Charles W. Rhodes

Planning factors for fixed and portable DTTV reception

The transition plan from the analog (NTSC) to digital terrestrial television (DTTV) in the USA was based on a simplified version of the Longley-Rice service prediction algorithm, and a link budget that mimicked the traditional planning factors for NTSC. It is now clear that the service prediction and the link budget both have serious shortfalls. This paper provides the formalism required for the development of realistic link budget and service grades for fixed and portable DTTV reception.

Interference between television signals due to intermodulation in receiver front-ends

With the introduction of Digital Television Broadcasting (DTV) the use of UHF Taboo channels and the first adjacent channels plus those already allotted to a community has become necessary due to spectrum scarcity. Most of the UHF Taboos are due to nonlinear interference mechanisms, which were, and still are characteristic of consumer receivers. Those mechanisms result in third and higher odd-order Intermodulation products some of which fall in the desired TV channel. Crossmodulation is a lesser problem than Intermodulation. Broadcasters need to understand these interference mechanisms to minimize their loss of service area. This knowledge may help them in choosing the future channel they will use for DTB broadcasting. This paper attempts to quantify these interference problems.

Some recent improvements in the design of DTV receivers for the ATSC standard

The DTV receiver and its antenna are viewed as a receiving system and it is improvements to this receiving system which are addressed. It appears possible to improve the signal-strength problem primarily with improvements in the antenna part of the system by means of a low noise preamplifier at the antenna, (active directional antennas) and to improve the multipath handling within the receiver. Improved receiver tuner design can also deal with the field strength problem. Adaptive antennas for diversity reception can also contribute to solving the multipath problems as shown.

DTV coverage and service prediction, measurement and performance indices

It is now clear that methods used to predict the replication of the NTSC service in the United States were idealized and, for the most part, not validated. The need to review the methods and procedures now in use is highlighted by the various field tests conducted in the U.S. and elsewhere. This paper outlines potential improvements in the modeling, methods and procedures now in use for prediction and measurement of the DTV service.

The 12.5T Modulated Sine-Squared Pulse for NTSC

In 1965 P. Wolf of the Institute fur Rundfunktechnik, Munich, Germany, made a significant contribution to the measurement of encoded color television signals with his introduction of the 20T modulated sine-squared pulse. It possesses the ability to measure relative chrominance gain and delay, or color misregistry. This signal enjoys widespread operational use abroad. Interest in a modulated sine-squared test signal for NTSC is at present quite significant. A properly scaled test signal for NTSC is presented. The proposed signal is properly called 12.5T modulated sine-squared pulse. Compared to a 20 T, it offers: 1) an increased sensitivity to relative chroma delay, and 2) a simple scale factor for 12.5T; ?= 10d, and for 20T; ?=15.9d. Nomographs are provided for both the 20T and 12.5T modulated sine-squared pulses for NTSC. Mathematical derivation for the waveform distortion as a function of delay distortion is given in terms of the significant pulse parameter.

Interference to DTV Reception due to Non-Linearity of Receiver Front-Ends

Terrestrial television broadcasting has always been an interference limited service. In 2009, the FCC plans to end analog TV transmissions by full power TV stations in the USA and to reduce the broadcast TV spectrum and to allow sharing of the remaining TV broadcast spectrum by unlicensed devices. DTV signals will use first adjacent channels in the same community and there will be no UHF taboos to protect against interference which results from receiver non-linearity, especially that due to multiple signals on certain channels which results in 3rd order intermodulation products which fall in the channel to which the receiver is tuned. This paper will explain the problems caused and suggest means to improve receiver performance .

Non-Invasive Testing Methods to Determine the RF Performance of Consumer DTV Receiving Appliances

Terrestrial DTV transmissions will be interference limited, not noise-limited in most cases. Methods to determine receiver robustness to interference are discussed and novel techniques which are non-invasive are disclosed.

New Challenges to Designers of DTV Receivers Concerning Interference

Growing needs for suitable spectrum sought by wireless service providers has led the Federal Communications Commission to propose sharing of broadcast spectrum by unlicensed transmitters. Such transmitters could operate on any locally unused TV channel. Signals from nearby transmitters may cause interference to DTV receiver operation.

Future spectrum demands will impact DTV and GPS receiver designs

Inefficient spectrum usage was historically acceptable because receiver complexity and cost could be minimized. Today, new demands for RF spectrum, especially to accommodate new broadband wireless services, require a change in the design philosophy of consumer receivers due to ever increasing interference in our limited RF spectrum.

Some Practical Problems in Implementing the Vertical Interval Reference Signal in Broadcasting

The VIR Signal, when applied as a program related signal, can be an effective means of reducing unwanted color variations in NTSC broadcasting. A number of technical problems must be overcome before widespread use of the VIR Signal by the broadcasting industry will bring full benefit to the public.