Transmission Line Transformer Based Broadband Differential Class-E PA for Cellular Handset

This paper reports a new design concept and fabrication results of a broadband high efficiency class-E PA. The reported new design concept is mainly to apply a common mode choke (CMC) balun and a transmission line transformer (TLT) as broadband output matching for fundamental frequencies and signal rejection for harmonic frequencies to achieve class-E PA operation. The fabricated prototype PA has been designed to cover multiple frequency bands of n77, n78 and n79 defined by The $3 ^{rd}$ Generation Partnership Project (3GPP). As a result of pulsed continuous wave (CW) measurement, the PA demonstrates 34.0 - 36.4 dBm of saturated power (Psat) and 47.3 - 51.5% of peak power added efficiency (PAEpk) under frequencies of 3.15 - 5.30 GHz. The achieved fractional bandwidth which PAEpk is maintained over 45% (FBW$_{45\% })$ is 51%.