JPH0725662U - TV receiver - Google Patents

Abstract

(57) [Abstract] [Purpose] Correctly select only the channels of TV broadcasting that can be actually viewed regardless of the strength of the electric field. [Structure] An input circuit unit 1, a high frequency amplification unit 3, a mixer unit 4, a voltage control oscillation unit 5, an IF processing unit 6, a video amplification unit 7, a display unit 8, an audio detection unit 9, Audio amplification unit 10, AGC circuit unit 12, CPU 13, operation unit 1
When the CPU 13 is instructed to automatically tune by the operation unit 14, the CPU 13 classifies the channel to be tuned into three types of VHF-L, VHF-H, and UHF, and each category. AG from the AGC circuit unit 12 for each
The number of horizontal synchronization signals included in the received radio wave is measured according to the C voltage, and the reception channel is selected depending on the number of horizontal synchronization signals. As a result, only channels that can be actually viewed can be selected.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a television receiver capable of automatically selecting a receiving channel.

[0002]

[Prior art]

 There is a known television receiver that counts the number of horizontal synchronization signals included in the received radio waves when selecting the receiving channel for television broadcasting and determines whether or not the receiving channel can be selected depending on the number. . In this type of television receiver, the upper and lower limits of the number of horizontal synchronization signals that serve as a reference for channel selection are set in advance, and only the channels whose number of horizontal synchronization signals received within a predetermined time falls within the reference range are selected. I'm trying to do it.

[0003]

[Problems to be solved by the device]

 In the case of a strong electric field, cross-modulation occurs in the channel adjacent to that channel, and a predetermined number of horizontal sync signals are generated even though there is originally no horizontal sync signal. It is necessary to set the range of the number of synchronous signals so that the channel in which the error occurs is not erroneously selected. On the other hand, in the case of a weak electric field, it is difficult to distinguish between noise and the number of sync signals.Therefore, noise is erroneously recognized as the number of sync signals, channels with noise only are erroneously selected, or noise is mixed in the sync signals. It may be judged that the selected channel cannot be selected. Therefore, in the case of a weak electric field, it is necessary to set the range of the number of synchronization signals according to the degree of noise. However, in this type of conventional television receiver, the reference range for tuning is always constant regardless of the electric field strength of the received radio wave, so setting the range of the number of synchronization signals according to the strong electric field causes a weak electric field. The above-mentioned inconvenience occurs, and conversely, when the range is set according to the weak electric field, the above-mentioned inconvenience occurs when the electric field is strong.

An object of the present invention is to provide a television receiver that can obtain desired tuning performance during automatic tuning regardless of the strength of the electric field.

[0005]

[Means for Solving the Problems]

 The present invention will be described with reference to FIG. 1 showing an embodiment. The present invention counts the number of synchronization signals included in a specific channel within a certain time, and determines whether or not the value is within a predetermined reference range. Then, the reference range is applied to a television receiver that determines whether or not to select the channel and detects the electric field strength of the received radio wave, and the reference range based on the detected electric field strength. The above object is achieved by including the reference range adjusting means 13 for adjusting. According to a second aspect of the present invention, in the television receiver according to the first aspect, the electric field strength detection means 5 is based on an AGC voltage output from an AGC circuit that suppresses fluctuations in electric field strength of a received radio wave. It is configured to detect the electric field strength of received radio waves. According to a third aspect of the invention, in the television receiver according to the second aspect, the television receiver according to the second aspect further includes a classifying unit 13 that classifies the receiving channel into two or more according to the frequency, and the reference range adjusting unit 13 is provided for each class. The reference range is adjusted based on the AGC voltage. According to a fourth aspect of the present invention, in the television receiver according to the second or third aspect, a channel for which the AGC voltage is a predetermined value or more is not selected.

[0006]

[Action]

 According to the first aspect of the invention, the reference range adjusting means 13 adjusts the range of the synchronization signal for judging whether or not tuning is possible, based on the electric field strength of the received radio wave detected by the electric field strength detecting means 12. To be done. According to the second aspect of the invention, the electric field strength detecting means 12 detects the electric field strength of the received radio wave based on the AGC voltage output from the AGC circuit, so that the electric field strength can be measured easily and accurately. According to the third aspect of the invention, the classification means 13 classifies the reception channels into two or more in accordance with the frequency, and the reference range adjustment means 13 adjusts the number of synchronization signals based on the AGC voltage set for each classification. To be done. In the device according to the fourth aspect, the receiving channel is not selected when the AGC voltage is an extremely weak electric field exceeding a predetermined value.

Incidentally, in the section of means and action for solving the above problems for explaining the configuration of the present invention, the drawings of the embodiments are used for the sake of easy understanding of the present invention. It is not limited to the example.

[0008]

【Example】

 FIG. 1 is a block diagram of an embodiment of a television receiver according to the present invention. In this embodiment, an example in which the television receiver according to the present invention is applied to a vehicle-mounted television receiver will be described. In FIG. 1, reference numeral 1 denotes an input circuit unit for inputting a radio wave received from the antenna 2. Reference numeral 3 is a high frequency amplification unit that amplifies the radio wave from the input circuit unit 1. A mixer circuit 4 frequency-converts the high-frequency signal from the high-frequency amplifier 3 into a low-frequency signal. Specifically, it is converted into a signal having a difference frequency fC-fL between the tuning frequency fC in the high frequency amplifier 3 and the oscillation signal frequency fL from the voltage controlled oscillator 5. An IF processing unit 6 detects (demodulates) only a video signal in the output from the mixer unit 4. The video signal detected by the IF processing unit 6 is amplified by the video amplification unit 7 and then displayed on the display unit 8. Reference numeral 9 denotes an audio detection unit that detects (demodulates) only an audio signal of the output from the mixer unit 4. The voice signal detected by the voice detector 9 is amplified by the voice amplifier 10 and then output as voice from the speaker 11. Reference numeral 12 is a well-known AGC (Auto Gain Control) circuit section that suppresses variations in electric field strength of radio waves due to fading or the like. In the AGC circuit section 12, when the output level of the mixer section 4 is equal to or higher than a predetermined value, a low voltage level AGC voltage is sent to the high frequency amplification section 3, and conversely when the output level of the mixer section 4 is lower than the predetermined value. Sends a high voltage level AGC voltage to the high frequency amplifier 3. Reference numeral 13 denotes a CPU that sends a voltage according to the reception channel to the voltage controlled oscillator 5 and determines whether or not the reception channel can be selected by the process of FIG. 2 described later. Reference numeral 14 denotes an operation unit for instructing automatic channel selection. When the operation unit 14 instructs automatic channel selection, the CPU 13 starts reception of radio waves from a predetermined frequency, and according to the process of FIG. Channels with high frequencies are sequentially received, and when a channel that can be actually viewed is found, that channel is selected.

FIG. 2 is a flowchart showing the receiving channel selection processing by the CPU 13. When the operation section 14 instructs the CPU 13 to automatically select a receiving channel, the CPU 13 sets a voltage according to a predetermined frequency in the voltage controlled oscillation section 5, and then starts the operation of this flowchart. In step S1, it is determined whether the currently receiving channel belongs to VHF-L (1 to 3 channels), VHF-H (4 to 12 channels), or UHF (13 to 62 channels). . As shown in FIG. 3, the relationship between the output level of the mixer unit 4 and the AGC voltage differs depending on the frequency band, that is, the AGC required to obtain the same output level. This is because the voltage varies depending on the frequency band.

When it is determined in step S1 that the currently receiving channel is VHF-L, the process proceeds to step S2, where the AGC voltage value is equal to or higher than the B voltage shown in FIG. Alternatively, it is determined which one of the voltages less than the D voltage belongs. When it is determined in step S2 that the voltage is not lower than the B voltage, the process proceeds to step S3, the channel larger by one channel is selected, and the process returns to step S1. When it is determined in step S2 that the voltage is less than the B voltage and equal to or more than the D voltage, the process proceeds to step S4, the output of the mixer unit 4 is read, and the number of horizontal synchronization signals included in 1 msec is 15 to 40. Determine if there is. When the determination is affirmed in step S4, the process proceeds to step S5, the voltage corresponding to the channel is sent to the voltage controlled oscillator 5, and the process is ended. As a result, the channel currently being received is selected and the radio wave of that channel is broadcast. On the other hand, if the determination is negative in step S4, the process returns to step S3, and a voltage corresponding to the channel frequency that is one channel higher than the channel currently being received is sent to the voltage controlled oscillator 5. As a result, the radio wave of a channel larger by one channel is received.

When it is determined in step S2 that the voltage is less than the D voltage, the process proceeds to step S6, and it is determined whether 15 to 26 horizontal synchronization signals have been received within 1 msec. If the determination is affirmative in step S6, the process proceeds to step S5, and if the determination is negative, the process returns to step S3 to select a channel one channel larger.

When it is determined that the frequency band is VHF-H in step S1, the process proceeds to step S7, and the AGC voltage value is equal to or higher than A voltage and lower than A voltage and equal to or higher than E voltage or lower than E voltage shown in FIG. Which of the two belongs to is determined. When it is determined that the voltage is equal to or higher than the A voltage, the process proceeds to step S3, when it is determined that the voltage is lower than the A voltage and equal to or higher than the E voltage, the process proceeds to step S4, and when it is determined that the voltage is lower than the E voltage, the process proceeds to step S6.

When it is determined that the frequency band is UHF in step S1, the process proceeds to step S8, and the AGC voltage value is either C voltage or more shown in FIG. 3, less than C voltage and more than F voltage, or less than F voltage. To determine if it belongs to. When it is determined that the voltage is equal to or higher than the C voltage, the process proceeds to step S3. When it is determined that the voltage is lower than the C voltage and equal to or higher than the F voltage, the process proceeds to step S4, and when it is determined that the voltage is less than the F voltage, the process proceeds to step S6.

When the processing of the flowchart of FIG. 2 by the CPU 13 is summarized, in steps S2, S7, and S8, when it is determined that the voltage is B voltage or more, A voltage or more, and C voltage or more (on the left side of the broken line A in FIG. 3), , The channel being received is judged to be an ultra weak electric field, and the channel is not selected. On the other hand, in the above-mentioned steps, if it is determined that the voltage is less than the B voltage, the voltage is the D voltage or more, the A voltage is less than the E voltage, and the C voltage is less than the F voltage or more (between broken line A and broken line B in FIG. 3). It is determined that the electric field is weak, and a wide range in which the number of horizontal synchronization signals is 15 to 40 is set as the tuning reference range. That is, in the case of a weak electric field, there is not much difference in level between the horizontal sync signal and noise, so the selection criterion is loosened in consideration of erroneously determining noise as the horizontal sync signal, and as much as possible. Allows you to tune in to the station. On the other hand, if it is determined in each of the steps described above that the voltage is less than D voltage, less than E voltage, and less than F voltage (on the right side of the broken line B in FIG. 3), it is determined that the electric field is strong, and the number of horizontal synchronization signals is increased. A narrow range of 15 to 26 is set as the tuning reference range. That is, in the case of a strong electric field, cross-modulation is likely to occur in the adjacent channel, and a horizontal synchronization signal is generated in the channel in which the cross-modulation has occurred. In comparison, the selection criteria will be stricter.

In the flowchart of FIG. 2, the lower limit value of the number of horizontal synchronization signals is common (15) for the strong electric field and the weak electric field, but different numbers may be set respectively. For example, in the case of a weak electric field, noise may be erroneously determined to be a horizontal synchronizing signal, so that the number of horizontal synchronizing signals measured by the CPU 13 increases. Therefore, in the case of a weak electric field, the lower limit value may be increased.

As described above, in the above embodiment, since the receiving channel is selected according to the receiving channel and the AGC voltage output from the AGC circuit, only the channel that can be actually viewed can be selected accurately. In other words, when the reception channel is in a strong electric field, the channel selection criteria for the reception channel are tightened, so that adjacent channels with cross-modulation cannot be erroneously selected. Also, in the case of a weak electric field, the channel selection criterion for the receiving channel is weaker than in the case of a strong electric field, so that it is possible to tune correctly without missing a TV broadcast containing noise. Furthermore, since the receiving channel of the ultra-weak electric field is not selected, a channel with too bad a voice or image is not selected. Furthermore, since the channel selection is performed by classifying the receiving channels in consideration of the circuit configuration, it is possible to correct the variation in the tuning standard between the receiving channels.

In step S2 of the flowchart of FIG. 2, VHF-L, VHF-H, and UHF are classified into three types according to the receiving channel, but the number is not limited to three, and may be classified into more than three types, or each reception type. A reference having a different AGC voltage may be provided for each channel. Further, since the characteristics shown in FIG. 3 differ depending on the circuit configurations inside the high frequency amplifier 3 and the mixer 4, it is desirable to classify the channels according to the characteristics determined by the circuit configurations. In the flowchart of FIG. 2, the channel is automatically selected in the direction in which the channel increases (received frequency becomes higher), but the automatic channel selection in the direction in which the channel decreases can be performed in the same manner. In the above embodiment, the channel selection criterion of the receiving channel may be determined by the number of vertical synchronizing signals instead of the horizontal synchronizing signals.

In the embodiment configured as described above, the AGC circuit portion 12 serves as the electric field strength detecting means, steps S4 and S6 of the flowchart of FIG. 2 serve as the synchronizing signal number adjusting means, and step S1 is the sorting means. , Respectively.

[0019]

[Effect of device]

 As described in detail above, according to the present invention, the number of synchronization signals for judging whether or not tuning is possible is adjusted based on the detected electric field strength. It is possible to correctly select only the channels of TV broadcasting that can be actually viewed. According to the second aspect of the invention, since the electric field strength of the received radio wave is detected based on the AGC voltage output from the AGC circuit, the electric field strength can be measured easily and accurately. According to the invention as set forth in claim 3, since the AGC voltage is set for each classification classified by frequency and the number of synchronization signals is adjusted, it is possible to correct the fluctuation of the selection reference between the reception channels. . According to the invention as set forth in claim 4, in the case of an ultra-weak electric field in which the AGC voltage is equal to or higher than a predetermined value, in order to prevent the receiving channel from being tuned, a channel in which the audio or video state is too bad is selected. There is no selection.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a television receiver according to the present invention.

FIG. 2 is a flowchart showing an operation of the CPU of FIG.

FIG. 3 is a diagram showing a relationship between an AGC voltage and an output level of a mixer section.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input circuit section 2 Antenna 3 High frequency amplification section 4 Mixer section 5 Voltage control oscillation section 6 IF processing section 7 Video amplification section 8 Display section 9 Audio detection section 10 Audio amplification section 11 Speaker 12 AGC circuit section 13 CPU 14 Operation section

Claims (4)

[Scope of utility model registration request] 1. A television that counts the number of synchronization signals included in a specific channel within a certain period of time and determines whether or not the channel is selected based on whether or not the value is within a predetermined reference range. A television receiver comprising: a receiver, which comprises electric field strength detection means for detecting electric field strength of received radio waves, and reference range adjustment means for adjusting the reference range based on the detected electric field strength. 2. The television receiver according to claim 1, wherein the electric field strength detection means is based on an AGC voltage output from an AGC circuit that suppresses fluctuations in the electric field strength of the received electric wave, and the electric field strength of the received electric wave. A television receiver characterized by detecting. 3. The television receiver according to claim 2, further comprising a classifying unit that classifies a receiving channel into two or more according to a frequency, and the reference range adjusting unit is based on the AGC voltage for each class. A television receiver characterized in that the reference range is adjusted according to the above. 4. The television receiver according to claim 2 or 3, characterized in that a receiving channel in which the AGC voltage is a predetermined value or more is not selected.