JPH0364112A - Electronic channel selection device - Google Patents

Abstract

PURPOSE:To suppress frequency fluctuation at a tuning frequency while a disturbing signal of an electronic tuner section is attenuated by using a comparison output of a comparator as a control signal to apply it to the electronic tuner section. CONSTITUTION:When the frequency of an intermediate frequency signal changes from f12 into f14 due to a temperature change, a frequency discrimination output (SFT voltage) of a frequency discrimination circuit 6 changes fro A12 into A14 and the output of an A/D converter 7 changes from [1011] into [1110]. Thus, a difference between the output [1110] of the A/D converter 7 and an offset data [1011] is obtained as a comparison output at the output of a comparator circuit 9, the comparison output is fed to an electronic tuner section 2 as a control signal and feedback is applied till the output of the A/D converter 7 is coincident with the offset data. Thus, the frequency fluctuation of the electronic tuner section 2 is suppressed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an electronic channel selection device, and in particular to an AFT (Automated Channel Tuning Device).
The present invention relates to an electronic tuning device having a Fine Tuning (Fine Tuning) function.

[Summary of the invention]

The electronic tuning device of the present invention includes: a frequency discrimination circuit that detects an analog AFT voltage according to frequency fluctuations of an intermediate frequency signal; an A/D converter that converts the analog AFT voltage of the frequency discrimination circuit into a digital signal; It consists of a memory that stores offset data indicating the deviation of the frequency of the intermediate frequency signal from the center value, and a comparator that compares the output of the A/D converter and the offset data read from the memory. By supplying the comparison output of the comparator as a control signal to the electronic tuning tuner section, it is possible to suppress frequency fluctuations in the tuning frequency at which the interference signal of the electronic tuning tuner section is attenuated.

[Conventional technology]

Conventionally, voltage combination 7i! with AFT function! (voltage synthesizer) type electronic tuning device, for example,
It is described in the publication No.-57768.

This conventional electronic channel selection device generates a digital channel selection signal by A/D converting the 8-character characteristic output voltage (AFT voltage) of a frequency discriminator centered on the video intermediate frequency of the television receiver. Subtraction (or addition) is performed, and this synthesized digital tuning signal is D/A converted and supplied to an electronic tuning tuner section, and corrected by AFT to maintain a right cone tuning state at the time of reception. There is.

[Problem to be solved by the invention]

However, in conventional electronic tuning devices, the field pack loop is normally closed by the AFT signal of the frequency discrimination circuit, but when beat disturbance of an adjacent channel occurs, the tuned frequency is shifted (offset) from the center value. When the field pack loop is open to attenuate the interfering signal.

When removing this interference signal, the tuning frequency changes from the set value due to the temperature characteristics of the electronic tuning tuner section, resulting in frequency fluctuations.

Therefore, an object of the present invention is to improve the above-mentioned drawbacks, and to use a voltage synthesizer method or a PLL (Phase
An object of the present invention is to provide an electronic channel selection device that can be easily applied to both the Locked Loop and Locked Loop systems.

[Means to solve the problem]

The electronic tuning device of the present invention includes a frequency discriminator circuit that detects an analog AFT voltage according to frequency fluctuations of an intermediate frequency signal of an electronic tuning tuner section, and an A/F discriminator circuit that converts the analog AFT voltage of the frequency discriminator circuit into a digital signal. D converter;
a memory that stores offset data indicating a deviation of the frequency of the intermediate frequency signal from the offshore center value; and a comparator that compares the output of the A/D converter and the offset data read from the memory. and is configured to supply the comparison output of the comparator to the electronic tuning tuner section as a control signal.

Further, the electronic channel selection device of the present invention is configured to D/A convert the comparison output of the comparator and supply it to the electronic tuning tuner section.

Further, in the electronic tuning device of the present invention, the tuning frequency of the electronic tuning tuner section is varied by a PLL circuit having a variable frequency divider, and the tuning frequency of the electronic tuning tuner section is varied by a comparison output of the comparator.
It is configured to control the frequency division ratio of the variable frequency divider of the LL circuit.

[Effect]

According to the electronic tuning device of the present invention, the field pack loop is closed so that the offset data read from the memory and the output of the A/D converter match, so that the interference signal of the electronic tuning tuner section is eliminated. Frequency fluctuations in the attenuated tuning frequency can be suppressed.

Further, if the control signal obtained by D/A converting the comparison output of the comparator is supplied to the electronic tuning tuner section, it becomes easy to apply the control signal to a voltage synthesizer type electronic tuning device.

Furthermore, if the frequency division ratio of the variable frequency divider of the PLL circuit is controlled by the comparison output of the comparator, it is possible to control the frequency division ratio of the variable frequency divider of the PLL circuit.
It is easy to apply to an electronic channel selection device using an L digital synthesizer method.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the basic configuration of the present invention.
2 is an antenna, and 2 is an electronic tuning tuner section composed of a local oscillation circuit having a variable voltage reactance and a ξ kisser circuit (not shown). 3 is an IF amplifier (intermediate frequency amplifier) to which the intermediate frequency signal of the electronic tuning tuner section 2 is supplied;
, 4 is a detection circuit to which the output of this F amplifier 3 is supplied,
5 is an output terminal to which the detection output is supplied. 6 is a frequency discrimination circuit connected to the IF amplifier, which has a three-character frequency discrimination output (hereinafter referred to as analog A
This is the frequency discrimination output that obtains the FT voltage (FT voltage).

7 is an A/D converter connected to the frequency discrimination circuit 6 and converts the analog AFT voltage into a digital signal of predetermined bits;
Reference numeral 8 denotes a memory that stores a value (offset data) by which the tuning frequency is shifted from the center value when beat disturbance of an adjacent channel occurs.

A comparator 9 compares the output of the A/D converter 7 with the offset data of the memory 8, and is configured so that the comparison output of the comparator 8 is supplied to the electronic tuning tuner section 2 as a control signal. .

To explain the operation in the above configuration, the analog AFT voltage of the frequency discrimination circuit 6 changes on the S-shaped characteristic Sv of the operation explanatory diagram used for the detailed explanation of the present invention in FIG. , only point 5 is shown). That is, when the normal AFT operation is performed in the frequency range of the intermediate frequency signal from flo to +6 (shaded area), and the tuning frequency of the electronically tuned tuner section 2 is varied in order to attenuate the beat interference of the adjacent channel. Assume that the frequency of the intermediate frequency signal is flg. The voltages A and t on the S-shaped characteristic Sv corresponding to the intermediate frequency fIz are, for example, 4 bits (1
011) is stored in advance in the memo +78 as offset data (the output of the A/D converter 7 is stored). When the frequency of the intermediate frequency signal changes from flg to +14 due to a temperature change, the AFT voltage of the frequency discrimination circuit 6 changes from A (z to A), and the output of the A/D converter 7 changes from (1011) to (1110). Therefore,
The output of the comparator 9 is the output of the A/D converter 7 (1110:
] and offset data (1011) is obtained as a comparison output, this comparison output is supplied to the electronic tuning tuner section 2 as a control signal, and feedback is performed until the output of the A/D converter 7 matches the offset data. This suppresses frequency fluctuations in the electronic tuner section 2.

Next, an embodiment of the present invention will be described with reference to a block diagram showing a first embodiment of an electronic channel selection device shown in FIG. FIG. 3 shows an example in which the present invention is applied to a voltage synthesizer type television receiver, and parts corresponding to those in FIG. 1 are given the same numbers and will be explained. 10 is a frequency setting means for generating a digital tuning signal, and the digital tuning signal of this frequency setting means 10 is supplied to an adder 11, where it is added to the comparison output of the comparator 9, and the output of the adder 11 is converted to D. The analog voltage is converted into an analog voltage by a /A converter 12, and the analog voltage is supplied to the electronic tuning tuner section 2 as a control signal. Note that 13 is a signal processing circuit that is connected to the video detection circuit 4 and performs color demodulation, synchronization signal detection, audio detection, and the like.

To explain the operation of the above configuration, the digital tuning signal corresponding to a predetermined broadcast frequency of the frequency setting means 10 is converted into a predetermined analog tuning voltage by the D/A converter 12 through an adder, and this analog tuning signal A voltage is supplied to the electronic tuning tuner section 2 and the desired broadcast frequency is received. In addition, when beat disturbance occurs in an adjacent channel, the offset data stored in the memory 8 is supplied to the D/A converter 12 through the comparator 9 and the adder 11 as described above, and the electronic data is set in a state where the beat disturbance is attenuated. Controls the tuning tuner section 2. When the frequency of the intermediate frequency signal of the electronic tuning tuner section 2 fluctuates due to temperature changes, etc., the frequency discrimination circuit 6 sends an analog AFT signal corresponding to the frequency fluctuation.
A voltage is obtained, and this analog AFT voltage is converted into a digital signal by the A/D converter 7 and supplied to the comparator 9. This digital signal is compared with the offset data in the memory 8 in the comparator 9, and if a frequency fluctuation occurs, the comparison output is passed through the adder 11 and the D/A converter 12 to generate a control signal. To maintain the tuning frequency of an electronic tuning tuner section 2 constant regardless of temperature changes.

Next, another embodiment of the present invention will be described with reference to a block diagram shown in FIG. 4 showing a second embodiment of the electronic channel selection device of the present invention. FIG. 4 shows an example in which the present invention is applied to a PLL digital synthesizer type television receiver.
The parts corresponding to those in FIG. 3 will be described with the same reference numerals.

In FIG. 4, numeral 14 indicates a PLL circuit, which has a reference oscillator (not shown), a phase comparator, and a variable frequency divider 14a, and constitutes a phase locked loop together with a local oscillator (not shown) of the electronically tuned tuner section 2.

Reference numeral 15 denotes a control circuit provided in place of the adder 11 in FIG. A digital control signal for controlling the variable frequency divider 4a is output. The output of a local oscillator (not shown) is supplied from the electronically tuned tuner section 2 to the PLL circuit 14, and an analog control signal is supplied from the PLL circuit 14 to the voltage-controlled variable reactance element (not shown) of the local oscillator of the electronically tuned tuner section 2. (not provided).

In the above configuration, the variable frequency divider 14 of the PLL circuit 14
The frequency division ratio of a is N, the reference frequency of the reference oscillator is fs, and the tuning frequency (local oscillation frequency) of the electronic tuning tuner section 2 is f
. In this case, fo=N-fs, so the variable frequency divider 14a divides the frequency according to the digital control signal obtained by adding the digital tuning signal of the frequency setting means 10 and the comparison output of the comparator 9 by the control circuit 14. By controlling the ratio N,
The tuning frequency f of the electronic tuning tuner section 2. can be varied. Therefore, in the case of a PLL digital synthesizer type television receiver, even when the beat interference of the adjacent channel is attenuated, as in the voltage synthesizer type television receiver shown in FIG. fo can be maintained constant regardless of temperature changes.

Note that the comparator 9, frequency setting means 10, and adder 11 in FIG. 3 and the comparator 9, frequency setting means 10, and control circuit 15 in FIG. 4 may each be constructed by a microprocessor.

Further, in the embodiments shown in FIGS. 3 and 4, the case where the present invention is applied to a television receiver has been described, but an electronic tuning device such as a radio receiver or an FM stereo receiver having an electronic tuning tuner section is described. The present invention can be applied to.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to suppress frequency fluctuations due to temperature changes or the like in the tuning frequency at which the interference signal of the electronically tuned tuner is attenuated.

Further, the present invention provides a voltage synthesizer method or a P
It has the advantage that it can be easily applied to an LL digital synthesizer type electronic channel selection device.

FIG. 4 is a block diagram showing a second embodiment of the electronic channel selection device of the present invention.

2...------Electronic tuner section 3--
-----------1...IF amplifier (V IF amplifier) 4--1-----Detector B (video detection circuit) 6--11 1~.----1 Frequency discrimination circuit 7-----A/D converter 8--
−−・・・・・・・・・・−・−Memory 9・〜・・−・・
...-Comparator 10--Frequency setting means 11--
・−・−−−−−−・・・Adder 12−・−・−・・・
-D/A converter 14-----11--PL
L circuit 14a ---- Variable frequency divider 15 --- Control circuit

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of the present invention, FIG. 2 is an operational explanatory diagram used for detailed explanation of the present invention, and FIG. 3 shows a first embodiment of the electronic channel selection device of the present invention. Diagram of the present invention's Bakufu San0 1 Ho ↑ Plow mother 2 Diagram 1 Explanation of the operation of the book Sanskrit 11; For... ◆ Operation explanation IN
Figure 3

Claims (1)

[Scope of Claims] 1. A frequency discrimination circuit that detects an analog AFT voltage according to frequency fluctuations of an intermediate frequency signal of an electronic tuning tuner section, and an A/D that converts the analog AFT voltage of the frequency discrimination circuit into a digital signal. a converter, a memory that stores offset data indicating a deviation of the frequency of the intermediate frequency signal from a center value, and a comparison that compares the output of the A/D converter and the offset data read from the memory. 1. An electronic tuning device comprising: a comparator, the comparison output of the comparator being supplied as a control signal to the electronic tuning tuner section. 2. The electronic tuning device according to claim 1, wherein a control signal obtained by D/A converting the comparison output of the comparator is supplied to the electronic tuning tuner section. 3. The tuning frequency of the electronic tuning tuner section is varied by a PLL circuit having a variable frequency divider, and the frequency division ratio of the variable frequency divider of the PLL circuit is controlled by the comparison output of the comparator. The electronic channel selection device according to claim 1, characterized in that: