Ronald G. Freitag

Class B Operation of Microwave FETs for Array Module Applications

In addition to the well known class B advantages of high eta /sub PA/ and self turn on for pulsed operation, it is shown herein that class B FET amplifiers have several other important features including: 1) Significantly reduced power dissipation 2) A dynamic range of typically 8-10 dB over which gain is constant and power added efficiency is >30%. 3) Phase behavior (static and dynamic) is comparable to that observed with similar FETs operated class A. 4) Absence of erratic phase behavior during pulse turn-on and turn-off. These features make class B operation of power FETs very attractive for phased array module applications.

A GaAs monolithic array of impedance matched antenna/detector pixels for a 94 GHz imaging system

The design, fabrication, and performance of a 4*4 pixel array of monolithic GaAs 94-GHz detector circuits is described. This large chip is developed to be a tile for much larger arrays consisting of thousands of pixels for 94-GHz imaging. Each pixel is a slot antenna on one face coupled through the GaAs to a microstrip circuit containing a Schottky-barrier diode on the opposite face. The microstrip circuit provides an optimum impedance match between the diode and the slot antenna so that no additional tuning to free space is required. The diode is fabricated using a selective ion implantation process optimized for uniformity, repeatability, and yield, and has zero-bias capacitance and series resistance, respectively, of 14 fF and 15 Omega . Process control is essential, because variations in diode parameters can mismatch and detune the circuit. With the diode optimally forward-biased for square-law operation and a video bandwidth of 1 MHz, the tangential signal sensitivity (TSS) peaked in the 92-96-GHz range and was always better than -50 dBm at 94 GHz.<<ETX>>

High Efficiency One, Two, and Four Watt Class B FET Power Amplifiers

A family of X-band amplifier utilizing the higher efficiency of class B operation has been designed and fabricated. This paper describes the circuitry and performance of 1 watt single-ended, 2 watt push-pull, and 4 watt dual push-pull amplifiers having typical power-added efficiencies of 45%, 40%, and 35%, respectively, in a 1 GHz bandwidth, with associated gains of 5.8 dB, 5.4 dB, and 5.0 dB . Additional data is given for fifteen each of the 1 watt and 2 watt units to show the consistency of their performance.

A Study of Optimal Matching Circuit Topologies for Broadband Monolithic Power Amplifiers

A large signal amplifier design technique for broadband monolithic amplifiers has been expanded to include studies of the optimal output circuit topology from the standpoint of large and small signal gain variations and stability.