst signal is phase modulated by passing through a differential amplifier,
The output signal of the differential amplifier is transmitted to a receiving system, and the receiving system has one surface acoustic wave device having the same configuration as the surface acoustic wave device, and two sets of interdigital transformers of the surface acoustic wave device. The burst signal transmitted from the transmission system and a synchronization impulse signal obtained based on the burst signal are respectively applied to the transducer, and the remaining one set of interdigital transducers corresponds to the polarity of the input signal. An intermittent transmission method characterized by outputting changes in voltage.