A 700-W peak ultra-wideband broadcast Doherty amplifier

A wideband high-power Doherty design technique enabling fractional bandwidths > 50% is described. It utilizes wideband impedance inversion, device output capacitance compensation and passive phase-optimized wideband input-signal splitting. As prove of concept a LDMOS based ultra-wideband broadcast Doherty amplifier is presented, which covers the UHF-TV 470MHz–803MHz (BW
rel
= 52%) band with average efficiencies between 38%–47% @P
avg
> 115W while maintaining peak power capability > 700W over the entire band. Predistortability is demonstrated by satisfying the digital TV linearity requirements (−38dBc) using a commercial DVB-T exciter. The proposed DPA is an excellent drop-in replacement for the low-efficiency wideband PA blocks currently in use in broadcast transmitters.