QuinStar Technology proposes to develop an efficient, solid-state power amplifier (SSPA), operating at V-band frequencies in support of NASA Earth and planetary science applications. This proposal addresses the critical need for high-efficiency, millimeter-wave amplifiers used in absorption radar for remote pressure sensing to improve weather models. Specifically, we propose to develop a pulsed power amplifier with a minimum duty cycle of 25% operating over the 65-71 GHz band. The maximum power of 10+ Watts at 65 GHz and 1+ Watts at 71 GHz will be achieved with a minimum associated PAE of 35% and 5% respectively. The efficiency and power goals of this program will be realized by employing a combination of state-of-the-art (SOA) device technology, innovative circuit design, and power combining techniques.
Simulations show that the power-added-efficiency (PAE) of 39% to 8.5 % in the MMIC can be achieved across the band of 65 to 71 GHz with an associated output power of 2.7 and 0.28 Watts respectively. An on-chip active low-pass network is developed to provide the 10:1 frequency-dependent power attenuation as required by the program. This high-Q, low-pass network integrated on-chip also minimizes efficiency loss by more than 4.6 percentage points as compared to using an ideal, lossless 10-dB attenuator in conjunction with the MMIC of 39% PAE. This translates into a saving of 4.6% in the total DC power consumption at 71 GHz.
To realize the required SSPA power level with high efficiencies, we are proposing to use high-efficiency wave-guide circuit combining techniques. A high-efficiency, 4-way H-tee combiner network will be exploited to realize a combining efficiencies of greater than 93%. These simulations have been experimentally verified at frequencies ranging from Q-band to W-band. The compact size and light weight of the SSPA are projected 2.2 x 2.0 x 1.0 inches and 6 oz. respectively, which make it suitable for application to CubeSat/SmallSat platforms.
The main application for NASA is absorption radar for pressure sensing. The introduction of a high efficiency power amplifier will help solve one of the “most important questions” mentioned in the decadal survey. The remote sensing measurement of pressure will drastically improve the numerical weather models. NASA has had proposals planned based on the demonstration of this technology. Further, NASA employs satellite-based, active sensors for Earth and planetary science applications. They would benefit from this high-efficiency SSPA approach.
Applications for this high-efficiency amplifier technology abound at other government agencies for frequencies above and below V-band. These include SATCOM and radar applications for all military services. There is an initiative within the FCC to expand the unlicensed frequency spectrum in V-band (57-64 GHz) to include the 64-71 GHz band where the technology is directly applicable.