SU64036A1 - Multichannel communication method on VHF - Google Patents

Description

The mastering by modern radio technology of generation, reception and sharply directed radiation of ultrashort (decimeter) waves gives a fundamentally new method for a radical solution to the problem of long-distance intercity radio communication.

This method consists in transmitting signals through a number of retransmitting radio stations, the distance between which is within the limits of direct visibility. .

The extremely high carrier frequency allows for a wide bandwidth that can be used to simultaneously transmit a large number of telephone conversations or other signals, for example, telegraph, photoshoot, and so on. The method recorded by Armstrong with sub-frequencies, their oscillations and double frequency modulation is suitable only for a small number of channels due to the too wide frequency band occupied by each of the channels.

The proposed method of implementing multi-channel transmission aims to take advantage of frequency modulation in terms of suppressing interference at the reception and, at the same time, achieve a narrowing of the baseband frequency in order to maximize the compaction of the radio link.

The essence of the proposed multi-channel communication method on VHF is that the carrier oscillation is modulated in frequency simultaneously by a larger number of signals superimposed on the subcarrier frequencies, and the subcarrier frequencies themselves and one of the side frequencies of each subcarrier oscillation are suppressed before the frequency modulator of the transmitter is fed, and at the reception the subcarrier vibrations are restored.

The proposed method is illustrated in FIG. 1 shows a skeletal diagram of a transmitter; FIG. 2 - the same receiver circuit, and in FIG. Figure 3 shows the spectrum of the modulating frequencies supplied to the transmitter modulator.

Each of the channels at the input of the transmitter consists of a sub-carrier oscillator 1 and a balanced modulator 2 or any other device for suppressing the sub-carrier oscillation and one sideband.

When the frequency of the subcarrier PI is to the modulation frequency, Fo at the output of the balanced modulator yields the frequency Fi -f-FO or Fi-F.

After mixing all the channels in mixer 3, the frequency modulator 4 of the transmitter 6 through the amplifier 5 serves frequencies that are located relative to each other in accordance with FIG. 3

At the reception after the frequency conversion of the signal in the converter 2 with the local oscillator 1, amplification of the intermediate frequency by the amplifier 3 and: limiting. the amplitudes of the limiter 4, the oscillation is subjected to detection in the frequency detector 5, as a result of which the frequency spectrum of FIG. 3

Channel separation can be performed by a filter system 6, each of which is designed to pass frequencies in the FO band at a center frequency close to the frequency of the corresponding subcarrier that can be restored at the reception site either using local oscillators 7 or from additional signals sent by the transmitter .

This method of multiple transmission, based on the combination of single-band amplitude modulation B of each of the channels with frequency modulation of the carrier oscillation of the transmitter, allows the following advantages to be realized: a) Complete loss of the channel in the pauses between conversations And a relatively small part of the time coming to full use of transmitter amplitude (at the moments of the maximum signal level in this channel).

b) The dramatic attenuation of "transitional conversations and" transitional noises, due to the absence of constantly operating subcarriers, harmonics and combination oscillations of which fall into adjacent channels and are the main source of difficulties in systems with sub-carrier frequencies.

c) Significant narrowing of the frequency band modulating the transmitter.

d) Significant gains in transmitter power, which can be obtained by taking into account the low probability that a significant deviation of the modulating voltage from the average level can occur simultaneously in a greater number of channels.

Subject invention

1. A multichannel communication method on VHF, characterized in that the carrier oscillation modulates in frequency simultaneously a large number of signals superimposed on the subcarrier frequencies, the subcarrier frequencies themselves and one of the side frequencies of each subcarrier oscillation being suppressed before being fed to the frequency modulator of the transmitter , and at the reception the sub-carrier vibrations are restored.

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