42 8

The calculations of small-signal gain from the measured phase velocity on several existing tubes are compared with the mea- sured gain, and a good correlation between the theoretical and measured gain is ob- tained.

4) Measurement and Evaluation of a High- Power Traveling-Wave Amplifier in Multicarrier Operation-?-. B. Brown of Hughes Aircraft Go., Los Angeles, Calif.; G. M . Koch and G. Kadar of R C A Viclou Go. Ltd., Montreal, Quebec, Canada. The multicarrier communication mea-

surements performed on a high-power broad- band traveling wave amplifier are described.

The technical requirements for FM multicarrier operation of satellite communi- cation links are now being established and these requirements depend heavily on the components presently available. One of the important but previously unevaluated com- ponents is the high-power wide-band ampli- fier for the ground stations. The measure- ments describe the performance of a new high-power traveling-wave amplifier in wide- band multicarrier operation.

The amplifier upon which the measure- ments were made was the recently developed Hughes 614H, an 8-kW traveling-wave am- plifier designed for ground transmitters in the 5.925 to 6.425 GHz band. ,4 general de- scription of the amplifier and measurement setups are included.

The measurements were made through a cooperative effort of RCA4 Victor Co. and Hughes Aircraft Co. and include third-order distortion, noise-power ratio, and crosstalk for two-carrier operation and noise-power ratio for four equally spaced carriers (two modulated and two unmodulated) over a 200-MHz bandwidth. Other parameters such as gain and power output for multicarrier operation AX-PM conversion factor, and group delay were also measured. The knowl- edge of these parameters enables the system designer: 1) to predict the operational char- acteristics of the power amplifier and 2) to optimize the available noise budget versus channel capacity and number of modulation carriers.

5 ) A 250-Watt CW Helix with Vapor-Phase Cooling for Use in Community Antenna Television Systems at 18 GHz-J. W. Hansen and L. T . King, Hughes Aircraft Co., Torrance, Calq. Development of a long-life 250-watt

high-reliability T W T for community an- tenna television systems is described. The system is amplitude modulated with carrier frequencies in the 18-GHz region. The na- ture of the modulation employed places stringent requirements on the intermodula- tion and spurious modulation in the TWT. Design details are described which permit operation with both intermodulation and spurious modulation a t 50 dB below the 0.5 watt carriers.

Long life and reliability are achieved through use of large area compression in the electron gun as well as through use of vapor- phase ccoling. This cooling ensures that no “hot spots” are encountered in the TiVT. Reliability is enhanced since the system re- quires no pumps or complex cooling pas- sages.

IEEE TRANSACTIONS ON ELECTRON DEVICES, JUKE 1968

Operation with a low-perveance electron beam was chosen to keep cathode loading to a low value. Because of the high voltage of operation, it is necessary to suppress any tendency for the TLVT to oscillate in the backward mode while at the same time maintaining sufficient gain in the output sec- tion to permit efficient forward-wave inter- action. Techniques employed for suppression of backward wave gain are described.

The solenoid construction is of a unique design made possible by the power-density handling capability of vapor phase cooling. This design makes possible a reduction of any transverse magnetic field components to less than 0.1 percent of the axial field value.

Excellent focusing of the electron beam is made possible by the uniform magnetic field obtained from the solenoid, by design- ing the electron gun for 50 percent immersed flow, and by the use of a precision “strong- back” assembly which serves to maintain helix barrel straightness. The “strongback” assembly also enhances the cooling of the helix barrel.

The TWT and solenoid are housed within a hermetically sealed vessel, which also em- bodies the FC-75 dielectric coolant and the condenser fins, making up a closed system which is easily replaced in the field.

Detailed tube performance data are re- ported.

6) A 100-Watt High-Efficiency TWT for Space Communications6O-L. A . Roberts, TTatkins-Johnson Co., Palo Al to , Galis. A high-efficiency PPM-focused traveling-

wave tube, which is capable of producing 100 watts of CW power output at 2.3 GIHz for space communication use, is described. The achievement of high overall efficiency is the most important aspect of this program since the dc power to the tube represents a major fraction of the total power available on the spacecraft. The tube has produced an over- all efficiency of 45 percent, including heater power, a t power levels between 60 and 100 matts at essentially constant gain. Detailed performance curves will be shown. Efficiency improvement work is continuing and any further results will be reported.

The tube is of metal-ceramic construc- tion and is designed to operate under launch environmental and space thermal-vacuum conditions. I t is mechanically rugged and has demonstrated very low incidental APvI and PM modulation under vibration. Cool- ing of the tube is by conduction. The overall weight of the encapsulated tube is 3.0 Ib.

Laboratory, California Institute of Technology, sgon- u This work was performed for the Jet Propulsion

sored by the h-ational Aeronautics and Space Ad- ministration under Contract NAS7-100.

7) Improved Reliability of TWTs Through the Use of a New Lightweight Heat Re- moval Device-A. Basiulis and M. C. Starr, Hughes Aircraft Co., Torrance, Calif. It has been demonstrated that “heat

pipe” cooling techniques can be applied to TWTs. Since the “heat pipe” will reduce operating temperatures and the temperature drop along the vacuum barrel, improved reliability can be attained. In addition, de- sign flexibility is increased and the overall T\tT weight may be reduced. On a specific

radially focused T W T design, the following improvements were obtained:

1) the radial temperature gradient be- tween the vacuum barrel and the tube hous- ing was reduced to less than 10°C;

2) The axial temperature gradient in the 10-inch-long vacuum barrel was reduced to less than 6OC for a heat flux density variation from 10 watts per linear inch to 100 watts per linear inch;

3 ) the collector’s cooling capacity was improved by reducing its axial and radial temperature gradients.

The “heat pipe” is a static, lightweight device. I t can be designed to operate under zero-gravity conditions. Although originally developed for high-temperature applica- tions, i t is also extremely well suited to the solution of microwave-tube cooling prob- lems. I t has the ability to transfer very high heat fluxes between components and to maintain an isothermal condition over a relatively large area. Several “heat pipe” configurations are described that are ap- plicable to specific T W T cooling problem areas. Among these are radial, axial, re- entrant, and wickless types. Typical working fluids and wick structures are discussed, with analytical results supported by experimental data.

SESSION 18-LARGE-SCALE INTEGRATED ELECTRONICS Panel Discussion Moderator: Richard L. Petritz , Texas

Instruments Incorporated, Dallas, Tex .

Panel &lernbers: J . M. Enrly, Bell Telephone Lab-

oratories, Allentown, Pa. W. E . Harding , I B M East Fish-

kil l Facili ty, Hopewell Junction, N . Y.

Gerald B. Herzog, R C A Labora- tories, Princeton, N . J .

Gordon Moore, Fairchild Serni- conductor , Palo Al to , Cal i f .

J a n A . Narud, Motorola Semicon- ductor , Phoenix , Ariz .

C. G. Thornton, Philco-Ford Mi- croelectronics, B lue Be l l , Pa.

SESSION 19-INTEGRATED ELECTRONICS I V : MICROWAVE Chairman: R. Engelbrecht Organizer: R. R. Webster 1) Beam-Lead Schottky-Barrier Diodes for

Low-Noise Integrated Microwave Mixers-N. P. Cerniglia, R. C. Tonner, G. Berkooits, and A . H. Solomon, Syl- vania Electric Products Inc., Woburn, Mass. Beam-lead technology inherently lends

itself t o integrated microwave devices.