JPH1051274A - Automatic channel selection method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a time required for automatic channel selection by deciding the pressure/absence of a station, except in the vicinity of a frequency which has already been set. SOLUTION: In the case of automatic channel selection, at first a demodulation circuit 16 is set to a SECAM system, and a presence/absence of station decision circuit 20 decides whether or not a reception frequency includes a broadcast signal, based on a synchronizing signal included in a composite video signal demodulated by the circuit 16. When the presence of station is decided, a microcomputer 22 sets the frequency. When the automatic channel selection for the SECAM system is finished, the demodulation circuit 16 is set to the PAL system, and frequencies including broadcast stations are set similarly to the foregoing. However, in the case of the automatic channel selection for the PAL system, presence/absence of station is decided, except in the vicinity of the frequencies already set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic channel selecting apparatus and an automatic channel selecting method, and more particularly to, for example, gradually switching a receiving frequency and determining whether a broadcast signal exists at the receiving frequency by means of a station / non-station determining means. The present invention relates to an automatic channel selection method and an automatic channel selection device for determining whether or not a broadcast signal exists and setting a frequency at which a broadcast signal exists.

[0002]

2. Description of the Related Art In a conventional multi-system receiver capable of receiving both a broadcast signal modulated by a SECAM system and a broadcast signal modulated by a PAL system, when presetting a broadcast station to be received, first, all the frequency bands are set in the SECAM system. , And then automatically tuned over all frequencies by the PAL system. In addition, regardless of such a receiver, in a general receiver, the sensitivity of automatic channel selection is set to a certain high level.

[0003]

However, the multi-method receiver described above has a problem that it takes about twice as long as a single-method receiver for automatic channel selection. In addition, since the sensitivity of the automatic channel selection is set to a certain high level, a broadcast station unnecessary for most users is captured, and there is a problem that usability is deteriorated. On the other hand, if the sensitivity of automatic channel selection is reduced, a small number of users who want to view a broadcast with a weak electric field suffer from annoyance.

[0004] Therefore, a main object of the present invention is to provide an automatic channel selection device capable of shortening the time for automatic channel selection. Another object of the present invention is to provide an automatic tuning apparatus which is easy for any user to use.

[0005]

Means for Solving the Problems The first invention is as follows: (a) The first invention
(B) determining whether the first broadcast signal is included in the demodulated signal by changing the reception frequency in the frequency range, and (c) determining whether the first broadcast signal is included in the demodulated signal. Is set, and (d) Steps (a) to (c) are repeated until the reception frequency reaches the first predetermined frequency. (E) The reception frequency is changed in the second frequency range to obtain the second frequency.
(F) It is determined whether or not the demodulated signal includes the second broadcast signal in the demodulated signal.
In the automatic channel selection method for setting a frequency including a broadcast signal, in the step (d), it is determined whether or not the second broadcast signal is included except for the vicinity of the already set frequency. This is a feature of the automatic channel selection method.

[0006] In a second aspect, the receiving frequency is changed,
In the automatic channel selection device for determining whether or not a broadcast signal is included in the received high-frequency signal by the station / non-station determining means and setting a frequency at which the broadcast signal exists, the automatic selecting apparatus differs from the station / non-station determining means. An automatic channel selection device including sensitivity setting means for setting sensitivity.

[0007]

According to the first aspect of the present invention, when automatic tuning is performed in the second mode after automatic tuning in the first mode is completed, except for the vicinity of the frequency set in the first mode, the second mode is selected. It is determined whether two broadcast signals are included. That is, first, a desired frequency is set by determining whether or not the first broadcast signal is included in the demodulated signal by the first method, and then the same operation is repeated by the second method. When determining whether or not the second broadcast signal is included in the demodulated signal according to the second method, the vicinity of the already set frequency is removed.

[0008] In the second invention, different sensitivities are set by the sensitivity setting means in the station / non-station deciding means for judging whether or not the received high-frequency signal contains a broadcast signal. For example, when the first sensitivity setting signal is given to the station / unstation determining unit, the station / unstation determining unit sets the sensitivity low,
When the second sensitivity setting signal is given, the station / non-station deciding unit sets the sensitivity higher. The occupied / unoccupied determining means counts, for example, every time the reception frequency is switched, the pulses included in the demodulated signal of that frequency, and compares the count value with two numerical data included in the sensitivity setting signal. Then, when the count value falls between the two numerical data, it is determined to be a station.

[0009]

According to the first aspect of the present invention, when automatic tuning is performed in the second mode, it is determined whether or not the demodulated signal includes the second broadcast signal except for the vicinity of a frequency which has been already set. Is determined, the time required for automatic channel selection can be reduced. According to the second aspect, since different sensitivities are set for the station / non-station determining means, the usability can be improved for any user.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0011]

Referring to FIG. 1, a television receiver 10 of this embodiment includes a tuner 14. The high-frequency signal received by the antenna 12 is provided to the high-frequency amplifier circuit 14b via the input circuit 14a, and is tuned to a desired frequency, and the high-frequency signal is amplified. In the mixer 14c, the high frequency signal from the high frequency amplifier circuit 14b and the oscillation frequency signal from the local oscillation circuit 14e are mixed, and the high frequency signal is converted into an intermediate frequency signal (IF signal). The IF signal is demodulated by the demodulation circuit 16 which is set to the PAL demodulation scheme or the SECAM demodulation scheme by the demodulation scheme setting signal from the microcomputer 22, and a composite video signal is generated. The IF signal is detected by an FM detection circuit, and an AFTS curve is generated.

[0012] The composite video signal is output to a video signal processing system and is also supplied to a sync separation circuit 18. The synchronization separation circuit 18 separates a horizontal synchronization signal from the applied composite video signal and supplies the horizontal synchronization signal to the station / non-station determination circuit 20. The sensitivity setting signal, the reset signal, and the enable signal are also supplied from the microcomputer 22 to the station / non-station deciding circuit 20. Based on these signals, the station / unstation determining circuit 20 determines whether or not a broadcast signal is present at the frequency currently being received. If there is no signal, the low level signal is given to the microcomputer 22 as stationless.

On the other hand, the FM detection circuit 24 converts the IF signal into an FM signal.
Detection is performed, and a detection signal having an S-curve characteristic is supplied to the microcomputer 22. The microcomputer 22 sets a predetermined tuning sensitivity in accordance with the control signal, and thereafter, in accordance with a high-level or low-level determination signal provided from the station / non-station determination circuit 20 and a detection signal provided from the FM detection circuit 24,
Controls local oscillation frequency. Specifically, the microcomputer 22
Supplies a frequency signal to the PLL circuit 14d, whereby the PLL circuit 14d adjusts the oscillation frequency of the local oscillation circuit 14e.

With reference to FIG.
Includes a counter 20a and a comparator 20b. The counter 20a increments the count value according to a synchronization signal given as a clock during a period in which the enable signal is given from the microcomputer 22, and resets the count value by a reset signal from the microcomputer 22.
Since the enable signal is active only for one field period, if the reception state is good, the counter 20a counts 1 / f _H (f _H : horizontal frequency) times during that period. However, if the synchronization signal contains noise, the counter 2
In the case of 0a, the noise may be counted as a clock. Comparator 20b compares the count value with the sensitivity setting signal. In other words, the sensitivity setting signal includes numerical data of (1 / f _H ) ± a at the time of low sensitivity setting, and the numerical value data of (1 / f _H ) ± b at the time of high sensitivity setting. Therefore, when the comparator 20b is set to low sensitivity, a high-level signal is output as a station when the count value satisfies Equation 1, and a low-level signal is output as no station when the count value does not satisfy Equation 1.

[0015]

(1) (1 / f _H ) −a ≦ count value ≦ (1
/ F _H ) + a where a: 100 Hz On the other hand, when high sensitivity is set, the comparator 2
0b outputs a high-level signal as a station when the count value satisfies Equation 2, and outputs a low-level signal when the count value does not satisfy Equation 2 as an station.

[0016]

(2) (1 / f _H ) −b ≦ count value ≦ (1
/ F _H ) + b where b: 500 Hz As described above, at a low sensitivity, a relatively small numerical value width of about 200 Hz is set, so that the count value greatly changes depending on the high frequency and the low frequency near f _H. In this case, the selection of the frequency can be eliminated. Further, in the case of high sensitivity, a large numerical value width of about 1 kHz is set, so that the frequency can be selected even when the count value changes greatly.

The microcomputer 22 processes the flowcharts shown in FIGS. 3 to 5 to perform automatic channel selection. That is, first, step S
At 1, it is determined whether or not the initialization signal has been input, and "NO"
It proceeds directly to step S5 if it, if "YES", the frequency data of the broadcast stations included in the ROM (E ² PROM) 26 in step S3 initializes step S5
Move to In step S5, the control signal is "0".
It is determined whether or not the control signal is "1". If "YES", the process from step S7 is performed, but if "NO", it is determined whether or not the control signal is "10" in step S19. If "YES", the process returns to step S5, but if "YES", the processes in and after step S21 are performed. On the other hand, "10" means an instruction for automatic tuning with high sensitivity, and automatic tuning with high sensitivity is performed in steps S21 to S17.

At the time of low-sensitivity channel selection, the microcomputer 22 executes step S
In step 7, the numerical data included in the sensitivity setting signal is converted to (1 / f _H ).
± a, and the reception frequency α is set to 54.7 in step S9.
The frequency is set to 5 MHz, and the demodulation method is set to SECAM in step S11. Then, in step S13, FIG.
SECA by processing the subroutine shown in
55.7 which is the frequency band (first frequency range) of M broadcast
Automatic tuning in the range of 5 MHz to 855.25 MHz is performed. When the automatic channel selection by the SECAM method is completed, the reception frequency α is set to 47.25 MHz in step S14, and the demodulation method is set to PAL in step S15. Then, in step S17, the subroutine shown in FIG. 5 is processed, and automatic channel selection is performed in the frequency band (second frequency range) of PAL broadcasting, which is 48.25 MHz to 855.25 MHz.

On the other hand, at the time of high sensitivity automatic channel selection, step S2
1 sets the numerical data of the sensitivity setting signal to (1 / f _H ) ± b, and sets the reception frequency α to 54.75 MH in step S23.
z and the demodulation method is set to SEC in step S25.
Set to AM. Thereafter, by performing the subroutine shown in FIG. 5 in step S27, automatic tuning is performed in the frequency band of the SECAM broadcast, and the process proceeds to step S14.

In step S31 shown in FIG. 4, it is determined whether or not the reception frequency α = α _E (855.25 MHz). If “YES”, the process returns. If “NO”, the process returns to step S33. The frequency α is incremented by 1 MHz. Next, in step S35, a reset signal is output to the station / non-station decision circuit 20 and the counter 20
Reset a. Subsequently, in step S37, the process waits for a predetermined time from when the high frequency signal of the reception frequency is received until the synchronization signal is extracted, and in step S39, an enable signal is given to the one-field period counter 20a. As a result, whether or not the count value is within the range of the numerical data included in the sensitivity setting signal is determined by the occupied / unoccupied circuit 20.

Thereafter, in step S41, it is determined whether the determination signal is at a high level. If "NO", the process returns to step S31. If "YES", the process returns to step S4.
In 3, the frequency is finely adjusted using the detection signal from the FM detection circuit 24. In step S45, the finely adjusted frequency data is stored in the ROM 26, and the process returns to step S31.
In this way, the same routine is repeated until the reception frequency becomes 855.25 MHz.

The subroutine shown in FIG.
Since this is the same as the subroutine shown in FIG. 4 except for the addition of, only the processing in step S55 will be described, and redundant description will be omitted. In step S55, the reception frequency α
Is the frequency data ± 4 MHz stored in the ROM 26
Is determined, the process returns to step S51 if “YES”, and to step S57 if “NO”.
Move to That is, although a considerable amount of time is required to wait for the predetermined time in step S59, since the frequency of the broadcast signal using the other method does not exist near the frequency of the broadcast signal using one method, steps S57 to S63 are performed.
The process is shortened by skipping the process.

When the flow chart is configured in this manner, when the user first operates the switch to supply an initialization signal to the microcomputer 22, all the frequency data in the ROM 26 is erased, and the automatic tuning in the preset mode is performed. It is possible. Here, if the user selects automatic tuning with low sensitivity, the microcomputer 22 supplies numerical data having a small difference to each other as a sensitivity setting signal to the terrestrial / non-station judging circuit 20 and SE
Automatic channel selection is performed in each of the CAM system and the PAL system. At the time of the second channel selection, that is, at the time of the channel selection by the PAL system, the determination of the presence / absence of the station is performed except for the vicinity of the frequency data already stored in the ROM 26. it can. Also, since only the broadcasting stations with good reception conditions are selected, the usability of most users who want to receive only such broadcasting stations can be improved.

When the same user desires automatic channel selection with high sensitivity, the microcomputer 22 supplies a sensitivity setting signal including numerical data having a large difference to the station / non-station decision circuit 20.
As a result, a broadcasting station whose reception state is not very good is also selected. Therefore, a user who desires high-sensitivity reception can set a desired frequency without performing manual operation. Note that the user can also perform automatic tuning with high sensitivity from the beginning.

In this embodiment, the automatic channel selection according to the SECAM system is performed first, but it is needless to say that the order may be reversed. Further, in this embodiment, the description has been made using the television receiver, but it is needless to say that the present invention can be applied to a radio receiver.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram showing a station / non-station decision circuit.

FIG. 3 is a flowchart showing a part of the operation of the embodiment in FIG. 1;

FIG. 4 is a flowchart showing a part of the operation of the embodiment in FIG. 1;

FIG. 5 is a flowchart showing a part of the operation of the embodiment in FIG. 1;

[Description of References] 10 ... television receiver 14 ... tuner 16 ... demodulation circuit 18 ... synchronization separation circuit 20 ... station / non-station decision circuit 22 ... microcomputer

Claims (4)

[Claims] (A) demodulating a reception high-frequency signal by a first method by changing a reception frequency in a first frequency range; and (b) determining whether or not the demodulated signal includes a first broadcast signal. (C) setting a frequency including the first broadcast signal, (d) repeating the steps (a) to (c) until the reception frequency reaches a first predetermined frequency, (e) (F) determining whether the demodulated signal contains a second broadcast signal by changing the reception frequency in a second frequency range and demodulating the received high-frequency signal in a second method; In the automatic channel selection method for setting a frequency in which the second broadcast signal is included, in the step (d), it is determined whether or not the second broadcast signal is included except for the vicinity of the already set frequency. An automatic channel selection method, characterized by determining. 2. The first system is a PAL demodulation system and S
2. The automatic channel selection method according to claim 1, wherein one of ECAM demodulation schemes, and wherein the second scheme is the other of the PAL demodulation scheme and the SECAM demodulation scheme. 3. An automatic selector for changing a receiving frequency, determining whether or not a broadcast signal is included in the received high-frequency signal by means of a terrestrial / non-station determining means, and setting a frequency at which the broadcast signal exists. An automatic channel selection device, wherein the station device includes sensitivity setting means for setting different sensitivities to the station / non-station determination means. 4. The sensitivity setting means outputs two different numerical data as a sensitivity setting signal, and the occupied / unoccupied determination means is included in the demodulated signal of the reception frequency every time the reception frequency changes. 4. The apparatus according to claim 3, further comprising a counter that counts pulses, and a comparator that compares a count value of the counter with the numerical data, and determines that the station is local when the count value falls between the two numerical data. 5. Automatic tuning device.