JPH02186858A - Orthogonal modulation/demodulation circuit - Google Patents

Abstract

PURPOSE:To simplify circuit constitution by generating a carrier whose phase is deviated by pi/2 from that of a certain carrier without using an original oscillation signal with a frequency higher than that of the carrier. CONSTITUTION:A phase comparator 11 outputs the phase difference signal 12 of the carrier 9 and the carrier 10 whose phase is deviated by pi/2 generated from a voltage controlled oscillator 14, and the phase difference signal 12 is converted to a voltage proportional to a phase difference by a loop filter 13, and controls the voltage controlled oscillator 14. Here, the phase comparator 11, the loop filter 13, and the voltage controlled oscillator 14 comprise a PLL circuit, and automatic control is performed so that the phase difference of two signals inputted to the phase comparator 11 can go to pi/2, therefore, no signal with the frequency of double the carrier is required. In such a way, an orthogonal modulation/demodulation circuit with simple circuit constitution can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an orthogonal modulation/demodulation circuit, and particularly relates to a quadrature modulation/demodulation circuit that uses a component that is in phase with a carrier wave and a quadrature component that is orthogonal to the carrier wave.
The present invention relates to an orthogonal modulation/demodulation circuit suitable for generating or demodulating a signal of a modulation method that imparts information to a component (rature).

[Prior Art] Figure 5 is a block diagram of a conventional orthogonal modulation/demodulation circuit shown in the literature "Experimental Study of Digital GMSK Modulator" (Preliminary 473 of the National Conference of the Telecommunications Division of the Institute of Electronics and Communication Engineers in 1981). 1 illustrates a digitized configuration. In the figure, (1) is the in-phase component input data that is input as an in-phase component, (2) is a low-pass filter that limits the band of the in-phase component input data (1), and (3) is the low-pass filter (2
) is a mixer that adds (9) to the output of frequency fc, (4) is orthogonal component input data input as orthogonal components,
(5) is a low-pass filter that limits the band of the orthogonal component input data (4), and (6) is a phase-shifted carrier wave (10) whose phase is shifted by π/2 from the carrier wave (9) at the output of the low-pass filter (5). The mixer (7) is a multiplexer that combines the output signals of mixers (3) and (6) and sends out a modulated wave output (8).

(21) is a flip-flop that converts the double frequency signal (19) of frequency 2fc into a carrier wave (9), (2-2)
is the carrier wave (9) based on the signal obtained by inverting the double frequency signal (19) with the inverter (20).
This is a flip-flop that generates a phase-shifted carrier wave (10) whose phase is shifted by π/2.

Next, the operation of the above-described configuration will be explained with reference to the waveform diagram of FIG. 6. By the way, Fig. 6 (a) shows the double frequency signal (19), (b) shows the carrier wave (9), and (c) shows the double frequency signal No. 13 (inverted by the inverter (20)).
19) and (d) respectively show phase-shifted carrier waves (10).

A series of in-phase component input data (1) is band-limited by a low-pass filter (2) using a filter or a memory element, and then input to a mixer (3). Similarly, the sequence of orthogonal component input data (4) is band-limited by a low-pass filter (5) and then input to a mixer (6).

On the other hand, 2 having a frequency 2fc twice the carrier frequency fc
The double frequency signal (one) is frequency-divided by two by a flip-flop (21), becomes a carrier wave (9), and is input to a mixer (3). The double frequency signal (19) is simultaneously sent to the inverter (
20), and then Furi Tsubu number Furo Tsubu (
22), the carrier wave (9) becomes a phase-shifted carrier wave (10) whose phase is shifted by π/2 and is input to the mixer (6). Mixer (3) and mixer (6)
The respective outputs are added together by a multiplexer (7) to produce a weekly wave output (8).

[Problems to be Solved by the Invention] Since the conventional orthogonal modulation/demodulation circuit is configured as described above, it is possible to generate a double frequency signal (1
Not only is the circuit configuration complicated, but if you try to apply it to a system that uses a very high frequency in the GHz band as a microtransmission wave, the generation of the double frequency of the carrier wave itself There were problems such as difficulty in

This invention has been made to solve the above-mentioned problems, and its object is to obtain an orthogonal modulation/demodulation circuit with a simple circuit configuration that eliminates the need for a signal with a frequency twice that of a carrier wave.

[Means for Solving the Problems] An orthogonal modulation/demodulation circuit according to the present invention includes a first mixer means that generates or separates an in-phase component of a signal based on a first carrier wave, and a first mixer means that generates or separates an in-phase component of a signal based on a first carrier wave; and the phase is π/2
A second carrier wave that is generated or separated based on the shifted second carrier wave.
mixer means, means for supplying a first carrier wave to the first mixer means, means for supplying a second carrier wave whose phase is shifted by π/2 from the first carrier wave to the second mixer means; An orthogonal modulation/demodulation circuit comprising a phase control means that compares the positions of the carrier wave and the second carrier wave and shifts the phase of the second carrier wave by π/2 with respect to the phase of the first carrier wave based on the phase difference between the two. This is what we provide.

[Operation] The orthogonal modulation/demodulation circuit according to the present invention generates or separates an in-phase component of a signal using a first mixer means using a first carrier wave, and generates an orthogonal component of a signal using a second mixer means using a second carrier wave. Alternatively, in separating, the phase of the first carrier wave and the second carrier wave are compared by the phase control means, and the phase of the second carrier wave is set by π/2 with respect to the phase of the first carrier wave based on the phase difference between the two carrier waves. It's shifted.

[Example] The present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an orthogonal modulation/demodulation circuit according to an embodiment of the present invention. In the figure, (14) is the closing frequency f
c and the carrier wave (9) given to the mixer (3) and π/
A voltage controlled oscillator (11) generates a phase-shifted carrier wave (10) with two phases shifted and sends it to the mixer (6), and (11) is composed of an exclusive OR circuit, etc.
(13) is a loop filter that generates a control voltage for the voltage controlled oscillator (14) based on the phase difference signal (12). be.

Next, the operation of the above configuration will be explained based on the timing charts of FIGS. 2 and 3. By the way, Figure 2 shows the waveforms of various parts in a steady state.
a) is the carrier wave (9), (b) is the voltage controlled oscillator (14)
The phase-shifted carrier waves (10) and (C), which are the output signals of, respectively indicate the phase difference signal (12) when the phase comparator (11) is configured with an exclusive OR circuit. On the other hand, Figure 3 shows the waveforms of various parts in an unstable state.
is the carrier wave (9), (b) is the output signal of the voltage controlled oscillator (14), and the phase shift carrier wave (10) CC) is the phase difference signal when the phase comparator (11) is composed of tM using an exclusive OR circuit. (12) respectively.

Now, the sequence of in-phase component human input data (1) is band-limited by a low-pass filter (2) and then input to a mixer (3). Similarly, the sequence of orthogonal component input data (4) is subjected to band limitation by a low-pass filter (5) and then input to a mixer (6).

On the other hand, the carrier wave (9) is input to the mixer (3) and also to the phase comparator (11). Phase comparator (11
) outputs a phase difference signal (12) between this carrier wave (9) and a phase-shifted carrier wave (10) generated by the voltage controlled oscillator (14) with a phase shift of π/2. The phase difference signal (12) is converted into a voltage proportional to the phase difference by a loop filter (13) to control a voltage controlled oscillator (14). Here, the phase comparator (11), loop filter (13), and voltage controlled oscillator (14) are PLL (PhaseL).

clc Loop) circuit, and automatically controls the phase difference between the two signals input to the phase comparator (11) to be π/2.

Now, in Figure 2, the phase difference between (a) and (C) is π/
2. At this time, since the phase difference signal (12) which is the output of the phase comparator (11) has a duty of 50%, the voltage controlled oscillator (14) oscillates at a free-running frequency. Here, if the free running frequency is the same as the carrier frequency fc, this state can be said to be a stable state.

On the other hand, as shown in FIG. 3, if the phase difference between (a) and (C) is not π/2, the phase comparator (1
The phase difference signal (12) which is the output of 1) has a duty of -5
It will not be 0%. Therefore, the oscillation frequency of the voltage controlled oscillator (14) is changed to change the phase relationship between (a) and (C), and control is continued until the phase difference between the two becomes π/2. It eventually settles into the stable state shown in Figure 2. At this time, the phase difference between the carrier wave (9) and the out-of-phase carrier wave (10) is π/2.

As described above, the carrier wave (9) whose phase difference is controlled to π/2 and the phase-shifted carrier wave (10) are transferred to the mixer (3), respectively.
), manually powered by the mixer (6).

Then, the mixer (3) combines the in-phase component input data (1) and the carrier wave (9), and the mixer (6) combines the orthogonal component input data (4) and the phase-shifted carrier wave (10), and each output is They are added together at the modulated wave output (8) and output as the modulated wave output (8).

In the above embodiment, the case of orthogonal modulation has been described as an example, but the present invention is similarly applied to an orthogonal detector (demodulator) as shown in FIG. In the same figure, (
15) is a received wave that is orthogonally modulated, and (16) is a branching filter that separates the received wave (15).

In this configuration, the mixer (3) combines the carrier wave (9) with the output of the duplexer (16), extracts the in-phase component waveform (17), and outputs it through the low-pass filter (2). On the other hand, the mixer (6) combines the phase-shifted carrier wave (1o) with the output of the splitter (16), extracts an orthogonal component waveform (18), and outputs it through the low-pass filter (5).

With the above operation, the received wave (1
5) to in-phase component waveform (17) and quadrature component waveform (18)
can be demodulated.

[Effects of the Invention] As described above, according to the present invention, a phase-shifted carrier wave having a phase difference of π/2 from a certain carrier wave can be generated without requiring an original oscillation signal of a higher frequency. Therefore, it is possible to use an orthogonal modulation/demodulation circuit with a simple circuit configuration and excellent economic performance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an orthogonal modulation/demodulation circuit according to an embodiment of the present invention, FIGS. 2 and 3 are timing charts for explaining the operation of the configuration shown in FIG. 1, and FIG. FIG. 5 is a block diagram of a conventional orthogonal modulation/demodulation circuit, and FIG. 6 is a timing chart for explaining the operation of the configuration shown in FIG. (2), (5) are low-pass filters, (3), (6) are mixers, (7) are multiplexers, (11) are phase comparators, (13)
is a loop filter, (14) is a voltage controlled oscillator, (16
) is a splitter. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] first mixer means for generating or separating in-phase components of the signal; second mixer means for generating or separating quadrature components of the signal; means for providing a first carrier wave to the first mixer means; means for providing a second carrier wave to the mixer means;
It is characterized by comprising a phase control means that compares the phases of the first carrier wave and the second carrier wave and shifts the phase of the second carrier wave by π/2 with respect to the phase of the first carrier wave based on the phase difference between the two carrier waves. Orthogonal modulation/demodulation circuit.