JPH0444412A - Automatic channel selection device for television receiver - Google Patents

Abstract

PURPOSE:To attain accurate automatic channel selection in a short time by scanning a frequency control signal discontinuously so as to scan a channel selection frequency till a broadcast frequency signal is received at a scanning width smaller than a band width of the channel selection frequency effective for discriminating the reception. CONSTITUTION:A data to scan a frequency control signal 9 for a prescribed interval is stored in a frequency management memory 1 as a serial data and when the data is read sequentially from the frequency management memory 1 to scan the frequency control signal 9 at a prescribed interval, a channel selection frequency at a front end 4 is scanned at the interval of DELTAf and a broadcast frequency is detected. Since the scanning interval DELTAf is smaller than the frequency band width for the reception criterion by an AFC signal 17 and an SD signal 18. Thus, since the scanning is attained at a maximum scanning width in a reception enable range, the software is simplified and the tuning time is shortened.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an automatic channel selection system for a television receiver.

[Background Art and its Problems] FIG. 4 is a block diagram showing the configuration of a conventionally used voltage synthesizer type automatic tuning system. In the figure, numeral 31 is a channel selection control section that controls the system, and includes a built-in microcomputer. 32 is a pulse width modulation (PWM) from the channel selection control section 31.
) converting the signal 37 into an analog tuning voltage 38;
D/A (
It is a digital/analog) conversion circuit. The front end 33 also receives a band switching signal 3 from the channel selection control section 31.
9, VHF-HIGH band, VHF-LOW band,
You can switch to a band such as the UHF band. The front end 33 receives a reception frequency tIF (intermediate frequency) signal 4 selected from among the RF signals 40 received by the antenna 34 by a tuning voltage 38 and a band switching signal 39.
1 and sends it to the detection circuit 35. The detection circuit 35 is I
The F signal 41 is detected and a video signal 45 is output to the television monitor. At the same time, an automatic frequency control (AFC) signal 42 from the detection circuit 35 is fed back to the front end 33 as a signal 43 via a switching circuit 47 to stabilize the reception state.

When performing automatic tuning, for example, when a tuning button is pressed, a pulse width modulation signal 37 is output from the tuning control section 31, and a tuning voltage 38 input from the D/A conversion circuit 32 to the front end 33 is output. Scanned continuously. On the other hand, the AFC signal 42 from the detection circuit 35 is transmitted to the channel selection control section 31.
Switched by a switching circuit 47 according to a switching signal 48,
A synchronization signal pulse that is input to the channel selection control section 31 as a signal 44 and included in a video signal 45 is separated from the video signal 45 by a synchronization separation circuit 36, and is input as an SD (station detection) signal 46 for channel selection. The tuning control unit 31 scans the tuning voltage while monitoring the receiving state using the AFC signal 44 and the SD signal 46. When the tuning control unit 31 determines that a broadcast has been received from the AFC signal 44 and the SD signal 46, it stops scanning the tuning voltage 38, switches the switching circuit 47 using the switching signal 48, and switches the AFC signal 43 to the front end. 33 to stabilize the reception condition.

However, in this voltage synthesizer type automatic tuning device, although data management is possible in the tuning control section, tuning frequency management cannot be performed. , it was unclear which channel was being received, and the channel could not be displayed. In addition, although the front end oscillates at a frequency that corresponds to the tuning voltage, the correspondence between the tuning voltage and the oscillation frequency is not constant (there are variations in sensitivity), so changes in the pulse width (scanning width) of the pulse signal are Unless the details are fine-tuned, it is not possible to make accurate reception judgments over the entire band, leading to problems such as time-consuming tuning and complicated software.

Further, FIG. 3 is a block diagram showing a frequency synthesizer-type tuning system. In the figure, 1 is a frequency management memory, which is a channel selection control i! ! 2 outputs a frequency control signal 9 corresponding to a predetermined frequency based on data stored in the frequency management memory 2. 3 is a PLL that converts the frequency control signal 9 output from the tuning control section 2 into a tuning voltage lO and inputs it to the front end 4.
(7 aids locked loop) circuit 5 receives a frequency-divided signal 12 obtained by dividing the oscillation frequency 11 of the front end 4 by 1/N.
This is a frequency divider that inputs the signal into the PLL circuit 3. Since the PLL circuit 3 controls the tuning voltage 10 so that there is no phase difference between the oscillation frequency 11 of the front end 4 and the frequency corresponding to the frequency control signal 9, according to this method, the tuning control section 2 Tuning frequencies can be managed.

Further, a band switching signal 13 is input from the tuning control section 2 to the front end 4.

The RF signal 14 received by the antenna θ is converted into an IP signal 15 by the front end 4, detected by the detection circuit 7, and outputted as a video signal 16 to a television monitor. In addition, the AFC signal 17 from the detection circuit 7 and the video signal 16
SD double signal synchronization signal which is synchronized and separated by the synchronization separation circuit 8)
18 is fed back to the channel selection control unit 2,
The channel selection control section 2 monitors whether reception is optimal by checking the APC signal 17 and the SD signal 18.

In the conventional frequency synthesizer type channel selection device having the above-mentioned configuration, the frequency management memory 1 stores the allocated frequency of each channel according to the Radio Law.

FIG. 5 is a flowchart showing the channel selection operation of the channel selection control section 2 when selecting a channel. The channel selection operation will be explained according to this 20-chart. First, when the user turns on the channel selection button (S51), the data corresponding to the set channel is read from the frequency management memory l, and the band switching signal 13 and the frequency control signal are sent from the channel selection control section 2. Signal 9 is output (S52), and the channel is directly selected. At the same time, the channel selection control section 2 reads the AFC signal 17 and the SD signal 18 (S53), and determines whether or not the reception state is optimal (S54). Here, if the reception is not optimal, the frequency control signal 9 is finely adjusted to finely adjust the tuning voltage 10 (555), and whether or not reception is optimal is checked again (853.54). If you can receive optimal reception in this way,
Ends the channel selection operation.

With such a single-type frequency synthesizer, it is possible to manage the channel selection frequency, and therefore, unlike a single-type voltage synthesizer, it is possible to selectively select a channel for each channel allocated under the Radio Law. Furthermore, since the PLL circuit and the frequency divider form a PLL loop, variations in front-end sensitivity can also be absorbed.

However, in this system, the user has to select a channel one by one, and if the user does not know whether a broadcasting station is available or not, the user has to select channels even when there is no broadcasting station.

[Problems to be Solved by the Invention] The present invention has been made in view of the drawbacks of the conventional examples described above, and its purpose is to achieve advantages such as frequency management (channel management). The purpose of this invention is to enable automatic tuning with a one-type frequency synthesizer tuning system, thereby enabling accurate automatic tuning in a short time with simple software processing.

[Means for Solving the Problems] The automatic channel selection device for a television receiver according to the present invention includes a front end and a detection circuit of the receiver body, and a PLL that converts a frequency control signal into a tuning voltage and inputs it to the front end. The circuit and the frequency control signal are input to a PLL circuit, and on the other hand, it is determined whether or not a broadcast has been received based on a signal taken out from a detection circuit of the receiver body, and when a broadcast is received, optimal reception is achieved. a tuning control unit that finely adjusts the frequency control signal; and means for discontinuously scanning the frequency control signal until the tuning frequency is received with a scanning width smaller than a bandwidth for determining reception. It is characterized by consisting of.

[Function] In the automatic tuning device of the present invention, when tuning is started, the frequency control signal is discontinuously changed by the tuning control section, and this signal is converted into a tuning voltage by the PLL circuit. , entered into the front end. In this way, the selected frequency is scanned with a scanning width smaller than the bandwidth in which reception can be determined, and the broadcasting station is detected. When a broadcast station is detected,
The channel selection control section determines whether or not the reception is optimal, and adjusts the frequency control signal so that the reception is optimal.

Since the automatic channel selection device for a television receiver according to the present invention is a one-type frequency synthesizer using a PLL circuit, the channel selection control section can know the channel selection frequency, making frequency or channel management possible. , it has the advantages of a frequency synthesizer type tuning device.

Moreover, in the automatic tuning device of the present invention, the tuning frequency can be scanned with the maximum scanning width within the range where reception and judgment can be made, so that it is possible to scan the tuning frequency with the maximum scanning width. In addition, there is no need for complicated software processing to absorb sensitivity variations in the front end or time-consuming tuning due to the scanning width that takes into account the maximum variation, allowing accurate tuning in a short time using simple software. can do.

[Example] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

The configuration of the automatic tuning device of the present invention is represented by the same block diagram as the one-type frequency synthesizer tuning device shown in FIG. Therefore, the block diagram of the automatic tuning device of the present invention will not be illustrated and explained again, and the points different from the conventional frequency synthesizer type tuning device will be explained using FIG. I will mainly explain.

The automatic tuning device of the present invention is a one-type frequency synthesizer using a PLL circuit, and has a configuration as shown in FIG. Here, data for scanning the frequency spread signal 9 at regular intervals is stored in the frequency management memory 1 as serial data. When the data is sequentially read from the frequency management memory 1 and the frequency control signal 9 is scanned at regular intervals, the tuning frequency in the front end 4 is scanned intermittently with a width of Δf, and the broadcast frequency is detected. Moreover, the scanning width Δf of the selected channel frequency is smaller than the frequency bandwidth (for example, 0.8 MHz<L) that allows reception to be determined by the AFC signal 17 and the SD signal 18. Therefore, for example, in the vicinity of channels 3 to 5, as shown in FIG.
... f3, ..., f38. f39. f4. f41.・
... f5, ... are indicated by arrows. ), even between channels 3 and 4, you can tune the selected frequency to several locations without jumping from channel 3 to channel 4 at once. Therefore, even if the broadcast frequency of channel 4 (broadcast frequency f4) is shifted by only The channel is selected at a frequency f38 or f3θ which is different from the scanning frequency f4 of , and it is possible to prevent the channel from being skipped over the four channels without being selected. In this way, when a channel is selected at one of the scanning frequencies, the channel selection control section 2 selects the AFC signal 1.
7 and SD signal 19, finely adjust the frequency control signal 9 to obtain the best selection, and tune the selection frequency to the broadcast frequency (in the above example, to f4-). Further, if there is no broadcast station on channel 4, scanning is performed to the channel where the next broadcast station is located (for example, channel 5), and channel 5 is received.

The operation order of the channel selection control section 2 will be explained according to the flowchart shown in FIG. When the user turns on the channel button for up or down (S21)
, the serial data of the frequency management memory l is read out,
Frequency control signal 9 and band switching signal 1 from tuning control section 2
3 is output (S22). Next, the channel selection control unit 2 reads the AFC signal 17 and the SD signal 18 (S 2
3).

It is determined whether the broadcast has been received (S24). In step 22, if the broadcast is not being received, new data is read from the frequency management memory 1, the control frequency is changed, the selected frequency is sent up (or down) by Δf (S22), and the broadcast is received again. It is checked whether or not it has been done (S23, 24). In this way, the tuning frequency is sequentially scanned by Δf, and when the broadcast is received, the tuning control section 2 controls the APC signal 17 and the SD
The signal 18 is read (S25), and it is determined whether or not the Benuto channel is selected (326). Here, if it is not the best selection,
Finely adjust the frequency control signal 9 to output the tuning voltage 10
527), and checks again whether it is the best channel selection (S25, 2B). When the best selection is obtained in this way,
Ends the automatic channel selection operation.

[Effects of the Invention] Since the automatic tuning device of the present invention has only one type of frequency synthesizer, the tuning stability is good. Furthermore, since frequency or channel management is possible, the user can be informed of the selected channel, resulting in a good usability. Moreover, since it can be managed by frequency, scanning can be performed with the maximum scanning width within the range in which reception can be determined, simplifying the software and shortening tuning time, which is better than the conventional voltage synthesizer one-type automatic tuning. Solve the problems with the equipment.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the operation of the automatic tuning device of the present invention, FIG. 2 is an explanatory diagram of the same operation, and FIG. 3 is a block diagram showing the configuration of a frequency synthesizer type tuning device.
FIG. 4 is a block diagram showing a conventional automatic tuning system using a voltage synthesizer, and FIG. 5 is a flowchart showing a conventional tuning operation in a tuning system using a frequency synthesizer. ■... Frequency management memory 2... Tuning control section 3... PLL circuit 4... Front end 7... Detection circuit 8... Synchronization separation circuit 9... Frequency side (goods) signal ○...Tuning voltage 7...AFC signal 8...SD double signal Applicant: Noritz Co., Ltd.

Claims (1)

[Claims] (1) A front end and detection circuit of the receiver main body, a PLL circuit that converts the frequency control signal into a tuning voltage and inputs it to the front end, and a PLL circuit that inputs the frequency control signal to the PLL circuit, while a tuning control unit that determines whether or not a broadcast has been received based on the signal extracted from the detection circuit, and finely adjusts the frequency control signal to achieve optimal reception when the broadcast is received; An automatic channel selection device for a television receiver, comprising means for discontinuously scanning a selected frequency with a scanning width within a range in which reception can be detected until reception is received.