Class-AB and class-J 22 dBm SiGe HBT PAs for X-band radar systems

A class-AB and a class-J PAs for X-band phased array radar applications are presented. The class-AB fully-differential design features the cascade of a 8-bit PGA and a PA core, leading to a gain variation range of over 50 dB with a phase shift deviation of <; 4° over a 25 dB attenuation range. The differential circuit shows 23 dB maximum gain, and 22 dBm saturated power at a PAE of 31%. Class-J operation is leveraged to increase the PA efficiency in a second design. The PAE is measured to be 36% at a saturated power level of 22 dBm. Integrated transformers are used to implement the input matching network and to synthesize the output class-J load, while providing single-ended to differential conversion. The amplifier shows a measured gain of 20 dB.