A 39 W Fully Digital Wideband Inverted Doherty Transmitter

Abstract

A high-power fully-digital Doherty transmitter (DDTX) is proposed. It features two segmented LDMOS output switch banks implemented in a custom V T -down-shifted LDMOS technology. A 40 nm CMOS controller digitally activates the individual LDMOS gate segments of the output stage at RF speed.An inverted Doherty power combiner is proposed that features non-short circuited 2 nd harmonic conditions for the main and peak switch banks to boost the RF bandwidth. To guarantee smooth output power and efficiency vs. frequency, a 2 nd harmonic trap is introduced in the power combiner, yielding an RF bandwidth of > 400 MHz . The realized demonstrator can achieve over 39 W peak output power. Its highest drain and system efficiencies, respectively 60 % and 57 %, were found at 34.2 W of output power, while in power back-off its peak drain and system efficiencies are 52 % and 48 % respectively. Over a 25 dB output range, the system efficiency is within 4 percent points of the drain efficiency.

A Wideband Energy-Efficient Multi-Mode CMOS Digital Transmitter

“…The difference between the drain and system efficiency is caused by the fixed power consumption of circuit blocks that do not scale with the output power. Therefore, if the output power increases, while the other blocks are unchanged, the SE becomes closer to the DE [40], [41]. The peak P Out and DE vary in different operation modes.…”