JPH01276860A - Psk modulating circuit - Google Patents

Abstract

PURPOSE:To prevent an unwanted phase modulated component from generating by providing first and second modulating circuits to PSK-modulate and output respectively a carrier and a delay carrier with a band limit signal and adding and outputting first and second modulated signals. CONSTITUTION:The title circuit is a PSK modulating circuit to phase-modulate a carrier with the digital signal of a clock period T, a second band limit signal, in which a digital signal is band-limited by a second replacing circuit and a second band limit circuit, is generated, and a first band limit signal having the approximately differential waveform of a second band limit signal waveform is generated by a first replacing circuit and a second band limit circuit. Two types of the carrier having the phase difference of 90 deg. mutually is PSK- modulated by respective first and second band limit signals, as the result, the first and second modulated signals generated are added by a synthesizing circuit 14 and outputted as a PSK modulated signal in which the amplitude is approximately constant. Thus, even when the non-modulating wave passes through a non-linear element, the unwanted phase modulated component is not generated.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention can be used in digital satellite communications, etc.
This invention relates to a K modulation circuit (phase modulation circuit).

"Prior Art" FIG. 4 is a block diagram of a conventional PSK modulation circuit. Fourth
Figure (a) shows the most basic PSK modulation circuit. In this circuit, a modulated wave W is obtained by manually inputting a carrier wave U and a digital signal V to a double-balanced mixer 1.

However, since the rectangular wave input as the digital signal V includes all harmonics, the frequency distribution is large. Therefore, in this circuit, the frequency band of the outputted modulated wave W becomes wider than necessary, and there is a risk of interfering with other signals in the 19-band range. Therefore, band limitation is performed. As shown in FIG. 4(b), the band-limiting method is to limit the band of the digital signal V with a low-pass filter 2, convert it into a signal X close to a sine wave, and then input it to the balanced mixer L.
The method for obtaining the modulated wave y is as shown in FIG.
There is a method of obtaining the modulated wave y by limiting the frequency range.

Figure 5 shows signals U~ in the circuits of Figures 4(a) to (c).
This shows the waveform of y. Here, the modulated wave y is '
The signal is amplified by a traveling wave tube (1”WT) and transmitted.

Then, on the receiving side, waveform 2 in FIG. 5 is obtained by synchronously detecting the modulated wave y, and this is passed through a low-pass filter to obtain waveform X. Then, the waveform is further shaped to restore the digital signal waveform (2).

"Problem to be Solved by the Invention" By the way, when a modulated wave y with a variation in envelope amplitude as shown in Fig. 5 is input to a nonlinear element such as 'I' W T, the variation is unnecessary. A phenomenon occurs in which the signal is converted into a phase modulation component. This adds a component different from the modulation component to the phase modulated wave, resulting in signal deterioration.

This invention was made in view of the above-mentioned circumstances, and an object thereof is to provide a PSK modulation circuit that does not generate unnecessary phase modulation components even when a non-modulated wave is passed through a nonlinear element such as a TWT. The purpose is

``Means for Solving the Problems'' The present invention provides a PSK modulation circuit that phase-modulates a digital signal (therefore a carrier wave) with a clock period T, the digital signal being delayed by T/2. a first replacement circuit that outputs a first replacement signal in which the high and low values of the signal are replaced with positive and negative voltages, respectively; and when the value of the digital signal changes, the high and low values of the digital signal are replaced. a second replacement circuit that replaces two values with positive voltage and negative voltage, respectively, for a time 'I', and outputs a second replacement signal in which the value of the digital signal is replaced with O volts when the value of the digital signal does not change; a first band-limiting circuit that inputs a first:ξ displacement signal and outputs a first 41-band-limited signal with its high frequency components attenuated; a second band-limiting circuit outputting a second band-limiting signal whose high frequency components are attenuated; a first outputting a modulated signal of
a modulation circuit, and PSK modulation of the delayed carrier wave which delayed the carrier wave by 90 degrees using the band limiting signal of either the it or the second one! I
A second modulation circuit that outputs a second modulated signal at AI L, and a synthesis circuit that adds and outputs the first modulated signal and the second modulated signal. There is.

``Operation'' According to the two-leg configuration, the second replacement circuit and the second band-limiting circuit generate a second band-limited signal in which the digital signal is band-limited; A first band-limited signal having a substantially differential waveform of a second +1 band-limited signal waveform is generated by the band-limited circuit.

Then, two types of carrier waves having a phase difference of 90 degrees from each other are PSK-modulated by first and second band-limited signals, respectively, and the resulting first and second modulated signals are added by a combining circuit. , PSK with almost constant amplitude
Output as a modulated signal.

"Embodiment" Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a PSK modulation circuit according to an embodiment of the present invention. In the circuit shown in FIG. 4 described above, the phase is directly changed depending on the input signal, but in this PSK modulation circuit, the phase is gradually changed in accordance with the clock cycle T of the input signal.

In FIG. 1, 4.5 is a register, which operates with a clock twice the clock frequency (1/T) of the input digital signal a. Therefore, signal S is T/2 behind human-powered digital signal a, and signal C is even further behind that by T/2.
2j11. 6 is an EXOR circuit, and signals a, c
An exclusive OR signal d is output. Switch 7 is E
When the output signal d of the XOrt circuit 6 is “0”, it is connected to the ground terminal, and when the signal d is rlJ, the signal 871+(“1
”, it is connected to the child terminal, and if the signal a is “0”, it is connected to one terminal, and the signal r is output. Further, the switch 8 is connected to one terminal side when the signal is "0", and connected to the child terminal side when the signal is "1", and outputs the signal e. 9.10 are filters with the same characteristics, and are Nyquist filters with arbitrary roll-off rates. Then, the filter 9 receives the signal f
is input manually, the band is limited, and a signal is output. Further, a signal e is input to the filter 10, and a signal g is output after being band-limited. +1 is a mixer, which manually inputs the signal 11 and the carrier wave via the 90-degree phase shifter 13, and outputs the modulated signal j. 12 is also Miki →)・, and the signal g
The carrier wave is input manually, and the modulated signal i is output. 14
is a combining circuit in which modulated signals j and i output from mixers 11 and 12 are added together to output a modulated signal k.

The signal waveform a of each part of the circuit explained below is as shown in FIG. Here, the signal g lags behind the human-powered digital signal a by T/2 and forms a band-limited, smooth waveform, and the waveform of the signal is close to the differential waveform of the signal g.

On the other hand, the carrier waves supplied to the mixer 12.11 (Jl-) have a phase difference of 90 degrees, the mixer 12 is supplied with the carrier wave cosωt, and the mixer 12.11 is supplied with the carrier wave sinωt. Each of these carrier waves is then sent to a mixer 12.
and mixed with signals g and h by I+,
Signals i and j are generated. At this time, the signals i and j
The amplitude of is changed according to the human input signals g and h. The signals i and j are then combined by a combining circuit 14 and output as a signal. FIG. 2 illustrates this synthesis principle. Here, the amplitude of the composite signal is k−(i・+
j・)F, and the amplitude of signals i and j (and the amplitude of the combined signal) changes to approximately 1.Demodulation is the same as in the conventional example, and the signal Q shown in Fig. 3 is obtained by synchronous detection. This is passed through a low-pass filter to obtain signal g.Then,
Further waveform shaping is performed to obtain signal e, and digital signal a
is restored.

"Effects of the Invention" As explained above, according to the present invention, the clock frequency 1
Phase modulation of the carrier wave by the dental signal of the librarian
) SK modulation circuit, which converts the digital signal into T/
The first delay signal is obtained by replacing the two values of /%I and low of the first delayed digital signal with a positive voltage and a negative voltage, respectively.
a first replacement circuit that outputs a replacement signal of the digital signal, and when the value of the digital signal changes, replaces the high and low values of the digital signal with positive voltage and negative voltage, respectively, for a time T; A second replacement circuit outputs a second replacement signal in which the value is not changed by replacing it with 0 port, and a second replacement circuit receives the first replacement signal and attenuates its high frequency components. 1, which outputs a band-limited signal of
a second band-limiting circuit that receives the second replacement signal and outputs a second band-limited signal with its high frequency components attenuated; a first modulation circuit that performs PSK modulation with one of the band-limited signals of the second band limit signal and outputs a first modulated signal;
a second modulation circuit that performs PSK modulation with the other band-limited signal and outputs a second modulated signal, and adds and outputs the first modulated signal and the second modulated signal. Since a combining circuit is provided, there is no fluctuation in the amplitude of the output modulated signal, and even if this modulated signal is transmitted through a line including a nonlinear circuit, unnecessary phase modulation components are not generated. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a PSK modulation circuit according to an embodiment of the present invention, FIG. 2 is a diagram of the principle of waveform synthesis in the synthesis circuit 14 in the embodiment, and FIG. 3 is a diagram showing the operation of each part of the embodiment. FIG. 4 is a block diagram of a conventional PSK modulation circuit, and FIG. 5 is a waveform diagram showing the operation of the circuit shown in FIG. 4. 4.5...Register, 7.8...Switch, 9.10...Low pass filter, 11, +2
...Mixer, I4...Synthesis circuit. Applicant Alps Electric Co., Ltd. Representative Kataka Katsutabe Figure 4 (a) (b)

Claims (1)

[Claims] A PSK modulation circuit that phase-modulates a carrier wave using a digital signal with a clock period T, wherein the high and low values of a first delayed digital signal obtained by delaying the digital signal by T/2 are respectively corrected. a first substitution circuit that outputs a first substitution signal substituted with a voltage and a negative voltage; and when the value of the digital signal changes, the two values of high and low of the digital signal are converted into a positive voltage and a negative voltage, respectively, over time. a second replacement circuit that replaces only T and outputs a second replacement signal in which the value of the digital signal is replaced with 0 volts when the value of the digital signal does not change; a first band-limiting circuit that outputs a first band-limited signal whose frequency components are attenuated; and a second band-limited signal that receives the second replacement signal and outputs a second band-limited signal whose high frequency components are attenuated. a second band-limiting circuit that outputs a first modulated signal;
a second modulation circuit that performs PSK modulation on a delayed carrier wave obtained by delaying the carrier wave by 90 degrees with one of the first and second band-limiting signals and outputs a second modulated signal; A PSK modulation circuit comprising: a synthesis circuit that adds the first modulated signal and the second modulated signal and outputs the sum.