High power added efficiency power amplifier with harmonic controlled by UWB filter with notched band at 6.42 GHz

A high power added efficiency (PAE) GaN inverse Class F PA (power amplifier) at 2.14 GHz with UWB (Ultra Wideband) bandpass notched filter is designed, fabricated and tested. For this amplifier, second harmonic and fourth harmonic are rejected by the bias circuit, while third harmonic is controlled by a UWB bandpass notched filter and fifth harmonic is tuned by a traditional λ/4 transmission line at 10.7 GHz. By applying this novel filter, third harmonic can be suppressed while for fundamental frequency, the filter works as a 50-Ohm transmission line with little insertion loss. With the interdigital hairpin line structure of the filter, the blocking capacitor is not needed in the load matching network. Compared with the conventional λ/4 transmission line at third harmonic, the size of this amplifier circuit is reduced. The measured PAE is 61.6% with 38.8 dBm output power at 2.14 GHz. The maximum gain is 15.9 dB.