JPH04310011A - Station searching method for offset signal - Google Patents

Abstract

PURPOSE:To improve the search speed by setting a frequency block of + or -nMHz around a carrier frequency and using a required block as an AFT operation inhibit block at researching based on a station presence point by searching. CONSTITUTION:A tuner 2 is controlled by a selection timer microcomputer 1 and searching to detect a horizontal synchronizing signal is implemented by an AFT operation. When the horizontal synchronizing signal is detected, the microcomputer 1 decides in which block point a station presence point exists or whether or not the point exists in a block by referencing a frequency block of + or -nMHz (n=0, 1, 2...) around a carrier frequency (f) and stores adjacent blocks at both sides of the block when the point exists in the block point and the block when the point is in existence in the block to the memory 3. The AFT operation is inhibited by the microcomputer 1 at researching and the undesired search block is not again searched for the stored block and the search speed is substantially increased.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention can be used in television receivers, video tape recorders, etc. equipped with a frequency synthesizer type channel selection device that can also receive channels whose frequencies are offset.

0002

[Prior Art] Conventional frequency synthesizer channel selection devices can perform AFT even for slightly offset stations (stations whose carrier frequency is set at a position deviated from the normal value) as long as the horizontal synchronization signal can be detected. I was able to receive the message using the auto search operation. however,
Channels that are offset from the center frequency of the station in a range that is greater than the range in which the horizontal synchronization signal can be detected cannot be received using the auto search operation. I was doing it.

[0003] By the way, in the CATV stations in the PAL area, there are a number of stations that are extremely offset (for example, stations that are offset +4 MHz away from the center frequency), so the center frequency of each channel is It is desired to be able to search all channel frequency bands and receive even extremely offset stations by automatic search operation, and for this purpose, an offset search operation as described below can be considered.

[0004] That is, this offset search operation is
Simply put, after outputting the center frequency of each channel,
Combining the range of ±4MHz with AFT operation,
It searches efficiently and uses (1) to (1) as shown below.
3) is performed according to the operating procedure. (1) Offset search operation procedure (see FIG. 6) - For an actual CH (channel), +1CH is output when searching in the UP direction, and -1CH is output when searching in the DOWN direction. ■ Outputs the frequency of center frequency - 1MHz, (2)
perform the following actions. ■Output the frequency of center frequency - 2MHz, (2)
perform the following actions. ■ Outputs the frequency of center frequency - 3MHz, (2)
perform the following actions. ■Outputs the frequency of center frequency - 4MHz, (2)
perform the following actions. ■Outputs the center frequency + 1MHz frequency, (2)
perform the following actions. ■Outputs the center frequency + 2MHz frequency, (2)
perform the following actions. ■Outputs the center frequency + 3MHz frequency, (2)
perform the following actions. ■Outputs the center frequency + 4MHz frequency, (2)
perform the following actions. (2) Even if the frequency of '+4 MHz is output, if no horizontal synchronizing signal is detected (that is, if there is no station), the center frequency of the next channel is output, and the search operation is continued from the operation (2) again. (2) Considering the response of the tuner,
After waiting for about sec), the presence or absence of a horizontal synchronization signal (stationed or non-stationed) is determined.

[0005] Here, if the horizontal synchronizing signal can be detected (if there is a station), the process shifts to AFT operation, and if the horizontal synchronizing signal cannot be detected (if there is no station), the offset search operation in (1) is performed. Move on to the next step. (3) AFT operation (see flowchart in Figure 5) AF
When the T operation starts, first, it is determined again whether the station is stationed or not, using the same method as in (2) (S1). Then, in the next step (S2), after waiting for 100 msec until the AFT/S curve output voltage becomes stable, the process moves to the next operations (a) to (c).

(A) AFT/S curve signal input>5/1
At 6Vcc (AFT/S curve signal input ≦5/16V
In the case of cc, the frequency is increased by 50 KHz every 20 msec (S4), and the following conditions are followed.

(a) AFT/S curve signal input ≦5/1
When it is determined in step S3 that the voltage has reached 6Vcc, (
Shift to operation b).

(b) Even if the output frequency is +1MHz,
If it is determined in step S6 that the condition (a) above is not satisfied, the process moves to the next step of the offset search operation in (1).

(a) When it is determined in step S3 that the AFT S curve signal input≦5/16Vcc, the frequency is decreased by 50 Hz every 20 msec (S7), and the following conditions are followed.

(a) AFT/S curve signal input≧11/
When it is determined in step S10 that the voltage has reached 16 Vcc, the process moves to operation (c).

(b) In step S9, the output frequency is -1MH.
If it is determined that the condition (a) above is not satisfied even when the offset search value z is reached, the process moves to the next step of the offset search operation in (1) (S16).

(c) In step S11, the frequency is increased by 2 by 50 KHz.
The frequency is increased every 0 msec, and the following conditions are followed.

(a) AFT/S curve signal input <11/
When it is determined in step S14 that the voltage has reached 16Vcc,
Stop (S15).

(b) Output frequency +1M in step S13
Hz, if it is determined that the condition (a) above is not satisfied, the process moves to the next step of the offset search operation in (1).

[0015]

By the way, when such an offset search operation is introduced, all channel frequency bands are searched by AFT operation, so that the conventional method (
If the horizontal synchronization signal is not detected, the search speed will be extremely slow compared to the search speed using the method of skipping to the center frequency of the next channel. [1 search cycle (until all channels are searched)
It takes about five times as long. ] Therefore, it is an object of the present invention to improve such search speed.

[0016]

[Means for Solving the Problems] The offset signal searching method of the present invention locates each frequency point of f±n (n=0, 1, 2,...) MHz centering on the regular carrier frequency f of a certain channel. A channel selection device detects a desired broadcasting station by detecting a horizontal synchronization signal, and when it is detected that a broadcasting station is present, performs a station search by AFT operation at that frequency point to search for a stationed point. In this case, the frequency range of f±n is taken as one search range, and this one search range is divided into 2n sections, and the point once determined to be stationed by the above search operation is defined as f±n(
n = 0, 1, 2, ...) MHz frequency point, the sections on both sides of the stationed point are set as AFT operation prohibited sections during re-search, and the station is temporarily determined by the above station searching operation. If the point located within the above-mentioned section exists, the section in which the stationed point exists is set as the AFT operation-prohibited section at the time of re-search, and in the AFT operation-prohibited section, the horizontal Even if a synchronization signal is detected, the AFT operation is not performed.

[0017]

[Operation] According to the above means, in the AFT operation prohibited section,
Even if the horizontal synchronization signal is detected, the AFT operation is not performed and the search operation moves to the next point to be searched.

[0018]

[Examples] Examples of the present invention will be described below.

In order to improve the search speed after introducing the offset search operation described above, it is conceivable to simply increase the search speed, but then the response of the tuner will not be able to keep up, and the search operation will not be able to catch any stations. (unable to receive data).

Therefore, in the present invention, instead of simply increasing the search speed, the offset search operation is stopped once and then the search operation is started (manually or automatically) using the method described later. This improves the search speed.

Examples of the present invention will be described below.

FIG. 5 shows a block diagram of a channel selection device embodying the present invention, in which 1 indicates a channel selection/timer microcomputer, 2
The channel selection is controlled by the microcomputer, and AFT/
A tuner that outputs S-curve voltage to the microcomputer, 3 a memory that stores channel selection information such as channel selection and band data, 4 a display that displays information such as channels,
5 is a remote control device, and 6 is a group of operation switches.

Next, the operation of the microcomputer 1 will be explained, but since the operations other than the following operations are the same as the offset search operation explained in the related art, the operation will not be explained again. .

(1) First, as shown in Figure 1, the range of ±4 MHz with respect to the center frequency (regular frequency) of each channel is defined as one search section, and this one search section is set as 1 MHz.
Each z is divided into eight sections (a to h).

(2) Next, in the search operation described in the prior art section, from the point where it is once determined that a station is present and the search operation is stopped, a specified section is set as an AFT operation prohibited section, Regulates the next AFT operation.

[0026] At this time, the above-mentioned AFT operation prohibition period can be set using the following two methods (1) and (2).

[0027] In each procedure of the offset search operation explained in the section of the prior art,
There is a stationary point at the point where the specified frequency at every z interval is output,
When the search operation stops at that fixed point, the sections on both sides of the frequency of the stopped point are set as the prohibited sections for AFT operation during re-search.

For example, when the point where the center frequency of a certain channel is output is determined to be stationed and the search operation is stopped, "d" and "e" are set as prohibited sections, respectively, as shown in FIG.

[0029] Also, (center frequency of channel) -
When the point that outputs the 2MHz frequency is determined to be stationed and the search operation stops, as shown in Figure 3, "d",
"c" is set as a prohibited section for search operation by AFT operation.

[0030] After outputting frequencies at intervals of 1 MHz from the regular frequency, AFT operation is performed at each point, and when the station stops between each section, the section including the stopped point is AFT This is set as a prohibited area for search operations.

For example, as shown in FIG. 4, if a station is available in the +2 to +3 MHz range and the search operation is stopped at that point, "g" is set as the prohibited range. (3) When performing the remaining offset search procedure for that channel by entering the key again (or automatically), (2)
), even if a horizontal synchronizing signal is detected, the search operation (AFT operation) is not performed and the process proceeds to the next step of the offset search.

[0032] Even after a fixed point is found in this way, the offset search of the remaining range of the channel is performed by key input again (or automatically) because the fixed point is a virtual image ( This is because the remaining range is searched in order to capture the real image, as there is a possibility that the point was determined to be a fixed point by capturing a ghost (ghost). Therefore, by the operation of the present invention, a fixed point will not be missed.

By the way, the range in which it can be determined that a station is present based on the synchronization signal (the range in which AFT operation is possible) is about 1 point above the station presence point.
MHz, approximately 2MHz range at the bottom, and during this period AF
A T action will be performed.

For example, in the case where there is a fixed station on the center frequency as usual as shown in FIG. 2, if this prohibited section is not provided, the offset search operation will not be performed even if the station is detected and then restarted. In the next step “■ Center frequency - 1
Even after the frequency of "MHz" is output, it is determined that there is a station, and the AFT operation is performed in the direction of the center frequency (a search is performed in the section "d").

Furthermore, if there is a station even after the output frequency of "■ center frequency - 2 MHz" in the next step, the AFT operation will be performed toward the stationed point here as well.

[0036]Furthermore, by turning back to “■center frequency +
Even after the frequency output of “4MHz”, it is judged that there is a station, and this time “e
” will be searched (AFT operation). If you do not set a prohibited section like this, the search operation (AFT operation) will be performed several times.
T operation) loss occurs.

However, by providing this prohibited section, “
Since no operation (AFT operation) is performed during the search in the sections ``d'' and ``e'', the overall search speed can be improved accordingly.

As described above, the present invention becomes more effective as the number of fixed points increases.

[0039]

According to the present invention, it is possible to improve the search speed required to search all channel frequency bands so that offset channels can also be received at the time of presetting.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a state in which one search section is divided according to the present invention.

FIG. 2 is a diagram showing a first example of a prohibited section set according to the present invention.

FIG. 3 is a diagram showing a second example of a prohibited section set according to the present invention.

FIG. 4 is a diagram showing a third example of a prohibited section set according to the present invention.

FIG. 5 is a schematic block diagram of a frequency synthesizer tuning device in which the present invention is implemented.

FIG. 6 is a diagram showing the procedure of an offset search operation.

FIG. 7 is a diagram showing a flowchart for explaining an AFT operation accompanying an offset search operation.

[Explanation of symbols]

1. Tuning/timer microcomputer 2 Tuner 3 Memory 4 Display unit 5 Remote control 6 Switch group

Claims (1)

[Claims] Claim 1: A horizontal synchronizing signal is detected at each frequency point of f±n (n=0, 1, 2,...) MHz centered around the regular carrier frequency f of a certain channel, and a desired broadcasting station is broadcast. In the channel selection device, when it is detected that a broadcasting station is present, a station search is performed at that frequency point by AFT operation to find a station presence point, and the frequency range of f±n is taken as one search range. , this one search range is divided into 2n sections, and the point once determined to be stationed by the above search operation is f±
If it exists on a frequency point of n (n = 0, 1, 2, ...) MHz, the sections on both sides of that stationed point are
If a point that was once determined to be stationed by the above-mentioned station searching operation exists within the above-mentioned section, the section in which the stationed point exists is set as an AFT operation prohibited section during re-search;
A method for searching for an offset signal, characterized in that, in the AFT operation prohibited section, an AFT operation is not performed even if a horizontal synchronization signal is detected on the frequency point during re-search.