A 39 W Fully Digital Wideband Inverted Doherty Transmitter
Robert Bootsman (TU Delft - Electrical Engineering, Mathematics and Computer Science)
Yiyu Shen (Broadcom Netherlands B.V., TU Delft - Electrical Engineering, Mathematics and Computer Science)
Dieuwert Mul (TU Delft - Electrical Engineering, Mathematics and Computer Science)
Mohadig Rousstia (Ampleon B.V.)
Rob Heeres (Ampleon B.V.)
Fred van Rijs (Ampleon B.V.)
John Gajadharsing (Ampleon B.V.)
Morteza S. Alavi (TU Delft - Electrical Engineering, Mathematics and Computer Science)
Leo C.N. de Vreede (TU Delft - Electrical Engineering, Mathematics and Computer Science)
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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.