SU467492A1 - Device for detecting dual frequency telegraphy signals - Google Patents

Description

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The invention relates to the field of telegraph communication and can be used in devices designed to receive dual frequency telegraphy.

A device for detecting signals of dual frequency telegraphy is known, comprising signals connected in series, separation filters, a descrambler, and threshold cascades.

However, the known device has the following disadvantages: the presence of manipulative interference, due to the fact that the signal goes directly to four filters, therefore, the outputs of all filters are EXCELLENT from zero RESPONSE, and ONLY in the steady state the signal will be at the output of that filter that is set to signal frequency; the presence of noise in the voltage filters reduces the noise immunity of the system, because the difference between the voltage from the signal plus the noise in the filter with the signal and the voltage from the noise in the other three filters decreases.

In order to improve noise immunity in the proposed device, group filters are connected in parallel between the reception path and separation filters, the outputs of the latter are connected to the inputs of a two-channel amplitude discriminator with cross-feedback, the outputs of which are connected to two pairs of separation filters, and their outputs through similar amplitude discriminators connected descrambler.

FIG. Figure 1 shows the structural scheme of the proposed device for detecting dual frequency telegraphy signals; in fig. 2 is a functional diagram of an amplitude discriminator with cross-feedbacks.

The proposed device for detecting double private telegraphy signals contains a signal receiving path 1, a pre-separation band-pass filter 2, tuned to two manipulation frequencies / i and / 2, a BAND pre-separation filter 3, tuned to two manipulation frequencies / 3 and / 4, amplitude discriminator 4 with cross-feedbacks, separation filters 5-8, tuned to the manipulation frequency / s / g, / 3 and / 4, respectively, amplitude discriminators 9 and 10 with cross-feedback, decoder II, poro The first channel 12 cascade 12, the second channel threshold cascade 13, devices 14 and 15, whose transmission coefficient decreases from 1 and tends to O as the control voltage increases from zero to the input voltage amplitude, the envelope detectors 16 and 17.

Amplitude cross-feedback discriminator operates as follows.

When applying to the input I and the input II (Fig. 2) radio signals with different levels of bending at the output, only the signal with an instantaneous envelope value greater than that of the other appears.

Moreover, the output waveform does not change. If a signal plus interference is at input I, and interference at input II, then when the signal power to interference power ratio is greater than 2: 3, the transmission coefficient of device 14 tends to 1, and device 15 approaches 0. Therefore, at output III, signal voltage plus interference; there is no voltage at output IV. There is a sort of “cleaning out the pauses between signals with a constant amplitude of signals.

The principle of operation of the proposed device for detecting signals of dual frequency telegraphy is as follows.

A radio pulse with a filling frequency equal to / 1 is fed to the inputs of filters 2, 3 (Fig. 1). In filter 3, a manipulative interference occurs, but it does not pass to the output, since the lower channel of amplitude discriminator 4 is closed by a signal in the upper channel. There is no interference voltage at the inputs of filters 7 and 8.

Passing the amplitude discriminator 4, the signal goes to filters 5 and 6. In filter 6, a manipulative interference occurs, but it does not pass to the output of the device, since the signal from the output of filter 5 closes the lower channel of the amplitude discriminator 9.

Consequently, a pulse appears on the upper input of the decoder; there is no voltage on the other three inputs. When applying to the input I radio pulses with different filling frequencies (/ g, / 3, / 4), the circuit works in a similar way.

Subject invention

A device for detecting signals of double frequency telegraphy containing serially connected signal receiving path, separation filters, descrambler and threshold stages, characterized in that, in order to increase the noise immunity, group filters are connected in parallel to the separation filters and the latter are connected

with inputs of a two-channel amplitude discriminator with cross-feedback, the outputs of which are connected to two pairs of separation filters, and a decoder is connected to their outputs through similar amplitude discriminators.

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