SU745008A2 - Device for detecting distortions of discrete information in communication channel for frequency-manipulated signal receivers - Google Patents

Description

 , -1 The invention relates to radio engineering and can be used to detect distortions of frequency-manipulated signals caused by interference in a communication channel. . According to the main author. St. No. 387532 a device is known for detecting distortions in a communication channel for frequency-manipulated-receiver receivers, that is, from a shaping node, the output of which is simultaneously connected to the INFFSMSH1-ION output to (} The junction node is connected to the input of signal quality detectors consisting of a second harmonic filler connected in series, a low-pass filter detector and a threshold node, with the outputs of the signal quality detectors combined by the OR circuit. However The known device has insufficient sensitivity to noise, which distorts the waveform very much. The purpose of the invention is to increase the reliability of distortion detection. For this purpose, a communication channel distortion detection device for receivers of Frequency-Manipulated Signals consisting of a shaping node, the output of which is constantly connected. to the inputs of the information and, according to the number of used frequencies, control channels, the output ({yupypyayuschiy node is connected to the input of the signal quality detectors, consisting of second filter of the second harmonic signal, detector, low-pass filter and threshold node, with the outputs of the detectors | the quality of the signals is combined by the OR circuit / serially connected di (div) module, an additional detector and an additional threshold block, the input of the differentiation unit connected to the output of the forming unit, and the output of the additional threshold block connected to the additional input of the OR circuit.

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FIG. G provides a structural electrical diagram of the proposed device; in fig. 2, 3, and 4 are graphs that determine the principle of operation of the device. The device for detecting distortions contains forming node 1, differentiation unit 2, additional detector 3, additional threshold block 4, circuit OR 5 and signal quality detectors b, consisting of a second harmonic filter 7, detector 8, a third-band width. These frequencies are 9 and the threshold node 10.

The device works as follows.

A sequence of rectangular pulses with a duty cycle 2 is formed from the input sinusoidal signal in the forming unit 1. The spectrum of such a pattern consists only of the fourth and even harmonics of the signal. If the signal is interfered with in the communication channel, its shape at the output of the terminal becomes different from the sinusdal, as a result of which the squaring of impulses at the output of the output node of the node 1 ceases to be equal to 2, and even harmonics of the signal appear in its Seektra. The highest level among them will have the second harmonic. In quality detectors 6, the second harmonic level is monitored for each of the transmission frequencies. If this level exceeds the threshold value, then by the operation of the threshold node 10, the occurrence of interference in the communication channel is determined.

The dependence of the voltage of the second harmonic in the spectrum of the T-pulse wave with the period T of LPG changes in the duration of these ampulses (the duty cycle is the ratio of the period of the pulses to their duration) is shown in FIG. 2. The ordinate axis shows the normalized magnitude of voltages of the second harmonic U, and the abscissa shows the duration of the pulses T, T-period of the pulses. This dependence can be obtained by expanding the levels of the second harmonics for different pulse durations using the known spectral decomposition formulas of the sequence of U-shaped pulses.

FIG. 2 that when changing the pulse duration by more than 50%, the level of the second g of the monica starts dropping from the drive, and, consequently, the sensitivity of the device also falls (interference to the noise causing such distortion).

With the help of a codenser (not shown in the drawing) in differentiation block 2, the constant component of the pulse train spectrum is eliminated.

from the output of the forming unit 1. This leads to the fact that at the output of the capacitor, the average value of the voltage becomes zero, i.e. the product of the amplitude of a positive pulse over its duration will be equal to the amplitude of the negative pulse produced by its duration (the areas of the positive and negative pulses become equal). If the signal is not distorted by interference, then

the durations of the positive and thrush pulses at the output of the differentiation unit 2 are equal to each other, since the duty cycle is 2. In this case, the t amplitudes of both pulses will be one,

Coves and, have a certain stationary value.

If the signal is distorted by interference, the ratio between the durations of pulses of different polarities changes, while their amplitudes change at the output of the capacitor (it follows from the condition of equality of areas that a shorter pulse will have a larger amplitude, and a longer pulse will have a smaller amplitude ). The amplitudes of both pulses will become different from the stationary value. With the help of detector 3 and threshold unit 4, this deviation is monitored. The output of the threshold unit 4 is combined with the outputs of the quality detectors 6 of the device according to the OR 5 scheme.

Dependence of the amplitude deviation of the pulses at the output of the block

Differencing 2 from stationary

Claims (2)

the magnitude of the change in pulse durations is shown in FIG. 3, where the pulse duration T is plotted on the abscissa axis, the absolute value of the amplitude deviation of these pulses from the stationary value (amplitude of the pulses at their T / g duration) is plotted on the ordinate axis, T is the frequency-signal period, is the output pulse amplitude. This dependence can be easily obtained from the following considerations: let T be the pulse duration of one polarity, X is its amplitude at the output of differentiation unit 2, T – T is the pulse duration of the other polarity, and its amplitude at the output of the differential block 2. the constant component at the output of the capacitor will be xT (2 Urrt -x) (T-t), from where the pulse amplitude will be x 2t tr-77 / T, and the absolute value of the pulse amplitude deviation from the stationary value of D-C) 7 / h5 and d :. The magnitude of the absolute deviation of the amplitude of a pulse from a stationary value increases linearly with a change (decrease or increase) in its duration from the value of T / g. Thus, for cases with noise that strongly distort the waveform, the total characteristic of the distortion detection device will look like that shown in Fig. 4, where the pulse duration T f is plotted along the abscissa axis and the ordinate voltage on the abscissa axis is caused by interference in the communication channel, in the device for detecting distortions, T is the period of the signal frequency, Uffj is the amplitude of the pulses at the output of the forming unit 1. From FIG. 4, it can be seen that for small derangements a greater sensitivity provides control over the level of garm nicks, and for large disorders - on. the magnitude of the amplitude deviation of the pulses from the stationary value at the output of differentiation unit 2, the signal of the communication channel goes to the forcing unit 1, which forms from it a sequence of rectangular pulses. The capacitor of differentiation unit 2 eliminates the constant component of the spectrum of this sequence. The signal from the output of the differentiation unit 7 8® 2 is detected by the detector 3 and compared on the threshold unit 4 with a stationary voltage equal to the amplitude of the pulses during their duty cycle 2. If the amplitude deviates from the stationary voltage in magnitude, the threshold unit 4 operates, which is a signal of the presence of interference. The use of the proposed device will make the device for detecting distortion of discrete information for the prikoshka frequency-modified signals sensitive not only to noise, slightly distorting the waveform, but also to noise, strongly distorting the waveform in the communication channel, thereby increasing the noise immunity of information transmission. The invention The device for detecting distortion of discrete information in the communication channel for receivers of frequency-manipulated signals according to the author's certificate No. 387532, which differs from the fact that, in order to increase the reliability of the detection of distortions,. A series-connected differentiation unit, an additional detector and an additional porrg unit are introduced, the input | di4x {) differentiation is connected to the output of the forming unit, and the output of the additional threshold unit is connected to the downstream input of the OR circuit. BUT"/ 4TF№: aasfe J) Tr.