Allen F. Podell

A wide-band GaAs monolithic spiral quadrature hybrid and its circuit applications

The design, performance, and circuit applications of a 2-6-GHz GaAs monolithic spiral quadrature coupler are presented. This 90 degrees coupler uses lumped spiral inductors and metal-insulator-metal (MIM) capacitors and is very small in size (14 mil*26 mil). The measured relative phase difference between the coupled and direct port over the 3:1 bandwidth was 93 degrees +or-6 degrees . Applications of this broadband hybrid in reflection phase-shifter, image-reject downconverter, and I-Q downconverter circuits have also been successfully demonstrated based on this structure. >

A novel cascode feedback GaAs MMIC LNA with transformer-coupled output using multiple fabrication processes

The design, development, and performance of a novel high dynamic range cascode feedback GaAs MMIC LNA with transformer-coupled output is presented. The baseline design (chip size: 48*48 mils) operates over any 1-GHz bandwidth (with a simple off-chip input inductor) in the 0.5-3-GHz frequency range and has typically 15-dB small signal gain, 2.1-dB noise figure, and greater than 15 dBm of output power at 1-dB gain compression point. Performance results of this circuit fabricated in three different foundry processes are presented.<<ETX>>

A wide-band push-pull GaAs monolithic active isolator

A 2-6-GHz push-pull GaAs monolithic active isolator has been designed and tested. This balanced MESFET isolator has better than 18-dB reverse isolation of 6 GHz and provides greater than 15-dB input and output return loss across the band. This small (actual chip area 12 mil*24 mil) isolator chip draws 20 mA of current from a single +5-V supply. The compact chip size makes it an ideal candidate for impedance matching for monolithic subsystems in which a ferrite isolator is not practical. >

A Cell-Based Wideband Monolithic Upconverter

A fully monolithic wideband upconverter has been developed and tested using a cell-based design approach. This upconverter consists of an RF amplifier cell, a broadband diode mixer cell, and an LO buffer amplifier cell. The chip (48 × 96 mils) has been tested at different LO frequencies between 9 and 14 GHz with a swept IF from 300 MHz to 1 GHz, and typically has 2 dB of conversion loss for upconverted output across the 8 to 15 GHz band. It has 4.8 dBm of output, 1 dB compression power at 10 GHz LO (with only 4 dBm of LO Power), and 1 GHz input frequency.

Design, Performance, and Behavior of Pulsed and CW Silicon Double-Drift Impatts

Double-drift silicon IMPATTs for high power pulsed and CW applications have been optimized by the proper design of the width and impurity concentration in both the N and P-layers. Peak pulse powers greater than 18 watts at a 25% duty cycle were obtained at 10 GHz with the junction temperature rise limited to 200°C. For similar temperature rises CW powers of 3.4 watts at 11.5 GHz and 4.2 watts at 8.5 GHz were achieved. Conversion efficiencies were between 10.5 and 13.7%. Some detailed measurements of the large-signal conductance and FM noise of the CW devices are presented.