CN201398214Y

CN201398214Y - Two-in-one circuit of electronic tuner and radio-frequency modulator

Info

Publication number: CN201398214Y
Application number: CN200920096482XU
Authority: CN
Inventors: 董海霞
Original assignee: HEGOEM (TIANJIN) ELECTRONICS CO Ltd
Current assignee: HEGOEM (TIANJIN) ELECTRONICS CO Ltd
Priority date: 2009-04-24
Filing date: 2009-04-24
Publication date: 2010-02-03
Anticipated expiration: 2019-04-24

Abstract

The utility model relates to a two-in-one circuit of an electronic tuner and a radio-frequency modulator in a set-top box circuit. The two-in-one circuit comprises an electronic tuner circuit and a radio-frequency modulator circuit which are arranged in a set-top box of a digital television and connected with each other through a standard interface. The two-in-one circuit is characterized in thatthe electronic tuner circuit and the radio-frequency modulator circuit are connected and arranged on one circuit board. By adopting the structure that the electronic tuner circuit and the radio-frequency modulator circuit in the set top box are connected and arranged on one circuit board, the reasonable arrangement and design are ensured; the size is reduced by half; with respect to performance, the interference between the two circuits is reduced, the reliability and stability of a product are increased; and the cost is reduced.

Description

The two-in-one circuit of electronic tuning unit and radio-frequency modulator

Technical field

The utility model relates to a kind of digital TV set-top box circuit, electronic tuning unit in particularly a kind of set-top box circuit and the two-in-one circuit of radio-frequency modulator.

Background technology

China Digital TV had entered the flourish phase in 2008, and according to " the radio, film and television science and technology the Tenth Five-Year Plan (2001-2005) and the long-range objectives to the year 2010 ", China in 2010 will stop the broadcast of analog TV broadcasting in 2015 with the round Realization digital broadcast television.Undoubtedly, popularizing of digital television program become inexorable trend, and the transition form of " simulated television+set-top box " of China's current make set-top box market in state-owned darker more vast market.

The full name of set-top box is called " digital TV set-top box ", and it is a kind ofly to convert digital television signal the conversion equipment of analog signal to, and its sends being reduced into analog signal through image of digitalization compressed and voice signal decoding into common television set.The operation principle of set-top box is: the composite video signal that receives from antenna at first will demodulate the digital intermediate frequency TV signal that needs through electronic tuning unit, the signal that is come out by demodulation carries out numeral, analog-converted in set-top box inside, digital television signal become enter into radio-frequency modulator behind the anolog TV signals analog signal is modulated, at last the signal that modulates is exported to analog machine.Wherein radio-frequency modulator and electronic tuning unit are two big important component parts of set-top box.

Present electronic tuning unit and radio-frequency modulator are two independently goods, and they have oneself input, output respectively in set-top box inside, and electronic tuning unit will be connected by the corresponding standard interface with radio-frequency modulator.Along with the CPU processing speed of set-top box inside is more and more faster, memory span is increasing, and mpeg decoder will be supported the decoding of multi-channel program simultaneously; The image display interfaces that the while user can directly see will be more clear, the function of set-top box also can be more and more abundanter, and electronic product all is to develop towards small and exquisite, frivolous direction, these have given set-top box better development space undoubtedly, but how to be faced with also simultaneously that function with set-top box increases and size does not increase, the volume of the important component part electronic tuning unit of set-top box and radio-frequency modulator will change like this, and performance also will have much room for improvement.Existing digital TV set-top box present situation does not reach development in science and technology and people's demand far away.

Summary of the invention

In view of the deficiency that prior art exists, the utility model provides a kind of electronic tuning unit and the two-in-one circuit of radio-frequency modulator.

The utility model for achieving the above object, the technical scheme of being taked is: the two-in-one circuit of a kind of electronic tuning unit and radio-frequency modulator, comprise the electronic tuning unit circuit and the radio-frequency modulator circuit that are arranged in the digital TV set-top box, described electronic tuning unit circuit and radio-frequency modulator circuit, connect by standard interface, it is characterized in that: described electronic tuning unit circuit is arranged on the wiring board with the radio-frequency modulator circuit and is connected.

This practical characteristics is: electronic tuning unit circuit in the TV set-top box is connected with the radio-frequency modulator circuit to be arranged on the wiring board altogether, and layout designs is reasonable, has reduced half than the volume of prior art; At aspect of performance, reduced interference each other, increased the reliable and stability of product; Reduced cost.

Description of drawings

Fig. 1 is that circuit of the present utility model connects block diagram and as Figure of abstract.

Fig. 2 be prior art circuit connect block diagram.

Fig. 3 is a fundamental diagram of the present utility model.

Fig. 4 is a circuit diagram of the present utility model

Embodiment

Shown in Fig. 1,3,4, the two-in-one circuit of electronic tuning unit and radio-frequency modulator, comprise the electronic tuning unit circuit and the radio-frequency modulator circuit that are arranged in the digital TV set-top box, the electronic tuning unit circuit is connected with the radio-frequency modulator circuit and is arranged on altogether on the wiring board.On function, in order to reduce electronic tuning unit and the radio-frequency modulator interference characteristic when the high frequency, when this circuit of design,, pcb has been divided into several sections according to its difference on function, wherein L1, L2, L3 be a part of; L4, L5, L6, L7, L8, L9, L10 are a part; L11, L12, L13 are a part wherein, utilize the frame that encloses of iron that these several parts are surrounded, separated, played excellent shielding effect, so both reduced the phase mutual interference between the electronic device when high frequency, reduced electromagnetic interference again, the performance of goods is improved under the situation that does not increase device like this.

Operation principle:

Electronic tuning unit is mainly put back to road, mixing, local oscillator loop by input circuit, height and is formed.

Its course of work is: input from the composite video signal of different channel after UHF, VHF-HIGH, VHF-LOW filtering, select the signal of corresponding band separately, sending into height puts back to the road and amplifies, mix mutually with local oscillation signal from the local oscillator loop in the mixing unit then, a fixing full tv-if signal 44MHZ gives television set or other video conversion apparatus carries out signal processing thereby go out by SDA, SCL control PLL phase-locked loop difference.

AGC gain reduction loop: put level because of VL, VH, UHF height and adopt a field-effect transistor, so AGC is reverse automatic gain control, the AGC terminal is an automatic control power supply.When the overflow that television set receives, the gain range of tuner output is too high, and the AGC voltage that television set is supplied with tuner is just low more, and the gain range of tuner output descends; When signal that television set receives excessively a little less than, the AGC voltage that television set is supplied with tuner is high more (reaching setting) just, the gain range height of tuner output.

The frequency dividing ratio that the PLL phase-locked loop provides by SDA, SCL is carried out dividing potential drop, the control voltage control transfiguration diode frequency-selecting that obtains with the VT voltage of 30V.

The RF radiofrequency signal of input is carried out Modulation and Amplitude Modulation (AM) to the Video signal by special-purpose modulation chip LA77000V, the Audio signal is carried out frequency modulation(FM) (FM) after, be transformed into RF (Radio Frequency) and export to corresponding apparatus.The demodulation IC that this electronic tuning unit adopts is SN761668.

Claims

1, the two-in-one circuit of a kind of electronic tuning unit and radio-frequency modulator, comprise the electronic tuning unit circuit and the radio-frequency modulator circuit that are arranged in the digital TV set-top box, described electronic tuning unit circuit and radio-frequency modulator circuit, connect by standard interface, it is characterized in that: described electronic tuning unit circuit is arranged on the wiring board with the radio-frequency modulator circuit and is connected.