JPS5944155A - Suppressing method of burst spectrum - Google Patents

Abstract

PURPOSE:To suppress a burst spectrum generated by a switch, by attenuating the output level of a phase modulator by the 1st burst signal and controlling the switch by the 2nd burst signal. CONSTITUTION:A data signal (a) and a burst signal 1S (c) are inputted to D flip-flop circuits IC23, IC22 respectively. The output of the circuit IC23 is gated by the output of the circuit IC22 and inputted to differential amplifiers Q21, Q22. At the low level of the burst signal 1S, reinput of the differential amplifiers is turned to the low level and the output B becomes 0V as shown in (b). The output from the differential amplifiers passes through an LPF4 and the carrier is modulated by a phase modulator A. The output of the modulator A is outputted through a switching circuit 2 of which switching is controlled by a burst signal 2S (d). The off time of the signal 2S is set up to a value shorter than the low level time of the signal 1S.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for suppressing the burst spectrum of a phase modulator wave in a time division multiplexed radio system.

The conventional method for suppressing burst spectrum is the first method.
As shown in the figure. In Fig. 1, 1 is a phase modulator, 2 is a switch circuit, and 3 is a band-pass type door filter with small passing loss (BP).
F) (or a roll-off filter that also has the purpose of reducing code amount interference), the burst spectrum generated by switching the output of the phase modulator 1 with a switch circuit 2 is attenuated with a narrow band filter 3. was.

However, in the case of the conventional method, the filter 3 cannot effectively reduce the tractram unless it has a narrowband filter configuration, and therefore requires an increase in pass loss and a very expensive and high-performance filter. There was a drawback.

The present invention does not require high-performance, expensive filters;
When transmission is stopped, the output level of the phase modulator is attenuated by 30 dB or more compared to when transmitting (by the first burst signal), and the first burst signal and the gate of the switch circuit connected next are controlled. By providing an effective time lag to the second burst signal, it is possible to sufficiently suppress burnout spectra and drums generated by the switch circuit, thereby making highly efficient transmission possible. Explain in detail.

FIG. 2 shows an embodiment of the present invention, in which IC21,
IC22 is a D free-lag flip circuit, IC23, IC'
24, IC25, IC26 are NAND circuits, A is a two-phase modulator, Q21. Q22 is a differential amplifier, 2 is a switch circuit, and 4 is a base/draw bass filter. Also, FIG. 3 shows signal waveforms at each part in FIG. 2.
The case of a two-phase variable wave will be explained using FIGS. 2 and 3.

The DATA signal shown in FIG. 3 is inputted to the D flip 70 tube circuit I C' as shown in FIG.
When input to C22, the TTL of the burst signal IS is L.
At the OW level, the outputs of IC24 and IC26 in FIG. 2 both become TTL LOW level. Differential amplifier Q
21. When a TTL LOW level voltage is applied to the base terminal of Q22, point B (baseband low i) in FIG.
The voltage at the input point of the 9-nu filter 4 becomes OV. Therefore, the DATA signal shown in FIG.
2, the voltage level at point B is as shown in Figure 3@, and when the burst signal IS is at LOW level (3rd
between at) in Figure e) becomes OV.

After this signal is phase-modulated by a two-phase modulator A via a baseband low/population filter 4 for not widening the transmission nupectrum, it is input to the switch circuit 2. At this time, the switch circuit 20 gates receive the burst signal 2 shown by ○ in FIG.
Switching is controlled by S.

This burst signal 2S has a slightly shorter stop time than the burst signal IS. (i.e.

The stop time cd of ○ in Figure 3 is included in the stop time ab of θ,
When the switch circuit 2 operates as a closed circuit, the burst signal IS is always in a stopped state. Also, in this embodiment) (-) the stop time cd of the strike signal 2S is 1 bit of the DATA signal ■ with respect to the burst signal ISO stop time ab,
It is shorter by an amount of time that is approximately the same as the width. ) In other words, in such a state,・(-nuN word IS
When the 2-phase modulator A stops, the input voltage of the 2-phase modulator A becomes OV, and 2
All diode diodes forming phase modulator A are turned off. At this time, the leakage of the two-phase modulator A to the carrier wave can be more than 30 dB, so the output level of the two-phase modulator A is attenuated by at least 3 Q dB, and the output level of the two-phase modulator A is attenuated by at least 3 Q dB. The generation of the Perstos wave tram will be sufficiently pressured. ) quest signal I
S and ノ (- Stoi word 2S are connected to the first column of 1i and il as shown in ○ and ○ in Figure 3, and switch circuit 2
Since the burst signal IS is always in a stopped state when the circuit operates as a closed circuit, the occurrence of a burst spectrum in the switch circuit 2 is suppressed.

As explained above, this embodiment has the advantage that it is possible to realize a switch circuit that compensates for the carrier wave leakage of the two-phase modulator A and also does not involve the generation of the worst spectrum.

Further, it is sufficient for the time difference between the burst signal IS and the burst signal 2S to be about 0.5 bits (assuming the width of the DATA signal is 1 bit) on the falling and rising sides, respectively. This has the advantage of enabling highly efficient transmission.

In this embodiment, the switch circuit 2 is provided on the output side of the two-phase modulator A, but the same effect can be achieved even if it is replaced on the carrier wave input side of the two-phase modulator A.

Further, the same effect can be obtained even if a polyphase modulator is used instead of the two-phase modulator A.

This method uses a switch circuit to attenuate the output voltage level of the phase modulator by destroying the circuit that can maintain the potential of the anode and cathode of the phase modulator at an equal potential by using a burst signal. The PSK method has the advantage of being able to suppress the occurrence of burst spectrum due to switching, and the PSK method has the advantage of suppressing the occurrence of burst spectrum due to switching.
It can be used in a burst suppression circuit using an M-scheme modulator.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a conventional method for suppressing tractram in bursts, FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG.
The figure is a signal waveform diagram at each part of FIG. 2. IC21, IC22...D flip-flop circuit, I
C23, IC24, IC25, I'C26...NAN
D circuit, A... two-phase modulator, Q21. Q22...Differential amplifier, 2...Switch circuit, 4...Baseband low-pass filter. Patent applicant Oki Electric Industry Co., Ltd.

Claims (1)

[Claims] In a burst spectrum suppression method of time-division multiplex radio using a burst communication method, when the transmission of the first burst signal is stopped, the signal level is set to a certain level, and when the first burst signal is transmitted, the signal level is set to a certain level, and when the first burst signal is transmitted, the signal level is a first means for creating a baseband signal for driving a modulator without changing the signal level in one direction or one direction; and a baseband filter receiving the output of the first means for not widening the transmission spectrum. , a modulator that takes the output of the baseband filter as an input and outputs a carrier wave that is attenuated by a considerable amount at the output end when the transmission of the first burst signal is stopped compared to when transmitting, and the output side of the modulator or a switch means provided on the carrier wave input side of the modulator and controlled by a second burst signal that always stops transmission when the transmission of the first burst signal stops;
A burst spectrum suppression method characterized by suppressing the spectrum caused by burst signals.