JPH0292133A - 4-phase psk modulator/demodulator - Google Patents

Abstract

PURPOSE:To execute the introduction to a 4-phase PSK modem system by constituting a Rayleigh wave device to possess a signal processing function such as a filter, a delaying circuit and a phase comparator. CONSTITUTION:At a transmission side, two pairs of input/output code fabric- shaped transducers of the device for modulation constitute four pairs of Rayleigh wave delaying lines in terms of the phase of a carrier and having a propagation distance different for pi/2[rad], and generate a 4-phase PSK signal accompanied by a phase delay. At a reception side, a reference phase carrier is impressed to a first code fabric-shape transducer group of the device for demodulation. To a second code fabric-shaped transducer group, the received 4-phase PSK signal is impressed, and a third code fabric-shaped transducer group synthesizes in phasewise respective surface acoustic waves to propagate while the phase delay from first and second code fabric-shaped transducer groups occurs. Further, by a coding means, only the maximum amplitude of the output signal of respective phases from the device for the demodulation is detected, waveform- shaped, and regenerated to a digital signal. Thus, the high degree and miniaturization of the function can be realized.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention uses surface acoustic waves (hereinafter abbreviated as SAW) to
tro-Mechanical (hereinafter abbreviated as EM)
The present invention relates to a 4-phase PSK modulation/demodulation device that can achieve higher functionality and smaller size than a purely electrical method by incorporating it into a functional component.

(Prior Art) SAW devices as EM functional components are also expected to be effective as signal processing devices in the field of digital communications.

Generally, a phase processing circuit in PSK modulation and demodulation is composed of a plurality of phase shifters, a phase detection circuit, and the like.

(Problems to be Solved by the Invention) Therefore, the present invention introduces a Rayleigh wave device into the processing circuit in order to realize a 4-phase PSK modulation/demodulation method (a communication method in which four phase information is carried and transmitted on a carrier wave). The purpose is to simplify and downsize the circuit configuration.

(Means for Solving the Problems) In order to achieve this object, the present invention modulates two carrier waves with equal frequencies and orthogonal phases into four phases on the transmitting side, and then carries a digital signal to be transmitted on this carrier wave. and transmit
4-phase PSK that demodulates and reproduces digital signals on the receiving side
In the modulation/demodulation system, the transmitting side consists of two sets of input/output interdigital transducers forming four sets of Rayleigh wave delay lines, each having a propagation distance that differs by π/2 [radl in terms of carrier wave phase. , 4-phase PSK with phase delay
A modulation device that generates a signal is provided, and on the receiving side, a first interdigital transducer group that applies a reference phase carrier wave corresponding to each of the four phases, and a received four-phase PSK signal is applied. a second group of interdigital transducers;
a demodulation device comprising a third interdigital transducer group that phase-combines each surface acoustic wave propagating with a phase delay from the first and second interdigital transducer groups; Encoding means was provided for detecting only the maximum amplitude of the output signal of each phase from the demodulation device, shaping the waveform, and reproducing it into a digital signal.

(Operation) According to the present invention having the above-described configuration, on the transmitting side, the two sets of input/output interdigital transducers of the modulation device have a carrier wave phase of π/2 [radl
Four sets of Rayleigh wave delay lines each having a different propagation distance are configured to generate a four-phase PSK signal with phase delay.

On the receiving side, a reference phase carrier wave is applied to a first group of interdigital transducers of a demodulating device. Then, the received 4-phase PSK is sent to the second interdigital transducer group.
A signal is applied, and the third interdigital transducer group phase-combines each surface acoustic wave propagating from the first and second interdigital transducer groups with a phase delay. Further, the encoder detects only the maximum amplitude of the output signal of each phase from the demodulation device, shapes the waveform, and reproduces the signal into a digital signal.

Therefore, the present invention can provide a 4-phase PSK modulation/demodulation device that can achieve the above-mentioned objects and can achieve both improved functionality and miniaturization.

(Example) Hereinafter, one embodiment of the present invention will be described based on the drawings.

First, the principle of modulation operation in the present invention will be explained based on the drawings together with experimental results.

FIG. 1 is a configuration diagram showing a SAW device for four-phase PSK modulation according to the present invention.

In the four-phase PSK modulation method, signals are transmitted in the form of carrying respective digital signals on two carrier waves having the same frequency and orthogonal phases.

5(bo, b+, t)=cos ((IJ Ct +b
oπ)+5in(ωct+b+x)...(1) The modulation device has a phase of π/2 [radl
It consists of four sets of Rayleigh wave delay lines, each having a different propagation distance, and these are used as phase shifters.

Two sets of input and output transducers (hereinafter referred to as ID
The separation distance φ(P) of the delay lines (abbreviated as T) is expressed in terms of phase, and is given by the following equation according to the group number p of the delay line.

φ(p)・φ. +pπ/2 (p・0.1.2.3)
...(2) Carrier wave 5(t) input to the demultiplexer in FIG. 1 = cos ωct ・
・ ・ (3) corresponds to the combination of binary message signals (ba, b+) input at TTL level.
applied to the input terminal of one of the delay lines of the set. The output S(p, t) from each device after passing through the delay line becomes a signal with a phase delay as shown in the following equation.

S (p, t) = cos (ωat-φ(p))(
p=O111213) (4) As a result, a four-phase PSK output signal of the form:

5=Th S(P, T)・cos (ω.−φ.−
pπ/2) (5) FIG. 2 is a configuration diagram showing a four-phase PSK Rayleigh wave device (for modulation) in this embodiment.

In the same figure, the substrate material is single crystal LiNb03 (128
°rot, Y-cut, X-propagation). Dimensions are 15x
On one surface of a 7×0.5 mm substrate, four pairs of interdigital electrodes each having an electrode period length (2p) of 80 μm and a number of electrode pairs of 9 are arranged so as to face each other.
ad] so that an acoustic phase delay occurs. φ in equation (2). corresponds to 12.5 wavelengths, and the center frequency of the modulation device is approximately 50 MHz. Figure 3 shows a data transmission rate of 0.1 Mbit/s,
FIG. 3 is a waveform diagram showing the observation results of the input and output waveforms of the device when the carrier frequency is 50 MI (z).

Next, the principle of demodulation operation in the present invention will be explained with reference to the drawings and experimental results.

FIG. 4 is a configuration diagram showing a SAW device for four-phase PSK demodulation according to the present invention, and FIG.
FIG. 2 is a configuration diagram showing an SK Rayleigh wave device (for demodulation). Unlike modulation, the demodulation device needs to apply a reference phase carrier wave as shown in both figures, and 3
It consists of a set of IDTs. When a QPSK signal is applied to the input IDT (left end of the piezoelectric substrate), the phase delay φ
(q) while propagating on the piezoelectric substrate, but this wave and the reference phase carrier wave (I at the right end of the piezoelectric substrate) for synchronous detection
The waves from the IDT at the center of the piezoelectric substrate
The output signal is taken out in a phase-synthesized form.

In this case, four signals d (P, Q) after synchronous detection are extracted from the output IDT.

T) is expressed by the following formula.

d(p, q, t)□cos((Ll at-φ(p)-
φ(Q) )+cosωct=2cos(φo+(
p+q)π/4)°cos(ωCt−φ0− (p+q
)π/4) (p, q・0.1.2.3) ...(6) The possible values of d(p, q, t) depend on the phase state φ(p) and the phase state given at the time of modulation. It is determined by the phase state φ(q) produced in the demodulating device. Equation (6) is two co
Although expressed in the form of a product of s terms, the former corresponds to an amplitude component and depends on the values of p and q.

FIG. 6 is a waveform diagram showing signal waveforms at each stage corresponding to the process of FIG. 4. As can be seen from FIG. 6(a), device outputs corresponding to p=Q to 3 and pulse outputs corresponding to the maximum amplitude are obtained in order from the bottom. In addition, since the maximum amplitude is obtained only for a specific phase state φ(p), in order to obtain a signal that turns on any one of the four signal lines, the necessary value "2" and other values are determined. An appropriate threshold value is determined to distinguish between the unnecessary value rOJ and "5 fingers", and only the maximum amplitude is detected by the peak value detector shown in FIG. After detection, the signal is waveform shaped and sent to TT.
It can be seen that the digital signal becomes an L level digital signal, the binary 2-bit original message signal (bo, b,) is reproduced through the encoder, and demodulation is completed. The actual observation results obtained at a data transmission rate of 0° IMbit/s and a carrier frequency of 50 MHz correspond well with the operating principle.

(Effects of the Invention) As explained above, according to the present invention, a Rayleigh wave device having signal processing functions such as a filter, a delay circuit, and a phase comparator is configured and introduced into a four-phase PsK modem system. be able to.

In addition, the circuit configuration can be made smaller, simpler, no adjustment is required, and can be applied to higher frequencies in the HF band, making it even more effective for introduction into existing communication means.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a SAW device for 4-phase PSK modulation according to the present invention, Fig. 2 is a block diagram showing a Rayleigh wave device (for modulation) for 4-phase PSK in this embodiment, and Fig. 3 is a block diagram showing a data transmission device. Speed 0.1Mbit/s, carrier frequency 50
A waveform diagram showing the observation results of input and output waveforms of the device at MHz, FIG. 4 is a configuration diagram showing the SAW device for 4-phase PSK demodulation according to the present invention, and FIG. 5 shows the 4-phase PSK demodulation SAW device in this embodiment
Block diagram showing K Rayleigh wave device (for demodulation), No. 6
The figure is a waveform diagram showing signal waveforms at each stage corresponding to the process of FIG. 4.

Claims (1)

[Claims] On the transmitting side, two carrier waves with equal frequencies and orthogonal phases are
In the 4-phase PSK modulation/demodulation method, in which a digital signal to be transmitted is modulated into a carrier wave and transmitted, and then demodulated on the receiving side to reproduce the digital signal, the transmitting side receives π in terms of the phase of the carrier wave. /2 [rad
] Consisting of two sets of input/output interdigital transducers constituting four sets of Rayleigh wave delay lines with different propagation distances, a modulation device that generates a four-phase PSK signal with phase delay is provided, and a modulation device is provided on the receiving side. , a first interdigital transducer group to which a reference phase carrier wave is applied, a second interdigital transducer group to which a received four-phase PSK signal is applied, corresponding to each of the four phases; a demodulation device comprising a third interdigital transducer group that phase-combines each surface acoustic wave propagating with a phase delay from the second interdigital transducer group; and each phase from the demodulation device. A four-phase PS characterized in that it is provided with encoding means for detecting only the maximum amplitude of the output signal, shaping the waveform, and reproducing the digital signal.
K modem.