Silicon IMPATT cascaded amplifier: 6 W (c.w.) at 9.6 GHz

A compact silicon IMPATT 4-stage coaxial amplifier has given 6.3 W (c.w.) with a power gain of 28 dB and an instantaneous bandwidth (¿1 dB) of 200 MHz centred at 9.6 GHz. A gain ripple of less than 0.2 dB and phase deviation from linearity of ±3° across a 30 MHz bandwidth slot was obtained at the full rated output power. The overall efficiency was 4.5%. Commercial devices and circulators were used throughout the unit and the power in the final stage was obtained by combining the available powers from four separate devices. Particular attention was paid to the circuits to reduce the onset of spurious oscillations under large-signal conditions.