Historically, the term microwave power module (MPM) has been associated with a small, fully integrated, self-contained radio frequency (RF) amplifier that combines both solid-state and microwave vacuum electronics technologies. Typically, the output power of these MPMs is on the order of about 100 Watts CW over an octave bandwidth. Because of their smaller size and lower mass compared to conventional traveling-wave tube amplifiers, these MPMs may have applications in electronic warfare systems.
The MPMs require both a solid-state amplifier at the front end and a microwave vacuum electronics amplifier at the back end; however, such MPMs cannot be utilized for communications because the MPMs are not optimized for linearity or efficiency. Also, the MPMs can be very expensive to manufacture, particularly when modules are produced in very small quantities for space applications. Also, a kilovolt (kV)-class power supply is required to power the traveling-wave tube amplifier, which is a part of the microwave vacuum electronics.
A solid-state MPM that powers radar, communications, and/or navigation interchangeably was developed at NASA’s Glenn Research Center in Cleveland, OH. The high-efficiency, all-solid-state MPM is based on a multi-stage, distributed-amplifier design that is capable of very wideband operation and can last a decade or longer. More compact and lightweight than conventional designs, the module offers further size reduction by eliminating the need for either a traveling-wave tube amplifier or its accompanying kV-class electronic power conditioner.
The MPM features much higher cutoff frequency and maximum frequency of oscillation than metal-semiconductor FETs (field effect transistors) offer, and the distributed amplifier’s wide bandwidth also results in much faster pulse rise times.
How it Works
The MPM includes a number of solid-state amplifiers configured to amplify a signal during a low-power stage, a medium-power stage, and a high-power stage. The low-power stage is a high-efficiency gallium arsenide (GaAs) pseudomorphic high-electron-mobility transistor (pHEMT)-based monolithic microwave integrated circuit (MMIC) distributed amplifier. The medium-power stage is configured to pick up and amplify the low-power signal. This stage can be either another high-efficiency GaAs pHEMT or a gallium nitride (GaN) HEMT-based MMIC distributed amplifier, depending on the need. The high-power stage, configured to pick up the signal from the second amplifier, is a high-efficiency GaN HEMT-based MMIC distributed amplifier that supplants the traveling-wave tube amplifier found in most microwave power modules.
The module also includes a low-power and/or low-noise amplifier, medium-power amplifier, and a high-power amplifier. The low-power and/or low-noise amplifier is configured to receive a signal from a radio frequency input and amplify the received signal into a second signal, which in turn amplifies the third signal to a level sufficient to perform navigation, radar, and communications functions.
A power conditioner is configured to receive power from a direct current (DC) input. The power conditioner causes a voltage sequencer to provide a negative voltage to a gate of each preamplifier, the medium-power amplifier, and the high-power amplifier before providing a positive voltage to a drain of each preamplifier and amplifier. The module amplifies signals over the 2- to 20-GHz and 20- to 40-GHz radio frequency ranges.
The MPM radar functions as a scatterometer, radiometer, and synthetic aperture imager. The high-speed communications system downlinks science data acquired by Earth-observing instruments. The navigation system functions like a transponder for autonomous rendezvous and docking and estimates the range information.
Commercial and military satellite communications, military radar systems, phased-array antenna systems, and aerospace (radar, communications, navigation) applications all can find uses for the MPM.