CN202127420U - Double demodulation circuit and set-top box with same - Google Patents
Double demodulation circuit and set-top box with same Download PDFInfo
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- CN202127420U CN202127420U CN2011201689225U CN201120168922U CN202127420U CN 202127420 U CN202127420 U CN 202127420U CN 2011201689225 U CN2011201689225 U CN 2011201689225U CN 201120168922 U CN201120168922 U CN 201120168922U CN 202127420 U CN202127420 U CN 202127420U
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- tuner
- wired
- gain control
- terrestrial television
- automatic gain
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- Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
Abstract
The utility model discloses a double demodulation circuit, which comprises a tuner. The tuner comprises a radio-frequency signal input end and an intermediate frequency signal output end. The double demodulation circuit further comprises a wired/terrestrial television demodulator which comprises a differential signal input end and a data output end. The differential signal input end of the wired/terrestrial television demodulator is connected with the tuner through a bus so as to receive intermediate-frequency signals sent by the tuner, conduct wired television demodulation processing or terrestrial television demodulation processing and enable processed data to be output through a data output end of the differential signal input end. The double demodulation circuit adopts the wired/terrestrial television demodulator and a built-in quadrature amplitude modulation (QAM) and orthogonal frequency division multiplexing (OFDM) demodulator, reduces hardware cost, and is particularly suitable for popularization in circuit design of household electrical appliances of digital televisions or set-top boxes and the like.
Description
Technical field
The utility model belongs to the radio digital communication technical field, specifically, relates to a kind of bilingual demodulation circuit that radiofrequency signal is received processing.
Background technology
STB is generally by master chip, internal memory, demodulator and look audio frequency output etc. and constitute.The effect of demodulator is that the modulated digital signal demodulation that transmits is reduced into MPTS; The difference of demodulator has just constituted different top box of digital machines; The satellite set top box (DVB-S) that for example is used for the QPSK demodulation, the terrestrial transmission top box of digital machine (DVB-T) that is used for the wired digital set-top box (DVB-C) of QAM demodulation and is used for the OFDM demodulation.
At present; Development along with DTV; Ground OFDM and cabled digital QAM television broadcasting are more and more general, for the front end implementation of QAM and OFDM DTV receiver, generally adopt two demodulators of QAM and OFDM to receive the intermediate-freuqncy signal that tuner is sent; Accomplish channel-decoding processes such as decoding, convolution deinterleave, RS decodes, and under the control of I2C bus, solve the TS signal flow and export to follow-up decoding processing circuit.There is following drawback in such scheme: system adopts two decoders and related peripheral circuit thereof on the one hand, and employed device is more, need take the bigger circuit board space of STB; On the other hand, because circuit devcie is more, debug difficulties, conformity of production is poor, and stability is not high.
Based on above reason, how to research and develop that a kind of service behaviour is high, to take little and bilingual demodulation circuit good reliability in PCB space be the utility model subject matter to be solved.
The utility model content
The existing existing use device of bilingual demodulation circuit is many, the problem of poor work stability in order to solve for the utility model, and a kind of bilingual demodulation circuit simple in structure is provided, and has saved the PCB space, has improved the demodulation performance of tuner.
For addressing the above problem, the utility model adopts following technical scheme to be achieved:
A kind of bilingual demodulation circuit; Comprise tuner, said tuner comprises RF signal input end and intermediate-freuqncy signal output, wherein; Also comprise a wired/terrestrial television demodulator; Said wired/the terrestrial television demodulator comprises differential signal input and data output end, said wired/terrestrial television demodulator differential signal input connects tuner through bus, receives the intermediate-freuqncy signal that tuner sends; Carry out cable TV demodulation or terrestrial television demodulation process, and the data after will handling are through its data output end output.
Wherein, the intermediate-freuqncy signal output of said tuner output two paths of differential signals, respectively through the capacitance-resistance filter network with said wired/the corresponding connection of two paths of differential signals input of terrestrial television demodulator.
Further, said wired/the terrestrial television demodulator is an integrated chip.
Further again, said integrated chip is exported regulation voltage through gain control circuit to the automatic gain control end of said tuner through its automatic gain control end, with the output amplitude of control tuner intermediate-freuqncy signal.
Specifically; Said gain control circuit comprises first resistance and a NPN type triode that is connected between said tuner automatic gain control end and the said tuner automatic gain control end; The base stage of said triode connects said integrated chip automatic gain control end; Collector electrode connects the 5V direct voltage, and emitter through a drop-down grounding through resistance, connects said integrated chip automatic gain control end through second resistance on the one hand on the other hand.
Based on above-mentioned bilingual demodulation circuit structure; The utility model provides a kind of STB that adopts said bilingual demodulation circuit design again; Comprise tuner, wired/terrestrial television demodulator and decoding circuit, said tuner comprises RF signal input end and intermediate-freuqncy signal output, wherein; Also comprise a wired/terrestrial television demodulator; Said wired/the terrestrial television demodulator comprises differential signal input and data output end, said wired/terrestrial television demodulator differential signal input connects tuner through bus, receives the intermediate-freuqncy signal that tuner sends; Carry out cable TV demodulation or terrestrial television demodulation process, and the data after will handling are exported to said decoding circuit through its data output end.
Compared with prior art, the advantage and the good effect of the utility model are: the bilingual demodulation circuit of the utility model adopts a wired/terrestrial television demodulator, built-in QAM and ofdm demodulator; Reduced peripheral components, saved circuit board space, circuit structure is simple; When realizing the signal demodulation, improved the reliability of system, reduced hardware cost; Be particluarly suitable for promoting the use of in the circuit design of household appliances such as digital television or STB, to improve the complete machine performance of product.
After the detailed description in conjunction with advantages the utility model execution mode, other characteristics of the utility model and advantage will become clearer.
Description of drawings
Fig. 1 is the circuit theory diagrams of a kind of embodiment of the bilingual demodulation circuit that proposes of the utility model.
Embodiment
Describe in detail below in conjunction with the embodiment of accompanying drawing the utility model.
To adopt discrete component to build the use component number that is caused many in order to solve existing bilingual demodulation circuit for the utility model; It is big to take the PCB space; The problem of conformity of production difference; Having proposed a kind of needs to adopt a wired/terrestrial television demodulator can realize the bilingual demodulation circuit that the correlation frequency demodulated signal is handled, compact conformation, and stability is strong.
Be example below with the top box of digital machine, come to set forth in detail the concrete establishment structure and the operation principle thereof of said bilingual demodulation circuit through a concrete embodiment.
Embodiment one, and referring to shown in Figure 1, the wired/terrestrial television demodulator of present embodiment specifically adopts demodulation chip N1H (for example model is the chip of Sti7162) to realize demodulation process.This chip is the audio/video decoding chip, and major function comprises ground and wired demodulation, supports MPEG2 and H.264 high definition decoding, and memory interface can be supported a plurality of interfaces such as nor flash, serial flash and nand flash.Concrete operation principle is following: the digital television signal on wired or ground; Deliver to the rf inputs of tuner by reception antenna or coaxial cable; After RF frequency reducing, frequency conversion, export intermediate-freuqncy signal, demodulation chip is according to the difference of wired or ground signal, carry out carrier wave recovery, equilibrium and FCC respectively after; Output TS signal supplies back-end processing.Said wired/the terrestrial television demodulator is because built-in QAM and ofdm demodulator; Make two kinds of patterns realize seamless switching on the one hand, accelerated the semaphore lock time, improved user's impression effect; Reduced the requirement of producing debugging on the other hand; Guaranteed the consistency that product lot quantity is produced, its channel index also can reach the industry higher level: 1. incoming signal level accommodation :-80-5dBm (OFDM) ,-63-5dBm (QAM); 2.E/N threshold value: 5.5dB (QPSK, FEC=3/4,2k).
Among Fig. 1; Radiofrequency signal is exported differential intermediate frequency IP, IN by rf terminals U1 (U2) input after RF frequency reducing, frequency conversion, the capacitance-resistance filter network that differential intermediate frequency is formed through resistance R F6, RF7, RF9, RF10 and capacitor C F4, CF5, CF7, CF8; After carrying out impedance matching filtering; Carry out necessary decay to unwanted low frequency and high-frequency signal, send among the differential signal input AL5, AM4 of demodulation chip N1H, demodulation chip N1H carries out output TS signal flow behind carrier wave recovery, equilibrium and the FCC to the differential signal that receives; D0-D7 exports to follow-up decoding circuit through its data-signal output, realizes the reduction output of vision signal.
Voltage amplitude for the intermediate-freuqncy signal of stablizing tuner U1 (U2) output; The control circuit that demodulation chip N1H forms via resistance R F12, RF13 and triode V2 through its automatic gain control end RF_LEVEL; To the automatic gain control end RF_AGC of tuner U1 (U2) a control voltage is provided; And then the multiplication factor of regulating tuner U1 (U2) internal amplifier; Realize and the amplitude compatibility of tuner gain controlling, can drive the 5V gain controlling of tuner to guarantee demodulation chip 3.3V gain voltage, thereby greatly improve the transmission performance of intermediate-freuqncy signal.
Specifically; Said gain control circuit comprises the first resistance R F11 and a NPN type triode V2 who is connected between said integrated chip automatic gain control end and the said tuner automatic gain control end; The base stage of said triode V2 connects said tuner automatic gain control end RF_AGC; Collector electrode connects the 5V direct voltage, and emitter through a drop-down resistance R F13 ground connection, meets said integrated chip automatic gain control end RF_LEVEL through the second resistance R F12 on the one hand on the other hand.Certainly, can adopt other circuit forms, this does not enumerate one by one yet.
Present embodiment proposed bilingual demodulation circuit sets up structure goes for equally digital television etc. need carry out in the circuit design of electronic product of signal demodulation, present embodiment be not limited in above for example.
The above only is the preferred embodiment of the utility model, is not to be the restriction to the utility model, and any professional and technical personnel of being familiar with possibly utilize the technology contents of above-mentioned announcement to change or be modified as the equivalent embodiment of equivalent variations.But every the utility model technical scheme content that do not break away to any simple modification, equivalent variations and remodeling that above embodiment did, still belongs to the protection range of the utility model technical scheme according to the technical spirit of the utility model.
Claims (10)
1. bilingual demodulation circuit; Comprise tuner; Said tuner comprises RF signal input end and intermediate-freuqncy signal output, it is characterized in that: also comprise a wired/terrestrial television demodulator, said wired/the terrestrial television demodulator comprises differential signal input and data output end; Said wired/terrestrial television demodulator differential signal input connects tuner through bus; Receive the intermediate-freuqncy signal that tuner sends, carry out cable TV demodulation or terrestrial television demodulation process, and the data after will handling are through its data output end output.
2. bilingual demodulation circuit according to claim 1; It is characterized in that: the intermediate-freuqncy signal output of said tuner output two paths of differential signals, respectively through the capacitance-resistance filter network with said wired/the corresponding connection of two paths of differential signals input of terrestrial television demodulator.
3. bilingual demodulation circuit according to claim 1 and 2 is characterized in that: said wired/the terrestrial television demodulator is an integrated chip.
4. bilingual demodulation circuit according to claim 3; It is characterized in that: said integrated chip is exported regulation voltage through gain control circuit to the automatic gain control end of said tuner through its automatic gain control end, with the output amplitude of control tuner intermediate-freuqncy signal.
5. bilingual demodulation circuit according to claim 4; It is characterized in that: said gain control circuit comprises first resistance and a NPN type triode that is connected between said integrated chip automatic gain control end and the said tuner automatic gain control end; The base stage of said triode connects said tuner automatic gain control end; Collector electrode connects the 5V direct voltage, and emitter through a drop-down grounding through resistance, connects said integrated chip automatic gain control end through second resistance on the one hand on the other hand.
6. STB with bilingual demodulation circuit; Comprise tuner, wired/terrestrial television demodulator and decoding circuit; Said tuner comprises RF signal input end and intermediate-freuqncy signal output, it is characterized in that: also comprise a wired/terrestrial television demodulator, said wired/the terrestrial television demodulator comprises differential signal input and data output end; Said wired/terrestrial television demodulator differential signal input connects tuner through bus; Receive the intermediate-freuqncy signal that tuner sends, carry out cable TV demodulation or terrestrial television demodulation process, and the data after will handling are exported to said decoding circuit through its data output end.
7. STB according to claim 6 is characterized in that: the intermediate-freuqncy signal output of said tuner output two paths of differential signals, respectively through the capacitance-resistance filter network with said wired/the corresponding connection of two paths of differential signals input of terrestrial television demodulator.
8. according to claim 6 or 7 described STBs, it is characterized in that: said wired/the terrestrial television demodulator is an integrated chip.
9. STB according to claim 8 is characterized in that: said integrated chip is exported regulation voltage through gain control circuit to the automatic gain control end of said tuner through its automatic gain control end, with the output amplitude of control tuner intermediate-freuqncy signal.
10. STB according to claim 9; It is characterized in that: said gain control circuit comprises first resistance and a NPN type triode that is connected between said integrated chip automatic gain control end and the said tuner automatic gain control end; The base stage of said triode connects said tuner automatic gain control end; Collector electrode connects the 5V direct voltage, and emitter through a drop-down grounding through resistance, connects said integrated chip automatic gain control end through second resistance on the one hand on the other hand.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011201689225U CN202127420U (en) | 2011-05-25 | 2011-05-25 | Double demodulation circuit and set-top box with same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011201689225U CN202127420U (en) | 2011-05-25 | 2011-05-25 | Double demodulation circuit and set-top box with same |
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| Publication Number | Publication Date |
|---|---|
| CN202127420U true CN202127420U (en) | 2012-01-25 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2011201689225U Expired - Fee Related CN202127420U (en) | 2011-05-25 | 2011-05-25 | Double demodulation circuit and set-top box with same |
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| CN (1) | CN202127420U (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104125503A (en) * | 2013-04-28 | 2014-10-29 | 深圳市同洲电子股份有限公司 | Set top box upgrading method and digital television terminal |
-
2011
- 2011-05-25 CN CN2011201689225U patent/CN202127420U/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104125503A (en) * | 2013-04-28 | 2014-10-29 | 深圳市同洲电子股份有限公司 | Set top box upgrading method and digital television terminal |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20120125 Termination date: 20190525 |