JPS5941922A - Channel selecting device - Google Patents

Abstract

PURPOSE:To pull-in tuning frequencies in a wide range, by pulling in a tuning frequency which is given to an electronic tuning tuner, to an optimum tuning frequency by an AFC circuit after changing the tuning frequency to the low frequency side by counting-down if the tuning frequency is shifted from the optimum tuning frequency to the high frequency side. CONSTITUTION:When an AFC voltage is lower than a reference voltage V1 and os higher than a reference voltage V2, and the tunig frequency is higher than an optimum tuning point, a channel selecting circuit 2 sends a signal to a count- down circuit 8 to count down the value, which is set in an up/down circuit 3 by the circuit 8 by a prescribed value, and changes the tuning frequency to the low frequency side. The circuit 2 discriminates the compared result between the AFC voltage due to an AFC circuit 4 and voltages V1 and V2, and the tuning frequency is hifted to the high frequency side by counting-up when the AFC voltage is shigher than the voltage V1, and the tuning frequency is shifted to the low frequency side by counting-down in the circuit 3. Thus, the tuning frequency is approximated to the optimum tuning frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital tuning tuning device that can be used in television receivers, FM and AM radio receivers, and the like.

In recent years, electronic tuning tuners have become mainstream in television receivers, FM, AM radio receivers, etc., which use variable capacitance diodes as the capacitance of the tuning circuit and tune by applying a tuning voltage to this. Tuning frequency can be controlled and channel selection can be performed using a so-called voltage synthesizer method in which the tuning voltage applied to the diode is processed as a digital quantity.

Hereinafter, a conventional channel selection device using a voltage synthesizer method shown in FIG. 1 will be explained.

In FIG. 1, from the switch means (1) to the channel selection means (2),
1, the tuning means (2) reads a digital amount corresponding to the tuning voltage from the storage means (5) and gives it to the up/down counting means (31). The digital output is sent to a digital-to-analog (D//\) converter (6) and converted to a DC voltage, the analog output of which is applied to an electronic tuning tuner (7) as at least part of the tuning voltage. The up/down count means (3) changes the tuning frequency toward a higher frequency when counting up, and changes toward a lower frequency when counting down.(4) is an automatic frequency adjustment ( A
FO) means.

Figure 2 (a) ib) and (C1 is the AFO means (4)
FIG. 3 is a signal waveform diagram for explaining the operation of FIG. Figure 2 (a
l indicates the automatic frequency adjustment (AFC) voltage that changes in a figure-8 curve near the tuning point when the tuning frequency is changed from the low frequency side to the high frequency side of the predetermined broadcasting frequency, and v1 and V2 are the reference voltages. In terms of voltage, if the center voltage of the AFO voltage is VO, then Vl)'Vo>V2.

ft)l in FIG. 2 is a signal waveform obtained by comparing the AFO voltage and the reference voltage Vl. When the AFO voltage is larger than vl, it is a H level, and when the AFO voltage is smaller than 1, it is a 1L level. Further, FIG. 2(O) shows a signal waveform comparing the AFO voltage and the reference voltage V2, and when the AFO voltage is larger than v2, it is t Ll level, and when the FO voltage is smaller than ■2, it is the °H level.

The AF'O means (4) is an electronically tuned tuner.
Compare the C voltage with the reference voltages Vl and V2, and when the AFO voltage is greater than Vl (from point A to point B in Figure 2 (a)
range), the up/down counting means (3) counts up and changes the tuning frequency to a higher frequency side. A
When the FO voltage is smaller than V2 (range from the dot to point E in Figure 2 (a)), the A F 0 means (4) counts down with the up/down count means (3) and shifts the tuning frequency to the lower frequency side. change. As mentioned above, the A F 0 means (41) judges the \FO voltage, changes the tuning frequency with the up/down count means (3), and calculates the WS2 figure (
It works to get closer to the optimal tuning point C in a).

Therefore, when the tuning voltage read from the storage means (5) is applied to the electronic tuning tuner, the FG voltage is compared with the reference voltages Vl and V2, and as a result, the point A in FIG.
to point E, the AEO means (4) can control the up/down count means (3) to pull the tuning frequency to the optimum tuning point C.

By the way, the tuning voltage read from the storage means by the tuning means (2) may not be pulled in by the AFO means (4) due to reasons such as temperature or drift of the electronic tuning tuner. For example, when a tuning voltage like point F in FIG. 2(A) is applied to an electronic tuning tuner, the
4) It is not possible to pull in to the point (01).The present invention provides a tuning device that improves the above-mentioned drawbacks and makes it possible to reliably pull in to the optimum tuning point.

FIG. 9J3 is a block diagram showing an embodiment of the present invention. In FIG. 3, 111 is a switch means that generates a signal for the channel selection means (2) to start channel selection;
(3: an up/down count means that receives a pulse signal and counts up or down the pulse signal; (6) a digital/analog converter that converts the digital output signal of the up/down count means (3) into a DC voltage; (71 is an electronic tuning tuner to which this DC voltage is applied as at least a part of the tuning voltage, (5) is a storage means for storing a digital amount corresponding to the tuning voltage, and (2) is an electronic tuning tuner to which this DC voltage is applied as at least a part of the tuning voltage. (2) is a storage means for storing a digital amount corresponding to the tuning voltage. The tuning means (4) reads the digital amount of tuning voltage from the storage means (5) according to the signal and supplies it to the up/down counting means to control tuning. AFO means (8) for comparing reference voltages Vl and v2;
) is a countdown means for causing the tuning means (2) to count down the value set in the up/down count means (3) by a predetermined value.

In such a configuration, the tuning means (2) receiving the tuning start signal from the switching means (1) causes the storage means (
A digital value corresponding to the tuning voltage is sent from 5) to the up/down counting means, and the up/down counting means (3) converts the digital output into a DC voltage via a digital/analog converter, and then outputs the digital value to the electronic tuning tuner. (7) is applied to the variable capacitance diode. A20 means (
4) compares the AFO voltage according to the applied tuning frequency with the reference voltages v1 and V2, and supplies the result to the tuning means. When the AFO voltage is smaller than the reference voltage V1 and larger than the reference voltage ■2, for example, when the tuning frequency is at a point F above the optimum tuning point C, the tuning means (4) starts the countdown means (8). ), the countdown means counts down the value set in the up/down count means (3) by a predetermined value, and changes the tuning frequency to the lower frequency side. Next, channel selection means (4)
successively judges the comparison result between the AFO voltage and the reference voltages V1 and v2 by the A20 means (4), and when the AFO voltage is greater than the reference voltage V1, the up/down count means (3)
) to change the tuning frequency to the higher frequency side, and when the AFO voltage is smaller than the reference voltage (2), count down by the up/down count means (3) to change the tuning frequency to the lower frequency side. As a result, the tuning frequency is brought closer to the optimum tuning frequency by the tuning means (4), the up/down counting means (3), and the A20 means.

When the AFO voltage based on the tuning voltage first read out from the storage means (5) is larger than the reference voltage ■1 or smaller than the reference voltage v2, the value set in the up/down count means (3) remains unchanged. A20 means (4)
This starts the operation of pulling in the optimum tuning frequency.

As described above, according to the present invention, the tuning frequency read from the storage means (5) by the tuning means (2) and given to the electronic tuning tuner (7) deviates to a higher frequency side than the optimum tuning frequency. In this case, the countdown means (8) counts down and changes to the lower frequency side, and then the AFO means (4) pulls in the optimum tuning frequency, so it is possible to pull in a wider range of tuning frequencies than the conventional one. .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional channel selection device, FIG. 2 is a signal waveform diagram for explaining automatic frequency adjustment operation, and FIG. 3 is a block diagram showing an embodiment of the present invention. In the figure, +I+ is a switch means, (2) is a channel selection means, (3) is an up/down count means, (4) is an automatic frequency adjustment (AFO) means, (5) is a storage means, and (6) is a digital/ An analog converter, (7) an electronic tuning tuner, and (8) a countdown means. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Makoto Kuzuno - Figure 1 Figure 3 Figure 2 Procedural amendment (voluntary) Commissioner of the Japan Patent Office 1, Indication of case Japanese Patent Application No. 158758-1983 3
, To the representative of the person making the amendment, Hitoshi Katayama, Department 4, Agent 5, Detailed explanation of the invention in the specification subject to amendment, Column 6, Contents of the amendment (1) The specification is corrected as shown.

Claims (1)

[Claims] up/down counting means for receiving a pulse signal and counting up or down the pulse signal; a digital/analog converter for converting the digital output signal of the up/down counting means into a direct current voltage;
An electronic tuning tuner to which the DC voltage is applied as at least a part of the tuning voltage, a switch means for generating a signal to start tuning, and a digital quantity corresponding to the tuning voltage applied as a pulse signal to the up/down counting means. a storage means for storing a digital signal from the storage means to the up/down count means according to a signal from the switch means, and a tuning means for controlling tuning by outputting a digital amount from the storage means to the up/down counting means; automatic frequency adjustment means for generating an automatic frequency adjustment voltage (AFO voltage) and matching the tuning frequency of the electronic tuning tuner to the predetermined receiving frequency via the up/down counting means and the digital/analog converter;
The AFO voltage is compared with a first predetermined voltage and a second predetermined voltage larger than the first predetermined voltage according to a signal from the channel selection means, and the AFO voltage is smaller than the first predetermined voltage and larger than the second predetermined voltage. A channel selection device comprising countdown means for counting down a digital value set in the up/down count means by a predetermined value.