CN2731861Y

CN2731861Y - TV signal level detecting circuit

Info

Publication number: CN2731861Y
Application number: CNU2004200852709U
Authority: CN
Inventors: 刘连军
Original assignee: DELI ELECTRONIC INSTRUMENT Co Ltd TIANJIN CITY
Current assignee: DELI ELECTRONIC INSTRUMENT Co Ltd TIANJIN CITY
Priority date: 2004-11-04
Filing date: 2004-11-04
Publication date: 2005-10-05
Anticipated expiration: 2014-11-04

Abstract

The utility model relates to a TV signal level detecting circuit, which mainly comprises a controllable attenuation unit, a signal demodulation detecting unit, a module / number conversion detecting unit, a microcontroller unit, an LCD displaying unit and a power supply unit. The MCU adjusts the ADJ-ATT controllable attenuation unit according to the measured strength of the RF signals, so that the signal strength inputted into the TUNERDEMO signal demodulation detecting unit is in the dynamic range of the detection; therefore, the accuracy of the signal detected is guaranteed. Then the MCU collects the direct current level outputted by the TUNERDEMO signal demodulation detection unit, via the A/D, and corresponds with the amplitude of the inputted signals to obtain the final detecting level which is displayed on the LCD at last. The traditional twice or more frequency conversions are simplified to only once frequency conversion, which simplifies the circuit, economizes the cost, decreases the failure rate, and saves the space of the printed board.

Description

The television signal level testing circuit

Technical field

The utility model relates to a kind of television signal level testing circuit.

Background technology

It is the mode of double conversion at least that traditional television signal level detects what adopt, and is accompanied by huge demodulation and level related circuit.

Summary of the invention

The purpose of this utility model provides that a kind of circuit is simple, and volume reduces, and power consumption is little, a kind of television signal level testing circuit that failure rate reduces.

For achieving the above object, the utility model by the following technical solutions

Television signal level testing circuit of the present utility model mainly comprises

The controlled attenuation units of a.ADJ-ATT, the regulating and controlling measured signal that is used to be subjected to the MCU microcontroller be by the signal energy size behind this element, and

B.TUNER DEMO signal demodulation detecting unit, be used for traditional TUNER electronic tuning unit is redesigned, this element mainly is made up of four parts: the control of AGC automatic gain---and mainly adjust signal gain automatically, thereby keep good dynamic monitoring scope according to signal is strong and weak; MIXER frequency mixer, PLL phase-locked loop, VCO voltage controlled oscillator---mainly be to carry out locking frequency, convert the RF radiofrequency signal to the IF intermediate-freuqncy signal; The FILTER filter---mainly be that the IF intermediate-freuqncy signal is separated; The DEMODULATION demodulation---mainly be demodulation IF intermediate-freuqncy signal, and according to the control of the strong and weak adjusting automatically of signal AGC automatic gain, and the direct voltage of output corresponding signal level intensity, this direct voltage is the magnitude of voltage of IFAGC, learn the size of corresponding level by the size that detects this magnitude of voltage, and

C.A/D---A/D mould/number conversion detecting unit: the major function of this element is that analog voltage signal is converted to digital signal, finally handles by MCU, and

D.MCU---MCU micro controller unit: this element is the central processing center of complete machine, comes detection signal level by the numerical value that reads A/D, and controls the state of attenuator, the frequency of detection, and finally shows testing result on the LCD LCD, and

E.LCD---LCD display unit: this element is a human-computer interaction interface, learns by the demonstration of LCD and detects frequency and level value, and

F.POWER---POWER power supply unit: this element is the feed unit of complete machine energy, provides each module required operating voltage.

In the work of complete machine, MCU adjusts the controlled attenuation units of ADJ-ATT automatically according to tested RF signal strength signal intensity, the signal strength signal intensity that is input to TUNER DEMO signal demodulation detecting unit is in the normal detection dynamic range, thereby make detected signal accurate, MCU gathers the DC level of being exported by TUNER DEMO signal demodulation detecting unit by A/D again, and correspondingly with input signal amplitude obtain final detection level, finally be presented on the LCD.

The beneficial effects of the utility model are:

1. reduce frequency conversion and survey number of times: be reduced to only single-conversion by traditional twice above frequency conversion, simplified circuit, saved cost, reduced failure rate, saved the printed board space

2. saved peak detection circuit: in traditional television signal level detected, peak holding circuit was absolutely necessary, and had omitted this testing circuit in this design, thereby simplified circuit once more, save cost, reduced failure rate, saved the printed board space

3. utilize ripe chip: this testing circuit has utilized level demodulator circuit chip behind the television set TUNER machine, makes design more reliable and more stable

4. this circuit of traditional detection of comparing has more, and circuit is simple, and cost is low, and volume reduces greatly, and power consumption is little, the plurality of advantages that failure rate reduces

Description of drawings

Fig. 1 is television signal level testing circuit figure

Fig. 2 is the internal frame diagram of TUNER DEMO

Number line is the signal flow line among Fig. 1, and some frame line is a power line, and real frame line is the MCU control line, can select the integral type chip for use in the frame of broken lines

Embodiment

Embodiment 1

Television signal level testing circuit figure as Fig. 1, MCU adjusts the controlled attenuation units of ADJ-ATT automatically according to tested RF signal strength signal intensity, the signal strength signal intensity that is input to TUNER DEMO signal demodulation detecting unit is in the normal detection dynamic range, thereby make detected signal accurate, MCU gathers out the DC level of TUNER DEMO signal demodulation detecting unit output again by A/D, and correspondingly with input signal amplitude obtain final detection level, finally be presented on the LCD.

Claims

1. a television signal level testing circuit mainly comprises

The controlled attenuation units of a.ADJ-ATT, the regulating and controlling measured signal that is used to be subjected to MCU be by the signal energy size behind this element, and

B.TUNER DEMO signal demodulation detecting unit is used for traditional TUNER is redesigned, and this element mainly is made up of four parts: AGC---and mainly adjust signal gain automatically, thereby keep good dynamic monitoring scope according to signal is strong and weak; MIXER, PLL, VCO---mainly be to carry out locking frequency, the RF conversion of signals is become the IF signal; FILTER---mainly be that the IF Signal Separation is come out; DEMODULATION---mainly be demodulation IF signal, and according to the strong and weak adjusting automatically of signal AGC, and the direct voltage of output corresponding signal level intensity, this direct voltage is the magnitude of voltage of (IF) AGC, learn the size of corresponding level by the size that detects this magnitude of voltage, and

C.A/D---A/D detecting unit: the major function of this element is that analog voltage signal is converted to digital signal, finally handles by MCU, and

D.MCU---MCU unit: this element is the central processing center of complete machine, comes detection signal level by the numerical value that reads A/D, and controls the state of attenuator, the frequency of detection, and finally shows testing result on LCD, and

F.POWER---POWER power supply unit: this element is the feed unit of complete machine energy, provides each module required operating voltage;

MCU adjusts the controlled attenuation units of ADJ-ATT automatically according to tested RF signal strength signal intensity, the signal strength signal intensity that is input to TUNER DEMO signal demodulation detecting unit is in the normal detection dynamic range, thereby make detected signal accurate, MCU gathers the DC level of being exported by TUNER DEMO signal demodulation detecting unit by A/D again, and correspondingly with input signal amplitude obtain final detection level, finally be presented on the LCD.