JPH02285725A - Improving method for interference between transmission and reception - Google Patents

Abstract

PURPOSE:To reduce interference between transmission and reception by synthesizing part of an output of a transmitter with a received wave while the amplitude and the frequency of the output of the transmitter are kept the same as those of an interference wave detoured to a receiver and the opposite phase is taken. CONSTITUTION:A part PT of an output FT of a transmitter TX of a sender side 10 is subject to amplitude and phase variable processing through an attenuator 1, a filter 2 and a phase shifter 3 so as to a compensated wave PC with the same amplitude and frequency characteristic but opposite phase as those of an interference wave F'T bypassed to a receiver side 20 from the sender side 10 in the same station. Then the received wave FR is synthesized with the wave F'T to attenuate the synthesized output between the interference wave F'T and the compensated wave PC to zero or nearly zero. Thus, the interference between transmission and reception is reduced and the transmission loss of the transmission wave FT of the main signal and the received wave FR is not increased, no equalizer is required, the characteristic of each filter is relaxed and the cost is reduced.

Description

[Detailed Description of the Invention] [Summary] In a radio relay station of a microwave multiplex line, one antenna is shared for both transmission and reception, and a part of the output of the transmitter in the same station goes around to the receiver and interferes with the received waves. Regarding a method for improving transmission and reception interference that reduces transmission and reception interference, it minimizes the increase in transmission loss of the main signal, does not require a special equalization layer to equalize the characteristics, has low filter characteristics, and is low cost. The purpose of the present invention is to provide a method for improving transmission and reception interference that can narrow the frequency interval between transmission and reception, and includes an attenuator that inputs a portion of the output of a transmitter to vary the amplitude, a filter that varies the frequency characteristics of the input amplitude, and A phase shifter that varies the phase of the input is provided, and the attenuator, filter, and phase shifter are connected, and a part of the output of the transmitter in the same station goes around to the receiver, and the interference wave, its amplitude, and the frequency characteristics of the amplitude are generated. It is configured to combine with the received wave with the same phase and opposite phase.

[Industrial application field]

The present invention relates to a radio relay station for microwave multiplexed circuits, and in particular, when one antenna is shared for transmission and reception within the same station, a part of the transmitted wave goes around the receiver and causes interference with the received wave. Concerning methods for improving interference. In particular, in the case of transmitting digitally modulated signals, as shown in the explanatory diagram in Figure 3, the spread of the transmitted wave spectrum occupies a wide band on the frequency axis, so it overlaps with the received wave spectrum, and transmission and reception interference becomes significant. Improvement methods are desired.

[Conventional technology]

As shown in FIG. 4, the conventional method for improving transmission and reception interference consists of a transmission side 10 that transmits a transmission wave F from a transmitter TX to one antenna 100, and a transmission wave F that is received from the antenna 100 to a receiver RX within the same station. At the receiving side 20 that receives the wave PR, the transmitting side 10 receives the received wave F(CHl', CH3).
', CH5')
EF) 12 is a band pass filter (BP
I, BF3. BFs) added to 11, receiving side 20
A band-elimination filter (BEF) 22 that removes the transmitted wave Ft (C81, CH3, CH5) is used to remove the received wave F,
I bandpass filters (BPI, BPI, BFs)
In addition to 21, a method of reducing the amount of interference in which a part p% of the transmitted wave F outputted by the transmitter TX on the transmitting side 10 goes around the receiver RX on the receiving side 20 and interferes with the received wave F. is taken.

[Problem to be solved by the invention]

The above conventional improvement method uses a band-elimination filter (BEF) 12 on the transmitting side 10 that removes the received wave F, and a band-elimination filter (BEF) on the receiving side 20 that removes the transmitted wave FT.
EF) 22, the main signal, the transmitted wave F
t and the transmission loss of the received waves F and I increase, and the system gain decreases. ■Since the transmission characteristics of the main signal, ``amplitude frequency characteristics'' and ``delay time frequency characteristics,'' are significantly degraded, a new equalizer is required to compensate for this, and the error in the equalization is remain. (2) The performance required of the bandpass filter 11 on the transmitting side 10 and the bandpass filter 21 on the receiving side 20 becomes stricter, and the cost increases accordingly. (2) There is a problem in that the frequency interval between the transmitted wave PT and the received wave F is limited and cannot be narrowed below a certain interval.

The present invention solves the above-mentioned conventional problems, minimizes the increase in transmission loss of the main signal, does not require an equalizer that specifically equalizes the characteristics, has not particularly strict filter characteristics, and is low cost. It is an object of the present invention to provide a method for improving transmission and reception interference that can narrow the frequency interval between transmission and reception.

[Means to solve the problem]

This problem is solved by taking advantage of the fact that, in general, when two waves with the same frequency are synthesized with the same amplitude and frequency characteristics of the amplitude, and only the phase is reversed, the combined output will be zero or close to zero. As shown in FIG.
A compensation wave Pc whose amplitude, amplitude frequency characteristic and phase are set to be the same as that of the interference wave FT' that goes around to the receiver RX as a part of the output pt, and only the phase is set to be opposite to that of the interference wave FT'.
This problem is solved by the configuration of the present invention in which the received waves Pi and Ft' are combined as follows.

In the principle diagram of FIG. 1 showing the basic configuration of the transmission/reception interference improvement method of the present invention, l is the output F7 of the transmitter TX of the transmitter 10 in the same station that uses one antenna 100 for both transmission and reception. Part Py
This is an attenuator that inputs and changes its amplitude.

2 is a filter that inputs the output Pt of the transmitter TX on the transmitting side 10 and changes the frequency characteristics of the amplitude thereof.

3 is the output P? of the transmitter TX on the transmitting side 10? This is a phase shifter that inputs and changes its phase.

Then, the attenuator 1, the filter 2, and the phase shifter 3 are connected, and a part pt of the output FT of the transmitter TX on the transmitting side 10 in the same station is converted into interference waves p, l of the transmitted wave that goes around to the receiving side 20. Received waves F and l are used as compensation waves Pc with the same amplitude and frequency characteristics of the amplitudes, and only the opposite phase.

p%.

[Effect]

The attenuator 1 of the present invention has an output F of the transmitter TX on the transmitting side 10,
The filter 2 changes the frequency characteristics of the amplitude, and the phase shifter 3 changes the phase to output the output of the transmitter TX on the transmitting side 10 in the same station. F
The interference wave F,' that sneaks around to the receiving side 20 at a part of T and interferes with the received wave is converted into a compensation wave Pc with the same amplitude and amplitude frequency characteristics and with only the opposite phase, Ft.
', the combined output of the interference waves p, l and the compensation wave Pc is attenuated to zero or close to zero, and only the original received wave F is received. There is virtually no increase in the transmission loss of the wave pt + received wave F, t, there is no need for a special equalizer to equalize the characteristics, and the characteristics required for the bandpass filters on the transmitting and receiving sides are particularly strict. This is not necessary, the cost is low, and the frequency spacing between transmitting and receiving can be narrowed to the extent that there are no other problems, so the conventional problems are solved.

〔Example〕

FIG. 2 is a block diagram showing the configuration of a method for improving transmission and reception interference according to an embodiment of the present invention.

In FIG. 2, the attenuator 1 of the present invention is composed of, for example, a variable resistance attenuator ATT, which inputs a portion Pt of the output of the transmitter TX on the transmitting side 10 to vary its amplitude. The phase shifter 3 is composed of, for example, a digital phase shifter ps, which varies the phase of the input P7, and changes the frequency characteristic of the amplitude of the input pT.
7, and have the same amplitude and frequency characteristics as the interference wave pT+ of the transmission wave that is a part of the output of the transmitter TX on the transmitting side IO in the same station and goes around the receiver RX on the receiving side 20. , received waves F, I as compensation waves Pc whose phases are opposite to each other.
, Ft', the combined output of the interference wave p% and the compensation wave Pc is attenuated to zero or close to zero, and only the original received waves F and R are received.

Therefore, the method for improving the transmission/reception interference in the embodiment shown in Fig. 2 is based on the equalization method, in which there is virtually no increase in the transmission loss of the main signal's transmitted wave FT + received wave PR, and special equalization of the frequency characteristics of the amplitude and delay time is performed. There is no need for particularly strict characteristics for the band-pass filters 11 and 21 on the transmitting side 10 and the receiving side 20 and the band-pass filter 2 for correcting frequency characteristics, and the cost is low. There is no problem because the reception frequency interval can be narrowed to the extent that there are no other problems.

〔Effect of the invention〕

As explained above, according to the present invention, the transmission loss of the transmitted wave and the received wave of the main signal can be minimized, and since it does not affect the amplitude characteristics and delay characteristics of the main signal, there is no need for an equalizer, and each filter The required performance is moderate and low cost, and the frequency interval for transmission and reception can be narrowed to the extent that there are no other problems, so if it is applied to the case where the antenna of a digital modulation wireless relay station is shared for transmission and reception, it will be possible to easily eliminate transmission and reception interference. The effect of significantly improving this can be obtained.

FIG. 3 is an explanatory diagram of conventional transmission/reception interference, and FIG. 4 is a block diagram of a conventional method for improving transmission/reception interference. In the figure, 1 is an attenuator, 2 is a filter, and 3 is a phase shifter.

[Brief explanation of drawings]

FIG. 1 is a principle diagram showing the basic configuration of the method for improving transmission and reception interference of the present invention. FIG. 2 is a block diagram showing the configuration of the method for improving transmission and reception interference according to an embodiment of the invention.

Claims (1)

[Claims] Leakage (F_T) of the output (F_T) of a transmitter (TX) in the same station that uses one antenna (100) for transmission and reception.
') wraps around the receiver (RX) and interferes with the received wave (F_R). In this method, a part (P_T) of the output (F_T) of the transmitter is input and the amplitude is varied. an attenuator (1) that varies the frequency characteristic of the amplitude of the input; and a phase shifter (3) that varies the phase of the input; The connected output (Pc) is set to have the same amplitude and frequency characteristics as the interference wave (F_T') caused by the leakage of the output of the transmitter in the same station and goes around to the receiver, and only the phase is set to be the opposite phase. Received wave (F_R, F
A method for improving transmission and reception interference characterized by combining with _T').