JPH10327363A - Reception circuit component and front end section of receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a receiver adopting reception circuit components by which an audio signal is clearly received even when no video image is displayed because of a weak electric field strength signal and which is not vulnerable to the effect of an external signal and to allow a video signal from hardly being affected by harmonics produced from a local oscillation circuit. SOLUTION: The component is configured by containing a tuner circuit 2 that extracts a video intermediate frequency signal and an audio intermediate frequency signal of a selected channel from a signal received by a reception antenna 3, a high frequency amplifier circuit 4, a filter circuit 6 that passes only the video intermediate frequency signal, a filter circuit 7 that passes only the audio intermediate frequency signal, and a video intermediate frequency amplifier circuit 8 that amplifies the video intermediate frequency signal passing through the filter circuit 6 into a metallic case 10 and integrated therein.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a receiving circuit component and a front end portion of a receiver. Specifically,
The present invention relates to a front end portion of a receiver that receives a high frequency signal (TV signal) including a video signal and an audio signal, and a receiving circuit component used for the front end portion.

[0002]

[Prior art]

(First Conventional Example) A receiver such as a television or a car navigation system is mounted on a moving body such as a vehicle. FIG. 4 is a block diagram showing a configuration of a front end unit 1 of a conventional receiver mounted on a moving body. The tuner circuit 2 extracts a signal of the reception channel selected by the channel selection control unit (not shown) from the high-frequency signals received by the reception antenna 3 and converts the channel-selected video signal to 58.75 MHz. Output as an intermediate frequency signal on a carrier wave and an audio signal of 54.25 MHz
Output as an intermediate frequency signal on the carrier wave. Also,
The gain in the tuner circuit 2 is controlled by an AGC (automatic gain control) voltage supplied from the video intermediate frequency amplifier circuit 5. The high frequency amplifier circuit 4 amplifies the video intermediate frequency signal and the audio intermediate frequency signal output from the tuner circuit 2.

The signal amplified by the high-frequency amplifier circuit 4 is 5
It is sent to a filter circuit (surface acoustic wave filter) 6 having a pass band of 8.75 MHz and a filter circuit (surface acoustic wave filter) 7 having a pass band of 54.25 MHz. The filter circuit 6 separates and passes only the 58.75 MHz video intermediate frequency signal. Further, the filter circuit 7 separates and passes only the 54.25 MHz audio intermediate frequency signal. The video intermediate frequency signal passing through the filter circuit 6 and the audio intermediate frequency signal passing through the filter circuit 7 are both amplified by the video intermediate frequency amplifier (ViF) 5 and then respectively output to the video terminal (Vi
DEO OUT) 8 and a sound terminal (SOUND OUT) 9. The broken line in FIG. 4 shows the metal case 10 in which the front end portion 1 is housed and integrated.

Although not shown, the video intermediate frequency signal output from the video terminal 8 is displayed as an image on a display device through a video receiving unit that performs video detection and the like.
The audio intermediate frequency signal output from the audio terminal 9 is
The speaker is operated through an audio receiving unit including an audio detection circuit, an audio intermediate frequency amplification circuit, and the like.

(Problems of the first conventional example) Generally, in a receiver mounted on a moving body such as a vehicle, when receiving while moving, the received signal level fluctuates in a range of 0 to 100 dBμV, and is about 30 dBμV. With a weak signal of, no image is displayed. Moreover, in the front end unit 1 having the configuration shown in FIG. 4, the video intermediate frequency signal and the audio intermediate frequency signal are separate signals, but the two filter circuits 6 and
Both the video intermediate frequency signal and the audio intermediate frequency signal output from 7 are amplified by the video intermediate frequency amplifying circuit 5, and the AGC voltage for adjusting the reception signal level, the audio detection, etc. When the received signal level is lower than about 30 dBμV, there is a problem that not only the video but also the audio is not output from the speaker.

(Second Conventional Example) FIG. 5 is a block diagram showing a configuration of a front end unit 11 of another conventional receiver. In the front end section 11, only the video intermediate frequency signal output from the filter circuit 6 is input to the video intermediate frequency amplification circuit 5, and the video intermediate frequency signal output from the video intermediate frequency amplification circuit 5 is connected to the video terminal. 8 is output. On the other hand, 5
The 4.25 MHz audio intermediate frequency signal is mixed with the local oscillation signal generated by the local oscillation circuit 13 in the mixing circuit 12 and converted to a 10.7 MHz signal. Here, the audio intermediate frequency signal is converted to 54.2 in the mixing circuit 12.
In order to convert a signal of 5 MHz to a signal of 10.7 MHz, the local oscillation circuit 13 requires 43.55 MHz.
The local oscillator signal is required, and the crystal oscillator 14 having an oscillation frequency of 43.55 MHz is used as the reference oscillator. Then, the audio intermediate frequency signal converted to 10.7 MHz by the mixing circuit 12 further has a filter circuit (BPF) 15 having a pass band at 10.7 MHz and a detection circuit 1.
After passing through 6, it is output to the audio terminal 9. FIG.
The broken line indicates the metal case 10 in which the front end portion 11 is housed and integrated.

(Problems of the second conventional example) In the front end unit 11 having the configuration shown in FIG. 5, the video intermediate frequency signal and the audio intermediate frequency signal are separately amplified and detected by two systems. As a result, even a weak signal of about 30 dBμV or less, at which a video is not displayed, makes sound clear. In addition, there is an advantage that it is strong against intermittent sounds due to fluctuations in the received signal level. However, the local oscillation circuit 13 and the quartz oscillator 1
4. Since the number of components is increased due to the necessity of the mixing circuit 12, etc., the front end unit 11 (or the receiving circuit components)
There was a disadvantage that the overall shape became large. further,
Audio intermediate frequency signal from 54.25 MHz to 10.7 MHz
vibration frequency 43.
Although the crystal oscillator 14 of 55 MHz is used, since the crystal oscillator 14 is incorporated in the same case, the harmonics of the crystal oscillator 14 are converted to the video intermediate frequency signal (58.75M).
Hz), which disturbs the video signal.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of the prior art, and has as its object to clear sound even when a receiver does not produce an image due to a weak signal. It is another object of the present invention to provide a receiving circuit component which can receive signals at a low speed, is hardly affected by external signals, and can be reduced in size.

Another object of the present invention is to provide a front-end part of a receiver in which a video signal is hardly affected by harmonics generated in a local oscillation circuit.

[0010]

DISCLOSURE OF THE INVENTION A receiving circuit component according to the present invention comprises a tuner circuit, a first filter circuit for classifying a video intermediate frequency signal from signals output from the tuner circuit, and a signal output from the tuner circuit. A second filter circuit for separating an audio intermediate frequency signal from the video signal and a video intermediate frequency amplification circuit 5 for amplifying the video intermediate frequency signal extracted from the first filter circuit are integrated in a shield member. It is characterized by.

[0011] A front-end part of the receiver according to the present invention comprises a receiving circuit component according to claim 1, a local oscillation circuit, and a mixing circuit for mixing a local oscillation signal from the local oscillation circuit into an audio intermediate frequency signal. And a detection circuit for detecting the audio intermediate frequency signal mixed with the local oscillation circuit in the mixing circuit, wherein the audio intermediate frequency signal output terminal of the second filter circuit and the local oscillation circuit in the receiving circuit component are connected to each other. The mixing circuit is connected to an input side, and the detection circuit is connected to an output side of the mixing circuit.

Since the receiving circuit component and the front end unit of the present invention separately amplify and detect the video intermediate frequency signal and the audio intermediate frequency signal in two systems, a weak signal of about 30 dBμV or less at which no video is displayed. Sound is clear even at the signal. In addition, there is an advantage that the apparatus is resistant to intermittent sounds due to fluctuations in the received signal level and eliminates intermittent sounds of voice. In addition, the mixing circuit, the local oscillation circuit, the detection circuit, etc.
Since these components are formed separately from the receiving circuit components, the size of the receiving circuit components can be reduced, and the degree of freedom in arranging the components can be increased, so that the entire front end can be reduced in size.

[0013] Further, since the entire receiving circuit component is housed in the shield member and integrated, it is hardly affected by an external signal and is resistant to noise. In particular, since it is less susceptible to harmonics generated in the local oscillation circuit, the possibility that the harmonics of the local oscillation circuit become beats of the video intermediate frequency signal and interfere with the video signal is reduced.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

(Basic Mode) FIG. 1 is a block circuit diagram showing a configuration of a receiving circuit component 21 according to an embodiment of the present invention. The receiving circuit component 21 includes a tuner circuit 2 for channel selection, a high-frequency amplifier circuit 4, a filter circuit (surface acoustic wave filter) 6 for separating a video intermediate frequency signal on a carrier wave of 58.75 MHz, and a 54.25 MHz filter circuit. A metal case (preferably, a closed case) for shielding an electromagnetic wave, comprising a filter circuit (surface acoustic wave filter) 7 for separating an audio intermediate frequency signal on a carrier wave and a video intermediate frequency amplifier circuit 5; Is stored within. An input of the tuner circuit 2 is connected to an antenna connection terminal 22 and a tuning control terminal 23 provided outside the case 10, and an output of the tuner circuit 2 is connected to the high frequency amplifier circuit 4.
Further, a filter circuit 6 for separating the video intermediate frequency signal (58.75 MHz) and the audio intermediate frequency signal (54.75 MHz) are provided.
The filter circuit 7 for sorting out the signals of 25 MHz is arranged in parallel, and the output of the high-frequency amplifier circuit 4 is connected to both filter circuits 6 and 7. The filter circuit 6 for outputting the video intermediate frequency signal is connected to the input of the video intermediate frequency amplification circuit 5, and the output of the video intermediate frequency amplification circuit 5 is connected to the video terminal 8 provided outside the case 10. I have. A filter circuit 7 for outputting an audio intermediate frequency signal;
Is connected to an audio terminal 9 provided outside the case 10.

FIG. 2 is a block circuit diagram showing an example of the front end unit 24 constituted by using the above-mentioned receiving circuit component 21. The reception antenna 3 is connected to the antenna connection terminal 22 of the reception circuit component 21, and the channel selection control terminal 23
Is connected to a tuning control unit 25. Further, the voice terminal 9 of the receiving circuit component 21 has a frequency 4 generated by the local oscillation circuit 13 using the vibration of the crystal unit 14 as a reference vibration.
The local oscillation signal of 3.55 MHz is mixed with the audio intermediate frequency signal output from the audio terminal 9 to obtain a frequency of 10.5 MHz.
Mixing circuit 12 for converting to 7 MHz intermediate frequency signal
, A filter circuit (bandpass filter) 15 having a pass band at 10.7 MHz, and a detection circuit 16 are connected in series.

In the front end section 24, the receiving antenna 3 receives a high-frequency signal (TV signal), and the tuner circuit 2 converts the signal of the receiving channel selected by the tuning control section 25. The video signal extracted and channel-selected is output as an intermediate frequency signal of 58.75 MHz, and the audio signal is output as an intermediate frequency signal of 54.25 MHz. The high frequency amplifier circuit 4 amplifies the video intermediate frequency signal and the audio intermediate frequency signal output from the tuner circuit 2 to a substantially constant level.

The filter circuit 6 allows only the 58.75 MHz video intermediate frequency signal out of the signals amplified by the high frequency amplification circuit 4 to pass therethrough, amplifies the video intermediate frequency signal by the video intermediate frequency amplification circuit 5, and receives the signal. Output from the video terminal 8 of the circuit component 21 to the outside. Although not shown, the video intermediate frequency signal output from the video terminal 8 is displayed on a display device through a video receiving unit including a video detection circuit and the like.

The filter circuit 7 allows only the audio intermediate frequency signal of 54.25 MHz among the signals amplified by the high frequency amplifier circuit 4 to pass therethrough and outputs the signal from the audio terminal 9 of the receiving circuit component 21 to the outside. The mixing circuit 12 mixes the audio intermediate frequency signal output from the audio terminal 9 of the receiving circuit component 21 with the local oscillation signal generated by the local oscillation circuit 13 to generate an audio signal of 10.7 MHz. The 10.7 MHz signal output from the mixing circuit 12 is
The signal passes through a filter circuit 15 having a pass band of 0.7 MHz, is subjected to sound detection by a detection circuit 16, and is output from a sound terminal 26 of a front end unit 24. Although not shown, a signal output from the audio terminal 26 of the front end unit 24 drives a speaker through an audio receiving unit.

In such a receiving circuit component 21 or the front end unit 24, the video intermediate frequency signal and the audio intermediate frequency signal are separately amplified and detected by two systems, so that they are mounted on a moving body and received. Is a weak signal of about 30 dBμV or less such that an image is not displayed,
The sound is output clearly, and there is no intermittent sound due to the fluctuation of the received signal level.

The mixing circuit 12, the local oscillation circuit 13,
Since the detection circuit 16 and the like are formed separately from the receiving circuit component 21, the size of the receiving circuit component 21 can be reduced. Further, the receiving circuit component 21, the mixing circuit 12, the local oscillation circuit 1
The degree of freedom in arranging each component such as 3 is increased, and the mounting area of the entire front end portion 24 can be reduced.

Further, since the entire receiving circuit component 21 is housed in the metal case 10, it is hardly affected by external signals, and the receiver can be made resistant to noise. In particular, since it is less susceptible to the harmonics generated in the local oscillation circuit 13 (crystal oscillator 14), the possibility that the harmonics of the local oscillation circuit 13 become beats of the video intermediate frequency signal and disturb the video signal is reduced. Is done.

FIG. 3 is a block circuit diagram showing a specific example of a receiving circuit component 21 for a television receiver according to the present invention. In the configuration of the receiving circuit component 21, the UHF radio wave received by the receiving antenna 3 and the VHF
The radio waves are mixed by a UV mixer (not shown) and input to the receiving circuit component 21 from the antenna connection terminal 22 as a UV signal. The UV signal input from the antenna connection terminal (ANT IN) 22 is separated by a splitter 27 into a UHF signal and a VHF signal.
Signal.

The VHF signal separated by the demultiplexer 27 is removed from the UHF band signal by a trap 28, passes through a band-pass filter 29 for protection against lightning, tuning an antenna, and the like, and is then amplified by a high-frequency amplifier circuit 30. And a band pass filter 3 having a pass band in the VHF band.
1 and is input to the mixing / local oscillation circuit (M / O) 35.

The UHF signal separated by the splitter 27 passes through a band-pass filter 32 for protection against lightning and antenna tuning, etc., and is amplified by a high-frequency amplifier circuit 33. , And is input to the mixing / local oscillation circuit 35.

A PLL (Phase Locked Loop) circuit 36
Generates a tuning voltage using the 4 MHz oscillation of the crystal oscillator 37 as a reference oscillation. When tuning data for selecting a desired reception channel is inputted from the tuning control terminal (DATA) 23, the tuning voltage is generated. To change the tuning voltage
The local oscillation frequency of the local oscillation circuit 35 is controlled. mixture/
The local oscillation circuit 35 mixes the signal selected from the VHF signal and the UHF signal with the local oscillation signal, thereby converting the channel-selected video signal to 5
It outputs as a video intermediate frequency signal of 8.75 MHz and an audio signal as an audio intermediate frequency signal of 54.25 MHz. 5 output from the mixing / local oscillation circuit 35
8.75MHz video intermediate frequency signal and 54.25MHz
Is output from the tuner circuit 2 through the band-pass filter 38.

58.7 output from tuner circuit 2
The 5 MHz video intermediate frequency signal and the 54.25 MHz audio intermediate frequency signal are amplified by the high frequency amplifier circuit 4 and then separated by the filter circuits 6 and 7 including surface acoustic wave filters. The video intermediate frequency signal that has passed through the filter circuit 6 is amplified by a video intermediate frequency amplification circuit (ViF) 5 and then the 4.5 MHz audio component is removed by the trap 40, and the loss due to the trap 40 is compensated by the amplification circuit 41. And output from the video terminal (ViDEO OUT) 8. The audio intermediate frequency signal that has passed through the filter circuit 7 is output from an audio terminal (SOUND OUT) 9.

The video intermediate frequency amplification circuit 5 includes an automatic frequency adjustment (AFT) circuit 39. The video intermediate frequency amplification circuit 5 automatically adjusts the gain of the high frequency amplification circuits 30 and 33 of the tuner circuit 2 by outputting the AGC voltage.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing a basic configuration of a receiving circuit component according to an embodiment of the present invention.

FIG. 2 is a block circuit diagram showing a configuration of a front end unit using the reception circuit component of the above.

FIG. 3 is a block circuit diagram showing a specific example of a receiving circuit component according to the present invention.

FIG. 4 is a block diagram showing a configuration of a front end unit used in a conventional receiver.

FIG. 5 is a block diagram showing a configuration of a front end unit used in another conventional receiver.

[Explanation of symbols]

 2 Tuner circuit 3 Receiving antenna 5 Video intermediate frequency amplification circuit 6, 7 Filter circuit 8 Video terminal 9 Audio terminal 10 Metal case

Claims (2)

[Claims] 1. A tuner circuit, a first filter circuit for separating an image intermediate frequency signal from signals output from the tuner circuit, and an audio intermediate frequency signal from signals output from the tuner circuit A receiving circuit component, wherein a second filter circuit and a video intermediate frequency amplifying circuit for amplifying a video intermediate frequency signal extracted from the first filter circuit are housed in a shield member and integrated. 2. The receiving circuit component according to claim 1, a local oscillation circuit, a mixing circuit for mixing a local oscillation signal from the local oscillation circuit into an audio intermediate frequency signal, and a local oscillation circuit using the mixing circuit. A detection circuit for detecting the mixed audio intermediate frequency signal, wherein an audio intermediate frequency signal output terminal of the second filter circuit in the receiving circuit component and a local oscillation circuit are connected to an input side of the mixing circuit. A front end section of the receiver, wherein the detection circuit is connected to an output side of the mixing circuit.