CEA-909 is the ANSI standard for 8VSB/ATSC smart antennas. The basic concept is that the smart antenna either physically rotates toward the signal, or is stationary, but has elements pointed in different directions and uses only those elements that maximize the received signal. This is accomplished by feedback from the control device, such as a digital-to-analog converter box, telling the smart antenna when the signal is stronger or weaker.
Analog televisions generally give instant feedback as the signal gets better or worse as you move the antenna. Digital television antennas can be difficult to aim correctly because of the cliff effect and because of delays in decoding and displaying the signal. Smart antennas remove the burden of positioning the antenna for digital TVs and can make the tuning process easier than it was with analog television.
There are two basic modes of operation for a CEA-909 antenna, mode A and mode B. Mode A allows for communication only from the tuner to the antenna and Mode B allows for bidirectional communication. A 14-bit pulse-width modulation data stream is sent to the antenna and if the antenna is mode B a 10-bit data stream is sent back. The timeout period for a response from a mode B antenna is 100 ms. The system uses a single wire for communication, possibly similar to I²C.
The 10 bits sent back from the antenna are largely unused. Only the first two bits are used with at least one of those being used for a transmission error flag; the remaining 8 bits are reserved. The contents of the 14 bits sent to the antenna are not revealed.
CEA-909-A is an update to CEA-909 that enables a single coaxial cable to connect smart antennas to smart antenna-capable DTV sets. A weakness of CEA-909 was that it required another control cable in addition to the coaxial cable. This revision was first approved by the Consumer Electronics Association R4 Video Systems Committee on 6 June 2007 and ANSI public review closed on 1 October 2007. After editorial review, it was published in December 2007.
The CEA R4 Video Systems Committee published this update in September 2010. Purchase price for the full publication is $81.
The data timing of the specification is divided into 125 μs symbol periods between 5 VDC for V_Hi and 0 V for V_Low. The PWM Logic 0 is V_Hi for the first 41.7 μs followed by V_Low for the rest of the symbol period while Logic 1 is V_Hi for the first 81.3 μs (V_Low for the rest). The preamble should send V-Hi for three periods then V_Low for one period then a logic 1 start bit.
The 14-bit data breaks down sequentially as follows:
Two bits for coarse direction or switching control, MSB sent first.
Two bits for fine direction control, MSB sent first.
One bit for polarization control
Two bits for preamp gain. The state 1,1 shall be maximum gain, state 0,0 minimum gain, and remaining states progressing monotonically.
7 bits for RF channel number (per CEA-542-B ), MSB sent first. (Note: this could allow for channel assignment from 0 to 127, but it is artificially limited to the range 2–69 and the post-transition channel range will be 2–51)
After the data is sent the system should send V_Low for 1 period and wait until next RF channel change (with a minimum of 10 ms between data streams to allow for the antenna controller logic to reset).
This means channels should be able to change and reset as fast as every ≈12.5 ms (≈80 Hz) or every channel in 0.85 seconds and with 16 'virtual' antennas (32 with two polarization states).
After the above rigorous, seven year standardization process by the Consumer Electronics Association leading up to the deployment of ATSC Digital television in the United States on June 11, 2009, two smart antenna models were brought to market:
And two models are causing consumer confusion:
The United States National Telecommunications and Information Administration (NTIA) ran a coupon-eligible converter box (CECB) subsidy program for the ATSC conversion, but did not subsidize the purchase of a smart antenna to mitigate the cliff effect of digital television, and many CECBs do not support smart antennas.
The official specifications are available for purchase from Global Engineering Documents.
A coupon-eligible converter box (CECB) was a digital television adapter that met eligibility specifications for subsidy "coupons" from the United States government. The subsidy program was enacted to provide over-the-air television viewers with an affordable way to continue receiving free digital over-the-air television services after the nation's television service transitioned to digital transmission and analog transmissions ceased. The specification was developed by the National Telecommunications and Information Administration (NTIA), with input from the broadcast and consumer electronics industries as well as public interest groups.DVD recorder
A DVD recorder is an optical disc recorder that uses optical disc recording technologies to digitally record analog or digital signals onto blank writable DVD media. Such devices are available as either installable drives for computers or as standalone components for use in television studios or home theater systems.
As of March 1, 2007 all new tuner-equipped television devices manufactured or imported in the United States must include an ATSC tuner. The US Federal Communications Commission (FCC) has interpreted this rule broadly, including apparatus such as computers with TV tuner cards with video capture ability, videocassette recorders and standalone DVD recorders. NTSC DVD recorders are undergoing a transformation, either adding a digital ATSC tuner or removing over-the-air broadcast television tuner capability entirely. However, these DVD recorders can still record analog audio and analog video.
Standalone DVD recorders have been relatively scarce in the United States due largely to "restrictions on video recording."Modified Modular Jack
The Modified Modular Jack (MMJ) is a small form-factor serial port connector developed by Digital Equipment Corporation (DEC). It uses a modified version of the 6P6C modular connector with the latch displaced off-center so standard modular connectors found on Ethernet cables or phone jacks cannot accidentally be plugged in. MMJ connections are used on Digital minicomputers, such as the PDP-11, VAX and Alpha systems, and to connect terminals, printers, and serial console servers.
The MMJ connector has six conductors, using a superset of the RS-423 serial communication standard. The six pins are Tx and Rx for the data transmission, their return paths, and DSR and DTR for handshaking. The transmit and receive signals are differential, i.e. each signal is the voltage difference between the line and its associated ground, as opposed to a voltage on a single connector relative to a common reference. The system can also emulate RS-232 signaling by combining the lower voltage sides of each signal to the RS-232 signal ground line.
When connecting two DTE devices such as a computer and a printer, the Digital BC16E crossover cable is used.
Thrustmaster is also using the MMJ connector for connecting its line of rudder pedals and racing pedals to either USB via a proprietary Thrustmaster Adapter, or directly to a joystick or racing wheel.
The more recent Lego Mindstorms sets, beginning with the NXT, used similar plugs for motors and sensors to prevent phone lines being plugged in.
CEA-909 uses the MMJ connector for control signals to a smart antenna, which can either physically or electrically rotate for maximum signal strength.Smart antenna
Smart antennas (also known as adaptive array antennas, digital antenna arrays, multiple antennas and, recently, MIMO) are antenna arrays with smart signal processing algorithms used to identify spatial signal signatures such as the direction of arrival (DOA) of the signal, and use them to calculate beamforming vectors which are used to track and locate the antenna beam on the mobile/target. Smart antennas should not be confused with reconfigurable antennas, which have similar capabilities but are single element antennas and not antenna arrays.
Smart antenna techniques are used notably in acoustic signal processing, track and scan radar, radio astronomy and radio telescopes, and mostly in cellular systems like W-CDMA, UMTS, and LTE.
Smart antennas have many functions: DOA estimation, beamforming, interference nulling, and constant modulus preservation..