JPH0779300B2 - Heterodyne relay system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a receiving local oscillation frequency and a shift frequency in a heterodyne relay system, and more particularly to maintaining frequency stability and improving non-linear distortion of heterodyne relay.

[Conventional technology]

Conventionally, in the heterodyne relay system, an independent local oscillation system having a reception and transmission local oscillator and a shift system for shifting a reception frequency by a difference between transmission and reception frequencies are used.

In the independent local oscillation method, the high frequency band local oscillator transmits and receives 2
In the shift system, one high frequency oscillator, one low frequency oscillator, and a mixer are used.

[Problems to be solved by the invention]

However, the independent local oscillation system uses two high-frequency oscillators and is therefore expensive, and the frequency deviation and the phase jitter in the case of heterodyne relay are doubled. Therefore, it is not suitable for heterodyne multi-repeat, which is highly sensitive to frequency deviation and phase jitter.

On the other hand, in the shift system, as shown in FIG. 5, it is composed of a high-frequency receiving local oscillator 2, a shift frequency oscillator 4'having an oscillation frequency of a transmission / reception signal frequency difference, and a shift frequency converter 3 '. . FIG. 6 shows a frequency array. In the case of heterodyne relay, the frequency stability depends on the shift frequency oscillator 4 '.
It is determined by the frequency stability of and becomes high stability when converted to high frequency stability. Further, even in the heterodyne multi-relay, the frequency deviation and the phase jitter in each relay station are small, but the non-linear distortion in the transmitting and receiving sections is added for each relay, so that it is not suitable for digital signal transmission or the like.

[Means for solving problems]

In order to improve the drawbacks in the system described above, in the present invention, the oscillation frequency (f ₀ ) of the shift frequency oscillator in the shift system is set to the transmission / reception signal frequency difference (f _S ) and the intermediate frequency (f _IF ) in the heterodyne relay. And f ₀ = f _S ± f _IF × 2, so that the high frequency stability is maintained and the nonlinear distortion generated in the transmitter and receiver is compensated for each relay. is there.

〔Example〕

FIG. 1 shows an embodiment of the present invention, in which the received signal (reception frequency f _R ) input to point a is input to the receiver 1 and is intermediate by the reception local oscillation frequency (f _RL ) of the reception local oscillator 2. It is converted to a frequency signal (f _IF ). On the other hand, a part of the signal of the reception local oscillator 2 is input to the shift frequency converter 3 and mixed with the output frequency (f ₀ ) of the shift frequency oscillator 4, and f _RL + f ₀ ( Alternatively, f _RL −f ₀ ) is selected and is supplied to the transmitter 6 as transmission local oscillation power.

On the other hand, the arrangement of these frequencies is f ₀ = f _{S as} shown in FIG.
+ f _IF × 2 (or f ₀ = f _S -f _IF × 2) (where f _S = | f _R -f _T
Since |, f _T is selected as the transmission signal frequency,
For example, if the reception local oscillation frequency f _RL is lower (or higher) than the reception signal frequency f _R , the transmission local oscillation frequency f _TL
Will be higher (or lower) than the transmitted signal frequency f _T.

3 and 4 show specific examples of compensation of nonlinear distortion in the case of the present invention. In FIG. 3, D ₁ is a non-linear distortion component at the receiver input terminal a, D ₂ is a non-linear distortion component in the intermediate frequency band, in the case of f ₀ = f _S + f _IF × 2. At this time, the local oscillation frequency f _RL is lower than the received signal frequency f _R , so the phase of the nonlinear distortion component does not change. The phase of this distortion component is converted by 180 ° because the transmitter local oscillation frequency is higher than the transmission signal frequency f _{TL in the} transmitter 6 by the shift frequency method. That is, the nonlinear distortion generated in the transmitter 6 has the opposite polarity, and the nonlinear distortion component is reduced. In the case of FIG. 4, when f ₀ = f _S −f _IF × 2 and the reception local oscillation frequency f _RL is lower than the reception signal frequency f _R , the nonlinear distortion component also decreases as in FIG.

〔The invention's effect〕

As described above, the present invention adopts the shift frequency system in the heterodyne relay system and sets the frequency (f ₀ ) of the shift frequency oscillator to f ₀ = f _{S with} respect to the transmission / reception signal frequency difference (f _S ).
By selecting as ± f _IF × 2 (f _IF : intermediate frequency),
While maintaining high frequency stability, phase jitter is reduced and nonlinear distortion is reduced, which is effective in improving high-speed digital transmission performance.

[Brief description of drawings]

FIG. 1 shows a block configuration example of an embodiment of the present invention, FIG. 2 shows a frequency array of each part of FIG. 1, and FIGS. 3 and 4 are reasons for reducing the non-linear distortion component in the present invention. FIG. 5 shows a conventional circuit example, and FIG. 6 shows a conventional frequency array. In the figure, 1 is a receiver, 2 is a receiving local oscillator, 3 is a shift frequency converter, 4 is a shift frequency oscillator, 5 is a band pass filter, and 6 is a transmitter.

Claims (1)

[Claims] 1. A method of obtaining a transmission local oscillation frequency (f _TL ) by shifting a reception local oscillation frequency (f _RL ) so that the shift frequency is | f _R -f _T | ± {intermediate frequency (f _IF ) X2} is a heterodyne relay system.