JPH059977B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a modulation/demodulation circuit, particularly to improvements in a delay detection demodulation circuit and a modulation circuit using a four-phase phase modulation method.

[Prior Art] Conventionally, as a modulation circuit that performs four-phase phase modulation, a circuit as shown in FIG. 2 has been known, and as a demodulation circuit that demodulates such a four-phase phase modulation signal, A circuit as shown in FIG. 3 is known.

The four-phase phase modulation circuit shown in FIG. 2 is constructed using a hybrid 2a, two mixers 3a and 3b, a carrier signal generator 4, a hybrid 2b, and a phase shifter 8.

In the figure, 6a is a data signal, 6b is a data signal which is a component orthogonal to this, and 201 is a four-phase phase modulation signal.

In this modulation circuit, the signal output from the carrier signal generator 4 is divided into two by the hybrid 2b, one is input to the mixer 3a, and the other is phased by π/2 by the phase shifter 8. , mixer 3
b.

Then, data signals 6a, 6b are sent to this modulation circuit.
is input, these input signals 6a and 6b are modulated by mixers 3a and 3b, and then output to the hybrid 2a.
is input.

In this way, the hybrid 2a combines the signals input from the mixers 3a and 3b and outputs it as a four-phase extended signal 201.

The conventional demodulation circuit shown in FIG. 3 includes a hybrid 2a, mixers 3a and 3b, and a distribution delay circuit 1.
1, and is configured as a differential detection demodulation circuit that demodulates a four-phase phase modulation signal.

Then, this demodulation circuit receives a four-phase phase modulation signal 20.
When 1 is input, this signal 201 is distributed into three signals 210, 211 and 212 by hybrid 2a. Of the three distributed signals, one signal 210 is input to the distribution delay circuit 11, subjected to distribution delay, and input to each mixer 3a, 3b as a reference signal for differential detection. Here, the distributed delay circuit 11 is composed of a hybrid 2b, two delay circuits 7, and a π/2 phase shifter 8.

Then, in the delay circuit 7, a delay equal to one bit of the data signal and ±(2n-1)π/4 (where n=1,
2, 3...) phase delays are performed.

In addition, the other two signals 211 and 21 of the three divided signals output from the hybrid 2a
2 are input to mixers 3a and 3b, respectively, and demodulated and output as data signals 6a and 6b.

[Problems to be Solved] However, in such a conventional circuit, when configuring a transmitting/receiving device, the modulation circuit shown in FIG.
It was necessary to provide separate demodulation circuits as shown in FIG.

For example, when configuring a simplex type transmitting/receiving device, this not only becomes an obstacle when downsizing the entire device, but also when configuring other duplex type transmitting/receiving devices. There was a problem in that a circuit had to be installed separately from the side, which required complicated work both in terms of manufacturing and maintenance of the equipment.

Furthermore, when performing this type of phase modulation or demodulation, the delay circuits and phase shifters used for this require high precision. There was a problem in that it was necessary to make fine adjustments to achieve accuracy.

The present invention has been made in view of such conventional problems, and an object thereof is to realize a demodulation circuit that can perform modulation and demodulation of a four-phase phase modulation method using a common circuit.

[Means for Solving Problems] In order to achieve the above object, the present invention comprises: a hybrid that distributes and combines modulated signals; two sets of mixer circuits that exchange data signals with modulated signals that are input to the hybrid; and a carrier wave. a carrier signal generator for outputting a signal; a switching circuit for selectively outputting either the distributed output of the hybrid or the output of the carrier signal generator; a distribution delay circuit that outputs signals to the mixer circuits, the distribution delay circuit includes a first interdigital electrode into which an output signal of the switching circuit is input, and a distribution delay circuit that outputs a distribution delay signal to the two mixer circuits. formed using a surface acoustic wave device comprising a second interdigital electrode and a third interdigital electrode, each of which outputs a signal that is propagated from the first interdigital electrode to the second interdigital electrode. The resulting signal has a delay equivalent to 1 bit of the data signal and ±(2n-1)π/4 (where n=1,
2, 3...), and the signal propagated from the first interdigital electrode to the third interdigital electrode has the first delay and is a configuration in which each interdigital electrode is arranged so that a second delay whose phase differs from each other by ±π/2 is applied.

[Example] Next, a preferred example of the present invention will be described based on the drawings. Incidentally, members corresponding to those of the conventional apparatus shown in FIGS. 2 and 3 are designated by the same reference numerals, and their explanations will be omitted.

FIG. 1 shows a preferred embodiment of the modulation/demodulation circuit according to the present invention, and the modulation/demodulation circuit of the embodiment includes a hybrid 2, a carrier signal generator 4, two sets of mixers 3a and 3b, It is composed of a switching circuit 5 and a distribution delay circuit 11.

In the present invention, this distribution delay circuit 11 has three
Two interdigital electrodes (hereinafter referred to as IDT) 101,1
Surface acoustic wave device with 02 and 103 (hereinafter referred to as
It is formed using SAW device) 1,
The signal input to the first IDT 101 is transmitted to the second IDT 102 and the third IDT 102 located at different positions.
The IDT 103 is outputted with a first delay and a second delay, respectively.

Here, if the first delay is T1 and the second delay is T2, the delays are expressed by the following equations.

T1=T0±(2n-1)/4 T2=T1±(π/2) However, n=1, 2, 3... T0: Delay equivalent to 1 bit of data signal In the device shown in Figure 1, n=2 In this case, each IDT 101, 102, 10 is set so that the first delay T1 and the second delay T2 are given by the following equation.
3 is installed.

T1=T0+(3/4)π T2=T0+(5/4)π As described above, the SAW device 1 used in the present invention is
By arranging the three IDTs 101, 102, and 103, a distribution function and a delay function necessary for delayed detection can be achieved. Moreover, this SAW device 1 can be formed as a single element if necessary.

The switching circuit 5 also connects the signal 210 distributed and output from the hybrid 2 to the carrier wave signal generator 4.
The SAW device 1 is configured to select one of the carrier wave signals output from the SAW device 1 and output it to the first IDT 101 of the SAW device 1.

The present embodiment has the above configuration, and its operation will be explained next.

First, when the device of this embodiment is used as a modulation circuit, the output of the carrier signal generator 4 is
The switching circuit 5 is controlled so that the signal is input to the IDT 101.

By doing this, the carrier signal becomes
The signal is divided into two by the SAW device 1 and supplied to each mixer 3a and 3b as signals that differ by π/2 from each other.

At this time, when the data signal 6a and the data signal 6b are applied to the mixer 3b, the input signals 6a and 6b are phase modulated and outputted to the hybrid 2. And hybrid 2
In this way, the signals output from each mixer 3a and 3b are combined and output as a modulated signal 201 subjected to quadrature phase modulation.

In this way, the circuit of this embodiment can be used as a modulation circuit.

Furthermore, when the circuit of this embodiment is used as a demodulation circuit, the output signal of hybrid 2 is
The switching circuit 5 is controlled so that the signal is input to the IDT 101. In this way, when the modulated signal 201 subjected to four-phase phase modulation is input to the hybrid 2, one signal 210 of the three signals outputted from the hybrid 2 after being divided into three of
It is input to IDT101.

Then, the SAW device 1 applies a delay of (3/4)π and (5/4)π, respectively, to the input signal 210 in addition to a delay equivalent to one bit of the data signal required for delayed detection. The signal is distributed into two signals with a phase delay. These two signals are outputted to mixer 3a and mixer 3b, respectively, as reference signals for differential detection.

At this time, the remaining two signals 211 and 212 of the three signals distributed by the hybrid 2 are input to the mixers 3a and 3b, respectively.

Therefore, mixer 3a and mixer 3b respectively perform delay detection on the remaining two signals 211 and 212 among the three divided signals outputted from hybrid 2, and output them as data signal 6a and data signal 6b.

In this way, the circuit of this embodiment can be used as a demodulation circuit.

Further, in the present invention, the mixer 3a and 3
Since mixers 3a and 3b can be formed using the same circuit, these mixers 3a and 3b can be formed using general double-balanced mixers.

An example of such a mixer is shown in FIG. 4, and when this mixer is used in the modulation/demodulation circuit according to this embodiment, the RF terminal 31 is connected to the hybrid 2, and the LO terminals 33 and 34 are connected. It is sufficient to connect it to the SAW device 1 and use the RF terminal 32 as an input terminal for data signals representing states of "1" and "0" using positive and negative currents.

Furthermore, in this embodiment, the amount of delay necessary for modulation and demodulation is obtained by the SAW device 1, but the accuracy of this delay is determined by the accuracy of the arrangement of the IDTs 101, 102, and 103.

The arrangement of the IDTs 101, 102, and 103 can be performed with high precision using integrated circuit printing technology, so if the SAW device 1 is formed as one element,
An element with an accurate amount of delay can be obtained at the manufacturing stage, and the modulation/demodulation circuit can be made without adjustment.

[Effects of the Invention] As explained above, according to the present invention, a surface acoustic wave device is used in the distribution delay circuit, and the switching circuit can switch between modulation and demodulation. When incorporated into a transmitting/receiving device, the entire device can be significantly miniaturized, and the number of parts can be reduced, so that manufacturing and maintenance management thereof can be simplified.

Furthermore, according to the present invention, since the surface acoustic wave device constituting the distribution delay circuit can be formed as a single element as necessary, there is no need for adjustment at the manufacturing stage. Cost reduction can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing a preferred embodiment of a modulation/demodulation circuit according to the present invention, FIG. 2 is a block circuit diagram showing an example of a conventional modulation circuit, and FIG. 3 is a block circuit diagram showing an example of a conventional demodulation circuit. Circuit Diagram, FIG. 4 is a block circuit diagram of a mixer circuit used in the circuit shown in FIG. 1...Surface acoustic wave device, 2...Hybrid,
3a, 3b...Mixer, 4...Carrier signal generator, 5...Switching circuit, 6a, 6b...Data signal, 7...Delay circuit, 8...Phase shifter, 11...Distribution delay circuit, 101, 102, 103...Cross finger electrodes, 201...4-phase phase modulation signal.

Claims (1)

[Scope of Claims] 1. A hybrid that distributes and combines modulated signals, two sets of mixer circuits that convert data signals and modulated signals that are input to the hybrid, and a carrier signal generator that outputs a carrier signal; a switching circuit that selects and outputs either the distributed output of the hybrid or the output of the carrier wave signal generator; and a distribution delay circuit that distributes and delays the output of the switching circuit and outputs the delayed output to the two mixer circuits. , the distribution delay circuit includes a first interdigital electrode into which the output signal of the switching circuit is input, and a second interdigital electrode which outputs the distribution delay signal to the two mixer circuits, respectively. and a third interdigital electrode, the signal propagated from the first interdigital electrode to the second interdigital electrode includes a 1-bit data signal. equivalent delay and ±(2n-1)π/4 (where n=1,
2, 3...), and the signal propagated from the first interdigital electrode to the third interdigital electrode has the first delay and A modulation/demodulation circuit characterized in that each of the interdigitated electrodes is arranged so that a second delay whose phase differs from each other by ±π/2 is applied.