What does a TV set HF tuner consist of

The TV high-frequency tuner is mainly composed of: high-frequency amplifier, local oscillator, mixer, and input loop.

The TV high-frequency tuner is an important device in the TV receiving terminal, commonly known as the high-frequency head. Ordinary TV tuner is to complete the process of receiving amplification, strobing, frequency conversion, and picture sound demodulation in an analog way, if there is distortion and distortion, the quality of the received image and accompanying sound will deteriorate.

Purpose:1Tune the selector and select the TV signal of the desired receiving channel.

2.Frequency conversion, which converts a high-frequency TV signal into an intermediate frequency TV signal.

The current color TV high-frequency tuner (also called high-frequency head) is mainly composed of integrated patch, and in order to cooperate with the bus technology, it is designed in the form of encoding, which is roughly divided into several steps: frequency reduction-mixing-encoding-decoding identification-parallel output, probably like this, the market is mainly based on 12 volt power supply and 5 volt power supply.

It is mainly composed of signal acquisition, local oscillator, signal processing, signal amplification, etc.

Mainly composed of:1High frequency amplifiers.

2.Native oscillator.

3.Mixer.

4.Input loop.

Input loops High frequency amplifiers, native oscillators, mixers,

1 high frequency, 2 native oscillation, 3 mixing, 4 inputs, 5 outputs

Electrical tuning circuits, frequency band switching circuits, etc.

The circuit of the high-value tuner consists of a VHF tuner and a UHF tuner. The VHF tuner is composed of an input loop, a high-frequency amplifier, a local oscillator circuit and a mixing circuit, and the mixing circuit outputs the IF signal. A UHF tuner also consists of an input loop, a high-frequency amplifier, and a frequency conversion circuit.

In the Split Belt Chang UHF tuner, the output IF signal Xingyu is also sent to the VHF mixing circuit, and then the mixing circuit of the VHF tuner becomes the intermediate amplifier circuit of the UHF tuner. Due to the high working frequency of the high-frequency tuner, in order to prevent external electromagnetic field interference and radiation of the local oscillator, the high-frequency tuner is sealed and packed in a metal box, and the metal box is grounded to play a shielding role.

There are three main functions of the high-profile frequency tuner.

1) Frequency selection. 2) Zoom in.

The weak and high-frequency liquid frequency TV signal received by the relay is amplified to improve the sensitivity of the whole machine.

3) Frequency conversion. The received image signal with a carrier frequency of FP and the chromaticity with a carrier frequency of FC are transmitted.

The signal and the accompanying sound signal with the carrier frequency of FS are mixed with the local oscillator signal FO respectively, and converted into an image intermediate frequency signal with a carrier frequency of 38MHz, a chromaticity intermediate frequency signal with a carrier frequency and an intermediate frequency signal with a carrier frequency of the first accompanying sound book, and they are sent to the intermediate frequency amplifier circuit.

The entire digital TV tuner consists of two functional circuits. As shown in the figure, the tuning circuit of the front end is responsible for the functions of radio frequency bucket simple reception, frequency conversion, filtering and automatic gain control, etc., in addition to realizing the basic function of signal reception, the stool sub-circuit should also deal with the problem of signal interference, common such as mirror signal interference, temporary channel interference and other problems, interference in analog TV will bring multiple graph lines, and when the interference in digital TV is serious, it can directly lead to the loss of the jujube pincha signal; The back-end demodulation circuit is responsible for AD conversion, demodulation, error correction and decoding.

With the practical technological breakthroughs in microelectronic technology, VLSI design technology, digital signal processing technology and computer technology, and the intensification of competition in the international market, the production of TV tuners is becoming more and more sophisticated, the performance is becoming more and more excellent, and the development of integration, miniaturization and high reliability, since the 70s of the last century, the circuit module composed of separated devices has been gradually replaced by the corresponding special integrated circuit, and with the development of integrated circuit design technology, Chips for TV tuners are becoming more and more integrated. The new digital TV tuning chip and application scheme realize the function of the front-end tuning circuit, and the back-end demodulation circuit adopts other demodulation special chips.

The TV tuner is an important device in the TV receiving terminal, commonly known as the high-frequency head. Ordinary TV tuner is to complete the process of connecting and amplifying, gating, frequency conversion, and picture sound demodulation in an analog way, if there is distortion and distortion, it will make the quality of the received image and sound poor. Rear projection TV belongs to digital TV,First change the analog TV signal to a digital signal,Compression、Transmission、Receiving、Processing、Storage、Recording and control base socks,The digital TV receiving terminal must first be carried out by the digital TV tuner for high stroke rate stimulation amplification、Comparative processing、Channel decoding and demodulation。

Then the back-end circuit of the digital TV receiver is processed to restore the original image and sound, if this process is distorted, it will cause bit error error, and if it exceeds the range that can be controlled by the tuner, the image and sound cannot be received.

1.The modulator adopts a four-way modulation integrated design, which saves the cabinet space in the computer room and is convenient for installation and commissioning.

2.The output signal is strong, the transmission distance is long, and the output image is optimized to make the picture clearer.

3.The modulator uses IF surface filtering with standard residual sideband characteristics.