SU790359A1 - Device for receiving frequency-modulated signals with large base - Google Patents

Description

a key, a synchronizer is connected between the output of the amplitude detector and the control input of the cascade being cascaded, the outputs of the synchronizers of both channels of the signal processing are connected to the control unit, the first output of which is connected to the control inputs of the integrators, the second output - to the control input of the subtractor, the third output - to the control the key and switch signal processing inputs, and the fourth with the key and switch control inputs of another signal processing channel

The drawing shows a structural electrical circuit of the proposed device.

The device contains a narrowband interference suppression unit 1, signal processing channels 2, subtractor 3, delay dispersion lines 4, amplitude detectors 5, switches 6, adders 7, gated stages 8, integrators 9, amplifiers 1O, keys 11, synchronizers 12 and control unit 13

The device works as follows.

The signal from the output of the receiver is fed to block 1 for narrowband interference. Block 1 includes a series of filters connected in parallel (e. Are not shown in the drawing). The output of the filter, in the band of which narrowband interference is present, is blanked.

The operation of the device is considered in two modes, in the acquisition mode and in the reception mode.

In the synchronization mode, the switch 6 connects to the first input of the adder 7 the outputs of block 1, and the key 11 is closed. The difference in the delay of the delayed delay line 4 is chosen N times less than the length of the parcel. Each segment of the input signal before the appearance of the resultant convolution undergoes a sequence of recirculation. Since the filling frequencies of convolutions of different signal regions are different, compression occurs in time — the resulting convolution by PM times. The signals at the output of the dispersion delay line 4 represent one or several maxima, depending on the structure of multipath in the channel. After detection with the amplitude detector 5, the signal is fed to the synchronizer. 12, which for several periods determines the time of arrival of the rays.

Claims (1)

The signals from the outputs of both synchronizers 12 are fed to the control unit 13, which switches the devices to the mode of receiving information. With the signal compression mechanism used by its N - fold recirculation, the noise power increases by a factor of N in the signal convolution time as compared to the compression of the signal in the dispersion delay line with a delay difference equal to the duration of the transmission. In order to receive information without reducing the reliability, in this device the control unit 13, by supplying commands to the control inputs of the switches 6, switches them to alternately connecting to the first input of the adders 7 of the filters of block 1 synchronously with the appearance of the corresponding frequency sections of the frequency control unit. signal. Since the keys are pressed and released, the opposite laws of frequency change, at each time point in channels 2 filters are connected, which are located in frequency mirror with respect to the average frequency of the signal. With rectangular frequency characteristics of filters, it is sufficient to choose the number of filters equal to N. Because the amplitude-frequency characteristics of the filters of block I are selected in the form of a trapezium, when the frequency characteristics of adjacent filters are intersected at a level of 0.5 to ensure linearity of the phase characteristics of block 1, the number of filters must be slightly larger and be 1.2-1.3 . By sending a command from the control unit 13 to the control input of the key 11, the last one in the information reception mode is closed at the instants of convolutions at the output of the dispersion delay line 4. In this connection, there is no increase in systemic interference due to subsequent recirculation of the minimized signal. At the moments determined by synchronizers 12, the signal is sampled in the strobe stage 8. In the integrators 9, the signals of the individual rays are added together and the resulting values are stored. The control unit 13 forms, at its second output, a command to interrogate the result of the comparison of the output signals of the integrators 9 in the subtractor 3. This command is issued after the first of the beams appears after a time interval exceeding the multipath interval. In accordance with the sign of spreading at the output of the miner 3, the decision signal is generated in the decision block (not shown). After the decision on the sign of the parcel is made from the control unit 13, commands are given to set the integrators 9 to the initial state. The introduction of separate synchronizers 12, gated cascades 8, integrators 9 in each channel 2 ensures the operability of the device with virtually no reduction in the reliability of reception and with Doppler shifts. Apparatus of the Invention A device for receiving frequency-modulated signals with a larger base, comprising a narrowband interference suppression unit, the outputs of which are connected to the inputs of two signal processing channels, the output of each of which is connected to the corresponding input of the subtractor, each signal processing channel containing serially connected the dispersion delay line and the amplitude detector, which is in such a way that, in order to increase the availability of frequency-modulated signals, with a large base during communication With a moving object, in each signal processing channel between the input inputs and the delay dispersion input, the switch and the adder are connected in series, and between the amplitude detector output and the output of the signal processing channel, the cascade and integrator are connected in series, between the output of the dispersion delay line and the other input of the adder is connected in series with the amplifier and the key, between the output of the amplitude detector and the control input of the gated cascade the synchronizer is connected, to the outputs of the synchronization In both signal processing channels, the control unit is connected, the first output of which is connected to the integrator control inputs, the second output to the subtractor control input, the third output to the control inputs of the key and switch of the same signal processing channel, and the fourth to the control inputs key and switch another channel signal processing. Sources of information taken into account in the examination I. Zaitsev, DL, et al. On the noise immunity of a system for transmitting discrete information by signals with linear frequency modulation. - Electrosv, 1968, N 4, p. 18, fig. I (prototype).