CN101742137B - Control circuit for integral high frequency head between digital cable television and digital terrestrial television - Google Patents
Control circuit for integral high frequency head between digital cable television and digital terrestrial television Download PDFInfo
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- CN101742137B CN101742137B CN2008102029969A CN200810202996A CN101742137B CN 101742137 B CN101742137 B CN 101742137B CN 2008102029969 A CN2008102029969 A CN 2008102029969A CN 200810202996 A CN200810202996 A CN 200810202996A CN 101742137 B CN101742137 B CN 101742137B
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Abstract
The invention relates to a control circuit for an integral high frequency head between a digital cable television and a digital terrestrial television. The control circuit comprises a radio frequency switcher, which belongs to GaAS IC, wherein the radio frequency switcher acts as a radio frequency single-pole double-throw switch specially used for switching between an input signal of the digital cable television (DVB-C) and the input signal of the digital terrestrial television (DMB-TH); when S2 is a high level (5V), the signal of DVB-C is communicated and the signal of DMB-TH is cut off; when S3 is the high level (5V), the signal of DMB-TH is communicated and the signal of DVB-C is cut off; a 75 ohm impedance matching network consists of C3, L1, C4, R4, R5 and L2; and the signal is amplified by a broadband amplifying circuit consisting of Q1 by 15dB to resist the insertion loss of a forestage circuit. Therefore, convenient switching between the signals of the digital cable television (DVB-C) and the digital terrestrial television (DMB-TH) is realized.
Description
Technical field
The present invention relates to a kind of digital cable TV (DVB-C) and digital terrestrial television (DMB-TH) integral high frequency head, relate in particular to the control circuit of this tuner.
Background technology
Also do not have compatible with digital cable TV (DVB-C) and digital terrestrial television (DMB-TH) integral high frequency head in the prior art, digital cable TV (DVB-C) solves with different DVB-C tuners and DMB-TH tuner respectively with digital terrestrial television (DMB-TH).This just causes same receiver can only be used for DVB-C or DMB-TH, and can not receive digital cable TV (DVB-C) and digital terrestrial television (DMB-TH) program simultaneously.
Technical problem wherein mainly contains 3:
How the one, makes things convenient for switching between digital cable TV (DVB-C) signal and digital terrestrial television (DMB-TH) signal;
Digital terrestrial television (DMB-TH) signal amplitude changes very greatly the 2nd, because digital cable TV (DVB-C) signal amplitude changes little, therefore automatic gain control (AGC) characteristic of the automatic gain of DVB-C control (AGC) characteristic and DMB-TH is different, is difficult to compatibility;
The 3rd. code check reaches 41.34 when being 6.98Mbaud owing to digital cable TV (DVB-C) 64QAM signal code rate, and is therefore higher to the phase noise performance requirement of tuner, requires low relatively to signal gain; And digital terrestrial television (DMB-TH), it requires high to signal gain, and this just makes the signal gain of tuner and phase noise design be difficult to.
Summary of the invention
The technical issues that need to address of the present invention have provided the control circuit of a kind of digital cable TV and digital terrestrial television integral high frequency head, are intended to solve the above problems.
In order to solve the problems of the technologies described above, the present invention is achieved by the following technical solutions:
The present invention includes: an end of first electric capacity that is connected with the digital cable TV digital television signal, the first electric capacity other end connects the 1st pin of radio frequency switch; Digital terrestrial television digital television signal end connects an end of second electric capacity, and the second electric capacity other end connects the 3rd pin of radio frequency switch, and radio frequency switch the 6th pin connects an end of second resistance, and the other end of second resistance connects 5V and 0V switches; The 4th pin of radio frequency switch connects an end of the 3rd resistance, and the other end of the 3rd resistance connects 5V and 0V switches; The 5th pin of radio frequency switch connects an end of the 3rd electric capacity, the other end of the 3rd electric capacity connects an end of the 4th resistance and first inductance, the other end of first inductance is by the 4th capacity earth, the other end of the 4th resistance connects the 5th resistance and second inductance, the 5th resistance other end ground connection, the second inductance other end connects the base stage and the 4th inductance of triode, the 4th inductance other end connects the 7th resistance and the 6th electric capacity by first resistance, the 7th resistance and the other end of the 6th electric capacity are connected the collector electrode of triode respectively, and digital television signal is from the collector electrode output of triode; The emitter of triode is respectively by the 5th electric capacity and the 6th grounding through resistance.
Compared with prior art, the invention has the beneficial effects as follows: same receiver can receive digital cable TV (DVB-C) and digital terrestrial television (DMB-TH) program simultaneously.
Description of drawings
Fig. 1 is a line map of the present invention.
Embodiment
Below in conjunction with accompanying drawing and embodiment the present invention is described in further detail:
As seen from Figure 1: the present invention includes: an end of first capacitor C 1 that is connected with the digital cable TV digital television signal, first capacitor C, 1 other end connects the 1st pin of radio frequency switch; Digital terrestrial television digital television signal end connects an end of second capacitor C 2, and second capacitor C, 2 other ends connect the 3rd pin of radio frequency switch, and radio frequency switch the 6th pin connects an end of second resistance R 2, and the other end of second resistance R 2 connects 5V and 0V switches; The 4th pin of radio frequency switch connects an end of the 3rd resistance R 3, and the other end of the 3rd resistance R 3 connects 5V and 0V switches; The 5th pin of radio frequency switch connects an end of the 3rd capacitor C 3, the other end of the 3rd capacitor C 3 connects an end of the 4th resistance R 4 and first inductance L 1, the other end of first inductance L 1 is by the 4th capacitor C 4 ground connection, the other end of the 4th resistance R 4 connects the 5th resistance R 5 and second inductance L 2, the 5th resistance R 5 other end ground connection, second inductance L, 2 other ends connect base stage and the 4th inductance L 4 of triode Q1, the 4th inductance L 4 other ends connect the 7th resistance R 7 and the 6th capacitor C 6 by first resistance R 1, the 7th resistance R 7 and the other end of the 6th capacitor C 6 are connected the collector electrode of triode Q1 respectively, and digital television signal is from the collector electrode output of triode Q1; The emitter of triode Q1 is respectively by the 5th capacitor C 5 and the 6th resistance R 6 ground connection;
Described radio frequency switch is the AS197 of SKYWORKS company.
The concrete numerical value of components and parts is seen Fig. 1 in above-mentioned circuit, these element electric capacity, the numerical value of resistance and inductance must be according to parameter (the thick 1mm of pcb board, dielectric constant=4.5 of PCB, copper thickness=1OZ, two laminates) and trace width and the length of PCB do ± adjust in 30% scope.
Radio frequency switch function and purposes: the radio frequency switch belongs to GaAS IC, and its function is the radio frequency single-pole double-throw switch (SPDT), and it is exclusively used in switches digital cable TV (DVB-C) input signal and digital terrestrial television (DMB-TH) input signal.DVB-C signal conduction when S2 is high potential (5V), the DMB-TH signal ends; DMB-TH signal conduction when S3 is high potential (5V), the DVB-C signal ends.Pass through again by C3, L1, C4, R4, R5 and L2 form 75 Ω impedance matching networks; Signal carries out the amplification of 15dB through the wideband amplifying circuit of being made up of Q1 again, is used to offset the insertion loss of front stage circuits, makes things convenient for switching thereby be implemented between digital cable TV (DVB-C) signal and digital terrestrial television (DMB-TH) signal.
The software driver of tuner is by the I2C agreement, and to the tuner write data, many performances of tuner are exactly write data by how, write what data and realize according to the tuner software data structure.
The present invention has done following configuration to the design of tuner software in order to solve digital cable TV (DVB-C) signal amplitude and to change little and digital terrestrial television (DMB-TH) signal amplitude changes the automatic gain that causes very greatly and controls the inconsistent contradiction of (AGC) characteristic:
According to tuner software data structure such as table 1:
Table 1
When receiving digital cable TV (DVB-C) signal, be 2s because signal amplitude changes the time constant of the little AGC of needs (automatic gain control), the electric current of AGC is that 220nA is to satisfy signal stabilization.Following configuration by software can reach this purpose.
ATC=0:AGC current=220nA; AGC time constant=2s; As table 2
Table 2
At this moment AGC data such as table 3:
Table 3
During digital terrestrial television (DMB-TH) signal, it is 50ms that the signal amplitude variation needs the time constant of AGC very greatly, and the electric current of AGC is that 9uA is to satisfy signal capture and locking.Following configuration by software can reach this purpose.
ATC=1:AGC current=9uA; AGC time constant=50m s; As table 4
Table 4
At this moment AGC data such as table 5:
Design by above software can solve digital cable TV (DVB-C) signal amplitude and change little and digital terrestrial television (DMB-TH) signal amplitude changes the automatic gain that causes very greatly and controls the inconsistent contradiction of (AGC) characteristic.
In order to solve that digital cable TV (DVB-C) signal requires height to the phase noise performance of tuner and digital terrestrial television (DMB-TH) signal to the demanding contradiction of signal gain, following configuration has been done in the design of tuner software:
When tuner receives digital cable TV (DVB-C), by the software CP value (phase-locked loop pump electric current) of configuring high-frequency, make the phase noise performance of tuner reach best (84dBC/1KHz), table 6 and table 7 are best software CP value allocation lists.
Table 6
Table 7
When tuner received terrestrial television (DMB-TH) signal, the software AGCtake-over point by configuring high-frequency made the gain of tuner reach optimum value 48dB.Table 8 is best software AGCtake-over point value allocation lists.
| AL2 | AL1 | AL0 | TYPICAL?TAKE-OVER?POINT?LEVEL |
| 0 | 0 | 0 | 124dBμV(p-p) |
| 0 | 0 | 1 | 121dBμV(p-p) |
| 0 | 1 | 0 | 118dBμV(p-p) |
| 0 | 1 | 1 | 115dBμV(p-p) |
| 1 | 0 | 0 | 112dBμV(p-p) |
| 1 | 0 | 1 | 109dBμV(p-p) |
| 1 | 1 | 0 | I AGC＝0；note?1 |
| 1 | 1 | 1 | V AGC＝3.5V；note?2 |
Table 8
Claims (2)
1. the control circuit of digital cable TV and digital terrestrial television integral high frequency head is characterized in that comprising: an end of first electric capacity that is connected with the digital cable TV digital television signal, and the first electric capacity other end connects the 1st pin of radio frequency switch; Digital terrestrial television digital television signal end connects an end of second electric capacity, and the second electric capacity other end connects the 3rd pin of radio frequency switch, and radio frequency switch the 6th pin connects an end of second resistance, and the other end of second resistance connects 5V and 0V switches; The 4th pin of radio frequency switch connects an end of the 3rd resistance, and the other end of the 3rd resistance connects 5V and 0V switches; The 5th pin of radio frequency switch connects an end of the 3rd electric capacity, the other end of the 3rd electric capacity connects an end of the 4th resistance and first inductance, the other end of first inductance is by the 4th capacity earth, the other end of the 4th resistance connects the 5th resistance and second inductance, the 5th resistance other end ground connection, the second inductance other end connects the base stage and the 4th inductance of triode, the 4th inductance other end connects the 7th resistance and the 6th electric capacity by first resistance, the 7th resistance and the other end of the 6th electric capacity are connected the collector electrode of triode respectively, and digital television signal is from the collector electrode output of triode; The emitter of triode is respectively by the 5th electric capacity and the 6th grounding through resistance.
2. the control circuit of digital cable TV according to claim 1 and digital terrestrial television integral high frequency head is characterized in that: described radio frequency switch is the AS197 of SKYWORKS company.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2008102029969A CN101742137B (en) | 2008-11-19 | 2008-11-19 | Control circuit for integral high frequency head between digital cable television and digital terrestrial television |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2008102029969A CN101742137B (en) | 2008-11-19 | 2008-11-19 | Control circuit for integral high frequency head between digital cable television and digital terrestrial television |
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| Publication Number | Publication Date |
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| CN101742137A CN101742137A (en) | 2010-06-16 |
| CN101742137B true CN101742137B (en) | 2011-09-28 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US8854111B2 (en) * | 2012-08-29 | 2014-10-07 | Richwave Technology Corp. | RF switch with adaptive drain and source voltage and associated method |
| CN103237241A (en) * | 2013-05-09 | 2013-08-07 | 无锡北斗星通信息科技有限公司 | Double-mode television (TV) capable of receiving ground TV signals and network TV signals |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1946155A (en) * | 2005-10-09 | 2007-04-11 | 广达电脑股份有限公司 | Tuner module |
| CN2932870Y (en) * | 2006-02-21 | 2007-08-08 | 成都旭光科技股份有限公司 | Electronic tuner for receipt of both analog and digital TV signals |
| CN101039390A (en) * | 2007-04-09 | 2007-09-19 | 海尔集团公司 | Method for switching digital/analog signal reception and television for realizing the function |
| CN101193218A (en) * | 2006-11-21 | 2008-06-04 | 青岛海信电器股份有限公司 | TV set for receiving digital signals and analog signals |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1946155A (en) * | 2005-10-09 | 2007-04-11 | 广达电脑股份有限公司 | Tuner module |
| CN2932870Y (en) * | 2006-02-21 | 2007-08-08 | 成都旭光科技股份有限公司 | Electronic tuner for receipt of both analog and digital TV signals |
| CN101193218A (en) * | 2006-11-21 | 2008-06-04 | 青岛海信电器股份有限公司 | TV set for receiving digital signals and analog signals |
| CN101039390A (en) * | 2007-04-09 | 2007-09-19 | 海尔集团公司 | Method for switching digital/analog signal reception and television for realizing the function |
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