JPH03162037A - Psk modulation circuit - Google Patents

Abstract

PURPOSE:To avoid duplication and discontinuity of a signal at changeover of a carrier wave by storing one period of a PSK (Phase Shift Keying) modulation signal into a ROM and using a PCM (Pulse Code Modulation) input signal so as to count up or down the ROM address thereby obtaining carriers of 0 deg. and 180 deg.. CONSTITUTION:Since a PCM input signal 8 is inputted to an upcount/down-count control terminal of a counter 2, the counter 2 is counted up when the PCM input signal 8 is at an H level and the output of the counter 2 reaches from 0 into 2M<-1>, from 0 into 2M<-1>,... In this case, an output data 5 of a ROM 4 is a 0 deg.C carrier signal data. On the other hand, when the PCM input signal is at an L level, since the counter 2 is counted down, the output of the counter 2 goes from 2M<-1> into 0, 2M<-1> into 0,... and the output data 5 of the ROM 4 is a data of 180 deg. carrier signal. Thus, the duplicate and discontinuous signal at the carrier signal changeover point is avoided.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is based on PCM (Pulsu Code
PSK (Phase Shift Keying) which performs two-phase phase modulation of the carrier wave using a modulation signal.
) relates to modulation circuits.

[Prior Art] Conventionally, there was a circuit of this type as shown in FIG. Fourth
In the figure. (7) is an enable signal for enabling the PSK output signal, (8) is a PCM input signal, (9
) is the PSK output signal, (10) is the carrier wave sine wave signal +' [11] is the buffer circuit, (12) is the phase inversion circuit that inverts the phase of the carrier wave sine wave signal (lO) by 180 degrees, (13) is (14) is a 180 degree carrier signal with a phase difference of 180 degrees from the carrier sine wave signal (1O) by a phase inversion circuit. (15) is PCM input signal (
8), a single-pole double-throw switch that switches and outputs the 0 degree carrier wave signal (13) and the 180 degree carrier wave signal (14), (
161 outputs the PSK output signal (
9) is a single-pole, single-throw switch.

Next, the operation will be explained. In Fig. 4, the carrier wave sine wave signal (10) is connected to the 0 degree carrier wave signal (l3) by a buffer circuit (11) and a phase inversion circuit (l2).
It is converted into an 80 degree carrier wave signal (l4), and the single pole double throw switch (l5) is controlled by the PCM input signal (8).

Therefore, the signal at the point where the output of the single-pole double-throw switch (l5) is short-circuited is that when the PCM input signal {8} is at the "H" level, the O degree carrier signal (l3) is at the "L" level. A 180 degree carrier wave signal (l4) appears. This signal is input to a single-pole, single-throw switch (16). enable signal (7
) and only valid signals are sent to the single-pole, single-throw switch (l
6) is output as a PSK signal (9).

[Problem to be solved by the invention] As described above, in the conventional circuit, the phase inversion circuit
In order to create a 0 degree carrier signal, it is difficult to make the phase of the 0 degree and 180 degree carrier signals, which are the carrier waves of the PSK modulation signal, exactly 180 degrees, and because the 0 degree and 180 degree carrier signals must be switched with a switch. ．． Problems such as signal duplication and discontinuity that occur during switching have arisen.

This invention was made in order to solve the above-mentioned problems, and it is possible to accurately change the phase difference of 180 degrees between the 0 degree and 180 degree carrier wave signals of the PSK modulation signal, and to switch between the 0 degree and 180 degree carrier wave signals. It is an object of the present invention to obtain a PSK modulation circuit without signal overlap and discontinuity at points.

[Means for Solving the Problems] The PSK modulation circuit according to the present invention uses a carrier wave of a PSK modulation signal! The period is R O M (Read Only M
emo・y). The ROM address is counted up and counted down by 1 using the PCM input signal to generate an O degree carrier wave and a 180 degree carrier wave, which are converted into analog signals by a D/A conversion circuit.

[Function] The PSK modulation circuit in this invention has... O degrees and 180
By storing the waveform of the carrier wave in ROM.
The phases of the two carrier waves are maintained at exactly 180 degrees, and by reading out the waveform in the ROM using a PCM manual signal, it is possible to eliminate signal overlap and discontinuity at the switching point of the two carrier waves.

[Example] Below. An embodiment of the present invention will be described with reference to the drawings. 1st
In the figure. (l) is P which is 2M times the PSK carrier frequency
SK carrier wave clock signal, (2) is an M-bit counter (hereinafter abbreviated as counter) with up count/down count control terminal (i3) is an address signal output by counter (2). (4) is a ROM that stores data in which one period of a sine wave is divided into 2M on the time axis and the amplitude is expressed in quantization number N bits. (5) is the output data of R O M (4), and (6) is a D/A conversion circuit having a positive/negative output with a quantization number of N bits and an output enable (OE) terminal. Note that (7) is an enable signal for enabling the PSK output signal, (8) is a PCM input signal, and (9) is a PSK output signal.

In Figure 1, the PSK carrier clock signal (1) has an up-count/down-count control terminal connected to a counter (
2) and becomes the address signal for ROM (4).

As shown in Figure 2, the ROM stores one period of a carrier sine wave, the address corresponds to the time axis of the sine wave, and the l address corresponds to 360 degrees/M (M: integer). There is.

The data is obtained by quantizing the amplitude of a sine wave using N bits (N: 9 numbers), and the minimum value is 1 and the maximum value is (2N-1).

The PCM input signal (8) is connected to the up-count/down-count control terminal of the counter (2). therefore.
The output of the counter (2) is P as shown in Figure 3 (C).
When the CM input signal (8) is at “H” level, the counter (2)
counts/up, so it goes from 0 to 2'-', from O to 2kl-1, and so on. At this time r{ OM (4
The output data (5) of 1 becomes the data of the 0 degree carrier wave signal as shown in FIG. 3(d). on the other hand. The PCM input signal is
Since the counter (2) counts down when the level is L'', the output of the counter (2) changes from 2v-+ to 0.2k''-1 to 0... as shown in Figure 3(d), and RO
The output data (5) of M(4) becomes data of a 180 degree carrier wave signal as shown in FIG. 3(d).

This ROM output N-bit data (5) is converted into an analog signal by a D/A conversion circuit (6) and becomes a PSK output signal (9). The enable signal (7) is connected to the output enable terminal of the D/A conversion circuit (6) and is used to stop the PSK output signal (9).

In the above embodiment, the D/A conversion circuit (6) is shown as 6 with an enable terminal, but a gate circuit is provided after the D/A conversion circuit without an output enable terminal, and an enable signal (7) is provided. The same effect can be achieved by opening/closing the gate circuit.

Further, although the ROM (4) is shown as storing one period of the carrier wave, the same effect can be obtained even if the period is stored as an integral number.

[Effects of the invention] As mentioned above. According to this invention, one cycle of the PSK modulation signal is stored in the ROM. ROM by PCM input signal
The configuration is such that addresses are counted up and down to obtain carrier waves of 0 degrees and 180 degrees, and then converted to analog signals using a D/A conversion circuit.
The phase difference of the 0 degree carrier signal is maintained at exactly 180 degrees. It also has the effect of eliminating signal duplication and discontinuity when switching carriers at 0 degrees and 180 degrees.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the PSK modulation circuit according to the present invention, and FIGS. 2 and 3 are diagrams showing the operation of the PSK modulation circuit according to the present invention. FIG. 4 is a diagram showing a conventional PSK modulation circuit. In the figure, (l) is P which is 2M times the PSK carrier frequency.
Clock signal for SK carrier wave, (2) is up count/
M-bit count with down count control terminal. (3
) is address signal, (4) is ROM, (5) is ROM
output data. (6) is a D/A conversion circuit, and (7) is an enable signal. (8) is a PCM input signal, (9) is a PSK output signal, and (10) is a carrier wave sine wave signal. (11)
is a buffer circuit. (12) is a phase inversion circuit, (13
) is a 0 degree carrier signal, (14) is a 180 degree carrier signal, (Is) is a single pole double throw switch. fl6) is a single pole single throw switch. In addition, the same or corresponding parts in the figures are indicated with the same reference numerals.

Claims (1)

[Claims] Input a clock signal with a carrier frequency of 2^M and calculate M(M
is an integer) A counter with up-count and down-count control terminals is used to divide the frequency, and the output of this counter is used as an address signal.N (n is an integer) period of data is quantized by a quantization number N (N is an integer) 1.) A PSK modulation circuit characterized by comprising a storage means for storing data in bits, and a D/A conversion circuit with a quantization number of N bits for converting the output from the storage means into an analog quantity.