A 5 GHz GaAs Monolithic astable multivibrator type voltage controlled oscillator has been developed. The monolithic oscillator uses 2 µm long self aligned TiW-silicide gate MESFETs, and GaAs Shottky diodes for capacitance. Good agreement between the experiment and calculations for oscillation frequency characteristics versus control voltage, is obtained by assuming donor density in the FET active layer to be a Gaussian distribution. This oscillator is useful for monolithic front ends and phase-locked oscillators used in microwave signal processing. X band oscillation frequency will be able to obtained with 1 µm long gate FET and low loss resonance inductors.

We report on suppressing adjacent-frequency interference (AFI) by using a RF receive bandpass-filter (BPF) with high-selectivity. By considering a high temperature superconducting (HTS) multi-pole BPF as a high selective BPF, the effect was estimated by numerical simulations. The simulations of the RF signals with an OFDM modulation transmitted to the demodulator via the BPF were carried out using the HTS BPF for 5 GHz band. The results confirmed the improvement of the bit error rate (BER) characteristic with the assumed HTS BPF with the high multi-poles under a strong AFI.

This paper describes the design of a 38-GHz high power MMIC amplifier using an improved load-pull technique. We improved the load-pull technique accuracy by using MMIC transtormers to match the input and output impedances of a GaAs MESFET to about 50 ohms. We used this technique to measure the large-signal load impedance of a FET with a 600-µm-wide gate. Using the data obtained, we developed an MMIC amplifier composed of two of these FET cells. At 38 GHz, the amplifier has an output power of 23.5 dBm for a 1 dB gain compression level.

We report on a subsystem of electromagnetic wave radiation and propagation estimation using high-Tc superconducting (HTS) receiving filters for S band. The subsystem, comprised of HTS filters, a rubidium standard signal generator (Rb SSG), a global positioning system (GPS) unit, etc., was used to evaluate the electromagnetic-wave (EMW) intensities, frequencies, the frequency interferences and the ground positions where the EM are measured. The developed subsystem showed high frequency selectivity for S band by using the HTS filters. Furthermore, we verified that the subsystem with the HTS filters operated on the moving car.