JPS6174411A - Television tuner - Google Patents

Abstract

PURPOSE:To reduce man-hour for manufacturing and to attain optimum recpetion by using a voltage controlled voltage to vary the tuning frequency near a frequency of a desired channel signal at automatic tuning, detecting its IF signal level and using a comparator circuit to detect the tuning point. CONSTITUTION:A channel command signal via a synthesizer controller 21 is fed to a tuning controller 22, which decides a DC voltage width fed to a variable varactor diode of tuners 2, 4, that is, a frequency width sweeping the tuning frequency of the tuners 2, 4 to sweep the tuning frequency. In order to discriminate the tuning point at that time, the output of an IF amplifier 7 is detected by an envelope detectors 24, and its level is read by the controller 22. Then read level is stored in a memory in the controller 22, the level and the next read level are compared repetitively in the comparator in the controller 22 to find out the tuning point being the maximum level.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a television tuner that is used in TV reception L VTRs and the like, and which has a platform that indicates a channel and automatically determines the optimum tuning point.

(Conventional example) FIG. 7 shows a block diagram of a conventional TV tuner.

In the figure, a high frequency signal including channel signals of 111 received by an antenna 101 is tuned and selected by a tuner 102 to select the frequency of the channel desired to be received. The tuning signal is amplified by a radio frequency (R') amplifier 103,
The signal is supplied to a frequency converter 105 via an i-device 104. The signal is mixed by the frequency a'a' converter 105 with the tuning signal and the oscillation signal of the local oscillator 118, and becomes the movie intermediate frequency'! converted SAW (surface external wave) filter
106, the signal is amplified by an intermediate frequency amplifier 107 and detected by a detector 108, and the signal is sent to the audio trap circuit 10.
At step 9, the audio signal is removed and only the video signal is sent to the video amplifier N.
The output signal of the detector 108 is amplified to a predetermined level by O and supplied to the output terminal 111. At the same time, the output signal of the detector 108 is supplied to the audio band pass filter 112, and its output signal 1:M
The audio signal is supplied to an intermediate frequency amplifier 113 and outputted to an output terminal 115 via a detection amplifier 114.

Furthermore, the output signal of the detector 108 is transmitted to the AGC amplifier 111.
The output signal controls the RF amplifier 103 and the intermediate frequency amplifier 107 so that even if the input signal level of the antenna 101 changes, the output signal of the intermediate frequency amplifier remains stable. There is.

The keyboard 120 indicates a particular channel to be received, and the instruction signal is supplied to a synthesizer controller 121. This synthesizer controller 121 includes an R quasi-signal oscillator, a reference signal frequency divider,
It consists of a programmable counter that frequency-divides the signal from the prescaler 119, a phase comparator, a charge pump, etc., and a channel instruction signal from the keyboard 120 sets the frequency division ratio of the programmable counter in the synthesizer controller 121.

The DC voltage output from the synthesizer controller 121 is input to the local oscillator 11, and the tuner 102 is configured to oscillate a frequency higher than the frequency of the channel to be received by the frequency of the intermediate frequency signal.
．． The variable capacitance diodes constituting the respective resonance circuits are controlled so as to be in tune with the frequency of the channel to be received by being input to the respective resonant circuits 104.

d3 in the tuner 104 and the synthesizer controller 12
The reason why two control signal lines of 1J:R are connected is that the internal configuration of the tuner 104 is two-stage tuning using transformer coupling.

The ΔFT detector 116 finely adjusts the oscillation frequency of the local oscillation Z 118 via the synthesizer controller 121 so that the intermediate frequency becomes a standard value from the output of the intermediate frequency amplifier "5107.

As explained above, in a conventional TV tuner, when a channel is specified using the keyboard 120, the synthesizer controller 121 that receives the instruction operates the tuner 102, 104, d3 and the local oscillator 118 at a frequency corresponding to the channel. A DC voltage such as this is supplied on the same output line. Synthesis I in each tunnel
The direct current (positive pressure) to be output from the air conditioner i-roller 121 is adjusted in a single manner for each band at the time of making the horn.

(Problems to be Solved by the Invention) As mentioned above, the conventional TV tuner has a tuner 102゜j0
Since the 4J5 and the local oscillator 118 are controlled by the same 1Δ signal, it is necessary to make a single adjustment for each band during manufacturing, and this If adjustment takes a lot of man-hours, and
It is also necessary to select variable Furori diodes and those! J in
The cost increased, and there was a problem with the shade, in which the synchronization in each block was not always optimal.

(Means for solving m points between points) In order to solve the above problems, the present invention provides a tuner whose tuning frequency can be varied by a control voltage, and a tuner whose amplification degree can be controlled until
A high-frequency amplifier that can be varied depending on the voltage, and the degree of amplification is controlled! 1
] A variable intermediate frequency amplification source 111 for supplying the 1tII voltage to the tuner;
#A circuit, an AGC amplifier for automatically controlling the amplification degrees of the high frequency amplifier and the intermediate frequency amplifier, a voltage generator for controlling the amplification degrees of the high frequency amplifier and the intermediate frequency amplifier, and the AGC amplifier and a voltage generator, a detector that detects the level of the intermediate frequency signal, a memory that stores the level detected by the detector, and a switch that changes the level stored in the memory and the next detector. When performing automatic tuning, the switch switches the voltage generator to reduce reception by the control voltage t11 output from the voltage control circuit.
7+ and -J channels (the frequency multiplication of the bow is performed by varying the tuning frequency of the tuner, the level of the intermediate frequency signal of the UJ is detected by the detector, and the tuning point is found by the comparison circuit). .

(Embodiment) FIG. 1 is a block system diagram of an embodiment of the television control tuner of the present invention, which will be explained with reference to the drawing.

The return 'f-p channel signal received by antenna 1 is a
・The high frequency signal is not received at tuning 32, and the frequency of the desired tunnel is the same: JI is selected, and the tuning 1 is set to high frequency (
RF) After being amplified by amplifier 3, frequency 2 is passed through tuner 4.
is supplied to the converter 5. The tuned signal is mixed with the oscillation signal of the local oscillator 18 by the frequency converter 5, converted to an intermediate frequency, passed through the SAW (surface bullet wave) filter 6, amplified by the intermediate frequency amplifier 7, and detected by the detector 8. be done.

The detected signal is passed through an audio trap circuit where the audio signal is removed and only the video signal is amplified to a predetermined level by an amplifier 10 and supplied to an output terminal 11.

At the same time, the output signal of the detector 8 is transmitted to the audio bandpass filter 1.
2, only the FM audio signal passes therethrough, is amplified by an intermediate frequency amplifier 13, demodulated by a detection amplifier 14, and the audio signal is supplied to an output terminal 15.

Next, the switchover J3 and signal control system will be explained. The output signal of the detector 8 is sent to an AGC amplifier,
17, and its output signal controls the gains of the RF amplifier 3 and the intermediate frequency amplifier 7 through the contact a of the switch 23, so that even if the input signal level of the antenna 1 changes, the output signal remains stable even when the input signal level of the antenna 1 changes. The output signal is set to 19.

The keyboard 20 is used to indicate a particular channel to be received, and the instruction signal is supplied to a synthesizer controller 21. This synthesizer controller 21 is equipped with a reference (No. 3j oscillator, a single signal frequency divider, a programmable counter that divides the signal from the prescaler 19, a phase comparator, a charge pump, etc.), and a channel from the keyboard 2o. The one-line indication signal controls the frequency division ratio of the programmable counter in the synthesizer controller 21 (il, l), and causes the local oscillator 18 to oscillate at a frequency higher than the frequency of the channel specified by the local oscillator 18 by the frequency of the intermediate frequency signal. DC voltage is supplied to the variable capacitance diode that determines the oscillation frequency inside.

The prescaler 19, local receiver 18, and synthesizer controller 21 constitute a PLL circuit.

The tuning controller 22 is a process sequencer,
Control! 2Il voltage generator, memory, DA converter (DA
C), AD-]] converter ADC> etc.
An example of its configuration is shown in FIG. The tuning controller 22 receives the information fFi of the channel to be received from the synthesizer controller 21 and controls the DC voltage supplied to the variable capacitance diode constituting the resonance circuit of the tuner 2.4.

The output signal of the intermediate frequency amplifier 7 is supplied to the ΔFT detector 1G and the envelope detector 24.

When the intermediate frequency deviates from the specified 1 frequency, the △FT detector 16 outputs a correction voltage corresponding to the deviation, and uses the correction voltage to change the frequency division ratio of the programmable counter in the signal 21. As a result, the oscillation frequency of the local oscillator 18 is compensated iE, and the intermediate frequency becomes regular. The envelope detector 24 detects the output of the intermediate frequency amplifier 7 and supplies the detected output signal to the tuning controller 22.

Next, automatic tuning when switching channels will be explained. When a desired channel for reception is designated from the keyboard 20, the system switches the R oscillation frequency of the local oscillator 18 to the frequency corresponding to the channel via the sinacon controller 21, as described above.

However, since the tuner 2.4 is not yet tuned, the output level of the intermediate frequency amplifier 7 is low, and the ΔFT detector 16 does not operate.

The channel indication signal via the synthesizer controller 21 is supplied to the tuning controller 22, and the tuning controller 22 sweeps the tuning frequency of the tuner 2.4 in a frequency range, that is, supplies it to the variable capacitance diodes of the tuners 2 and 4. Determine the DC voltage width and determine the tuning frequency. The DC voltage width is determined by performing automatic tuning for at least one FT channel for each broadcast band at the time of rough construction and transmitting the information to the tuning controller 2.
J3 is stored in the non-volatile memory of No. 2, and the DC voltage width applied to J3 on the δ channel is calculated and determined based on the value. In order to determine the tuning point at that time, the output of the intermediate frequency amplifier 7 is detected by an envelope detector 24,
The tuning controller 22 reads the level. The read level is stored in the memory in the tuning controller 22, and the level read next is compared with the next read level by the comparator in the tuning controller 22 to find the highest level tuning point.

The tuning characteristic shown in FIG. 2 is a graph showing the relationship between the swept tuning frequency and the level detected by the envelope detector 24.

As shown in the figure, initially, the frequency width to be swept is widened and the measurement points are made coarse, and the results are obtained as shown by "." 17.

From this, the tuning design pa is first found, then the section a near the tuning point is linked, the measurement points are also crossed, and the detection output is obtained to find the optimal tuning point. The DC voltage supplied to the variable capacitance diode of the tuner 2 or 4 at that time is the optimum type B-.

In the method described above, the first stage of tuner 2 and tuner 4,
Perform automatic tuning of all tuners in the order of the second stage tuning circuit? 1 Perform appropriate tuning.

When performing automatic tuning, since the tuning is not correct at first, the level detected by the envelope detector 24 is low, so the tuning controller 2 is used to increase the measurement sensitivity.
2 controls the DC voltage applied to the control terminals 1q and 1j of the RF amplifier 3 and the 120-frequency IV amplifier 7 through the contacts of the switch 23, thereby increasing the degree of amplification. Then, when the tuning is matched and the No. 13 level rises, the RF amplifier 3.
The tuning controller 22 detects this so that the intermediate frequency amplifier 7 does not saturate the old number level, and sets the RI:
The DC voltage applied to the first 17 control I terminals of the amplifier 3 and the intermediate frequency amplifier 7 is controlled to lower the amplification degree.

As automatic tuning progresses, the input signal level of the AFT detector 16 increases and reaches a level at which AFT detection is possible, so that the AFT detector 1G performs its original function.

As described above, when the automatic tuning of the chitunnel instructed by the keyboard 20 is completed, the switch 23 is connected from the contact point A to the contact point a, and the normal receiving state is established. This self-help tuning occurs instantaneously each time the channel is switched.

In the above embodiment, if the envelope detector 24 is set to J3 as shown in FIG. 3 (D) or (B), more accurate level detection becomes possible.

In the figures (A) and (B), the detector 26 may also serve as a one-envelope detector, a synchronous detector, or a video detector. Since the maximum amplitude of the carrier wave is at the tip of the synchronization signal and is a constant amplitude regardless of the video information, the output of the detector 2G is resampled and held as a synchronization signal by the number-and-hold circuit 27, and the video [multiple Detection is achieved at a level that does not affect information.

In the third step 4 (Δ), the output voltage of the sample-and-bold circuit 27 is supplied via the integrator 28 to the A[) converter (ADC) having the width of the tuning controller 22.

In FIG. 3(B), the output voltage of the sample-and-hold circuit 27 is supplied to a VCO (voltage controlled oscillator) 29, a frequency signal proportional to the hold voltage is counted by a counter 30, and the output signal is sent to the tuning controller 22 as data. , and is reset each time.

Another example of finding the tuning point of the tuners 2 and 4 is to change the DC output voltage of the tuning controller 22 stepwise from the lower side, that is, change the tuning frequency stepwise from the lower side. There is also a method of reading the detection output level of the envelope detector 24 at that time. The tuning characteristics in that case are shown in FIGS. A and 5.

In Fig. 4, if the first detection output voltage is Vn and the next one is Vn+1, then the difference △V =
When V jl+l V n, the next predicted voltage is predicted linearly as V'=Vn, l+△V±α (
α is the maximum error from the linear prediction predicted from the range of change in the tuning frequency).

Then, use the comparator in the tuning controller 22 to determine whether the actual detection output voltages v1, 2 are within the range of V'q+1, and go to ■If r≧ is within the range of V' It is judged that the previous value f-y is correct, and if there is something out of range, it is judged that zon+1 is wrong, and the data is recorded. If the measured value is still outside the predicted range, the data is taken again from the previous data. The tuning frequency is detected through this process.

Furthermore, an example of a pond for finding the tuning point of the tuner 2.4 is shown. Two points rLn, fHn (
Find the detection output at ⇠ (integer) and move the tuning frequency to the side with the larger average value. This operation is repeated until a point where there is no difference in the detection outputs of two points fLn and fHn separated by Δf across the tuning point is detected. fL at this time
The tuning point can be detected by n and fHn.

(Effects of the Invention) The television tuner of the present invention automatically tunes the channel each time the channel is changed during use, so it is possible to receive signals in the optimum condition, and During manufacturing, single adjustment work for each band and selection of variable capacitance diodes are not required, resulting in a reduction in man-hours.

[Brief explanation of drawings]

FIG. 1 is a block system diagram of an actual IJI example of the television tuner of the present invention, FIGS. 2, 4, and 5 are tuning characteristic diagrams in FIG. 1, and FIG. Another embodiment of the tuning level detection section, FIG. 6 is a block diagram of an example of a tuning controller, and FIG. 7 is a block diagram of an example of a conventional television tuner. 1.1oi...antenna, 2,4. 102. 104...tuner, 3, 10
3...RF amplifier, 5. 105... Frequency converter, 6, ioe... S A W filter, 7, 1
07...Intermediate frequency amplifier, 8.26. 108...detector, 16. 116...
・AFT detector, 17, 117... AGC amplifier, 18, 118... Local oscillator, 19. 119・
...Prescaler, 20, 120...Keyboard, 2L 121...Synthesizer controller, 22
... 1-ning controller, 23... switch, 24... envelope detector, 27... sample and hold circuit, 28... integrator, 29... VCO130... counter. 2f211 3 years old 4n 5 years old 6 years old

Claims (1)

[Claims] a tuner whose tuning frequency can be varied by a control voltage; a high frequency amplifier whose amplification degree can be varied by a control voltage; an intermediate frequency amplifier whose amplification degree can be varied by a control voltage; A supply voltage control circuit,
an AGC amplifier for automatically controlling the amplification degrees of the high frequency amplifier and the intermediate frequency amplifier; a voltage generator for controlling the amplification degrees of the high frequency amplifier and the intermediate frequency amplifier; the AGC amplifier and the voltage generator. a switch for switching the intermediate frequency signal, a detector for detecting the level of the intermediate frequency signal, and a memory for storing the level detected by the detector;
and a comparator that compares the level stored in the memory with the next detected level, and when performing automatic tuning, the switch switches to the voltage generator to adjust the control voltage output from the voltage control circuit. The tuning frequency of the tuner is varied near the frequency of the channel signal desired to be received, the level of the intermediate frequency signal at that time is detected by the detector, and the tuning point is found by the comparison circuit. Television tuner.