JPH1013476A - Fsk transmitter receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a simple and inexpensive FSK(frequency shift keying) modulation transmitter by using a surface acoustic wave element equipped with a 1st input electrode which is excited at a frequency f0 , a 2nd input electrode which is excited at a frequency f1 , and a 3rd output electrode with a small number of couples of electrode fingers between those electrodes. SOLUTION: The 1st input-side inter-digital electrode 31 is provided at one end of a piezoelectric substrate 30, and a burst pulse signal of carrier frequency f0 is applied to its input terminal 34 to excite a surface acoustic wave on the piezoelectric substrate. On the other end of the piezoelectric substrate 30, the 2nd input-side inter- digital electrode 32 is provided and a burst pulse signal of carrier frequency f1 is applied to its input terminal 35 to excite a surface acoustic wave on the piezoelectric substrate. The 3rd output-side inter-digital electrode 33 is provided between the electrodes 31 and 32. The electrode 33 is made less in the number of couples of electrode fingers than the electrodes 31 and 32 to have broadband frequency characteristics, and outputs the frequencies f0 and f1 . Consequently, the simple FSK transmitter can be constituted and a spread of spectra due to a sudden shift in phase can be suppressed. A simple receiver can be constituted by replacing the input-side electrode and output- side electrode of the SAW element with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FSK (f
requency shift keying).

[0002]

BACKGROUND OF THE INVENTION FSK modulation, in a manner that frequency modulates a radio carrier by a pulse signal as is well known, for example, when the carrier frequency is f _0, "0" of the transmission signal is f _0,
“1” is transmitted using f ₁ whose frequency is shifted by Δf. FIG. 5 is a diagram schematically showing the configuration of a conventional FSK transmitter. In the figure, 1 is a signal input terminal, 4 is a high-frequency amplifier, 5 is a transmitting antenna, 41 is an oscillator, 42 is a keyer (frequency converter), 43 is a frequency multiplier.

Next, the operation will be described. The oscillation frequency input from the oscillator 41 to the keyer 42 is shifted according to either the binary signal “0” or “1” input from the signal input terminal 1, and the modulated signal is At 43, the signal is multiplied by carrier high frequencies f ₀ and f ₁ , amplified by a high frequency amplifier 4 and converted into an FSK signal by an antenna 5
Is output wirelessly.

[0004]

The conventional FSK transmitter is constructed and operated as described above. However, in the circuit construction, an oscillator 41 oscillating at an accurate frequency and a frequency multiplier for increasing the frequency up to a carrier high frequency are used. 43 is required, the number of parts is large, the configuration is complicated, and the cost is high. Further, in this method, the phase does not change continuously at the transition of the frequency, the spectrum of the occupied frequency in the communication band is widened, and it is disadvantageous in terms of required bandwidth such as affecting other adjacent channels. . Note that FSK
CPFSK (continuous ph
ASE FSK) and MSK (minimum shift keying) are also available, but there are problems such as a more complicated circuit configuration.

The present invention has been made in order to solve such a problem, and provides an FSK transceiver which does not require an accurate oscillator or frequency multiplier and can continuously change the phase to suppress the spread of the frequency. It is intended to be.

[0006]

An FSK transmitter according to the present invention includes an FSK (frequency shift keying) modulation circuit.
It is characterized in that a modulation / demodulation surface acoustic wave element is used.

Further, at least the above surface acoustic wave element comprises:
A first input interdigital transducer for exciting the carrier frequency f ₀ , a second input interdigital transducer for exciting the frequency f ₁ , the first input interdigital transducer and the second interdigital transducer; And an output interdigital transducer capable of inputting the excitation frequencies f ₀ and f ₁ and converting the electric signals into electric signals by reducing the number of electrode finger pairs to these input interdigital transducers. Features.

Accordingly, in the surface acoustic wave device having the above-mentioned electrode structure,
An FSK modulated signal is obtained, and a high-precision oscillator or frequency multiplier is not required, and the spread of the spectrum can be suppressed.

Further, the FSK receiver according to the present invention has a FS
The present invention is characterized in that a modulation and demodulation surface acoustic wave element is used in a K (frequency shift keying) demodulation circuit.

Further, the surface acoustic wave element having the above-mentioned electrode configuration has at least an input-side interdigital electrode capable of exciting the carrier frequency f ₀ and the frequency f ₁ by making the number of electrode fingers smaller than that of the output-side interdigital electrode. , provided on both sides of the input-side interdigital electrode, a first output-side interdigital transducer for converting an electrical signal to input excitation frequency f _0, the excitation frequency f ₁
And a second output-side interdigital transducer for converting the input into an electric signal.

Therefore, a demodulation circuit can be constituted by using the same surface acoustic wave element as that of the above-mentioned FSK transmitter.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining an embodiment of an FSK transmitter according to the present invention.
1 is a signal input terminal, 2 is a coder, 3 is a surface acoustic wave element (hereinafter, referred to as a SAW element), 4 is a high frequency amplifier, and 5 is a transmitting antenna.

FIG. 2 is a diagram showing an example of the configuration of the SAW element 3. In the figure, reference numeral 30 denotes a piezoelectric substrate, 31 denotes a first input-side interdigital electrode, and an input terminal 34 has an impulse signal (burst pulse). ) Is applied to excite a surface acoustic wave having a center frequency f ₀ on the piezoelectric substrate. 32
In the second input-side interdigital transducer, the impulse signal to an input terminal 35 (burst pulse) is a surface acoustic wave of the center frequency f ₁ on a piezoelectric base is excited by being applied. Reference numeral 33 denotes an output-side interdigital electrode. The number of electrode finger pairs is smaller than that of the input-side interdigital electrodes 31 and 32 to provide a broadband frequency characteristic. The frequencies f ₀ and f _{1 of the} two surface acoustic waves are provided.
And outputs an electric signal of this frequency.

Next, the operation will be described. In FIG. 1, when a binary signal of “0” or “1” is input to a signal input terminal 1, a coder 2 converts the binary signal into a burst pulse, and further converts the binary signal of “0” or “1”. The signal is switched, and the signal of “0” is input to the input terminal 34 and the signal of “1” is input to the input terminal 35. When the burst pulse is input to the input terminal 34 as described above, the surface acoustic wave is propagated to the output-side interdigital electrode 33 and the output terminal 36
Outputs an electric signal of frequency f ₀ . When a burst pulse is input to the input terminal 35, the surface acoustic wave is propagated to the output-side interdigital electrode 33, and its output terminal 36
Electrical signal of the frequency f ₁ is outputted from. Further, the surface acoustic waves from the left and right input electrodes 31 and 32 that are sequentially excited are combined as waves near the center output electrode 33, and both components are output from the output terminal 36.

FIG. 3 is a time chart showing the state of the shift of the surface wave in the SAW element.
Indicates the passage of time. In (a), the piezoelectric substrate 30 is excited by the data “0” input from the input electrode 31,
The surface wave having the frequency f ₀ advances rightward. In (a), at the same time when the frequency f ₀ starts to be output from the output-side electrode 33, “1” is input as the next data by the input-side electrode 32.
There excites the piezoelectric substrate 30, the process proceeds surface acoustic wave having a frequency f ₁ is to the left. In (c), the frequency f _{0 is} output from the output electrode 33.
Is output. In (d), the output side electrode 33 has the frequency f
₀ waves and a wave of frequency f ₁ receives simultaneously, so that the output of both components. Further, since the component of the frequency f ₀ gradually decreases and the component of the frequency f ₁ increases, the frequency component of the output gradually shifts from f ₀ to f ₁ . That is, since all components including the phase gradually change,
The spread of the spectrum due to the conventional discontinuous phase change can be suppressed.

As described above, the FSK transmitter of the present invention
The operating frequency of the AW element is several tens of MHz to several tens of GHz, a wide frequency characteristic can be provided by reducing the number of electrode fingers of the output side interdigital electrode 33, and the frequency shift required for FSK modulation In view of the fact that the shift amount does not need to be large, the SAW element 3 performs oscillation, FSK modulation, and conversion to high frequency, eliminating the need for a high-precision oscillator and frequency multiplier as in the prior art. The configuration is simplified and the configuration is inexpensive. Also,
By performing FSK with the SAW element as described above, the phase can be continuously changed, and the spread of the spectrum can be suppressed.

Although the FSK transmitter has been described in the above embodiment, it goes without saying that an FSK receiver can be constructed by replacing the input side electrode and the output side electrode of the same SAW element. FIG. 4 is a block diagram schematically showing a configuration example of an FSK receiver using a SAW element according to the present invention. In FIG.
An element, 8 is a high-frequency amplifier, 9 is a decoder, 10 is a signal output terminal, 11 is an amplifier, and 12 is a detector.

[0018]

As described above, in the FSK transmitter of the present invention, an inexpensive transmitter having a simple configuration with a small number of parts can be constructed by using a SAW element in an FSK modulation circuit. The spread of the spectrum due to a sudden change in the phase can be suppressed. Further, there is an effect that an FSK receiver can be configured by exchanging the input side electrode and the output side electrode of the SAW element used for the transmitter.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of an FSK transmitter according to the present invention.

FIG. 2 is a diagram showing an example of a configuration of a SAW element 3 used in FIG.

FIG. 3 is a time chart showing a state of surface wave shift on the SAW element 3;

FIG. 4 is a diagram illustrating an embodiment of an FSK receiver according to the present invention.

FIG. 5 is a diagram schematically illustrating a configuration of a conventional FSK transmitter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Signal input terminal 2 Coder 3 SAW element 4 High frequency amplifier 5 Transmitting antenna 6 Receiving antenna 7 SAW element 8 High frequency amplifier 9 Decoder 10 Signal output terminal 11a, 11b Amplifier 12a, 12b Detector 30 Piezoelectric substrate 31 First input side interdigital Electrode 32 Second input interdigital transducer 33 Output interdigital transducer 34, 35 Input terminal 36 Output terminal 41 Oscillator 42 Keyer 43 Frequency multiplier 44 High frequency amplifier

Claims (4)

[Claims] 1. An FSK transmitter characterized in that a modulation and demodulation surface acoustic wave element is used in an FSK (frequency shift keying) modulation circuit. 2. The surface acoustic wave element includes at least a first input interdigital transducer for exciting a carrier frequency f ₀ , a second input interdigital transducer for exciting a frequency f _1, and the _first input interdigital transducer. Provided between the input-side interdigital transducer and the second interdigital transducer, the number of electrode fingers is made smaller than those of the input-interdigital transducer, and the excitation frequencies f ₀ and f ₁ are input to an electric signal. 2. An FSK transmitter according to claim 1, wherein said FSK transmitter comprises an output-side interdigital electrode capable of conversion. 3. An FSK receiver characterized in that a modulation and demodulation surface acoustic wave element is used in an FSK (frequency shift keying) demodulation circuit. Wherein said surface acoustic wave device, at least an input having a wide band characteristic from the output side which can be excited and the frequency f ₁ carrier frequency f ₀ and less than the output-side interdigital transducer electrode finger pairs A side interdigital transducer, a first interdigital transducer provided on both sides of the input interdigital transducer, for inputting an excitation frequency f ₀ and converting it into an electric signal;
FSK receiver of claim 3 wherein wherein a is composed of a second output interdigital transducer for converting an electrical signal to input excitation frequency f _1.