20-WATT X-BAND SOLID-STATE TWTA REPLACEMENT
International Telemetering Conference Proceedings / October 22-25, 1984 / Riviera Hotel, Las Vegas, Nevada === In the past, traveling wave tubes have dominated the power amplifier field in space flight transmitter applications. TWTAs however, are expensive, and high-power TWTAs may be relatively u...
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| Language: | en_US |
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International Foundation for Telemetering
1984
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| Online Access: | http://hdl.handle.net/10150/611467 http://arizona.openrepository.com/arizona/handle/10150/611467 |
| Summary: | International Telemetering Conference Proceedings / October 22-25, 1984 / Riviera Hotel, Las Vegas, Nevada === In the past, traveling wave tubes have dominated the power amplifier field in space flight
transmitter applications. TWTAs however, are expensive, and high-power TWTAs may be
relatively unreliable when considering end-of-mission operating requirements of up to
10 years and longer.
Recent improvements in reliable solid-state designs including Gallium Arsenide FETs have
resulted in efficient X-band devices which operate at multi-watt levels. A number of these
devices would be combined in parallel to achieve the power output desired.
This paper discusses the development of an efficient 20 watt X-band solid-state power
amplifier to be used as a TWTA replacement for space flight applications.
The 20-watt assembly shown in Figure 1 consists of two stand-alone, 8-channel, 11-watt
assemblies operating in parallel through a 2-way switched power combiner. Particular
emphasis is placed on the power amplifiers and a one-step, 8-way power divider/combiner
pair. Each power amplifier channel has 3 stages of gain and develops 1.6 watts of RF
output with 18 dB of compressed gain. A driver amplifier module provides additional
system gain and a 0.5-watt drive level for the high power sections.
The GaAs FET devices utilized are from the output of a device improvement program
which has a goal of a minimum power added efficiency of 40%. The one-step combiner
utilizes a novel technique to achieve a combining efficiency of 90%. The full system,
including the DC-DC power converter, yields an overall system efficiency of 25%.
A thermal sensor in the power conditioner is used to hold amplitude variations to ±0.3 dB
from 0 to 50°C and phase variations to ±10° over the same range.
The assembly also operates in a low power mode producing 9 watts of RF when only one
11-watt assembly is powered and the switched combiner open circuits the off channel. |
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