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1、Electronic Industries Association August 5,1997 - ERRATA TO: Recipients of New Standards and Engineering Publications To all those who received the originai mailing of EMS-105.1 “Decoder Interface Standard“. Due to a typographical error in the title, replacement document cover page, recipient letter
2、 and announcement page are attached. We are sorry for any inconvenience this may have caused. Sincerely, Phillip .otton Engineering Publications Office 2500 Wilson Boulevard Arlington, Virginia 2220 1-3834 (703) 907-7500 FAX (703) 907-750 i Copyright Consumer Electronics Association Provided by IHS
3、under license with CEA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 20:50:03 MDTNo reproduction or networking permitted without license from IHS -,-,- I S T D - E I A IS-LOS=L-ENGL 1777 323qb130 058q840 877 E I z EIA INTERIM STANDARD Decoder Interface Standard EIA/
4、IS-105.1 .JULY 1997 ELECTRONIC INDUSTRIES ASSOCIATION ENGINEEING DEPARTMENT Copyright Consumer Electronics Association Provided by IHS under license with CEA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 20:50:03 MDTNo reproduction or networking permitted without li
5、cense from IHS -,-,- NOTICE EIA Engineering Stank : G E E Figure 4. Expander IF Connection - The Expander has two or more outputs to serve two or more Decoders. It also may, at the manufacturers option, be equipped to provide +12 volt power to the Decoders. This will remove the necessity for a subsc
6、riber using multiple Decoders, to have an individual wail power supply for each. If the Expander provides power, it shall provide +12 volts to power supply connectors, one connector for every IF output provided. Current should be limited to less than 1.0 Amperes on each output. A female connector sh
7、all be provided on the Expander. 6 Copyright Consumer Electronics Association Provided by IHS under license with CEA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 20:50:03 MDTNo reproduction or networking permitted without license from IHS -,-,- EIMS-105.1 Decoders
8、and Feature Units shall preferably be powered from either 1 15 Vac (internal power supply, with ac cord) or +12 VDC. If powered from +12 VDC the maximum current drawn should not exceed 1.0 Ampere. The unit should operate normally with a z Maximum when applied voltage is 50kQ Minimum between O and 9.
9、5 volts port Leakage resistance to ground Shunt capacitance to ground from any 7. ANNEXES 1OOkQ Minimum 500 pF Maximum 7.1 A: Triple Beat Measurement Figure 14 shows the test Set-up for the measuring .tripie beat (TB) distortion product of the expander, as referenced in Table 3. Three CW oscillators
10、, operating at frequencies as shown, are combined. Use of attenuators as shown is recommended in order to minimize interaction between oscillators. The combined output is set to a level of +30 dBmV per carrier, and supplied to the device under test (DUT). Verify that the input to the DUT is free of
11、significant distortion. The amplitude of the TB distortion product appearing 0.5 MHz below the 46 MHZ tone is measured w i t h respect to the amplitude of the 39.75 MHz 46 M Hz 51.75 M Hz 46 M Hz 39.75 51.75 Spectrum analyzer r DUT u Frequency Figure 14. Triple Beat Measurement 46 MHz component. Thi
12、s is the required triple beat product. 26 Copyright Consumer Electronics Association Provided by IHS under license with CEA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 20:50:03 MDTNo reproduction or networking permitted without license from IHS -,-,- - STD-EIA IS-
13、LOS-1-ENGL 1797 = 323qb00 0582b20 352 EMS-1 05.1 7.2 B: Watch and Record Scenarios This appendix illustrates ways in which various watch and record scenarios may be accomplished using the interface. The situations shown with one analog and one digital Decoder are illustrative only. Any combination o
14、f analog and digital Decoders may be used. 7.2.1 B1: Cable Ready TV and VCR with One Decoder Connected to TV I - i Figure 15. Cable Ready TV and VCR with One Decoder Connected to TV (a.) Watch and record same Scrambled channel: Tune channel on TV tuner. Decoder outputs audio and video to TV on V1, A
15、l and A2, and to VCR on V3, A3 and A4. (b) Watch and record two different unscrambled channels: TV and VCR each use their internal IF; IF interface and AVBus not required. (c) Watch a scrambled channel and record a clear channel: Tune scrambled channel on TV tuner. Decoder receives IF input from TV;
16、 Audro and video from decoder to TV on V1, Al and A2. VCR uses its internal IF, audio and video signals. (d) Watch a clear channel and record a scrambled channel: This case requires an IF switch (see figure 18). 7.2.2 B2: Cable Ready TV and VCR with One Decoder Connected to VCR TV inputs on “CR lF,!
17、 % I l I AVBus % I Figure 16. Cable Ready TV and VCR with One Decoder Connected to VCR (a) Watch and record the same scrambled channel: Tune channel on VCR tuner. Decoder outputs audio and video to TV on V1, Al and A2; and to VCR on V3, A3 and A4. 27 Copyright Consumer Electronics Association Provid
18、ed by IHS under license with CEA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 20:50:03 MDTNo reproduction or networking permitted without license from IHS -,-,- EMS-105.1 (b) Watch and record two different unscrambled channels: TV and VCR each use their internal IF
19、; IF interface and AVBus not required. (c) Watch a scrambled channel and record a clear channel: This case requires an IF switch (see figure 18) (d) Watch a clear channel and record a scrambled channel: Tune scrambled channel on VCR tuner. Decoder receives IF input f i - o m VCR; Audio and video fro
20、m decoder to VCR on V3, A3 and A4. TV uses its internal IF, audio and video signals. 7.2.3 B3: Cable Ready TV and VCR with Two Decoders TV inputs on IF/AGC VCR IF/AG V3, A3, A4 % 1 DIGITAL j I DECODER I 1 DECODFR I AVBus Figure 17. Cable Ready TV and VCR with Two Decoders (a) Watch digital channel,
21、record same digital Digital Decoder receives IF fi-om TV and outputs video and audio to TV on V 1, A 1 and A2; audio and video to VCR on V3, A3 and A4 (both TV and VCR are using the TVs tuner). (b) Watch analog channel, record same analog channel: Analog Decoder receives IF from VCR and outputs sign
22、als to TV and VCR as above (both TV and VCR are using VCRs tuner). (c) Watch digital channel, record analog Digital Decoder receives TVs IF and analog Decoder outputs audio and video to VCR on V3, A3 and A4 (TV using the TVs tuner and VCR is using the VCRs tuner). (d) Watch analog channel, record di
23、gital Analog Decoder receives VCRs IF and digital Decoder receives TVs IF. Audio and video to TV analog Decoder on V1, AI and A2; audio and video from digital Decoder to VCR on V3, A3 and A4 (TV using VCRs tuner and VCR is using TVs tuner). 28 Copyright Consumer Electronics Association Provided by I
24、HS under license with CEA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 20:50:03 MDTNo reproduction or networking permitted without license from IHS -,-,- 7.2.4 B4: Cable Ready TV and VCR with One Shared Decoder n/ inputs on I-GiF/AGC VCR V3, A3, A4 for switch speci
25、fications. . 1 DECODER 1 Figure 18. Cable Ready TV and VCR with One Shared Decoder (a) Watch and record the same scrambled channel: Tune channel on either TV or VCR tuner and switch decoder input to appropriate IF. Decoder outputs audio and video to TV on V1, Al and A2, and to VCR on V3, A3 and A4.
26、(b) Watch and record two different unscrambled channels: TV and VCR each use their internal IF; IF interface and AVBus not required. (c) Watch a scrambled channel and record a clear channel: Decoder receives IF input from TV; VCR uses its internal IF, audio and video signals. Audio and video from de
27、coder to ?Ir on V1, Al and A2. (d) Watch a clear channel and record a scrambled channel: Decoder receives IF input from VCR and outputs audio and video to VCR on V3, A3 and A4. TV processing is all internal. 29 Copyright Consumer Electronics Association Provided by IHS under license with CEA License
28、e=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 20:50:03 MDTNo reproduction or networking permitted without license from IHS -,-,- EMS-105.1 7.2.5 B5: Cable Ready TV and VCR with Two Shared Decoders c TV inputs o VCR inputs on V3, A3, A4 Figure 19. Cable Ready TV and VCR wit
29、h Two Shared Decoders (a) Watch digital channel, record same digital channel: Digital Decoder receives either TV or VCR IF and outputs video and audio to TV on V1, Al and A2; Decoder outputs audio and video to VCR on V3, A3 and A4. (b) Watch analog channel, record same analog channel: As above but a
30、nalog Decoder receives wither TV or VCR IF and outputs audio and video as above. (c) Watch digital channel, record analog channel: Digital Decoder receives TV IF and analog Decoder receives VCR IF. Digital Decoder outputs audio and video to TV on V1, Al and A2 Analog Decoder outputs audio and video
31、to VCR on V3, A3 and A4. (d) Watch and record two different clear channels: TV and VCR use internal Ifs and tune to required channels. No IF interface nor AVBus required. 7.3 C: LoopDynamics This section includes information that should be useful in understanding the intended operation of the delaye
32、d AGC loop. In the mode in which the Decoder is controlling video demodulation, it must generate the delayed AGC signal used by the Receiver front end. This makes the dynamic performance of the AGC loop partially the domain of the Receiver, and partially the domain of the Decoder. In order for this
33、to work, this document has attempted to outline a set of characteristics that should permit a stable loop under all conditions. This section provides background on how this is to be accomplished. The primary pole in the delayed AGC closed loop response is R1-CI (see figure 3). In order to have essen
34、tially the same pole location regardless of the source of control, resistor R1 must be high compared with R2, the pull-up resistor for the Receiver RF AGC. When the Decoder is not 30 Copyright Consumer Electronics Association Provided by IHS under license with CEA Licensee=IHS Employees/1111111001,
35、User=Wing, Bernie Not for Resale, 03/30/2007 20:50:03 MDTNo reproduction or networking permitted without license from IHS -,-,- EMS-105.1 controlling AGC the output of amplifier Al is at a high impedance (this may be accomplished by disabling the amplifier, or by a switch on the amplifier output). T
36、he signal from the Receiver may also drop close to zero volts, and this should not cause Al to go to a low impedance state. Figure 20 shows a typical delayed AGC curve, TUNER GAIN DELAYED stated in t e m of tuner gain vs. delayed AGC voltage supplied by the Decoder will need to be nine volts plus or
37、 minus 0.5 volts to ensure the noise figure. As the signal increases the system moves to the left on the x-axis, lowering the gain. INPUT To voltage. At high gain (low signai level) the +30dBmV . AGC NOMINAL TO DECODER SiEEPECT j SLOPE, AND HENCE i LOOP GAIN, WILL tuner is operating at maximum gain
38、and lowest CLOPE=X ! VARYOMRA dBNOLT i LARGERANGE The gain vs. voltage curve becomes very non =20 1 VOLT linear. Since this is a component in the loop gain 9v DELAYED VOLTAGE MIN NOMINAL AGC of the delayed AGC, the loop dynamics are likely to vary considerably as a function of the gain reduction. Th
39、is is not a problem so long as the designer takes the gain into account properly. As a guideline, the maximum slope is specified to be 25 dEVvolt. The Decoder designer must ensure stability with this and all lower gains. Granted the loop dynamics will be particularly sloppy at some points, but this
40、should not be a problem, as the signal level on the cable should not change rapidly. Figure 20. Delayed AGC Cuwe In order to ensure that the delayed AGC threshold is placed where the tuner manufacturer intends, there must be a standardized IF level at the interface. This will allow the Decoder desig
41、ner to accurately control the onset of delayed AGC control, while allowing the tuner manufacturer to set gain and AGC take-over (at the input) at a point deemed most suitable. Note however, that there is a tolerance to the maximum IF output level of the tuner, and the Decoder on-set of delayed gain
42、control. If the Receivers IF output is at the low end of the tolerance and the Decoder is at the high end of its tolerance, the tuner could be operating at 4 dE3 more output than intended, causing the third order distortion ratios (CTB, crossmodulation, etc.) to be 8 dB higher than expected. Of conc
43、ern too, is the need to ensure that the Decoder can effect a sufficiently wide gain control range. To so ensure, the specification includes the minimum delayed AGC voltage that should occur when the input to the Receiver is +20 BmV. This permits the Decoder designer to know that the delayed AGC volt
44、age can be controlled at the highest signal level anticipated. Nothing disastrous should happen if the signal level exceeds +20 BmV, though the Decoder could loose gain control ability above this level, allowing the distortion characteristics of the tuner to increase to undesirable levels. 31 Copyri
45、ght Consumer Electronics Association Provided by IHS under license with CEA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 20:50:03 MDTNo reproduction or networking permitted without license from IHS -,-,- EMS-1 05.1 Figure 21 shows the operating range of the IF outp
46、ut Receiver-Decoder system. At low input levels (dBmV) (toward the left in the figure) the tuner exhibits a certain gain, determined by the tuner manufacturer +32 +30 within limits. That minhum gain is +24 dB, +28 measured from the Receiver?s input to the IF output from the Receiver to the Decoder.
47、The minimum gain value allows a reasonable noise +24 figure for the Decoder, consistent with high carrier to noise ratio. In most practical cases the gain will be higher. RF input O +15 (dBmV) As the input level increases, the Receiver?s IF output increases proportionally until the output is +30 BmV
48、, which is defined as the delayed AGC threshold. It is controlled in two parts: First, the Decoder manufacturer will hold the delayed AGC volage high (+9 volts nominal) until the Receiver?s IF output reaches +30 BmV. At this point, the Decoder begins reducing the delayed AGC voltage to hold the Receiver?s IF output constant. Next, the tuner manufacturer will determine the delayed AGC threshold for the tuner, by controlling the gain to the Decoder port. e r a t i n g