JPS6139630A - Simultaneous transmitting and receiving communication system using receiver local oscillator and transmitter channel oscillator in common - Google Patents

Abstract

PURPOSE:To cancel crosstalk components of a modulation signal perfectly in a simultaneous transmitting and receiving communicator using a channel oscillator and the first local oscillator (LO) in common, by making the spectrum of the second local oscillator signal and the first IF signal equal. CONSTITUTION:A channel oscillator OSC output of which is modulated by output of an aural signal circuit AF is used in common with an LO1 of a receiver RX and the output is inputted to the first mixer MIX1. On the other hand, a modulation signal is inputted to a level adjusting circuit VOL, and a phas shifter PS, and an output of the second local oscillator LO2 modulated by the output is inputted to the second mixer MIX2 of the receiver RX. The center frequency of a filter BPF1 is conformed with that of the second local oscillator LO2, and its passing band is made equal to the first intermediate frequency filter IF1. Consequently, the modulation spectrum of an LO2 becomes substantially the same with that of the filter IF1. Accordingly, modulation signal components detoured from the channel oscillator OSC through the first mixer MIX1 are canceled perfectly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a simultaneous transmitting/receiving communication system in which a local oscillator is shared with a channel oscillator.

Conventionally, there have been attempts to use the channel oscillator of the transmitter and the local oscillator of the receiver in order to reduce the cost of communication equipment in simultaneous transmitting/receiving communication equipment. When input to the first mixer, the modulated signal, such as voice, is directly demodulated by the receiver.

This can be heard as sidetone, which is very bad.

In order to solve this problem, the inventor of the present application has already filed a patent application in 1983-
155327, as shown in FIG.
m power is directly input to the receiver R/X first mixer MIX1 as the output of the first local oscillator, and the audio signal is adjusted to the required value through the level adjustment circuit VOL and the phase thick PS=z. and thereby modulate the second local oscillator output, and use the output to cancel all modulated signal components included in the first mixer MTXl of the receiver R.X in the second mixer M I X 2. We proposed a simultaneous transmitting and receiving communication method.

However, although the above method is theoretical, in reality, the spread of the spectrum of the signal containing the modulation component input to the second mixer MIX2 of the receiver (X) is limited by the first intermediate frequency filter F1. On the other hand, the spectrum of the output signal from the second local oscillator LO2 is limited only by the splatter filter of the audio signal circuit AP, which is the modulation signal source, so there is some phase difference between the spectra of the two signals. However, the channel oscillator modulation component contained in the received signal 4 cannot be completely canceled.

The present invention has been made in order to eliminate the drawbacks of the above-mentioned conventional simultaneous transmitting and receiving communication system in which a channel oscillator and a first local oscillator are shared. Reception in which the second or subsequent local oscillator output is input to the second or subsequent mixer of the receiver through a bandpass filter whose band has characteristics equivalent to the receiver's first intermediate frequency filter. The overall purpose of the present invention is to provide a simultaneous transmitting/receiving communication system in which a machine local oscillator and a transmitter channel oscillator are shared.

The present invention will be explained in detail below by referring to embodiments shown in the drawings.

FIG. 2 is a block diagram showing an embodiment of the simultaneous transmission and reception communication system according to the present invention.

That is, the channel oscillator 08Ci modulated by the audio signal circuit AP output is shared with the first local oscillator of the receiver R/X, and this output is directly transmitted to the first mixer MI of the receiver R/X.
Input into Xl.

On the other hand, the level and phase of the output of the audio signal circuit AP, which is a modulation signal, is adjusted by a level adjustment circuit VOL and a phase shifter PS, and the output of the second local oscillator L02 is modulated using the output state. The modulated output is sent to the receiver R via a bandpass filter D, PFti.
Input to 1X second mixer.

At this time, if the center frequency of the band-pass filter BPFt is made to match that of the second local oscillator LO2 and the passband is made equal to the first intermediate frequency filter (F1) of the receiver R.X, this band-pass filter), l P F
l The modulation spectrum of the output of the second local oscillator I, 02 that has passed through the first intermediate frequency filter I'FI
The modulated signal component that is substantially equivalent to that of the output signal and that has circulated from the channel oscillator O8C through the first mixer MIX 1f can be completely canceled in the second mixer MIX2.

In FIG. 3, instead of the band-pass filter BPF1, a band-pass filter BPFz4 whose phase delay amount is equal to that of the first intermediate frequency filter IP+ and whose center frequency is equal to that of the second local oscillator L02 is used. As shown, it goes without saying that the phase shifter PS'Ir may be removed.

Since the present invention is configured and functions as explained above, it can be used in a relatively simple circuit configuration and can be used in an expensive transmitter channel oscillator and receiver in a simultaneous transmitting/receiving communication device used in a high frequency band of several hundred MHz or more. The first local oscillator can be shared with the first local oscillator, and at the same time, it is possible to completely eliminate modulated signal components such as voices that go around to the receiver and are demodulated and heard as sidetones, so they do not harm the quality of communication in any way. This has a significant effect on reducing device costs without requiring much effort.

9. The present invention is not necessarily limited to the embodiments described above, and the modulation of the transmitter channel oscillator can be applied not only to audio signals but also to suitable digital signals.

For example, FSK or the like may be used, and it is obvious that signal transmission can be applied to both wired and wireless methods.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a conventionally proposed simultaneous transmitting and receiving communication device that uses a shared channel oscillator/first local oscillator, and FIG. 2 shows an embodiment of a communication device that implements the communication method according to the present invention. Block Diagram FIG. 3 is a block diagram showing another embodiment. AP・・・・・・Audio signal circuit, OSC・
......Channel oscillator, LOl...
・・・・・・First local oscillator, vor,...
...Signal level adjustment circuit. PS・・・・・・・・・Phase shifter + L O2・
......Second local oscillator, BPF+ and BPF2...Bandpass filter. Patent applicant: Toyo Tsushinki Co., Ltd. 71

Claims (2)

[Claims] (1) In a communication device using a simultaneous transmitting and receiving communication system in which the transmitter's channel oscillator output modulated by an audio signal etc. is used as the receiver's first local oscillator output, the signal level is adjusted to the required value and the phase is adjusted. A second or subsequent local oscillator output modulated by a modulation signal shifted by a required value has characteristics equivalent to the band of the first intermediate frequency filter of the receiver and whose center frequency is equal to the second or subsequent local oscillator output. The modulated signal component contained in the output of the first mixer is canceled by inputting it to the second or subsequent mixer of the receiver via a bandpass filter having a center frequency equal to the center frequency of the local oscillator. A simultaneous transmitting and receiving communication system that uses a receiver local oscillator and a transmitter channel oscillator in common. (2) A phase shift of the modulation signal input to the second local oscillator is made unnecessary by making the phase delay amount of the bandpass filter equal to that of the first intermediate frequency filter. Simultaneous transmission and reception communication method described in Range 1.