JPH04192976A - Tv broadcasting receiving system for frequency synthesizer tuning system - Google Patents

Abstract

PURPOSE:To shorten time for detecting an optimum point by storing a synchronizing deciding area, to which the detected optimum point belongs, in a storing means and starting the search operation of the optimum point from the stored synchronizing deciding area. CONSTITUTION:A CPU 5 stores the synchronizing judging area, to which the optimum point of a local oscillation frequency for correctly receiving the broadcasting of a desired station first detected belongs, in a second data storage part 8 and when tuning the original channel again, the former optimum point synchronizing judging area concerning the tuning channel is read out of the storage part 8. Then, a correspondent synchronizing deciding area is read out of a first data storage part 7 and it is set as the local oscillation frequency. Thus, time for detecting the optimum point can be considerably shortened, and time disturbing pictures on a TV screen can be shortened at the degree of almost not noticing it.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a TV broadcast receiving system using a frequency synthesizer channel selection method.

<Prior Art> FIG. 4 shows a schematic configuration of a conventional frequency synthesizer channel selection TV broadcast receiving system.

In Fig. 4, ■ is a receiving antenna, 2 is a P, LL tuner, 3 is an IF circuit, 4 is a data input section, 5 is a CPU,
6 is a synchronization determination circuit, and 7 is a data storage unit (ROM).

The high frequency video signal received by the receiving antenna 1 is PL
The signal is input to L tuner 2. In PLL tuner 2, C
It has a built-in local oscillation circuit that generates a frequency according to the tuning data from the PU5, and by mixing the local oscillation signal and the high-frequency video signal, it generates a frequency intermediate between the local oscillation frequency and the high-frequency video signal frequency. A frequency signal (IF signal) is generated and sent to the IF circuit 3.

The 1F circuit 3 extracts a video signal and an audio signal by detecting a signal of a certain frequency. Also, I
The F circuit 3 generates an AFT voltage, generates an LJP request signal and an I) OWN request signal from this AFT voltage, and outputs a CP
L: Send to 5. The UP request signal requests an increase in the local oscillation frequency of the local oscillation circuit of the PLL tuner 2, and the DOWN request signal requests a decrease in the local oscillation frequency. In the synchronization determination circuit 6, the IP circuit 3
Determine whether or not the horizontal synchronization signal is included in the input signal from
H” level) is sent to the CPU 5.

7th IN(a>, (b) shows the relationship between the AFT voltage, the no-synchronization signal, the UP request signal, and the DOWN request signal.

The CPU 5 receives the no-synchronization signal, the UP request signal, and the DOW signal.
Based on the N request signal, the tuning data is controlled to a local oscillation frequency (hereinafter referred to as an optimum point) at which the broadcast of the desired station can be correctly received.

The data storage unit 7 stores in advance local oscillation center frequency data corresponding to each channel, and when the selected channel is determined based on the channel data input from the data input unit 4, the CPU 5 The center frequency data of the more determined channel selection is read out, and the channel selection operation is performed as described above.

FIG. 5 shows the center frequency f determined for a certain broadcast channel. ! On the other hand, it shows how the entire search area (fo c) to (fo = c) of the channel is divided into five synchronization determination areas (synchronization determination points 0 to 4).

The channel selection operation by the CPU 5 is performed according to the flowcharts of FIGS. 6 and 3. Note that the flowchart in FIG. 3 is also common to the embodiments of the present invention to be described later.

In step Sll, a level counter N for counting which synchronization determination area is being searched is set to O.

In step 312, the center frequency fo of the synchronization determination area corresponding to level counter N=0 is read out from the data storage section 7 and set, and the local oscillation frequency of the local oscillation circuit built in the PLL tuner 2 is set to the center frequency f0. Set.

In step S13, the state of the no-synchronization signal from the synchronization determination circuit 6 is determined to determine whether a horizontal synchronization signal has been detected. When a synchronization signal is detected, the process proceeds to step 5100, but when it is not detected, the process proceeds to step S14, where the level counter N is incremented by -1, and in step 515, the content of the level counter N is the maximum level of the synchronization determination point. Determine whether it exceeds 4. If not, the process returns from step S12 to step S13, and it is determined whether a synchronization signal is detected at the synchronization determination point)1 (f, -a).

If no synchronization signal is detected, the level counter N is sequentially incremented and the synchronization judgment point is set to (fe
b)-” (fa +a)= (f6 +
Transfer as shown in b). In other words, search for a synchronization signal in the local oscillation state at each center frequency indicated by the thick line in Figure 5, and if it is not found, search for a synchronization signal at the center frequency at the next synchronization determination point in the order of the arrows. It is.

Even when the level counter N=4, no synchronizing signal is detected, and in step 314, the level counter becomes N=5, and step S
If YES is determined in step 15, that is, if no synchronization signal is detected in all five synchronization determination areas, it means that there is no broadcast on the desired channel. In such a case, the process proceeds to step S16, where the local oscillation frequency is set to the center frequency f0 when the level counter N=O, and then the channel selection operation is terminated (in this case, a channel selection failure occurs).

When a synchronization signal is detected in any of the five synchronization determination areas, the process proceeds to step 5100, and an optimum point is searched for in the synchronization determination area at that time. That is, in the first step, a synchronization determination area where a synchronization signal can be detected is determined, and in the second step, an optimal point is searched and determined in the synchronization determination area. The subroutine for this optimal point search operation is as shown in FIG. 3 (described later).

In step 5300, it is determined whether or not the optimum point has been detected. If detected, the channel selection operation is ended, but if not detected, the process returns to step S14. Returning from step 5300 to step S14 is an operation when the optimal point exists between (fo +1)) and CIO+C) (described later).

Next, the search operation for the optimal point is shown in Figures 3 and 7 (b).
).

The search range is determined for each synchronization determination area, and the data is stored in the data storage section 7 in advance. For example, in the synchronization determination area O where the level counter N=O, as shown in FIG. 5, the search upper limit is (f0+a) and the search lower limit is (f o a ).

When starting the search operation, the CPU 5 first clears the optimal point presence flag in step 5101. In step 5102, it is determined whether there is a DOWN request signal.

When there is no DOWN request signal, the no synchronization signal is “L”
Within the synchronization period that is the level, the synchronization judgment area (top ■) at the start of the search is located on the lower frequency side than the optimal point 1 - fX (local oscillation frequency during just tuning). become.

Therefore, when it is determined that there is no DOWN request signal, the process proceeds to step 5103, where the local oscillation frequency is increased by one step, and after passing through steps S104 and 5105, the state where there is no DOWN request signal is resolved in step 5106. (in other words, whether a DOWN request signal has been detected).

In other words, the local oscillation frequency is increased one step at a time as shown in the upper row ■−■−■−■−■, and the optimum point f
, a DOWN request signal is issued, and this is detected. In addition, the optimal point) fx is DO
Needless to say, both the WN request signal and the UP request signal are within the range where they are at the "L" level.

When the DOWN request signal is detected, the process proceeds to step 5113, where the local oscillation frequency is lowered by one step as shown in the upper row (■-■). The local oscillation frequency at this time becomes the frequency that determines the optimum point fX.

In the next step 5114, the flag with optimal points is set, so in step 5300 (Figure 6), YES is selected.
It is determined that this is the case, and the search operation is terminated. As a result, it is possible to receive the desired TV broadcast on the reception frequency at the optimum point.

If it is determined in step 5102 that the DOWN request signal is present, the synchronization determination region at the start of the search is located on the higher frequency side than the optimal point fx (lower ■). Therefore, the process proceeds to step 5107, where the local oscillation frequency is lowered by one step, and after steps 3108 and 5109, the UP is performed in step 5110.
Determine whether a request signal is present.

In other words, the local oscillation frequency is lowered one step at a time as shown in the lower row ■−■−■−■−〇−〇, and the optimal point f
By setting it lower than X, an UP request signal is issued. When the IjP request signal is detected, the local oscillation frequency is increased one step at a time in steps 5i11.5l12 in the manner shown in the lower row ■-■-■-■ until the DOWN request signal is detected.

When the DOWN request signal is detected, the process proceeds to step 3113 and the local oscillation frequency is changed to the lower stage ■-[
[phase], lower it by 1 step, like [phase].

The local oscillation frequency at this time becomes the frequency that determines the optimal point fX, and the television broadcast of the desired channel can be received at the reception frequency of the optimal point.

The reason why the search operation is not terminated at the bottom ■ in this case is as follows.

If there is only one point where there is a synchronization signal and no tJPUP request signal and no OWN request signal, that is the optimal point, but in reality, due to variations in circuit constants, there are two points like the above. There are more than one.

Therefore, if you finish the search operation at the bottom ■,
Even with just tuning, when the search operation is started from the lower side of the reception frequency band (upper row ■~■) and when the search operation is started from the higher side (lower row ■~■)
Therefore, the optimum point) fx becomes inconsistent, with one being ■ and the other being ■, which is not desirable. (optimal point no matter which direction you start the search operation) fx
In order to make it so that there is only one tube place, as shown above, the stage of the lower stage ■ ~ [phase].

It performs a pull operation (Sl11.5112, 5113).

Note that if the local oscillation frequency reaches the search upper limit or search lower limit in steps 5114 and 3108, or as a result of amplifying or lowering the local oscillation frequency, step 510
5. If there is no synchronization signal at 5109, the search operation is ended and the process proceeds from step 5300 to step 514 in FIG. Make sure to do the following.

<Problems to be Solved by the Invention> However, the conventional example having such a configuration has the following problems.

As is clear from the flowchart in FIG. 6, when starting the channel selection operation, the level counter N is initialized to 0↓ in step Sll, and synchronization is always determined from the center frequency f0 of the local oscillation. The further away the frequency position where the optimal point is located from the center frequency f0, the greater the number of synchronization determination regions that are subject to synchronization determination until reaching the optimal point.

When a synchronization signal is not detected, the local oscillation frequency is changed to switch the synchronization determination area, but it takes a certain amount of time for the PLL tuner and IF circuit including the local oscillation circuit to become stable. Therefore, the optimal point is the center frequency f
The further away from 0, the longer the time required for the channel selection operation and the longer the time for image disturbance on the TV screen.

In the synchronization determination area where a synchronization signal has been detected, a search operation is performed in which the local oscillation frequency is changed by one step. However, the frequency range in which the non-synchronization signal becomes "L" level is set to be quite wide, and multiple Since the points may exist over the synchronization determination area, the optimum point may not be detected even by a search operation in one synchronization determination area. In such a case, the search operation will be performed also in the adjacent synchronization determination area (for example, if the optimal point is between the frequency (f0+b) and lr, ↓C), first, the area WiN= Although the search operation is performed at 34, the optimum point is not detected, and the search operation must then be performed at the area N=4), so the search operation takes a longer time.

Such a search operation over two regions can occur not only in the case of N-3 and N-4 but also in any of the adjacent 2Si regions.

The present invention was devised in view of these circumstances, and an object of the present invention is to shorten the time required for channel selection as much as possible.

<Means for Solving the Problems> In order to achieve the above object, the present invention has the following configuration.

That is, the present invention divides the entire search area for the local oscillation frequency for each channel into a plurality of synchronization determination areas, extracts the synchronization determination area in which a synchronization signal is detected from among these multiple synchronization determination areas, and then In a TV broadcast receiving system using a frequency synthesizer channel selection method, in which the local oscillation frequency is changed in steps in the extracted synchronization determination area to detect an optimal point, means for storing the synchronization determination area to which the optimal point belongs; , comprising means for reading out the optimal point synchronization determination area from the storage means upon the start of tuning, and means for performing an optimal point detection operation by step change of the local oscillation frequency in the read optimal point synchronization determination area. It is characterized by:

<Effect> The effects of the above configuration of the present invention are as follows.

In the conventional example, the optimum point of the local oscillation frequency detected when performing a tuning operation for a certain channel is erased when performing a tuning operation for another channel. In contrast, in the case of the present invention, the optimal point is first detected in the same manner as in the conventional example, but once detected, the synchronization determination area to which the detected optimal point belongs is stored in the storage means. Since it is stored, it will not be erased even if another channel is selected.

Then, when selecting the original channel again,
Instead of repeating exactly the same operation from the beginning as in the conventional example, the synchronization judgment area to which the optimal point that was previously found and stored belongs is read out, and the synchronization judgment area is immediately started from the stored optimal point synchronization judgment area. Since the search operation for the optimal point is started, the time required to detect the optimal point is significantly shortened.

<Example> Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing the electrical configuration of a TV broadcast receiving system using a frequency non-synthesizer channel selection method according to an embodiment of the present invention.

In FIG. 1, 1 is a receiving antenna, 2 is a PLL tuner with a built-in local oscillation circuit, 3 is an IF circuit with a built-in AFT circuit, 4 is a data input section, 5 is a CPU, 6 is a synchronization determination circuit, and 7 is a synchronization determination circuit. 1 is a data storage unit (ROM), and 8 is a second data storage unit (RAM). What differs from the conventional example (Fig. 4) in this configuration is the synchronization determination area in which a synchronization signal was detected during the previous channel selection operation for each channel, and it was determined that the optimal point belonged to it by the search operation. This is achieved by adding a second data storage unit 8 for storing the area number of the optimum point synchronization determination area.

Next, the operation of this embodiment will be explained according to the flowchart of FIG.

The number of divisions into which the entire search area is divided into multiple synchronization determination areas, the center frequency of each synchronization determination area, the search upper limit, and the search lower limit are based on the conventional example (Figure 5).
Assume that it is the same as

When the channel selection operation is started, in step S1, the CPU 5 selects the previous optimal point synchronization determination area x for the channel selection from the second data storage unit 8 (x is any one of the numbers O to 4 in FIG. 5). ) is read out and added to the level counter N.

In step S2, the synchronization determination area corresponding to level counter N=x (for example, f0+b when x=4) is read from the first data storage section 7 and set as the local oscillation frequency.

In step S3, the state of the no-synchronization signal from the synchronization determination circuit 6 is determined to determine whether a horizontal synchronization signal has been detected. In most cases, the synchronization signal will be detected in the same optimal point synchronization determination area X as the previous time. When a synchronization signal is detected, the process advances to step 5100, and the flow shown in FIG. 3 (steps 8101 to 5114) is executed in the same manner as in the conventional example. That is, a search operation similar to that shown in FIG. 7(b) is performed.

Then, in step 5200, it is determined whether the optimum point has been detected or not based on whether the optimum point presence flag is set. If a synchronization signal is detected in the same optimal point synchronization determination area , the content X of the level counter N at that time (same as the previous time) is written into the second data storage unit 8 as the area number of the latest optimum point synchronization determination area, and the channel selection operation is completed.

In the judgment in step S3, if no synchronization signal is detected in the optimum point synchronization determination area X, as in the previous time, the process proceeds to step S4, where the level counter N is incremented by +1 and the next synchronization determination area is designated. Then, in step S5, it is determined whether the contents of the level counter N have returned to the original optimal point synchronization determination area X after completing one cycle through repeated incrementing. If it has not returned, proceed to step S6 and determine whether the content of the level counter N has reached the maximum (i4 or not; if not, return from step S2 to step S3 and increment) & new synchronization determination area The detection of the synchronization signal is determined by . When the content of the level counter N exceeds 4 in step S6, since there is no corresponding synchronization determination area, the process advances to step S7 to initialize the content of the level counter N, and then returns to step S2.

If no synchronization signal is detected, the contents of the level counter N are sequentially incremented. If a synchronization signal is detected before the content of the level counter N returns to the previous optimal point synchronization determination area Now, the content of the level counter N indicating the synchronization judgment area when the synchronization signal is detected is set as the area number of the latest optimum point synchronization judgment area, and the area number of the previous optimum point synchronization judgment H@x is replaced with the area number of the second optimum point synchronization judgment area. Write to data storage section 8.

If a synchronization signal is not found even after the above-described sequential increment, and the content of the level counter N goes around and returns to the previous optimal point synchronization determination area X, the local oscillation frequency is changed to the optimal point synchronization determination area X. After adjusting to the previous synchronization determination area, the channel selection operation ends.

The flow in FIG. 2 is fundamentally different from the flow in FIG. 6 in the difference between step S1 and step Sll and the presence or absence of step 3201.

In the conventional example, the contents of the level counter N were always initialized at the start of the channel selection operation, whereas in the present invention, the detection of the synchronization signal starts from the previous optimum point/indo synchronization determination area X. , and to newly store in the second data storage section 8 the synchronization determination area in which the synchronization signal was detected and the optimum point was found.

In the present invention, since detection of the synchronization signal is started from the previous optimal point synchronization determination area X, the time required to detect the optimal point can be considerably shortened.

For example, when the optimal point is between (fo + b) and (f0 + C), in the conventional example, the detection of the synchronization signal is first started from the N=O region, and the detection region is switched to N=1-2-3. If a synchronization signal is detected when N=3, then N=
In the region of 3, detailed and time-consuming control involving a one-step change in the local oscillation frequency is performed, but the optimal point is not found in the region of N=3, and in the end N=
It takes a very long time to detect the synchronization signal in the area No. 4 and search for the optimum point.

On the other hand, in the present invention, the synchronization signal is detected and the optimal point is searched for in the N=4 region, so the time required to detect the optimal point can be significantly shortened. Therefore, the time period during which the screen is disturbed can be shortened.

Note that it is possible to further shorten the channel selection time by increasing the number of divisions of the entire search area and narrowing the frequency width of one synchronization determination area.

<Effect of the invention> According to the present invention, the following effects are achieved.

The previous optimal point synchronization determination area is memorized, and in the next channel selection operation, synchronization signal detection and optimal point search operations are immediately started from the same optimal point synchronization determination area as the previous time, until the optimal point is detected. The time required to complete the process can be significantly shortened, and screen disturbances will become almost unnoticeable.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the electrical configuration of a frequency synthesizer channel selection TV broadcast receiving system according to an embodiment of the present invention, FIG. 2 is a flowchart for explaining the operation of the embodiment, and FIG. 3 is an implementation example. 3 is a flowchart of a search operation common to the example and the conventional example. Figures 4 to 7 relate to conventional examples, where Figure 4 is a block diagram of a conventional frequency synthesizer channel selection TV broadcast receiving system, Figure 5 is an explanatory diagram of synchronization signal detection operation, and Figure 6 is A flowchart of the channel selection operation. Figure 7(a) is a waveform diagram of the AFT voltage and synchronization signal. Figure 7(b) is a waveform diagram of the UP request signal, DOWN request signal, and no synchronization signal, and the optimum point search operation. It is an explanatory diagram. Figure 5 (Gama G&Hiroshi's blind clearing map) Rei Figure 6 (Conventional F1 Fronamat)

Claims (1)

[Claims] (1) Divide the entire search area for the local oscillation frequency for each channel into multiple synchronization determination areas, extract the synchronization determination area where the synchronization signal is detected from among these multiple synchronization determination areas, and then In a TV broadcast receiving system using a frequency synthesizer tuning method in which an optimal point is detected by changing the local oscillation frequency in steps in a synchronization determination area, the system includes means for storing a synchronization determination area to which the optimal point belongs; The method further comprises means for reading out the optimal point synchronization determination area from the storage means upon start, and means for performing an optimal point detection operation by step change of the local oscillation frequency in the read optimal point synchronization determination area. A TV broadcast receiving system featuring a frequency synthesizer channel selection method.