SU68670A1 - Radio - Google Patents

Description

The object of the present invention is to divide a channel into two differentially connected branches to compensate for interference. According to the invention, in such a receiver, the differentially connected elements are connected to the unbranched part of the channel through valves, one of which is supplied with a blocking voltage varying along the envelope of the low-frequency spectrum of the received signal.

The invention is illustrated in the drawing; in FIG. 1 and 4 of which diagrams of the proposed receiver are shown, and in FIG. 2 and 3 are curves explaining its effect.

The basic scheme of a broadcasting receiver is shown in FIG. 1. Here, the diodes D and D of the lamp L, work as gates, one of which is always open, and through it provides the connection of the intermediate frequency circuit with the communication coil L. The second diode Dj, when receiving the station, is locked by supplying its anode negative with respect to voltage cathode with potentiometer f. The locking voltage is its magnitude corresponding to the modulation coefficient of the main components of the signal frequency. The greater the modulation coefficient of the signal, the greater the positive blocking voltage. Thus, the diode Yes of the lamp 77. is locked at all changes in the signal modulation coefficient. If there is no signal, the negative voltage is automatically removed and the DZ diode opens. Then, the intermediate frequency oscillations also appear in the coil, modulated in this case only by the voltage of the noise. The blanking voltage created by the noise is disproportionate to their value, due to the clipping of a significant part of the noise spectrum by the LCo filter included in the low-frequency amplifier circuit of the auxiliary channel.

The coils L and L are connected so that the voltages induced in the coil L of the intermediate frequency circuit CZ by the intermediate frequency current flowing through these coils are in antiphase, i.e. mutually destroyed. There is no connection between the K and KS circuits, due to which there are no interferences to the detector and the receiver paths following it. This achieves noiseless receiver settings.

247

When tuned to a radio station, the diode Da is locked by the negative bias that appeared on its anode, and the connection between the circuits Kg is restored by diode D. Since the stopping voltage at small signal modulation coefficients is small and easily overcome by the voltage of the jammer (here, those that are not of a periodic nature, but appear to be cracked, clicking is atmospheric interference), then diode D opens, and the connection of circuit K is established through this diode to the communication coil L .. But in this case , what already The above indicated that the effect of interference in the circuit K does not occur and, therefore, the interference is limited (more precisely, the mutual compensation of the interference voltage in the circuit KS) - Since the blanking voltage varies in proportion to the change in the modulation factor of the signal, the limit threshold will also be proportional to the depth of the module signal (Fig. 2).

The blanking voltage is obtained as follows: the voltage taken from the intermediate frequency circuit KI is detected by an auxiliary detector on the left diode of the Ld lamp. The audio voltage from the load of this detector through the filter L Cj, which cuts off high frequencies, is fed to the grid of the lamp L of a low-frequency triode amplifier. The amplified sound voltage is rectified by a diode rectifier on the right diode of the lamp RL-P With a potentiometer R, a variable in magnitude negative negative voltage is taken, proportional to the depth of signal modulation. The spreading filter is made with such a constant time that it does not allow a quick increase in the blocking voltage due to a short-term pulsed disturbance.

As is known, when the tone is adjusted, the interference is reduced when the high frequencies of the signal are cut off, also by cutting the high frequency components of the frequency spectrum of the interference. In the auxiliary channel, without sacrificing transmission quality, frequencies can be cut off more than 1500-2000 Hz, which results in better signal enveloping with a variable threshold for limiting interference. In this case, the limit threshold will be proportional to the main frequency components of the signal voltage. This is illustrated schematically in FIG. 3, on which lines 1, 2, 3, 4, 5 show the relative magnitude of the amplitudes of the frequency components of the signal spectrum (for a human voice), and line a-a gives an approximately uniform spectral distribution of interference in the O-5000 Hz region. In the case of a constant interference limit threshold (line b-b), the limitation effect would be determined by area S. In the case of a variable limitation threshold, schematically indicated by the bb line cdegfk - the limitation effect is determined by the sum of the areas Sj -} - Sy.

The minimum initial limit threshold is set with a potentiometer in the absence of noticeable transmission distortion and maximum interference suppression.

The reception scheme for continuous telegraph signals is as shown in FIG. four.

Here the filter is tuned to the beat frequency of the intermediate frequency and the frequency of the second local oscillator. It is easy to see that in this case, if there is no signal (key is pressed), the signal on the circuit / Сз is not received, while the key is pressed, reception occurs.

Subject invention

A channel-divided radio receiver into two differential-connected branches to compensate for interference, characterized in that the differential-connected elements are connected to the unbranched part of the channel through gates, to one of which a blocking voltage is applied, varying along the envelope of the low-frequency spectrum of the received signal.

FIG. one

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Kj AfrCKTOPy ON

to NLSKALUUSR.CH

FIG. 2

threshold ozpot ujef uji

interference

FIG. 3

hfr

FIG. four