Prototype constant-efficiency amplifiers

This paper describes two Constant Efficiency Amplifiers (CEA) using cathode s, novel grids and novel cavities similar to those used in our Inductive Ou tput Tubes together with five-electrode, multi-stage, depressed collectors in either Poly Alpha Olefin (PAO) oil-cooled or forced-air-cooled versions. The air-cooled version is capable of 65 kW peak 8VSB or COFDM operation, a nd the oil-cooled tube will provide the performance of our higher power IOT s in either 8VSB, COFDM or NTSC service with much higher average efficiency . PAO oil (similar to synthetic automobile engine oil) is a low-cost coolan t that simultaneously solves insulation and corrosion problems. These tubes meet the expectations that were discussed in our 1997 and 1998 NAB papers. Design and performance are described together with application data useful to transmitter designers. Collectors may be connected together to minimize the number of independent voltages required or operated indepen dently to maximize efficiency and minimize power supply size for a wide var iety of signal statistics. A single Thyratron crowbar circuit which will si multaneously short circuit up to five voltage sources is described. The CEA design and its application are covered by U.S. and foreign patents issued and pending. Adoption of this technology win save television broadcasters i n the order of one billion dollars of electrical power cost over the life o f these patents.