SU1385329A1 - Device for automatic trimming of television set local oscillator frequency - Google Patents

Abstract

The invention relates to television technology and extends the capture band. The device contains UHF 1, mixer 2, local oscillator 3, OPCH 4, amplitude detector 5, analyzer 6 presence of synchronism, amplitude selector B, amplifier 11 frequency detector, frequency detector 12, adder 13, block 14 settings. The sound signal analyzer 7 is introduced, logical. block 9, control source 10 voltage. The device allows the bandwidth to be expanded without the danger of falsely capturing adjacent channels, since frequency tuning of the local oscillator under the action of the source 10 occurs depending on the initial detuning in a certain direction. In tab. given logical voltage levels at the outputs of block 9, depending on the state of reception of the television signal. According to the table. m. structure obtained by standard methods logical. block 9 when implemented in the selected element basis. 1 tab. 3 il. (Oh (L

Description

Chrig.

The invention relates to television technology and can be used as part of television receivers.

The purpose of the invention is the expansion of the capture band.

Figure 1 shows the structural electrical circuit of the device for automatically adjusting the local oscillator frequency of the television receiver; Fig. 2 shows a sound signal analyzer, option; on fig.Z - analyzer presence synchronism, option.

The device for automatic tuning of the local oscillator frequency of a television receiver (FIG. 1) contains high frequency amplifier 1 (UHF), mixer 2, local oscillator 3, intermediate frequency amplifier 4 (IF amplifier), amplitude detector (AD) 5, analyzer 6 synchronization (ANS). ), sound signal analyzer 7 (AESC), amplitude selector (AC) 8, logic unit 9, controlled voltage source 10 (UIN), frequency detector amplifier 11 (), frequency detector (PD) 12, adder 13 and b lock 14 settings.

The analyzer 7 - sound signal (figure 2) can be made in the form of serially connected intermediate-frequency amplifier 15 sound (UPCR), rectifier 16 low-pass filter 17 (LPF). And comparator 18.

The analyzer presence of synchronism (fig.Z) can be made in the form of a series-connected element AND NOT 19, a peak detector 20 and a driver .21.

A device for automatically adjusting the local oscillator frequency of a television receiver operates as follows.

Depending on the accuracy of the pre-setting of the local oscillator when the APCG is turned off, the following states of the device are possible.

The TV receiver is tuned to such a frequency that it ensures reliable reception of both the image and sound, the tuning frequency of the local oscillator 3 is close to the nominal one.

The TV receiver is tuned so that the frequency of the local oscillator 3 is significantly higher than the nominal one. In this case, between 3853292

exact image frequency

 R.

suppressed, and intermediate frequency

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sound (f

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The TV receiver is tuned so that the local oscillator frequency. 3 is significantly lower than nominal, in this case f.

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suppressed, and f pr IEEVR passes without weakening.

The TV receiver is upset, and no TV program signal is being received.

In the first state of reception of a television signal, in which both image synchronization and reception of sound accompaniment are provided, the output of the ANS 6 and the output of the APSS 7 form O levels that arrive at the second and first inputs of the logic unit 9. At the third and first outputs logical block 9, the level O is formed, and at the second output - level 1. The logic levels from the third and first 5 outputs of logic block 9, arriving at the corresponding inputs of the UIN-10, block the restructuring and save to

its output is the initial voltage equal to zero., and level 1 from the second

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the output of logic block 9 is fed to the corresponding input of the PDC 11 by the action of which the latter is turned on.

In this case, the operation of the local oscillator frequency control system is ensured, since with the inclusion of PDD 11, the loop loop of the local oscillator 3, mixer 2, UPCH 4, PDC 11, PD 11, adder 13, and local oscillator 3 closes, and in adder 13 the tuning voltage applied from the block 14 settings, and the voltage error coming from the output of the BH 12.

In the second state of TV signal reception, in which there is no image synchronization, but there is sound, the auto-tuning system works as follows: the first input of logic block 9 receives level 1 from the output of APSZ 7, and the second input of logic block 9 comes from the output of ANS 6 level O.

At the same time, at the third output of logic block 9, there is level 1, and at the first and second outputs - levels O. Level O, coming from the second output of the logic unit

9 to the second input of the PDC 11, turns it off and, accordingly, the circuit 11 of the FBG TV receiver.

Under the action of a combination of the voltage supplied to the first and second inputs of the UIN 10, the latter will slowly change the output voltage, which is added in the adder 13 with the tuning voltage supplied to the second input of the adder 13 from the output of the unit 14, is fed to the input of the local oscillator 3 and begins to tune its frequency downward until it reaches a value close to the nominal value, at which the TV receives sound, which corresponds to the first state of the television signal reception. In this case, in the ANS 6, the logical block 9, the PDD P and the UIN 10, the switchings correspond to the first state, and the voltage at the output of the UIN 10 is blocked and remains unchanged during the whole time of reception of this television channel, to which tv set up.

As a result of the switchings corresponding to the first state of the television signal reception, the feedback loop of the APSG closes, as it was indicated above, and in the adder 13 three voltages are added: the tuning voltage coming from the tuning unit 14, the voltage of the UIN

10 and the voltage of the fault from the output of the RR 12. In the third state of reception of a television signal, in which there is no sound accompaniment, and the synchronization of the image is ensured, the auto-tuning system works as follows:

the input of logic block 9 with AC3G 7 receives level O, since there is no audio reception, the second input of logic unit 9 from the output of ANS 6 receives level 1 since the image synchronization is provided. At the same time, at the second and third outputs of logic block 9, there is a level O, and at the first output - level 1.

The level O supplied from the second output of the logic unit 9 to the PDD 11 disables it and thereby opens the loop of the APCG.

Under the action of a combination of voltages entering the inputs of the UIN 10,

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the latter will slowly change the output voltage, which, adding in the adder 13 with the tuning voltage supplied from the tuning unit 14 to the second input from the mmator 13, enters the input of the local oscillator 3 and tunes its frequency upward until it reaches the value close to to the nominal, at which the TV provides sound reception and image synchronization, i.e. the first reception state of the television signal is reached. At the same time, in the APSS 7, the logic unit 9, the PDD 11, and the UIN 10, the switchings correspond to the first state, and the voltage on the output of the UIN 10 is blocked and remains unchanged during the whole time of reception of this television channel to which the TV receiver is tuned. .

As a result of the switchings corresponding to the first reception state of the television signal, the feedback loop of the APSG closes, and in the adder 13 three voltages are added: the tuning voltage from the tuning unit 14, the voltage from the PIN 10 output and the error voltage from the output RR 12, and provides accurate tuning of the frequency of the local oscillator 3.

In the fourth state of receiving a television signal, in which both sound and synchronization are absent, O levels are received at the first and second inputs of logic block 9, and O levels are also formed at its outputs.

At the same time, the UIN IO is blocked, UChD 11 is disabled, the loop of the APCG circuit is open - the APCG system is disabled.

When switching a television receiver from channel to channel, as well as when it is included in the network, the blocking pulse of the APSG generated in the tuning block 14 resets the output voltage of the UIN 10 by feeding this pulse to the third input of the UIN 10.

The table shows the logical voltage levels at the inputs of logic unit 9 depending on the state of reception of the television signal.

According to this table, the structure of block 9 can be obtained by standard methods when it is implemented in the chosen element basis.

ASZS 7 (.fig. 2) works as follows.

The voltage differential frequency voltage, generated by the EGG 15, is rectified by the transducer 16, filtered by the LPF 17, is fed to the comparator 18 with a fixed triggering threshold. The threshold of the comparator 18 is selected so that, in the absence of a signal, only noise is formed) a level is formed at its output Oh, and in the presence of a signal received by a TV receiver - level 1.

ANS 6 (fig.Z) works as follows.

In the presence of synchronism, i.e. when the Horizontal scanning circuit is clocked with the signal received by the TV receiver, pulses are generated at the output of the NE-NE 19 at the instants of coincidence of the horizontal sync pulses and the horizontal sweep pulses. After accumulation and storage by the peak detector, the voltage generated from the said pulses is converted into standard logic levels by a driver 21 fulfilled, for example, at the NAND element used as a block of the threshold block.

Thus, the proposed device allows to expand the acquisition band of the APSG without the risk of falsely capturing the adjacent channels, since the frequency tuning of the local oscillator under the action of the UIN occurs depending on the initial detuning in a certain direction.

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Claims (1)

Invention Formula A device for automatically adjusting the local oscillator frequency of a television receiver, comprising a series-connected high-frequency amplifier, a mixer, an intermediate frequency amplifier, a frequency detector amplifier, a frequency detector, an adder and a local oscillator, the output of which is connected to the second mixer input, the second output of the intermediate frequency amplifier is connected through serially connected amplitude detector and amplitude selector with the first input of the analyzer presence of synchronism, the second input of which is The input of the horizontal reversing pulses, the second input of the adder is connected to the first output of the tuner, which is different from the fact that the analyzer 5 of the sound signal, the logic block and the controlled voltage source, included in series between the output of the amplitude detector and the third input of the adder, the output of the analyzer presence of synchronism is connected to the second input of the logic unit, the second output of which is connected to the second input of the frequency detection amplifier pa, and the third The output to the second input of the controllable voltage source, a third input coupled to the second output of the tuner. 0 0 five 2 3 four one Oh oh Ltd one oh oh about t 5 Ki, 2 Fig.Z