JP2570293B2 - Ultrasound modulator / demodulator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modem for transmitting and receiving a phase-shift-modulated message signal of a pulse train.

(Prior Art) High-speed phase shift keying (PSK) digital data communication is becoming widely used in various fields, and the need to simplify the structure of modems communicating with PSK is required. Is also expensive.

However, the conventional phase shift keying modulator / demodulator individually has a circuit for performing signal processing such as signal filtering, phase comparison, and phase on the transmission side and the reception side in relation to the phase shift keying. .

(Problems to be Solved by the Invention) As described above, the conventional modulator and demodulator based on phase shift keying is
Since it is necessary to provide individual circuits for the various signal processings as described above, there has been a problem that the configuration of the apparatus becomes complicated.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a modem using ultrasonic phase shift keying that can simplify a signal processing circuit related to modulation and demodulation. The purpose is to:

(Means for Solving the Problems) The modem using ultrasonic phase shift keying according to the present invention switches the carrier signal according to the logical level of 0 or 1 of the message signal to the transmitting unit, thereby converting the carrier signal into the signal. An analog switch that outputs two output signals obtained by modulating with a message signal; and a piezoelectric plate that excites in a zero-order symmetric mode, wherein a phase delay of the two output signals propagating on the piezoelectric plate is provided. A first acoustic wave device for phase-shift-modulating the two output signals, and a carrier recovery circuit for generating a carrier signal synchronized with a carrier frequency on the transmitting side from the phase-shift-modulated received signal in a receiving unit And a piezoelectric plate that excites in a zero-order symmetric mode, wherein two of the received signal propagating on the piezoelectric plate and the carrier signal from the carrier recovery circuit are phase-discriminated A second elastic wave device that demodulates the two signals into a baseband signal; a detector that converts the two signals into a baseband signal; and a logical determination of 0 or 1 for the two baseband signals from the detector. And an encoder for outputting the message signal.

(Operation) According to the present invention, since the modem is configured as described above, the signal processing functions such as filtering, phase comparison, and phase shift of signals related to modulation and demodulation are respectively performed on the transmission side and the reception side. It is executed collectively on an elastic wave device in one-element format.

(Embodiment) FIG. 1 is a block diagram of a modem showing an embodiment of the present invention. First, a part functioning as a transmission unit will be described. The analog switch 1 inputs a message signal composed of a pulse train to the first input, and the number of cycles from the second input is 5.
Two output signals 1a or 1b obtained by switching a 6 MHz carrier signal according to the logic level of a message signal having a bit rate of 5 KB / s and modulating the carrier signal with the message signal.
Is a switch that outputs Signals 1a and 1b are Lamb wave devices 2
Is input to

The Lamb wave device 2, which will be described in detail below with reference to FIG. 2, has a so-called band filtering function, a two-phase shift keying (BPSK) function, a synchronization function for a carrier signal, and the like. It outputs a BPSK signal 2a which is transmodulated, that is, given a phase of 0 or 180 degrees according to the message signal.

FIG. 2 is a perspective view showing a schematic configuration of the Lamb wave device 2. As shown in FIG. 2, the Lamb wave device 2 has a piezoelectric ceramic substrate 3. The piezoelectric ceramic substrate 3 has a length of 10 mm, a width of 8 mm,
It is made of a piezoelectric ceramic having a thickness of 0.15 mm, is designed to be most efficiently excited in a zero-order symmetric mode, and is sold under the trade name NEPECH-94. On the piezoelectric ceramic substrate 3, four interdigital transducers (IDTs) 4, 5, 6 and 7 each having an IDT of 2.5 and a period length of 600 μm are formed.

The first electrode of IDT4 introduces signal 1a of analog switch 1 and the first electrode of IDT5 receives signal 1b of analog switch 1.
And the second electrodes of the IDTs 4 and 5 are grounded.

The IDTs 6 and 7 are based on the phases of the carrier waves propagating through the piezoelectric ceramic substrate 3 in order to obtain a function as a modulator.
They are spaced phi _o +0 °, the phi _o +180 ° distance from each. The first electrodes of the IDTs 6 and 7 are connected to each other to derive a PSK signal 2a obtained by performing phase shift modulation on the signals 1a and 1b. Out to the outside. The second electrodes of the IDTs 6 and 7 are grounded.

Next, with reference to FIG. 1 again, a portion functioning as a receiving unit will be described. The switch 8 is set at a position opposite to the position shown in the drawing at the time of reception, and the BPSK signal 8a inputted as a reception signal
To the signal carrier recovery circuit 9 and the Lamb wave device 10. The signal carrier recovery circuit 9 is a circuit that generates a carrier signal 9a synchronized with the input BPSK signal 8a. The Lamb wave device 10, which will be described in detail below with reference to FIG. 3, has the same structure and function as the Lamb wave device 2, and the input BP
This is a circuit that discriminates the BPSK signal 8a from the SK signal 8a and the carrier signal 9a according to the modulation phase and outputs signals 10a and 10b. The signals 10a and 10b are input to the detector 11.

The detector 11 converts the signals 10a and 10b into baseband signals 11a and 11b and inputs the signals to the encoder 12. Encoder 1
2 makes a logical decision on the signals 10a and 10b, reconstructs the original pulse train message signal 12a, and outputs it.

FIG. 3 is a perspective view showing a schematic configuration of the Lamb wave device 10. As shown in FIG. As shown in FIG. 3, the Lamb wave device 10 is a Lamb wave device 2.
And has a piezoelectric ceramic substrate 13. Four IDs with interdigital electrodes on piezoelectric ceramic substrate 13
T14, 15, 16, and 17 are formed.

The first electrodes of the IDTs 14 and 15 receive the BPSK signal 8a from the switch 8.
And the second electrodes of the IDTs 14 and 15 are grounded.

IDTs 16 and 17 are used to obtain a function as a demodulator.
ID based on the phase of the carrier wave propagating on the piezoelectric ceramic substrate 13
From each T14,15, φ _o +0 °, it is arranged at phi _o +180 degrees distance. The first electrodes of the IDTs 16 and 17 are connected to each other, and derive signals 10a and 10b that have undergone phase discrimination from the BPSK signal 8a. A carrier signal 9a is input to the second electrodes of the IDTs 16 and 17 from the signal carrier recovery circuit 9 for demodulation.

Next, the operation in the case of transmission will be described with reference to FIG.
This will be described with reference to the waveform diagram of FIG. A message signal to be transmitted (here, 0101) shown in FIG. 4A is input to the analog switch 1, and as shown in FIGS. 4B and 4C, a signal 1a corresponding to 0 of the message signal and a message signal Of 1
Is obtained. The IDTs 4 and 5 of the Lamb wave device 2 receive the signals 1a and 1b, and shift the phases corresponding to 0 ° and 180 ° of the carrier signal, that is, perform phase shift keying.
BPSK signal 2a shown in FIG. The BPSK signal 2a is guided to the outside via the switch 8.

This phase shift modulation can be described by the following equation: signals 1a.1b
Is represented by φ (b) = φ _o + πb (b = 0,1) (1). Therefore, the BPSK signal 2a is the signal 1a, 1b
Therefore, if b = 0,1, then s (t) = sin {2πft-φ (b)} = sin (π ｛2ft-b)｝ (2) Here, φ _o is a phase corresponding to four wavelengths of the carrier signal.

Next, the operation in the case of reception will be described with reference to FIG.
This will be described with reference to the waveform diagram of FIG. Of the message to be received
The BPSK signal 8a has a carrier frequency as shown in FIG.
5.6 MHz, the phase is 0 ° or 180 ° (b = 0.1), and is input to the Lamb wave device 10 via the switch 8. Signal 8a is applied to IDT14,15 on the piezoelectric ceramic substrate 3, the propagation delay phi _t to reach the IDT16,17 is, b, When p = 0, 1, represented by the following equation.

φ _t (b, p) = φ (b) + (p) = 2φ _o + π (b +
p) (3) The carrier signal 9a (= sin2) is transmitted to the IDTs 16 and 17 of the Lamb wave device 10.
πft), the signal 10 shown in FIGS.
a, 10b is s' (t) = sin ( 2πft-φ t) + sin (2πft) = 2cos (φ t / 2) sin (2πft-φ t / 2) = 2cos {φ o + π / 2 (b + p)} × sin {2πft−φ _o −π / 2 (b + p)} (4) In the above equation, the sin and cos terms correspond to the carrier signal 9a and the component and envelope components.

The detector 11 converts such signals 10a and 10b into baseband signals 11a and 11b as shown in FIGS. The encoder 12 outputs a signal 12a corresponding to the original message signal, as shown in FIG.

(Effects of the Invention) As described in detail above, according to the present invention, modulation and demodulation are performed using the Lamb wave device.
There is an effect that the configuration of the modulator / demodulator using the ultrasonic phase shift keying can be simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram of a modulator / demodulator using ultrasonic phase shift keying according to the present invention, FIGS. 2 and 3 are perspective views showing the structure of the Lamb wave apparatus of FIG. 1, and FIGS. FIG. 2 is a waveform chart for explaining the operation of the modem shown in FIG. 1. 1 ... Analog switch, 2,10 ... Lamb wave device, 4,5,6,7,14,15,16,17 ... IDT.

Claims (3)

(57) [Claims] 1. An ultrasonic phase shift keying modulator / demodulator comprising a transmitting unit and a receiving unit for transmitting and receiving a message signal of a pulse train by phase shift keying, wherein the transmitting unit has a logic value of 0 or 1 of the message signal. An analog switch that outputs two output signals obtained by modulating the carrier signal with the message signal by switching the carrier signal according to a level; and a piezoelectric plate that excites in a zero-order symmetric mode. Due to the phase delay of the two output signals propagating on the piezoelectric plate,
A first elastic wave device that performs phase shift modulation on the two output signals, wherein the receiving unit generates a carrier signal synchronized with a carrier frequency on the transmission side from the phase shift modulated received signal; A second elastic wave having a piezoelectric plate excited in a zero-order symmetric mode, and demodulated into two signals by phase discrimination from the received signal propagating on the piezoelectric plate and the carrier signal from the carrier recovery circuit; A detector for converting the two signals into a baseband signal; an encoder for performing a logical decision of 0 or 1 on the two baseband signals from the detector to output the message signal; A modulator / demodulator based on ultrasonic phase shift keying, comprising: 2. A first elastic wave device is formed on a piezoelectric plate, and applies first and second signals obtained by modulating the carrier signal with the message signal.
Interdigital transducers, and output third and fourth transducers formed on the piezoelectric plate and arranged at a distance from the first and second interdigital transducers respectively defined by a wavelength of a carrier signal. 2. The modulator / demodulator based on ultrasonic phase shift keying according to claim 1, further comprising an interdigital transducer. 3. The second acoustic wave device is formed on a piezoelectric plate, and receives first and second received signals.
A third interdigital transducer, arranged on the piezoelectric plate and at a distance from the first and second interdigital transducers respectively defined by the wavelength of the carrier signal, and having an electrode to which the carrier signal is applied. And a fourth interdigital transducer. 3. A modulator / demodulator based on ultrasonic phase shift keying according to claim 2, further comprising: