1、 ANSI/CEA Standard Antenna Control Interface ANSI/CEA-909-B January 2011 NOTICE Consumer Electronics Association (CEA) Standards, Bulletins and other technical publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitat
2、ing interchangeability and improvement of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his particular need. Existence of such Standards, Bulletins and other technical publications shall not in any respect preclude any member or nonmember
3、of CEA from manufacturing or selling products not conforming to such Standards, Bulletins or other technical publications, nor shall the existence of such Standards, Bulletins and other technical publications preclude their voluntary use by those other than CEA members, whether the standard is to be
4、 used either domestically or internationally. Standards, Bulletins and other technical publications are adopted by CEA in accordance with the American National Standards Institute (ANSI) patent policy. By such action, CEA does not assume any liability to any patent owner, nor does it assume any obli
5、gation whatever to parties adopting the Standard, Bulletin or other technical publication. Note: The users attention is called to the possibility that compliance with this standard may require use of an invention covered by patent rights. By publication of this standard, no position is taken with re
6、spect to the validity of this claim or of any patent rights in connection therewith. The patent holder has, however, filed a statement of willingness to grant a license under these rights on reasonable and nondiscriminatory terms and conditions to applicants desiring to obtain such a license. Detail
7、s may be obtained from the publisher. This CEA Standard is considered to have International Standardization implication, but the International Electrotechnical Commission activity has not progressed to the point where a valid comparison between the CEA Standard and the IEC document can be made. This
8、 Standard does not purport to address all safety problems associated with its use or all applicable regulatory requirements. It is the responsibility of the user of this Standard to establish appropriate safety and health practices and to determine the applicability of regulatory limitations before
9、its use. (Formulated under the cognizance of the CEA R4 Video Systems Committee.) Published by CONSUMER ELECTRONICS ASSOCIATION 2011 Technology Phone 800-854-7179; Fax 303-397-2740; Internet http:/; Email 2.2 Informative References The following standards contain provisions that, through reference
10、in this text, constitute informative provisions of this standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions
11、of the standards listed in Section 2.2.1. 2.2.1 Informative Reference List 4. ANSI/SCTE 02 2006 “Specifications, F Connector, Female, Indoor,” 2.2.2 Informative Reference Acquisition ANSI/SCTE Standards: Society of Cable Television Telecommunications Engineers (SCTE), 140 Philips Road, Exton PA 1934
12、1; Phone 800-542-5040; Fax 610-363-5898; Internet http:/www.scte.org; Email infoscte.org 3 Introduction The antenna control interface specified in this document enables the receiving system, which includes both the antenna and the DTV receiver, to provide improved digital television reception. CEA-9
13、09-B describes a means to optimize a suitably designed receiving antennas directional pattern, gain, polarization, and tuning for each channel. Control of the antenna parameters is via a serial bitstream issued by the receiver over one of two defined interfaces: a separate dedicated connector or the
14、 antenna CEA-909-B 2input coaxial connector. The determination of optimum antenna pattern, gain, etc. is achieved within the receiver by analysis of the received signal at different antenna settings. The search algorithm to determine the optimum setting is not specified in this document, and creatin
15、g a rapid and effective search routine is expected to be a point of competition among manufacturers. Determination of the optimum antenna parameters involves more than simply maximizing the signal level. The interface in this document inherently treats the receiver and antenna as a single system. De
16、modulators in digital TVs can regard the antenna as an additional controllable resource, beyond gain control, equalization, error correction, etc. to improve signal recovery. For example, the null(s) in an antenna pattern can be steered to reduce some difficult multipath or reduce the level of inter
17、ference from a particular direction. Receivers following this Standard can determine optimum antenna settings by analyzing the received signal, using metrics already part of the digital demodulation process. Such metrics include, but need not be limited to, bit or packet error rate, equalizer activi
18、ty, S/N, and signal level. Different metrics may be more appropriate at different points in the search for the optimum setting, since some metrics may indicate an undesirable setting more rapidly. While not part of this Standard, the following comments are offered regarding the analysis of the recei
19、ved signal and the achievement of a quick and accurate search for the optimum antenna setting: In order to achieve the performance intended by this Standard, it is necessary that the signal quality be analyzed at different antenna settings. Analysis of any state cannot be complete until the equalize
20、r, AGC, and other conditions have stabilized. Some metrics may be available more quickly than others and might be used to maximize speed of optimization, but conclusions about signal quality should be regarded as tentative until all metrics are known. Commands that change the antenna state should no
21、t be issued until analysis of the present state is complete. A 10 msec “pause” is specified between issuances of the serial bitstream. This is to be regarded as a minimum and is intended only to allow the antenna logic and control time constants to settle with a side benefit of enabling shorter prod
22、uction sample test times. Analysis of the signal by the receiver is likely to take longer than this, and signal analysis should begin after this settling time. The most useful search algorithms are unlikely to be those that simply step through all available states in sequence. While much of this doc
23、ument is written from the standpoint of a receiver controlling an electrically steered antenna with no moving parts, the Standard also defines an optional command sequence that can be used to control a mechanically steered (rotor) antenna. 4 Initialization The initialization process differs dependin
24、g on whether or not the TV supports control over the coax ( see section 7.2) or control via a separate dedicated connector (see section 7.1) In both cases, the TV sends interrogations to an antenna. When a smart antenna is detected per 7.1.2 or 7.2.2 the DTV receiver shall determine the operating mo
25、de. The process for this determination is defined in section 8 and its subsections. In case of communication over the antenna coax, before applying power and control voltage, a test is required to be performed by the DTV receiver to see whether a smart antenna is connected to the coaxial connection.
26、 This test is explained in section 7.2.2 and its subsections. NOTE Designers are cautioned that incidental RF energy on the antenna control connector may significantly affect antenna performance, and therefore, efforts should be made to minimize the presence of incidental RF energy on this interface
27、. CEA-909-B 35 Data Signaling Characteristics 5.1 Transmission Rate The data transmission rate shall be 8 kHz 5%. 5.2 Symbol Rate The symbol rate shall be 1 bit per symbol. 5.3 Symbol Period The symbol period shall be 125 microseconds (s) 5%. 5.4 Symbol Rise other devices that might plausibly be con
28、nected inadvertently to the single-wire smart antenna interface will not have such a diode. See the example functional block diagram in Figure 16 in Annex A, section A.3. Because of the diode, at a test voltage of 0.3 V (or other voltage below the diode conduction threshold) the current drawn by the
29、 smart antenna is negligible compared to the current drawn by other devices such as signal splitters, passive antenna balun transformers or certain active devices, such as some types of set top boxes. At a test voltage above the diode threshold (for example, 2 V), both the smart antenna and other de
30、vices will draw easily measurable current. The means by which the test voltages can identify a smart antenna from other devices can be understood from the diagram of Figure 4.This diagram shows two overlapping regions, one for the smart antenna and one for other devices that might be connected to th
31、e TV receiver. The region of smart antenna resistance represents the range of currents that may be drawn by a smart antenna at various voltages. Passive devices such as splitters are expected to have a maximum resistance of 225 ohms, which determines the left edge of the region of passive device res
32、istance. The exception to these rules is the case of a device that presents an open circuit to the connection at DC. CEA-909-B 9Signal High14V to 17.5 VSignal Low10.8V to 13.2 VTest Low0.2V to 0.4VTest High1.8V to 2.2V150 mA15 mAZero Ohms225OhmsRegion of Smart Antenna Resistance (with one Si diode)R
33、egion of Passive Device ResistanceOpenCircuit1/16 Watt LineFigure 4 Antenna Impedance Regions The 1/16 W limit line is shown as an indication of an upper dissipation limit to protect devices other than a smart antenna that may be connected. Since the instantaneous power to be supplied to a smart ant
34、enna is a maximum of 2.1 W (14 V x 150 mA), it must be controlled so that it is not applied to other devices. This may be done by sensing the current drawn by a connected device when the two lower test voltages (0.3 V and 2.0 V) are applied, and then applying full power based on the detection of no
35、conduction at the lower test voltage and conduction at the higher test voltage. As shown in the diagram, neither test voltage will dissipate more than 1/16 W in the connected device, provided current is limited to 30 mA. When a smart antenna has been detected, the receiver may apply the full supply
36、and signaling voltage. However, the receiver should also detect when supplied current drops to zero (indicating a disconnect), and return to the test-voltage mode until the presence of a smart antenna can be re-verified. Since the antenna control signals are generated by varying the supplied voltage
37、 to the smart antenna, the smart antenna must include means to utilize the varying supply without compromising performance. The AC input impedance of the smart antenna must also be high enough so that it does not require excessive transient current (above 200 mA) from the receiver during signaling p
38、ulses. In addition, the smart antenna should draw sufficient current under normal operation to be easily distinguished from an open circuit. CEA-909-B 108 Communication Modes This standard describes two modes, one called mode A, which is a one-way serial data stream, and mode B, which is a two-way (
39、single duplex) data stream, which provides two-way communication. The symbol rate (in both directions) and relative signaling voltages for Mode B shall be the same as for Mode A. Mode A is mandatory and mode B is optional. 8.1 Mode Detection After detection that a CEA 909 antenna is present per 7.1.
40、2 or 7.2.2, a receiver that supports mode B shall use the following handshaking sequence to establish whether to use Mode A or Mode B operation. 1) The DTV receiver shall transmit a Mode A serial data stream per section 8.2 with all RF channel number bits set to 0 (zero). The DTV receiver shall star
41、t a 100 ms timeout for the antennas reply. No acknowledgement (from the antenna) within the timeout period shall result in Mode A operation. 2) A mode B-capable antenna shall communicate its capability by using a reply format per the signaling voltage and timing parameters as defined in section 5, w
42、ith a start bit per followed by a message length of 10 bits containing a code value defined in or allowed by Table 2. The last bit shall be sent not later than 90ms after the receipt of the transmission per (1) immediately above. After sending the last bit the antenna shall start a 100 ms timeout fo
43、r a reply from the DTV receiver. A reply from an antenna containing a Mode B Program Code (see 8.3.1) shall indicate to the DTV receiver that a Mode B-capable antenna is connected. See section 8.3 for mode B operation. Figure 5 Mode B Antenna Response Signal 8.2 Mode A The logic line shall be set in
44、itially at V_low. Upon changing RF channels (or after an antenna detection sequence), the TV shall transmit the serial digital data stream described in this section and diagrammed in Figure 6. CEA-909-B 11sec0 500 1000 1500 2000Power up however, the presence of both modes would be preferable. Some r
45、eference applications follow in Annex A (Informative). Reference designs are in Annex B (Informative). CEA-909-B 17Annex A Examples (Informative) Some examples of circuits that may be used to implement CEA-909 are included in Annex A (informative). These are examples only, and in no way are they int
46、ended to be or represented as final or production ready designs. These examples provide an introduction to the interface and allow designers to begin evaluating the interface. A.1 Example 1 - TV Emulator/Data Stream Transmitter Figure 7 shows a programmable processor used to generate the data stream
47、. A series of 14 DIP switches are used to set each respective bit of the serial data stream with LEDs giving a visual indication of the settings. Switch SW1 emulates Mode A of the interface. With each push of SW1, a single data stream is sent out. SW2 enables a repeating data stream with a period of
48、 approximately 8 ms. This mode can be used for experimentation and circuit development. CEA-909-B 18+5V+5V+5V+5V+5V+5VSI P 4Z86D8608P27P26P25P24P23P22P21P20P37P36P35P34P33P32P31PREF1P07P06P05P04P03P02P01P00XTAL1VDDVSSXTAL2Re v 1Pulse Width Modulator6/ 28/ 01C8.1UF.1UFC6C5.1UFP36P37321282726252416171
49、51413121118765423212019108229U1P35P34P22P21P27P26P25P24P23P26P25P24P23P22R3 010K4321J1CR9P01P0210KR27P0010KR2 5150R1 0CR1 1R2 810KCR1 2150R1 1CR1 3R1 215010KR2 9C710UFR2 410K10KR2310KR2 110KR1 9P00P0147KR1 49 8765432161514131211101SW31101112131415162345678 9SW4R6150R5150R4150R3150R2150R1150R1 6150R1 5150TP2TP1C4.01UF.1UFC3C127PFC227PFY14MHZSW1R1347KCR1 4SW2CR1CR2CR3CR7CR6CR5CR4CR8150R7R8150R9150CR1 0P0210KR1 7R1 810KR2 010KR2 210KR2 610KP20P21P27P20.1UFC9Figure 7 TV Emulator Data Stream Transmitter CEA-909-B 19The output stream
