JPH1065979A - Channel selection system for television receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the channel selection system in which a broadcast wave receptible actually is detected independently of the electric field strength for each area without needing complicated setting. SOLUTION: A reception strength detection circuit 58 outputs a noise level included in a voice of a broadcast wave being received, a search control section 30 sets reception level data detecting a broadcast wave having the reception state equal to the broadcast wave being received, and sends an instruction to a frequency sweep section 32, which starts frequency sweep-out. A broadcast wave discrimination section 34 compares the reception level data with a noise level included in the voice of each tuning frequency to discriminate the voice of the broadcast wave. When no broadcast wave is detected even when frequency sweep is circulated, the reception level data are revised to improve the detection sensitivity by one step and 2nd search is conducted or the reception level data are revised to improve the detection sensitivity by further one step and 3rd search is conducted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a channel selection system for a television receiver which automatically detects a receivable broadcast wave by sweeping a frequency.

[0002]

2. Description of the Related Art Some in-vehicle or portable television receivers have a so-called search function of automatically detecting a receivable broadcast wave by sweeping the frequency in one direction. As a broadcast wave detection method, for example, a method is known in which a noise component included in an audio signal transmitted together with a video signal is extracted, and when this noise level is reduced, it is determined that a broadcast wave exists. I have.

FIG. 6 is a circuit diagram showing a configuration of a conventional broadcast wave detecting circuit for realizing a search function. As shown in the figure, a noise component is extracted from a voice signal output from a voice circuit 90 by a noise detection circuit 92, and this noise component is converted into a DC voltage by a DC conversion circuit 94 and applied to the base of a switching transistor 96. I do. In the frequency region where no broadcast wave exists, the noise component included in the output of the audio circuit 90 increases, so that the output voltage of the DC conversion circuit 94 increases, the switching transistor 96 is turned on, and the broadcast wave output from the collector is detected. The signal goes low. In such a state, the frequency is swept in one direction, and when the frequency reaches the frequency region where the broadcast wave exists, the noise component included in the output of the audio circuit 90 decreases.
The output voltage of the DC conversion circuit 94 decreases, the switching transistor 96 turns off, and the broadcast wave detection signal goes high. As described above, it is possible to detect a change in the broadcast wave detection signal, which is the output of the switching transistor 96, to a high level during the frequency sweep, and to detect a broadcast wave capable of receiving a video signal satisfactorily.

[0004]

In a television receiver to which the above-mentioned conventional broadcast wave detection method is applied, the switching transistor 96 is turned on or off depending on the level of the noise level. The boundary value of the noise level for judging the presence / absence was fixed. However, the level of the noise component included in the audio signal of the same broadcast wave differs between the case where the television receiver is placed in the strong electric field region and the case where the television receiver is placed in the weak electric field region. If the above-described boundary value is set for a region, the search function may not work sufficiently in television receivers in other regions.

[0005] The reception state of the television receiver is as follows.
(A) a receiving state in which colored video is obtained; (b) a receiving state in which color information is lost but a black and white video is obtained; (c) a receiving state in which video cannot be received but only audio can be reproduced;
It can be divided into four stages of the state without a station. In particular, in the case of an in-vehicle television receiver, it is conceivable that a broadcast wave is received in a place where the reception state is poor, so that all of the above-mentioned reception states (a), (b) and (c) are supported. It is necessary to receive broadcast waves.

However, if the above-described boundary value is set so that a broadcast wave in a reception state in which only the sound of (c) can be reproduced can be detected, a receivable broadcast wave can be detected satisfactorily in a weak electric field region. If the television receiver is used in a strong electric field area, there arises an inconvenience that the frequency sweep stops at a frequency adjacent to the frequency of the original broadcast wave. Conversely, if the above-described boundary value is set so that the broadcast wave can be detected in the receiving state where the colored image of (a) is obtained, the receivable broadcast wave can be detected well in the strong electric field area.
When this television receiver is used in a weak electric field area, there arises inconvenience that a broadcast wave which originally exists cannot be detected.

The present invention has been made in view of the above points, and its purpose is to eliminate the need for complicated settings.
It is an object of the present invention to provide a method of selecting a television receiver capable of detecting a broadcast wave that can be actually received irrespective of the electric field strength for each region.

[0008]

In order to solve the above-mentioned problems, a tuning method for a television receiver according to the present invention comprises a tuner section for selecting a component having a predetermined tuning frequency from a received signal, A frequency sweeping unit that sweeps a tuning frequency of a tuner unit in a predetermined direction, a reception state determination unit that determines a reception state of a broadcast wave included in a reception signal, and a reception state determination unit when a broadcast wave being received exists. A detection sensitivity corresponding to the determined reception state of the broadcast wave being received is set, a broadcast wave detection unit that detects the broadcast wave based on the output of the tuner unit at the time of frequency sweep, and a predetermined sweep start instruction is given. And a search control unit that starts the frequency sweeping by the frequency sweeping unit and stops the frequency sweeping by the frequency sweeping unit when the broadcast wave is detected by the broadcast wave detecting unit. The reception state of the broadcast wave being received is determined, and the search for the broadcast wave is performed on the broadcast wave having the same reception state. Therefore, there is no need to perform complicated settings, and the electric field strength for each region is not required. Regardless of this, it is possible to detect a broadcast wave that can be actually received.

In general, it is possible to detect the presence or absence of a broadcast wave by checking the magnitude of a noise component included in the sound of a received signal. Therefore, the apparatus further includes a sound extracting unit for extracting a sound signal from the output of the tuner unit. Accordingly, the above-described reception state determination unit can easily determine the reception state of the broadcast wave based on the noise level included in the extracted audio.

[0010] Specifically, the broadcast wave detection unit described above includes:
A threshold corresponding to the noise level included in the audio of the broadcast wave being received is set, and the noise level included in the audio in the received signal extracted by the reception state determination unit during frequency sweep can be easily compared with the threshold. Broadcast wave detection.

[0011] Further, when no broadcast wave other than the broadcast wave being received is detected in the first frequency sweeping operation, the above-described search control unit increases the detection sensitivity of the broadcast wave detection unit and again performs the frequency sweeping by the frequency sweeping unit. The sweep is started, and when the broadcast wave is detected by the broadcast wave detection unit, the frequency sweep by the frequency sweep unit is stopped. This second frequency sweep is 1
The detection sensitivity may be increased not only twice but also twice or more times. As described above, by gradually increasing the detection sensitivity and performing the frequency sweeping a plurality of times, even if a broadcast wave having the same reception state as the broadcast wave being received cannot be detected, the local area may be detected. Thus, the next broadcast wave having the best reception state can be detected without performing complicated settings and complicated operations.

More specifically, the above-mentioned broadcast wave detecting section includes:
A first threshold value corresponding to a first noise level included in the sound of the broadcast wave being received and a second threshold value corresponding to a second noise level larger than the first noise level are set. At the first frequency sweep, the noise level included in the sound in the received signal extracted by the reception state determination unit is compared with a first threshold value, and at the second frequency sweep,
By comparing with the threshold value, it is possible to easily detect another broadcast wave whose reception state is worse than that of the currently received broadcast wave.

[0013] Further, as a specific configuration of the above-described reception state determination unit, a noise extraction unit that selectively outputs a noise component having a frequency equal to or higher than the audio frequency band from the output of the audio extraction unit, and an output from the noise extraction unit A rectifying / smoothing unit that rectifies and smoothes the noise component to be provided, and a converter that converts the output of the rectifying / smoothing unit into digital data. The presence or absence of a broadcast wave can be easily determined by digital processing.

In addition to the case where the detection sensitivity of the broadcast wave detecting section is made to correspond to the reception state of the broadcast wave being received in the first frequency sweep, the detection sensitivity is always set to be low at first and the frequency sweep is performed in the second and subsequent times. Thus, the detection sensitivity may be gradually increased. By setting the detection sensitivity in this way,
Even when a broadcast wave is not being received, it is possible to detect a broadcast wave with the best reception sensitivity in that area without making complicated settings.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION According to the channel selection method of a television receiver of the present invention, first, a frequency sweep is performed with a detection sensitivity corresponding to a reception state of a currently received broadcast wave, and a first broadcast wave is performed. Performs a search and, if a broadcast wave is not detected, raises the detection sensitivity and conducts the second and subsequent searches to enable appropriate detection without the user being aware of the radio wave condition in the area where the television receiver is located. The feature is that the search function can be used with sensitivity. Hereinafter, a television receiver according to an embodiment of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a television receiver according to one embodiment to which the present invention is applied. The television receiver 100 of the present embodiment shown in FIG.
0, a tuner unit 1 for extracting a desired tuning frequency component from the signal received through the frequency converter 0 and performing frequency conversion on the extracted signal, and a PLL control for performing PLL control on the tuning frequency of the tuner unit 1. The tuning control section 3 is configured to sweep the tuning frequency of the tuner section 1 in one direction and stop the frequency sweep when a broadcast wave is detected.

The above-described tuner 1 includes an input circuit 10,
A high-frequency amplifier circuit 12, a mixing circuit 14, and a local oscillation circuit 16 are provided. The input circuit 10 is for matching the impedance of a connection line for drawing a received signal from the antenna 40 with the input impedance of the high frequency amplifier circuit 12. The high-frequency amplifier circuit 12 has a predetermined bandwidth (6 M
Hz), a tuning operation for selecting and outputting a predetermined frequency component from a received signal input via the input circuit 10 is performed, and high-frequency amplification is performed on the tuned output. The mixing circuit 14 mixes the signal output from the high-frequency amplification circuit 12 with the signal output from the local oscillation circuit 16 and outputs an intermediate frequency signal having a frequency equal to the difference between these two signals. The frequency of the intermediate frequency signal is set to 58.75 MHz for the video carrier and 54.25 MHz for the audio carrier. The local oscillation circuit 16 is a voltage-controlled oscillation circuit whose oscillation frequency can be set according to an applied control voltage, and this control voltage is applied from the PLL control unit 2.

The above-described PLL control unit 2 includes a frequency divider 20,
24, phase comparator 22 and reference frequency oscillator (reference O
SC) 26, and each of these components forms a phase locked loop together with the local oscillation circuit 16 in the tuner unit 1 described above, and sets the frequency of the local oscillation circuit 16. The reference frequency oscillator 26 is a fixed frequency oscillator having a high frequency stability using a crystal oscillator or the like, and its oscillation output is frequency-divided by one frequency divider 24 having a fixed frequency division ratio. It is input to one input terminal. The other frequency divider 20 is a variable frequency divider whose frequency division ratio N can be arbitrarily set, and a signal obtained by dividing the output of the local oscillation circuit 16 by the frequency division ratio N is output from the phase comparator 22. It is input to the other input terminal. The phase comparator 22 includes two frequency dividers 20, 24
And a control voltage for reducing the phase difference is applied to the local oscillation circuit 16, and the oscillation frequency of the local oscillation circuit 16 is set at the above-mentioned variable frequency division ratio N. It is controlled to a predetermined value determined.

The above-mentioned tuning control unit 3 includes a search control unit 3
0, a frequency sweep unit 32 and a broadcast wave determination unit 34. The broadcast wave judging unit 34 detects a level of a noise component included in the demodulated audio signal by a reception intensity detection circuit 58.
, It is determined whether or not a broadcast wave is included in the signal of the current reception frequency. Details of the reception intensity detection circuit 58 will be described later. The search control unit 30 sets a threshold to be compared with the output of the reception intensity detection circuit 58 when the broadcast wave determination unit 34 determines the presence or absence of a broadcast wave, and sets a threshold value in response to an instruction from the key input unit 42. 32, the start timing of the sweep operation is instructed. The key input unit 42 is used by a user to give various operation instructions.
Various operation keys such as a "search" key for instructing a search operation for searching for receivable broadcast waves by performing frequency sweep in one direction are provided. The frequency sweeping unit 32 sweeps the tuning frequency of the tuner unit 1 in one direction by sequentially increasing or decreasing the variable frequency division ratio of the frequency divider 20.

Also, the television receiver 1 of the present embodiment
Reference numeral 00 denotes, in addition to the above-described configuration, a video intermediate frequency amplification circuit 44, a video detection circuit 46, and a video amplification circuit 48 for reproducing a video from a received signal by reproducing an audio signal from the received signal. Audio intermediate frequency detection circuit 5
0, an FM detection circuit 52 and a low frequency amplification circuit 54.

The video intermediate frequency amplifying circuit 44 amplifies an intermediate frequency signal including a video signal and an audio signal output from the mixing circuit 14 of the tuner unit 1 and passes only a component in a necessary frequency band. Have a predetermined selectivity characteristic. Further, even if the level of the input signal fluctuates due to automatic gain control, the level of the output signal does not change.
6 and an audio intermediate frequency detection circuit 50. The video detection circuit 46 detects the video intermediate frequency signal amplified by the video intermediate frequency amplification circuit 44 and extracts a composite video signal. Generally, in order to faithfully reproduce the video signal, the video detection circuit 46 performs diode detection with little distortion. Low-level video detection (LL
D) is used. The video signal detected in this manner is further divided into a luminance signal and a carrier chrominance signal after passing through a video amplification circuit 48. The carrier chrominance signal is color-demodulated and combined with the luminance signal again, and is not shown. Video display from a liquid crystal display device or the like is performed.

The audio intermediate frequency detection circuit 50 extracts a 4.5 MHz SIF signal (beat signal) from a 54.25 MHz audio intermediate frequency signal included in the output of the video intermediate frequency amplification circuit 44. Representative methods for extracting the SIF signal include an intercarrier method and a separate carrier method. The FM detection circuit 52 is connected to the 4.5 MHz SIF output from the audio intermediate frequency detection circuit 50.
The signal is subjected to FM detection, and the detected audio signal is amplified by the low frequency amplifier circuit 54 and then output from the speaker 56. The signal output from the FM detection circuit 52 is also input to the reception intensity detection circuit 58.

In the configuration of the television receiver 100 according to the above-described embodiment, the reception intensity detection circuit 58 and the search control unit 30 include the broadcast wave determination unit 3 in the reception state determination unit.
4 and the search control unit 30 correspond to the broadcast wave detection unit, respectively.

FIG. 2 is a diagram showing a detailed configuration of the reception strength detection circuit 58. The reception intensity detection circuit 58 shown in FIG.
Includes a high-pass filter (HPF) 60, an amplifier 62, a rectifier circuit 64, a low-pass filter (LPF) 66, and an analog-digital converter (A / D) 68.
In the high-pass filter 60, the cutoff frequency is set to a frequency higher than the voice band, and the FM detection circuit 52
Only the noise component obtained by removing the audio signal from the signal output from is output. The noise component is amplified by the amplifier 62, rectified by the rectifier circuit 64, and further passed through a low-pass filter 66 to remove the AC component and smooth the noise component. In this way, a signal of a DC voltage level proportional to the noise level included in the output of the FM detection circuit 52 is extracted from the low-pass filter 66. The analog-digital converter 68 converts a signal output from the low-pass filter 66 into digital data having a predetermined number of bits.

The television receiver 100 of the present embodiment has such a configuration, and its operation will be described next. FIG. 3 is a diagram illustrating a relationship between reception intensity detection data corresponding to a noise level included in an audio signal and a broadcast wave reception state. As described above, the reception intensity detection circuit 58 amplifies and rectifies the noise component included in the audio signal and converts it to digital data.
Received intensity detection data (digital data) which is the output of 8
Indicates a noise level included in the audio signal. The reception states are (a) a reception state in which a colored image is obtained, (b) a reception state in which color information is lost but a black and white image is obtained, and (c) a video cannot be received but only audio can be reproduced. There are four types, a reception state and (d) a state without a station.
The reception state (a) corresponds to the case where the noise level is the lowest and the reception intensity detection data is equal to or less than S3. The reception state (b) corresponds to a case where the noise level is the second lowest and the reception intensity detection data is larger than S3 and equal to or smaller than S2. The reception state (c) corresponds to the case where the noise level is large and the reception intensity detection data is larger than S2 and equal to or smaller than S1. The reception state (d) corresponds to the case where the noise level is the highest and the reception intensity detection data is larger than S1.

The above-described search control unit 30 converts the reception level data, which is a threshold for judging the presence or absence of a broadcast wave, into the above-described S.
1, S2, or S3. The setting of the reception level data is automatically performed when the “search” key of the key input section 42 is pressed (details will be described later).
By pressing a predetermined key of the key input unit 42, the user can directly specify any one of S1, S2, and S3. The broadcast wave determination unit 34 receives the reception level data set by the search control unit 30 and the reception intensity detection circuit 5
Then, if the received intensity detection data is smaller than the set reception level data, it is determined that a broadcast wave of the current reception frequency is present.

FIG. 4 is a flowchart showing an operation procedure of the television receiver of the present embodiment, and mainly shows an operation procedure focusing on a search operation of a broadcast wave under the control of the channel selection control unit 3. Further, it is assumed that a predetermined search operation is performed when any broadcast wave is currently received and the “search” key of the key input unit 42 is pressed thereafter.

The search control unit 30 constantly monitors whether the "search" key of the key input unit 42 has been pressed (step 400). When the "Search" key is pressed,
Next, the search control unit 30 checks the reception state of the currently received broadcast wave (step 401), and sets reception level data according to the reception state (step 402). For example, when the reception state of the currently received broadcast wave is a reception state in which a colored image can be obtained (range (a) in FIG. 3), S3 shown in FIG. 3 is set as the reception level data. Similarly, in a reception state where color information is missing but a black-and-white image is obtained (range (b) in FIG. 3), S2 shown in FIG. 3 is set as reception level data. Also, in the reception state where video cannot be received but only audio can be output, or when there are no stations (ranges (c) and (d) in FIG. 3), S1 shown in FIG. 3 is set as reception level data. You.

Next, the search controller 30 controls the frequency sweeper 3
The frequency sweeping unit 32 sends a frequency sweeping instruction to the frequency band 2 and starts the frequency sweeping in the frequency increasing direction or the frequency decreasing direction using the frequency of the currently received broadcast wave as the search start frequency. (Step 4
03). Thereafter, the search control unit 30 sets the broadcast wave determination unit 3
Based on the comparison result of Step 4, it is determined whether or not a broadcast wave of the frequency being swept exists (Step 404), and it is monitored whether or not the frequency sweep has been completed (Step 405). The broadcast wave determination unit 34 includes the search control unit 30
When the reception intensity detection data smaller than the reception level data set by the above is input from the reception intensity detection circuit 58, it is determined that there is a broadcast wave having a desired reception state, and this determination result is used for search control. Send to section 30.
Upon receiving the determination result of the presence of the broadcast wave, the search control unit 30 stops the frequency sweeping operation by the frequency sweeping unit 32 (step 406), and thereafter reproduces the video and audio of the broadcast wave detected by the search operation.

If a broadcast wave other than the currently received broadcast wave cannot be detected even after one round of the frequency sweep, the search control unit 30 next sets the received level data having the highest detection sensitivity. It is checked whether or not it is S1 corresponding to the reception level (step 407). If not, the reception level data is changed from S3 to S2 or from S2 to S2.
The level is lowered by one to one (step 408), and the search operation from step 403 onward is repeated. If the reception level data is S1 and a broadcast wave other than the currently received broadcast wave cannot be detected even after one round of the frequency sweep, a "search" key is displayed indicating that there is no other receivable broadcast wave. For example, a predetermined alarm sound is output from the speaker 56 in order to notify the person who pressed the button (step 409).

As described above, the television receiver 100 of this embodiment checks the reception state of the broadcast wave currently being received by the channel selection control unit 3 and finds that the reception state is the same as or better than the reception state of the broadcast wave. A first search is performed on broadcast waves having a reception state. Therefore, for example, when a color image is currently being received, a search is made for a broadcast wave capable of reproducing the color image. If there is no broadcast wave having the same reception state as the currently received broadcast wave, the search is performed by expanding the range of the reception state of the broadcast wave to be searched by one step. For example, if the first search is performed on a broadcast wave having the same reception state as that of a colored video and a broadcast wave other than the broadcast wave being received cannot be detected,
The detection sensitivity is increased by one step, and a second search is performed for broadcast waves having a reception state similar to that of a black and white video. Similarly,
If a broadcast wave cannot be detected in the second search, the detection sensitivity is further increased to further expand the range of the reception state of the broadcast wave to be searched, and the broadcast wave in the reception state in which only audio can be reproduced is obtained. Perform a third search on the target.

As described above, since the broadcast wave is searched by checking the reception state of the broadcast wave currently being received, the broadcast wave having the optimum reception state in the area is detected without setting the reception level or the like. be able to. In particular, when considering the in-vehicle television receiver 100, it is conceivable that the reception state of the broadcast wave greatly changes depending on the traveling position of the vehicle, but even in such a case, the broadcast wave cannot be detected. Since the search is automatically performed by changing the reception level data from S3 to S2 and further from S2 to S1, it is possible to receive broadcast waves in a reception state as good as possible.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention. For example, the television receiver 100 of the above-described embodiment performs the second or third search operation continuously when there is no broadcast wave other than the currently received broadcast wave. The frequency sweeping may be temporarily stopped every time one round has been made, and an alarm or the like indicating that there is no broadcast wave may be output to the user.

The above-described television receiver 100
In the first search, a broadcast wave having a reception state equivalent to that of the currently received broadcast wave is searched in the first search by checking the reception state of the currently received broadcast wave prior to the search operation. Instead of checking the current reception state and setting the reception level data, the first search is always performed by setting the reception level data to S3, and when the broadcast wave cannot be detected, the reception level data is gradually changed. The search may be changed to S2 or S1, and the second or third search may be performed.

FIG. 5 is a flowchart showing an operation procedure of the television receiver when the first search is always performed using the reception level data S3. The operation procedure shown in the figure is almost the same as the operation procedure shown in FIG.
01 (investigation of the reception state of the currently receiving broadcast wave) and step 402 (setting of the reception level corresponding to the reception state of the currently receiving broadcast wave) to the processing of step 401a in which the reception level data is always set to S3. It has been replaced.
In particular, when performing a search according to the operation procedure shown in FIG.
It is necessary to receive any broadcast wave at the start of the search. However, when the search is performed by the operation procedure shown in FIG. 5, it is not always necessary to receive the broadcast wave at the start of the search. For example, even when the vehicle is moved to an area having a different broadcast wave frequency and it is not easy to receive the first broadcast wave when the power is turned on, there is no need to perform complicated settings and the like. By simply pressing the "" key, it is possible to easily search for a broadcast wave having the best reception state.

[0036]

As described above, according to the present invention, the reception state of a broadcast wave being received is determined, and a search for a broadcast wave is performed for broadcast waves having the same reception state. Therefore, it is possible to detect a broadcast wave that can be actually received irrespective of the electric field strength in each area.

In general, it is possible to detect the presence or absence of a broadcast wave by checking the magnitude of a noise component included in the sound of a received signal. Therefore, the apparatus further includes a sound extracting unit for extracting a sound signal from the output of the tuner unit. Accordingly, it is possible to easily determine the reception state of the broadcast wave based on the noise level included in the extracted audio.

In particular, a threshold corresponding to the noise level included in the sound of the broadcast wave being received is set, and the broadcast can be easily performed by comparing the noise level included in the sound in the received signal with the threshold during the frequency sweep. Wave detection can be performed.

When no broadcast wave other than the broadcast wave being received is detected in the first frequency sweeping operation, the broadcast wave is re-started by increasing the detection sensitivity of the broadcast wave and the frequency sweeping section is started again. When the frequency sweep is stopped. As described above, by gradually increasing the detection sensitivity and performing the frequency sweeping a plurality of times, even if a broadcast wave having the same reception state as the broadcast wave being received cannot be detected, the local area may be detected. Thus, the next broadcast wave having the best reception state can be detected without performing complicated settings and complicated operations.

In particular, a first threshold value corresponding to a first noise level included in the sound of a broadcast wave being received and a second threshold value corresponding to a second noise level larger than the first noise level. Is set, and the noise level included in the audio in the received signal is compared with the first threshold value during the first frequency sweep, and is compared with the second threshold value during the second frequency sweep. It is possible to easily detect other broadcast waves whose reception condition is worse than that of the waves.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a television receiver according to an embodiment to which the present invention has been applied.

FIG. 2 is a diagram illustrating a detailed configuration of a reception strength detection circuit.

FIG. 3 is a diagram illustrating a relationship between reception intensity detection data corresponding to a noise level included in an audio signal and a reception state of a broadcast wave.

FIG. 4 is a flowchart showing an operation procedure of the television receiver of the embodiment.

FIG. 5 is a flowchart showing a modification of the operation procedure of the television receiver of the embodiment.

FIG. 6 is a circuit diagram showing a configuration of a conventional broadcast wave detection circuit that enables a search function.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tuner part 2 PLL control part 3 Tuning control part 30 Search control part 32 Frequency sweep part 34 Broadcast wave judgment part 50 Audio intermediate frequency detection circuit 52 FM detection circuit 58 Reception intensity detection circuit

Claims (7)

[Claims] 1. A tuner section for selecting a component having a predetermined tuning frequency from a received signal, a frequency sweeping section for sweeping a tuning frequency of the tuner section in a predetermined direction, and reception of a broadcast wave included in the received signal. A reception state determination unit for determining a state, and when a broadcast wave being received is present, a detection sensitivity corresponding to the reception state of the broadcast wave being received determined by the reception state determination unit is set, and a frequency sweep is performed. A broadcast wave detector that detects a broadcast wave based on the output of the tuner unit, and when a predetermined sweep start instruction is issued, starts a frequency sweep by the frequency sweeper, and the broadcast wave detector detects the broadcast wave. A search control unit for stopping frequency sweeping by the frequency sweeping unit upon detection. 2. The sound extraction device according to claim 1, further comprising: a sound extraction unit that extracts a sound signal from an output of the tuner unit, wherein the reception state determination unit includes the sound signal extracted by the sound extraction unit. A receiving state of a broadcast wave is determined based on a noise level to be received. 3. The broadcast wave detection unit according to claim 2, wherein a threshold value corresponding to a noise level included in the sound of the broadcast wave being received is set in the broadcast wave detection unit, and the threshold is extracted by the reception state determination unit during frequency sweep. A method for selecting a television receiver, comprising detecting a broadcast wave by comparing a noise level included in audio in a received signal with the threshold. 4. The search control unit according to claim 2, wherein when no broadcast wave other than the broadcast wave being received is detected in the first frequency sweep operation, the detection sensitivity of the broadcast wave detection unit is increased and the search control unit is re-executed. A tuning method for a television receiver, comprising: starting frequency sweeping by the frequency sweeping unit; and stopping frequency sweeping by the frequency sweeping unit when a broadcast wave is detected by the broadcast wave detecting unit. 5. The broadcast wave detection unit according to claim 4, wherein the broadcast wave detection unit includes: a first threshold value corresponding to a first noise level included in the sound of the broadcast wave being received;
And a second threshold value corresponding to a second noise level that is larger than the noise level of the received signal. The noise level included in the sound in the received signal extracted by the reception state determination unit at the first frequency sweep is determined by the The noise level included in the sound in the reception signal extracted by the reception state determination unit at the time of the second frequency sweep is compared with the second threshold value.
A broadcast wave detection is performed by comparing with a threshold value of a television receiver. 6. The noise extraction unit according to claim 2, wherein the reception state determination unit selects and outputs a noise component having a frequency equal to or higher than an audio frequency band from an output of the audio extraction unit. A rectifying / smoothing unit for rectifying and smoothing the output noise component; and a converting unit for converting the output of the rectifying / smoothing unit into digital data, wherein the magnitude of the noise component included in the audio signal corresponds to the digital data. A channel selection method for a television receiver, wherein the channel is output. 7. A tuner section for selecting a component having a predetermined tuning frequency from a received signal, a frequency sweeping section for sweeping a tuning frequency of the tuner section in a predetermined direction, and a plurality of detection sensitivities are selectively set. A broadcast wave detection unit that detects a broadcast wave based on the output of the tuner unit during frequency sweeping, and sets a low detection sensitivity of the broadcast wave detection unit initially when a predetermined sweep start instruction is given. The frequency sweeping unit performs frequency sweeping, and when a broadcast wave is not detected by the broadcast wave detecting unit, the detection sensitivity of the broadcast wave detecting unit is sequentially increased, and the second and subsequent frequencies by the frequency sweeping unit are increased. A search control unit for performing sweeping, and a tuning method for a television receiver.