This work presents an RF-input outphasing power amplifier (RFIO PA) operating at X-band. A simple passive “inphasing” network implemented with PIN diodes is described that produces the required phase- and amplitude-modulated signals needed to drive an existing outphasing PA MMIC. The approach eliminates the need for multiple modulated input signals to drive the outphasing PA, particularly important at X band where phased-array applications demand low-complexity PA solutions.
The proof-of-concept X-band RFIO PA is demonstrated using pulsed CW signals to have a peak drain efficiency of 63% at 35.05 dBm output power. Dynamic performance is characterized using modulated RADAR signals for enhanced spectral confinement with 10µs pulse duration and 100µs repetition period, and achieves -10 dB improvement on the first sidelobe of the spectrum when digital predistortion is applied. Average efficiency of the RFIO PA is measured at 51.8% for a conventional rectangular RF pulse and 18.3% for an amplitude-modulated pulse with raised-cosine profile.