JPS608664B2 - FM heterodyne relay method - Google Patents

Description

[Detailed description of the invention] The present invention relates to an FM heterodyne relay system.

FIG. 1 shows an example of the configuration of a transmitting section of a conventional FM heterodyne relay system.

The input signal 1 has the AM component added to the amplitude limiter 101 suppressed. The output signal 2 of the amplitude limiter 101 with the AM component suppressed is mixed with the transmission/transmission local oscillation signal of the transmission local oscillator 103 applied to the transmission frequency converter 102 . The high frequency band transmission signal 3 output from the transmission frequency converter is routed to the circuit 1.
04 and is applied to a bandpass filter 105. The high frequency band transmission signal 4 is subjected to band restriction by a band filter 105 and is input to a high frequency amplifier 106, where it is amplified and sent to the next station. In this case, the FM modulated wave is
The M component is generated and converted into a PM component by AM-PM conversion in the high frequency amplifier 106, changing the frequency shift of the FM modulated wave, and deteriorating the amplitude characteristics in the high frequency band of the low frequency band when the FM modulated wave is demodulated. Conventional repeaters do not usually correct such low frequency band amplitude characteristics, which is particularly problematic when transmitting television signals. An object of the present invention is to provide an FM heterodyne repeater that eliminates the above-mentioned drawbacks. FIG. 2 shows an example of the configuration of a transmitting section of the FM heterodyne relay system of the present invention, which has a function of compensating for low frequency band amplitude characteristics.

The present invention is directed to the output side of the intermediate frequency band amplitude limiter in the transmitting section.
Next slope delay element 108 and delay element 10 having exactly opposite characteristics to the delay element 108 that enters the input side of the intermediate frequency band amplitude limiter.
7, and these two delay elements compensate for the low frequency band amplitude characteristics. As shown in FIG. 2, when a delay element 108 having a group delay time characteristic of a first-order slope is inserted after the amplitude limiter 101, the output FM modulated wave has an AM component.

In other words, since the first-order slope of the group delay time characteristic is a second-order phase characteristic, the side beam nd of the FM modulated wave has an AM component because the phase changes with respect to the carrier wave. Furthermore, since the phase characteristic is quadratic, the side Mn whose frequency is further away from the carrier wave has a larger phase change, so the AM component becomes larger. This FM modulated wave with an AM component is converted into a PM component by the AM-PM conversion of the transmission frequency converter 102 and the transmission high frequency amplifier 106, and the frequency deviation of the FM modulated wave is changed and the FM modulated wave is demodulated. Changes the amplitude characteristics in the high range of the low frequency band. Therefore, by selecting an appropriate combination of the delay primary gradient characteristic of the delay element 108 and the transmitter AM-PM conversion coefficient, it is possible to compensate for the deterioration of the low frequency band amplitude characteristic occurring within the repeater. At this time, when there is an interrupt signal 10 from the transmitting local oscillator 103, the main signal 4 side has a first-order delay slope characteristic, which is not affected by the first-order delay slope characteristic with respect to the interrupt signal side. However, if this delay characteristic is compensated for in the receiving system of the next station, the main signal side will be compensated, but conversely, the interrupt signal side will be subject to the first-order delay slope characteristic by the receiving system's compensation delay equalizer. When combined with the main signal, it becomes quasi-conversational noise due to the i-th order delay slope characteristic, causing distortion noise in the main signal. Therefore, according to this method, although it is possible to compensate for the low frequency band amplitude characteristics, quasi-crosstalk noise is generated due to the combination of the interrupt signal and the main signal. The object of the present invention is to compensate for the low frequency band amplitude characteristics by eliminating the generation of quasi-crosstalk noise due to the combination of the interrupt signal and the main signal.

In other words, as shown in FIG. 2, by inserting a delay element 107 whose delay characteristics are opposite to those of the delay equalizer 108 before the amplitude limiter 101, the input signal 4 of the transmission frequency converter 02 is
has a flat delay characteristic, so both the main signal and the interrupt signal are sent to the next station with their delay characteristic flat, without being affected by the delay slope characteristic that causes quasi-crosstalk noise due to the combination of the main signal and the interrupt signal. . At this time, the AM component generated by the delay slope characteristic before the amplitude limiter 101 is suppressed by the amplitude limiter 101. Since this intermediate frequency band amplitude limiter has little AM-PM conversion action, it suppresses the AM component without generating a low frequency band amplitude characteristic. This amplitude limiter 1 01
The output signal 3 has no AM component and has a first-order delay slope characteristic. This signal 3 is transmitted to the delay element i08 after the amplitude limiter 101.
1, the delay characteristics are equalized and become flat, but the output signal 4' of this delay element 108 becomes a signal having an AM component as described above due to the delay slope characteristic of delay element 0108.
Thereafter, this signal 4 is sent to the transmission frequency converter 102 with a flat delay characteristic and an AM component due to the first-order slope of the delay characteristic. Here, a low frequency band amplitude characteristic is generated by AM-PM conversion within the transmission frequency converter 102 and the transmission high frequency amplifier IQ65. In other words, by changing the magnitude and polarity of the delay slope characteristics of a pair of delay elements having first-order delay slope characteristics with opposite characteristics, which are placed before and after the amplitude limiter IQ, the amplitude can be reduced without deterioration due to interrupt signals. Can compensate for frequency band 0 amplitude characteristics.

[Brief explanation of the drawing]

FIG. 1 shows an example of the configuration of a transmitting section of a subordinate FM heterodyne relay device, and FIG. 2 shows an example of the configuration of a transmitting section of an FM heterodyne relay device according to the present invention. In the figure, 101...amplitude limiter, 102...transmission frequency converter, 103...local oscillator, 104...
Circulator, 105... Bandpass filter, 106... Amplifier 107, 108... Delay element. Fig. 1 Fig. 2

Claims (1)

[Claims] 1. In a relay system having an FM heterodyne transmitter/receiver, an intermediate frequency band amplitude limiter, a transmission frequency converter,
a transmitting local oscillator that generates an interruptible signal in a low frequency band; and first and second delay elements having predetermined delay characteristics and opposite characteristics on the output side and the input side of the amplitude limiter, respectively, The combination of the predetermined delay characteristic of the first delay element and the AM/PM conversion coefficient of the transmission frequency converter compensates for the deterioration of the amplitude characteristic in the high range of the low frequency band of the main signal, and the second delay element An FM heterodyne relay system, characterized in that the delay characteristic of the first delay element is canceled out by the delay characteristic of the first delay element to prevent deterioration of the main signal transmission characteristic during the interrupt signal modulation operation.