This innovation is a wideband, high-power, high-efficiency, all-solid-state microwave power module (SSMPM) or amplifier for a multifunction spacecraft payload that operates, depending on the need, as a radar system, communication system, or navigation system. The construction of the module is based on a wideband multi-stage amplifier design. The low-power stage is a high-efficiency GaAs pHEMT-based MMIC (monolithic microwave integrated circuit) distributed amplifier. The medium-power stage is either a high-efficiency GaAs pHEMT (high-electron-mobility transistor) or GaN HEMT-based MMIC distributed amplifier. The high-power stage is a high-efficiency GaN HEMT-based MMIC distributed amplifier.
The microwave power module does not include a traveling-wave tube amplifier (TWTA), and the high-power output stage is built around a GaN HEMTbased MMIC distributed amplifier instead of a TWTA. The distributed amplifier design is inherently capable of very wideband operation of typically a decade or more.
The microwave power module is small in size and lightweight. In addition, by substituting a transistor-based high-power amplifier in place of a TWTA in the output stage, the need for a kV-class electronic power conditioner (EPC) is eliminated, which further reduces the overall size and mass. GaN is a wide bandgap semiconductor, and devices constructed from this material can operate at elevated temperatures and are also inherently radiation-hard. GaN HEMTs typically operate at voltages as high as 30 V, which is closer to the spacecraft bus voltage, and hence the design of the DC-to-DC converter in the EPC is simplified.
HEMTs have much higher cut-off frequency ft and maximum frequency of oscillation fmax than MESFETs (metal-semiconductor-field-effect-transistors). Distributed amplifiers inherently have a very large-gain bandwidth product. The decade-wide bandwidth of the distributed amplifier employed here translates into pulse rise times on the order of a few tens of picoseconds, which is several orders of magnitude smaller than the nanosecond rise time required by the radar pulses.