JPH0725633U - Radio receiver - Google Patents

Abstract

(57) [Summary] [Purpose] Muting incoming radio waves whose electric field strength is below a specified value to remove background noise that is offensive to the ears and noise images that are offensive to the eyes. [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 muting unit 7, a CPU 8, a video amplification unit 9,
It is applied to a radio wave receiver including a display unit 10, a voice detection unit 11, a voice muting unit 12, a voice amplification unit 13, an AGC circuit unit 15, and an operation unit 16, and a CPU 8
Reads the AGC voltage from the AGC circuit unit 15,
When the C voltage continuously exceeds a predetermined value for a certain period of time, a muting signal is sent to the audio muting unit 12 and the video muting unit 7, and the audio output and the video output are stopped.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a radio wave receiver that mutes the video output or audio output when the electric field strength of the received radio wave becomes weak when receiving television or radio broadcasting.

[0002]

[Prior art]

 In order to avoid noise and video disturbance that occur when switching the reception channel or when turning on the power, a television receiver that mutes the video and audio when switching the reception channel, that is, stops the video and audio output for a predetermined period. Is known (see Japanese Patent Laid-Open No. 4-176277).

[0003]

[Problems to be solved by the device]

 However, it is desirable to perform the muting processing of video and audio not only when the receiving channel is switched or when the power is turned on, but also when the electric field strength of the electric wave being received becomes weak. In other words, if the electric field strength of the frequency being received becomes weak due to interference with signals of other frequencies, etc., the receiver will output annoying background noise or annoying noise image. It is desirable to remove these noises by muting. However, in conventional receivers, muting cannot be applied depending on the strength of the electric field strength, so the viewer had to operate the volume, power switch, etc., which was very troublesome. On the other hand, if the electric field strength changes greatly with the movement of the vehicle, such as an in-vehicle radio wave receiver, if muting is applied every time the electric field becomes weak, audio and video output will frequently turn on.・ It is desirable to control the muting taking this point into consideration as it will be annoying when turned off.

An object of the present invention is to provide a radio wave receiver for removing an annoying background noise or an annoying noise image by muting a received radio wave whose electric field strength is a predetermined value or less. is there.

[0005]

[Means for Solving the Problems]

 The present invention will be described with reference to FIG. 1 showing an embodiment. The present invention relates to a radio wave receiver including muting units 7 and 12 for muting the signals output from the receiving units 1, 3 and 4. When applied, the electric field strength detecting means 15 for detecting the electric field strength of radio waves received by the receiving sections 1, 3, 4 and the muting of the muting sections 7, 12 when the detected electric field strength is below a predetermined value. The above-mentioned object can be achieved by including a control means for executing. The invention according to claim 2 is the radio wave receiver according to claim 1, wherein the receiving units 1, 3 and 4 output the audio signal and the video signal, and the muting units 7 and 12 include the audio signal and the video signal. Muting at least one of the two. According to a third aspect of the present invention, in the radio wave receiver according to any one of the first and second aspects, the control means 8 is configured to operate when the detected electric field intensity continues for a certain period of time or less. The muting units 7 and 12 are configured to execute muting. According to a fourth aspect of the present invention, in the radio wave receiver according to any one of the first to third aspects, the electric field strength detecting means 15 is output from the AGC circuit 15 that suppresses fluctuations in the electric field strength of the received electric wave. The electric field strength is detected based on the AGC voltage.

[0006]

[Action]

 According to the first aspect of the present invention, when the electric field strength of the received electric wave detected by the electric field strength detecting means 15 is a weak electric field or less, the control means 8 causes the muting parts 7, 12 to be muted. Is executed. According to the second aspect of the invention, muting is applied to at least one of the audio signal and the video signal output from the receiving units 1, 3, and 4 by the muting units 7 and 12. In the device according to the third aspect, the control means 8 controls the muting parts 7 and 12 when the detected electric field strength is below a predetermined value for a certain period of time so that muting is not frequently applied during a weak electric field. Execute muting. In the device according to the fourth aspect, the electric field strength detection means 15 detects the electric field strength based on the AGC voltage output from the AGC circuit 15 which suppresses the fluctuation of the electric field strength of the received radio wave. And it is measured accurately.

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 radio wave receiver according to the present invention. In this embodiment, an example in which the radio wave 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. Reference numeral 4 denotes a mixer unit that frequency-converts the high-frequency signal from the high-frequency amplifier unit 3 into a low-frequency signal. Specifically, the signal 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 of the output from the mixer unit 4. An image muting unit 7 performs a muting process on the video signal detected by the IF processing unit 6. The video muting unit 7 stops the output of the video signal when a muting signal is input from the CPU 8 described later, and outputs the video signal from the IF processing unit 6 as it is when the muting signal is not input. . The video signal from the video muting unit 7 is amplified by the video amplification unit 9 and then displayed by the display unit 10. Reference numeral 11 denotes an audio detection unit that detects (demodulates) only an audio signal of the output from the mixer unit 4. Reference numeral 12 denotes an audio muting unit that performs a muting process on the audio signal detected by the audio detection unit 11. The audio signal that has been muted by the audio muting unit 12 is amplified by the audio amplification unit 13 and then output from the speaker 14.

Reference numeral 15 is a well-known AGC (Auto Gain Control) circuit section that suppresses fluctuations in electric field strength of radio waves due to fading or the like. In the AGC circuit section 15, 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. The CPU 8 selects a reception frequency instructed by the operation unit 16, and sends a voltage according to the selected reception frequency to the voltage controlled oscillator 5. Further, the CPU 8 sends a muting signal to the video muting unit 7 and the audio muting unit 12 according to the flowchart shown in FIG.

FIG. 2 is a flowchart showing the muting process by the CPU 8. In step S1, the AGC voltage output from the AGC circuit unit 15 is read and it is determined whether the voltage is 3V or higher. When it is determined that the AGC voltage is 3 V or higher, it is determined that the electric field strength is weak, and the process proceeds to step S2. In step S2, the timer is started. This timer measures the time when the AGC voltage continues to be 3 V or higher. In step S3, it is determined whether the time during which the AGC voltage continuously rises to 3 V or higher is 50 msec or longer. If the determination is affirmative, the process proceeds to step S4, and a muting signal is sent to the video muting unit 7 and the audio muting unit 12. As a result, the video output and the audio output are stopped.

Next, in step S5, it is determined again whether or not the AGC voltage is 3 V or higher. If the determination is affirmed, the process returns to step S4 to continue muting. On the other hand, if the determination is negative, the process proceeds to step S6, the output of the muting signal to the video muting unit 7 and the audio muting unit 12 is stopped, and the process proceeds to step S7. As a result, video and audio are output at the signal level before muting. In step S7, the timer is reset and the process proceeds to step S1.

When it is determined in step S1 that the AGC voltage is lower than 3 V, it is determined that the electric field strength is sufficiently strong, and the process proceeds to step S7. In step S3, if the AGC voltage continuously rises to 3 V or more for less than 50 msec, the process returns to step S1 without muting. In this case, the reason why muting is not applied is that the electric field strength may weaken for a short time while the vehicle is running.If muting is applied in such a case, video and audio output are frequently turned on and off. This is because it is annoying to the viewer.

As described above, in the above embodiment, the muting is applied to the video and audio outputs only when the AGC voltage exceeds the predetermined value for a certain period of time, so that the viewer's intention is met. Video and audio output are possible. That is, when the received electric field strength changes as shown in FIG. 3 (a), as shown in FIG. 3 (b), the electric field strength is a constant value, for example, 50 dBμV or less (below the broken line in FIG. 3 (a). In this embodiment, as compared with the case where muting is always applied, in this embodiment, as shown in FIG. 3 (c), muting is not applied unless the period of 50 dBμV or less continues for a certain period of time. Output is obtained. If the receiver is not a vehicle-mounted receiver, muting may be performed below a certain value as shown in Fig. 3 (b).

In the above embodiment, the muting is applied when the AGC voltage becomes 3 V or higher for 50 msec or longer, but the AGC voltage value and the duration are not limited to the above values. It is desirable to select the predetermined value in consideration of the circuit configuration and radio wave condition. It is also possible to prepare some of these values in advance and freely select them. In the above embodiments, the example in which the radio wave receiver is applied to the television receiver has been described, but it may be applied to the radio receiver. In that case, the IF processing unit 6, the video muting unit 7, the video amplification unit 9, and the display unit 10 in the block diagram shown in FIG. 1 are unnecessary. When the muting signal is input from the CPU 8, the audio muting unit 12 of the above embodiment stops outputting the muting signal. However, the audio output level may be lowered by a predetermined value, for example, 20 dB. Good. When the radio wave receiver of the above embodiment is applied to a television receiver, muting may be applied only to audio output or video output.

In the embodiment configured as described above, the input circuit unit 1, the high frequency amplifier unit 3, and the mixer unit 4 serve as a receiving unit, and the video muting unit 7 and the audio muting unit 12 serve as a muting unit. , AGC circuit section 15 corresponds to the electric field strength detection section, and CPU 8 corresponds to the control means.

[0016]

[Effect of device]

 As described in detail above, according to the present invention, muting is applied to a received electric wave whose electric field strength is less than or equal to a predetermined value. Can be removed. Further, according to the present invention, muting can be applied to only one or both of the audio signal and the video signal. According to the third aspect of the invention, the muting is applied when the electric field intensity is below a predetermined value for a certain period of time, so that the video and audio outputs do not frequently turn on and off. According to the invention as set forth in claim 4, since the electric field strength is detected based on the AGC voltage output from the AGC circuit, the electric field strength can be measured easily and accurately.

[Brief description of drawings]

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

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

FIG. 3A is a diagram showing a change in electric field strength, FIG. 3B is a diagram showing a muting process in which time is not taken into consideration,
(C) is a figure which shows the muting process which considered time.

[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 muting section 8 CPU 9 Video amplification section 10 Display section 11 Audio detection section 12 Audio muting section 13 Audio amplification section 14 Speaker 15 AGC circuit section 16 Operation section

Claims (4)

[Scope of utility model registration request] 1. A radio wave receiver equipped with a muting unit for muting a signal output from a reception unit, comprising: an electric field strength detection means for detecting electric field strength of a radio wave received by the reception unit; When the electric field strength is less than or equal to a predetermined value, control means for executing the muting of the muting unit,
A radio wave receiver comprising: 2. The radio wave receiver according to claim 1, wherein the receiving section outputs an audio signal and a video signal, and the muting section mutes at least one of the audio signal and the video signal. A radio wave receiver that is characterized by hanging. 3. The radio wave receiver according to claim 1, wherein the control unit controls the muting unit to operate when the detected electric field intensity is equal to or lower than the predetermined value for a certain period of time. A radio wave receiver characterized by performing muting. 4. The radio wave 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 radio wave. A radio wave receiver characterized by detecting electric field strength.