SU1075447A1 - Device for suppressing impulse noise under receiving television signals in communication system with frequency modulation - Google Patents

Abstract

A DEVICE TO SUPPRESS PULSE INTERFERENCES WHEN TELEVISION SIGNALS ARE RECEIVED IN COMMUNICATION SYSTEMS WITH FREQUENCY MODULATION, containing, a band-pass filter, an adder, the first switch, the second switch, a pulse shaper, the output of which is connected to the control switch of the first switch, the unit has a plug-in unit, a plug-in unit, a plug-in unit, a plug and one unit, a plug-pin unit, a plug-in unit, a plug and one component, a plug-pin unit, a plug-in unit, a unit, a unit, a unit and a unit, is attached to a device, the second switch, the pulse shaper, the output of which is connected to the control signal of the first switch, the second switch, the pulse driver, the output of which is connected to the control switch of the first switch, and the device is connected. a torus, a phase shifter, a first delay element, the output of which is connected to the first 1.1 input of the first switch, and a second delay element, characterized in that, in order to increase noise immunity, has introduced a third switch whose output is. device output, and the first input is connected to the output of the adder, between the output of the first switch and the first input of the adder is included the first low-pass filter, the output of which is connected to the input of the first delay element, between the output of the second switch and its first input are connected in series the second low-pass filter multiplier whose output is connected to the second input of the adder and the input of the second delay element, and the other input is connected to the output of the phase shifter, the subtractor, the other input of which is connected to the output of the field an axial filter and a synchronous detector, another input of which is connected to the output of the phase shifter, frequency discriminator is connected between the input of the device and the second input of the first switch, between the output of the bandpass filter whose input is connected to the output of the frequency discriminator, and the input of the phase shifter are connected in series with the phase detector, fourth fourth switch , the other input of which is connected to the output of the frequency demodulator, the third filter of the lower clock and the controlled oscillator, the output of which is connected to another input from the phase detector, between the output of the second delay element and the second input of the second switch, an amplitude detector is connected, between the output of the device and the control input of the third switch are connected in series a horizontal pulse shaper and TpHireji, between the output of the frequency discriminator and the second switch of the third switch the third delay element is on , between the pulse driver output and the other 42 trigger inputs, a fourth delay element is connected, controlling the inputs of the second and fourth switches with the output of the pulse generator, the output of the second delay element is connected to the input of the frequency demodulator.

Description

The invention relates to a technique of television and can be used to suppress impulse plots in communication lines along which color television signals are transmitted through the SECAM system using frequency modulation. A device for the suppression of impulse noise is known, comprising a impulse noise detector, a switch, a linear interpolator and two delay elements l. However, the device does not allow for the suppression of sh-pulsing interference in the reception of color television signals due to the uncertainty in the implementation of the linear interpolator for the television signal. The closest to the invention to the technical essence is a suppression device. pulse noise when receiving television signals in communication systems with frequency modulation, containing a band-pass filter, an adder, the first one / Iytator, a second switch, a pulse shaper, the output of which is connected to the control input of the device, a frequency demodulator, a phase shifter, the first element delay, the output of which is connected to the first input of the first switch, and the second delay element. In the known device, a full video signal is delayed by the duration of the TC of one line and the color difference signal by the length of the STs. In the event of a hit, a substituted signal is formed, the lacquer co 1 point of which represents the luminous signal of the previous line, and the color difference signal is formed from the line that is 2 t behind the replaced line. Upon detection of a dropout in this device, the signal of the affected line is completely replaced by the signal formed from the signals of the previous lines 2j coming to the device output. A disadvantage of the known device is that it does not allow the signal to be restored in the case (which is just the case in practice under the influence of impulse noise on receiving devices) when the disturbance affects more than one (all is possible) signal floor. This is due to the fact that when a pulsed disturbance hits several lines in this device, it is impossible to generate a 3-channel signal. The purpose of the invention is to increase Mv security. This goal is achieved by the fact that the device suppressing impulse noise when receiving television signals in communication systems with frequency modulation, contains. bandpass filter, adder, first switch, second switch, pulse shaper, the output of which is connected to the control input of the first switch, and the input is the device input, frequency demodulator, phase shifter, first delay element, the output of which is connected to the first input of the first switch, and a second delay element, a third switch is introduced, the output of which is the output of the device, and the first input is connected to the output of the adder, the first filter is turned on between the output of the first switch and the first input of the adder low pass, the output of which is connected to the input of the first delay element, between the output of the second switch and its first input are connected in series the second low pass filter, the distributor, the output of which is connected to the second input of the adder and the input of the second delay element, and the other input is connected to the output of the phase shifter, subtractor,. another input of which is connected to the output of the bandpass filter, and a synchronous detector, another input of which is connected to the output of the phase shifter, between the input of the device and the BTOpfjM input of the first switch includes a frequency discriminator, between the output of the band pass filter whose input is connected to the output of the frequency discriminator and the input of the phase shifter a phase detector is connected in series, a fourth switch, another input of which is connected to the output of a frequency demodulator, a third low-pass filter and a controlled oscillator, an output to connected to another input of the phase detector, between the output of the second element, the delay and the second input of the second switch is an amplitude detector, between the output of the device and the control input of the third switch are connected in series shaper pulse generator and trigger, between the output of the frequency discriminator and the second input of the third switch included the third delay element, between the pulse driver output and the other trigger input, is included the fourth delay element, the control inputs of the second and a fourth kogF utatorov connected to the output of the pulse shaper, the output of the second delay element coupled to an input of the frequency demodulator. The drawing shows a structural electrical circuit of the proposed device.

Pulse suppression device. interference when receiving television signals in C:; communication topics with frequency modulation contains frequency demodulator 1, frequency discriminator 2, driver 3 pulses, 5 first delay element 4, first switch 5, band-pass filter 6,

the second delay element 7, the first low-pass filter 8, the adder 9, the second switch 10, the shaper 11 horizontal pulses, the phase detector 12, the third loader 13, the second low-pass filter 14, the trigger is a controlled oscillator 16, a subtractor 17, a synchronous detector , 15 18, fourth switch 19, third low-pass filter 20, third delay element 21, multiplier 22, phase shifter 23, amplitude detector 24, fourth delay element 25 delay, block 26 forming a replacement luminous signal and block 27 shaping the retarding color difference signal.

 The device works in the following way.

On; the inputs of the third switch 13 receive two signals: one - directly from the output of the frequency dis-. the criminator 2 through the third delay delay 21 and the other - the replacement signal from the output of the adder 9. The third switch 13 is controlled by a signal from the output of the trigger 15, which is reset to the position with O pulses from the output of the former 11 horizontal pulses. In this position, the trigger 15 to the output of the device connects the received signal acting at the output of the third delay element 21. In position 1, the trigger 15 is set by pulses, arriving through the fourth delay element 25 from the driver side of the pulse generator 3, which generates 45 pulses every time a pulse noise arrives at the device input. When the trigger 15 is in position 1, it connects the output of the device to the output of the adder 9, 50

Thus, when impulse noise is affected, the entire part of the received signal line, starting from the first detected impulse pulse and ending with the horizontal sync pulse, is replaced by the most important signal. If the pulse interference is absent, then the received signal goes to the output of the device. -60

The formation of a replacement signal is carried out in two blocks: a block 26 for forming a replacement brightness signal and a block 27 for forming a replacement color difference 5

signal. The signals from the outputs of blocks 26 and 27 are added up in the adder 9 to form a complete replacement signal. Signal portions of previous lines that were not impressed by impulse noise are used to form a replacement signal. Such portions in the received signal are always present, since in practice the impulse noise is asynchronous and its duty cycle is small. Typically, it is 0.2-0.02 / i.e. under the action of impulse noise, most of the lines of the affected signal are free from impulse noise.

The formation of a replacing luminous signal occurs as follows. The full signal from the output of the frequency discriminator 2 is fed to the input of the first KONOviyTaTopa 5 to the other input of which a replacement luminous signal delayed by one line arrives at the output of the block 26. If there is no pulse interference, there are no pulses at the output of the imaging unit 3 and the first KovMyTaTop 5 connects the input of the first filter 8 to the output of the frequency discriminator 2, i.e. in this mode, at the output of the first filter 8, the velocity component, selected by this filter from the received signal, acts.

When an impulse disturbance acts on the input receiver, a pulse is generated in the shaper 3, the duration of which is equal to the duration of the impulse disturbance. This impulse acts on the control input of the first switch 5, connecting to the input of the first filter 8 the output of the first delay element per line, on which the luminous power of the previous line operates. In this way, the affected area of the luminous signal is replaced with the section of the previous line. Since the correlation between the signals of adjacent lines in a television image is all great, such a replacement does not lead to distortions of the formed substitution of the high-frequency signal.

The signal forming replacing the color subcarrier is carried out with the following. Consider the formation of a replacement signal in the absence of a strong interference. B. In this case, the second switch 10 and the fourth switch 19. Connect the outputs of the phase detector 12 and the synchronous detector 18 to the inputs of the second filter 14 and the third filter 20, respectively. The bandpass filter 6 extracts from the received signal a color subcarrier. In the SECAM system due to use. when forming the signal of the high-frequency predistortion circuit and additional amplitude modulation, the color subcarrier is modulated both in phase and amplitude. Phase tracking of the received subcarrier is monitored by a phase locked phase (PLL) circuit containing a phase detector 12, a third filter 2.0 and a controlled oscillator 16. The tracking of the amplitude variation of the color subcarrier is carried out by a circuit containing subtractor 17 , a synchronous detector 18, a third filter 20, and a variable 22. The phase of the controlled oscillator 16 varies according to the same law as the phase of the received color subcarrier. Thus, if the signal at the output of the bandpass filter is denoted by W (t) A (t) sin J t + Cf (t.), (I TO, the voltage at the output of the controlled generator) 16 can be written as Wo (t ) (t) .t) J, (2J where Cf (t) -) (t) is the phase estimate of the signal by the PLL system. The input voltage W (t) 2sin (jt + C (Ct)) enters the input of the synchronous detector 18 from the output of the phase shifter .23 to 90 °. (3) If we denote the voltage acting at the output of the second filter 14, A ( t), for the signal acting on the output of the multiplier 22, we can write the following expression W (t) A. (t) sin about t + Cf (t) .. (M The signal W (t) is fed to the input of the subtractor 17, s whose output to the input of the synchronous detector 18, is given a signal W (t)) A (t) 4 (t) JA (t) 3-in w t + C (t) A (t) (t) s: Ln.t0.tf Cf "(t). (In expression (5) it is taken into account that tf (t) (f (t). Taking into account that the reference signal supplied to the synchronous detector 18 has the form of an expression (we find that the voltage y (t) A acts on its output (t) - A (t). This voltage is filtered by a third filter 20. If necessary, it can be amplified by an amplifier with a high gain factor (not shown j. Since the passband of the third filter 20 should be sufficient for undistorted transmission of the spectral components of the monitored process A (t), then for the voltage A (t) acting on the output of the amplifier, o write the following equation A (t) KU (t) (t) -A "(t). (7) It follows that with K IA (t) A (t), (8) Thus, we have (f ( t) Cf (t) and A-4t) A (t) Therefore, W (t) W (t), i.e., a copy of the received color subcarrier acts at the output of block 27. The signal from the output of multiplier 22 is fed to the second delay element 7 for the duration of two lines. At the output of the amplitude detector 24, a voltage UA (t) A Ct-2Tc is generated. At the output of the frequency demodulator 1 a voltage U (t) If (t-2Tg) is formed. In the event that the receiving signal is impacted by impulse noise, the shaper 3 produces pulses that are temporarily connected to the inputs of the third filter 20 and the second filter 14 instead of disturbed voltages acting on the outputs of the phase detector 12 and the synchronous detector 18, substitute stresses and RD and Uj (t). Since, as noted above, there is a very significant correlation between the signals of adjacent lines in a television signal, such a replacement does not lead to distortions of the signal that replaces the color subcarrier generated in block 27. Due to the inertia of the PLL, the phase of the substituting color difference signal does not experience a jump at the time of switching and therefore, in the proposed device, there is no interference in the chromaticity channel at the moment of pulsing interference due to phase mismatch caused by phase mismatch of the color subcarriers in rows with a mutual delay of 2Ts.

71075447

Thus, the positive effect of the frequency leads, and the effect in the proposed device, improved from the known device, is caused by the construction of a block, due to noticeable distortions of the channel, forming a replacement color and color. This allows a differential signal to be collected; design a replacement signal from the piece to replace the affected impulses related to the received and noisy sections of the signal on the low-delayed 2T lines.

Claims (1)

PULSE INTERFERENCE SUPPRESSION DEVICE WHEN RECEIVING TELEVISION SIGNALS IN COMMUNICATION SYSTEMS WITH FREQUENCY MODULATION, comprising, a band-pass filter, an adder, a first switch, a second switch, a pulse shaper whose output is connected to the control input of the first switch, and the input is a device input, a frequency demodulator, a phase shifter, the first delay element, the output of which is connected to the first input the first switch, and the second delay element, characterized in that, in order to increase the noise immunity, a third switch is introduced into it, the output of which is. the output of the device, and the first input is connected to the output of the adder, between the output of the first switch and the first input of the adder includes a first low-pass filter, the output of which is connected to the input of the first delay element, a second low-pass filter is connected in series between the output of the second switch and its first input, a multiplier whose output is connected to the second input of the adder and the input of the second delay element, and the other input is connected to the output of the phase shifter, a subtractor, the other input of which is connected to the output of the strip a filter, and a synchronous detector, the other input of which is connected to the output of the phase shifter, between the input of the device and the second input of the first switch, a frequency discriminator is connected, between the output of the bandpass filter, the input of which is connected to the output of the frequency discriminator, and the input of the phase shifter, a phase detector, the fourth switch, are connected in series drzpgoy kotoro- _Q th input connected to the output of the frequency de $ modulator, a third low pass filter and a controlled oscillator, whose output is connected to another input of the phase de a tektor, between the output of the second delay element and the second input of the second switch, an amplitude detector is turned on, between the output of the device and the control input of the third switch, a line pulse generator and a trigger are connected in series, between the output of the frequency discriminator and the second input of the third switch the third delay element is connected, between the output of the shaper pulses and another trigger trigger included the fourth delay element, the control inputs of the second and fourth switches are connected to the output rmirovatelya pulses, the output of the second delay element coupled to an input of the frequency demodulator. 1075447 1