CN2433793Y

CN2433793Y - Multifunction reference signal source

Info

Publication number: CN2433793Y
Application number: CN00223958U
Authority: CN
Inventors: 弋建利
Original assignee: BEITONG COMMUNICATION Co Ltd CHENGDU
Current assignee: BEITONG COMMUNICATION Co Ltd CHENGDU
Priority date: 2000-08-15
Filing date: 2000-08-15
Publication date: 2001-06-06
Anticipated expiration: 2010-08-15

Abstract

The utility model is composed of a white electrical level composite signal generator, a phase reversal shaping circuit, a safety circuit, a pulse stretching shaping circuit, a variable delaying circuit, an N-circuit disturbing control unit, etc. The utility model can be used for the disturbing control of a cable television system and can ensure that the timing standard of row synchronizing pulse is the same; the time relationship of the control pulse and the time relationship of the row synchronizing impulse are the same to avoid the compression of travel. The row envelope can be simultaneously and effectively suppressed to cause the control pulse to have a steep front edge and a steep back edge. The utility model has characteristics of digital signals, can fundamentally solve the problems of disturbing failure rate and stability, and can improve the CATV business of China.

Description

Multi-functional reference signal source

The utility model relates to the reference signal source that a kind of scrambling equipment uses.

At present, most of scrambling equipment have all adopted horizontal synchronizing pulse " compression " technology, this be because this technology has that implementation method is simple, confidentiality better, low cost of manufacture, be convenient to characteristics such as control.But reflection after a lot of users use, scrambling degree of depth wild effect occurs more, and the scrambling failure probability is higher.

At the problem that above-mentioned scrambling equipment exists, the purpose of this utility model is a kind of multi-functional reference signal instrument that fundamentally solves scrambling failure probability and stability problem of design.

Design feature of the present utility model has reached above-mentioned purpose of design, it comprises the modulation of N road, scrambling passage and splitter, it is characterized in that having white level composite signal generator, paraphase shaping, press down circuit such as guarantor's row, pulse stretching shaping, variable time delay, white level composite signal generator is provided with two road signal output parts.One termination paraphase shaping circuit, a termination variable delay circuit, paraphase shaping circuit signal output part connect but a row circuit is protected in the field, press down field guarantor's row circuit signal output termination pulse stretching shaping circuit, and pulse stretching shaping circuit signal output part links to each other with splitter; Another splitter of variable time delay circuit signal output termination, this splitter links to each other with N road scrambling circuit with modulator by time-base circuit respectively, signal after the paraphase shaping also links to each other with N road scrambling circuit respectively behind splitter, and two road signals superpose in scrambling circuit.

White level composite signal generator produces has the white level signal of composite sync as the benchmark synchronizing signal, one the road delivers to the variable time delay circuit carries out the time delay that time delay is △ T, the signal of Shi Yanhou is divided into the N road and advances the line timebase calibration process, make N road signal in amplitude and in full accord on the time, promptly realize the frame synchronization of N road TV signal.Variable delay circuit is finished the time delay adjustment to the system synchronization signal, makes Synchronization Control pulse and system synchronization signal not produce difference in the time-delay accumulation of different transmission path.Another road signal of white level composite signal generator is sent into relatively shaping circuit of paraphase, presses down guarantor's row treatment circuit and horizontal blanking impulse broadening shaping circuit and enters scrambling control unit as control impuls.The TV synchronousing signal of this control impuls and transmission all comes from same synchronous generator, and its cycle time is consistent synchronously with television line.

Pressing down guarantor's row circuit is to separate with the time domain of vertical blanking impulse width according to the horizontal blanking impulse width.Because the pulse width time of circuit is set, when the horizontal blanking impulse signal arrives, the horizontal blanking impulse signal normally passes through, and when vertical blanking impulse arrives, because vertical blanking impulse width (1612 μ s) is far longer than horizontal blanking impulse width (12 μ s), this moment, circuit quit work, treat that vertical blanking impulse finishes, when horizontal blanking impulse arrived, circuit recovered operate as normal, go round and begin again, press down the purpose that vertical blanking impulse is protected horizontal blanking impulse thereby reached.

The pulse stretching shaping circuit is with the benchmark of horizontal blanking impulse time cycle as the broadening shaping circuit, for add, the descrambling unit provides excitation signal, it will be by the long-pending trailing-edge broadening △ T that closes the horizontal blanking signal pulse behind the circuit, by obtaining having numerical characteristic behind the shaping circuit, and with the reference signal of horizontal blanking impulse synchronised.Its pulse stretching width is controlled, by adjusting, effectively solve the active line compression phenomena of TV signal, this circuit makes the center strictness of scrambling burst length match with the horizontal blanking impulse time centre, change on the basis that the strict time center that is adjusted at of pulse duration matches, so both guaranteed the scrambling effect to have guaranteed the engineering design surplus again, simultaneously, just reached the purpose of adjusting N road scrambling pulse duration by adjustment to total road scrambling pulse duration.

In sum, because the utility model has adopted white level composite signal generator to make same benchmark synchronizing signal, can guarantee that the horizontal synchronizing pulse time standard is in full accord; Adopt the variable time delay circuit, guarantee that the time relationship of control impuls is consistent with the time relationship of horizontal synchronizing pulse, avoided the compression of active line, can effectively suppress the row envelope again simultaneously; A guarantor's row and a broadening shaping circuit are compared, press down in the shaping of adopting, and make control impuls have good and precipitous edge, front and back, have the digital signal feature.

The utility model has overcome scrambling degree of depth instability, signal in the prior art also original error, problem that the scrambling failure rate is high, adopt one tunnel time control of adjustment just can change the means of multichannel time control, fundamentally solved scrambling failure rate and stability problem.The utility model will be for promoting and the positive effect of development China cable TV cause performance.

Describe the utility model in detail below in conjunction with accompanying drawing:

Fig. 1 the utility model circuit block diagram

Fig. 2 white level composite signal generator circuit figure

Fig. 3 variable time delay circuit diagram

Fig. 4 presses down guarantor's row circuit diagram

Fig. 5 pulse stretching shaping circuit figure

Fig. 6 paraphase is shaping circuit figure relatively

As seen from Figure 1, this multi-functional reference signal source by white level composite signal generator, paraphase shaping, press down protect that row, pulse stretching are whole, variable time delay circuit and No. two splitters constitute, the output signal of white level composite signal generator is divided into two the tunnel, one the tunnel through variable delay circuit, carry out △ T time delay, the signal of Shi Yanhou is divided into the N road and advances the line timebase calibration process, makes N road signal in amplitude and in full accord on the time, promptly realizes the frame synchronization of N road TV signal.This time delay is used for the time delay adjustment to the system synchronization signal, eliminates Synchronization Control pulse and the synchronizing signal difference in the accumulation of different transmission path time delay.

Another road signal of white level composite signal generator is sent into paraphase and is compared shaping circuit, presses down a guarantor's row treatment circuit and a horizontal blanking impulse broadening shaping circuit, enters scrambling control unit as control impuls.Should press down and protect that serrated pulse, dyke that a row circuit makes TV signal dash and equalizing pulse is not impaired, thereby improve the reduction effect of TV signal greatly.

The adding of pulse stretching shaping circuit, the one, in order to improve the scrambling effect, the 2nd, be used to adjust the scrambling pulse duration, reduce the active line loss of signal, like this, both guaranteed the scrambling effect, guaranteed the engineering design surplus again, by the adjustment of total road scrambling pulsewidth being realized identical adjustment each road, N road.

Fig. 2 is a white level composite signal generator electrical schematic diagram.This circuit is by IC ₁(Z80 single board computer), IC ₂(2764 memory), IC ₃(D flip-flop), IC ₄(D/A converter), IC ₅(controller), IC ₆(clock-signal generator), IC ₇(chromacoder) and emitter follower Q ₀And the peripheral circuit composition, this circuit, is sent out a frame " white level " complex digital signal that is stored in the memory, by being converted into " in vain " level composite signal behind the D/A converter under the internal memory instruction repertorie is supported again and again by the veneer calculator.

Fig. 3 is the variable time delay circuit diagram.This circuit is mainly by variable potentiometer VR ₁(0～50k Ω) and capacitor (C ₁=0.01 μ F) constitutes.When pulse signal arrives, by charge constant τ=VR ₁C ₁The charge circuit of forming makes pulse front edge time-delay △ T, when changing VR ₁During resistance, △ T also changes thereupon.

Fig. 4 is for pressing down guarantor's row circuit, by triode Q ₁, Q ₂, two time capacitor C ₂, C ₃With timing resistor R ₂, R ₃Constitute the controlled traction oscillating circuit of bistable state multi resonant, triode Q ₃And resistance R ₆, R ₇Constitute emitter follower.Adjust C ₁, C ₂, R ₂, R ₃Value, the frequency of oscillation that makes multivibrator is near 15625HZ, and pulse duty factor is about 5: 1 (promptly 64: 12), like this, as input video line rate pulse signal (f ₀=15625HZ) arrive after, the frequency of oscillation of oscillator will be drawn on the video line rate frequency, makes the line frequency signal obtain keeping, and when the field frequency pulse arrives, because the field frequency frequency is far smaller than the oscillator frequency of oscillation, and be in low level state, make oscillator quit work, and be output as low level, after treating that field pulse finishes, the line frequency pulse begins again to draw oscillator work, goes round and begins again, and reaches to press down a purpose of protecting row.

Fig. 5 is pulse stretching shaping circuit figure, and it is made up of integrating circuit and comparison shaping two parts circuit.Integrating circuit is by diode D ₁, capacitor C ₄, variable resistor VR ₂And resistor R ₁₀Constitute, work as C ₄During=2000pf, VR ₂A certain desired value in desirable 0～47K Ω scope.Relatively shaping circuit is by high speed voltage comparator IC ₉, divider resistance R ₈, R ₉Form.Its R ₈, R ₉The divider resistance span makes threshold voltage V ₂Get final product about ≈ 2V.

By D ₁, C ₄, VR ₂And R ₁₀In the integrating circuit of forming, charge constant τ=C ₄(R ₁₀+ r), wherein r is the diode internal resistance, can ignore, so the rising edge of a pulse variation is very little, and discharge loop timeconstant=C ₄(VR ₂+ R ₁₀), the velocity of discharge is slow, changes VR ₂Can change the discharge time of pulse trailing edge, by comparison threshold voltage, comparator output rising edge of a pulse time effects is very little, and trailing edge is with VR ₂The variation of value and changing is adjusted VR thereby reach ₂It is the purpose of expandable gate width △ T and paired pulses waveform shaping.

Fig. 6 is the paraphase comparison circuit, and phase inverter is by Q ₄And R _11-14Form, relatively shaping circuit is by high speed voltage comparator IC ₈And R ₁₅, R ₁₆Form its R ₁₅, R ₁₆Partial pressure value provide comparison threshold voltage for comparator.By Q ₄The phase inverter of forming is with the paraphase of input pulse signal, owing to select R ₁₃, R ₁₄Value is almost consistent, so circuit no-voltage amplification only plays inverting function.Adjust R ₁₅, R ₁₆Value, make comparator that a suitable threshold value be arranged, make the circuit both can be anti-interference, can reach the purpose of comparison shaping again.

Claims

1. multi-functional reference signal source, comprise splitter and N road scrambling unit circuit, it is characterized in that having white level composite signal generator, the paraphase shaping, press down guarantor's row, the pulse stretching shaping, circuit such as variable time delay, white level composite signal generator is provided with two road signal output parts, one termination paraphase shaping circuit, one termination variable delay circuit, paraphase shaping circuit signal output part connects and presses down guarantor's row circuit, press down guarantor's row circuit signal output termination pulse stretching shaping circuit, pulse stretching shaping circuit signal output part connects the paraphase shaping circuit, and paraphase shaping circuit signal output part connects N road scrambling circuit respectively; The variable time delay circuit respectively with N route time-base circuit, the scrambling unit circuit that modulator and scrambling circuit constitute links to each other, the Signal Terminal of two branch roads all is connected to scrambling circuit.

2. multi-functional reference signal source as claimed in claim 1 is characterized in that time delay circuit adopts the RC series circuit of variable resistance and capacitors in series, and signal output part is positioned at the connection mid point of resistance, electric capacity.

3. multi-functional reference signal source as claimed in claim 1 or 2, it is characterized in that pressing down guarantor's row circuit is a flip and flop generator and the emitter follower that is connected in output.

4. multi-functional reference generator as claimed in claim 1 or 2 is characterized in that the pulse stretching shaping circuit is made of integrating circuit and comparison shaping circuit, and integrating circuit is connected in the comparator front end.

5. multi-functional reference generator as claimed in claim 3 is characterized in that the pulse stretching shaping circuit is made of integrating circuit and comparator, and integrating circuit is connected in the comparator front end.