Christos Tsironis

A Self-Oscillating Dual Gate MESFET X-Band Mixer with 12 DB Conversion Gain

An x-band receiver stage including preamplifier, mixer and local oscillator has been realized by a dual gate GaAs MESFET in common source configuration. The conversion gain for a signal frequency of 10 GHz and an I.F. of 1GHz was 12 dB by appropriate matching the input (gate 1) and output (drain) port. A variable short, connected to gate 2 controlled the L.O. x-band oscillation. The isolation between drain and gate 1 was 16 dB. Using disc and BaTi4O9 resonator matching on Al2O3 substrate with only I.F. external tuning enabled conversion gain of 5dB. The tuner matched circuit had DSB noise figure of 5.5dB and associated conversion gain of 4dB at an I.F. of 1GHz whereas the best noise figure achieved by the disc-tuned circuit was 7.7dB at an I.F. of 300MHz and associated conversion gain of ¿1.5dB.

X and Ku-Band Dual Gate MESFET Oscillators Stabilized Using Dielectric Resonators

Stable X- and Ku-band oscillators have been realized using GaAs dual gate MESFETs with a geometry of 2 × 0.8 ¿m × 150 ¿m. Frequency stability was obtained by coupling the second gate with Ba2Ti9020 dielectric resonators. The design was accomplished by an experimental large signal analysis technique. The achieved output power at 10.8 GHz, 14.2 GHz and 18.05 GHz was 14 to 16 mW and the frequency stability was 0.5 to 4 ppm/K in the ¿20°C to + 80°C temperature range. Due to critical coupling, the values of Qext were between 1000 and 2000. Drain bias pushing at 18.05 GHz was as low as 300 kHz/V.

A New Method to Test and Design Multistage Power Amplifiers Using Load Pull Data

As an alternative to designing single or two-stage power amplifiers using transistor models, non-linear load pull data can be used to characterize transistors when designing amplifiers. The input, output, and interstage matching networks can then be chosen and modified to optimize any parameter included in the load pull data. Parameters which can be measured and optimized include output power, efficiency, intermodulation, ACPR, harmonic load information, and many others. This new technique has the advantages of being very accurate, extremely fast, and is transistor independent. All that is required for rapid optimization of the amplifier design are the transistor S-parameters and swept input power load pull data over the entire load impedance range.

Optimum Design of Dual Gate MESFET Amplitude Modulators

Ku band variable gain-constant phase amplifiers have been developed using dual gate FETs and appropriate CAD techniques. Obtained performances of the realized MIC at 15 GHz are: gain control of 26 dB associated with phase modulation of about 10 degrees and a maximum transmission gain of 4 dB in a bandwidth of 2 GHz.