Design, development and characterisation of microstrip IMPATT oscillator

Solid state microwave oscillators are becoming increasingly important in microwaves, millimeter-waves and submillimeter wave frequency ranges. Previously, traditional waveguide based oscillators using IMPATTs have been popular. The paper deals with the design, development and characterization of a microstrip IMPATT oscillator in the Ku-band. Since IMPATTs large signal behaviour usually is not well understood and the circuits are electromagnetically complex, it is difficult to characterize accurately the circuit performance in a microstrip configuration. Therefore, a simple circuit topology is adopted using a GaAs IMPATT diode with an operating frequency range of 14-17 GHz and a design center frequency at 14 GHz. The entire design is realized on a polytetrafluroethylene-5880 substrate with a dielectric constant of 2.2. All line lengths and widths are calculated using EESOF´s Microwave software packages-LINECALC and TOUCHSTONE. The results show an output power of 190 mW at 12.7 GHz, with a slight modification, an oscillator frequency of 13.88 GHz is achieved. Conclusions and future scope of work are also discussed. The design presented is first step towards the development of a microstrip IMPATT oscillator. Experimental work is on for further improvements in performance