A fully integrated Doherty-amplifier for 5.6 GHz WLAN applications

In this paper, a fully integrated Doherty power amplifier (DPA) for application in IEEE 802.11a wireless local area network (WLAN) transmitters is proposed. The DPA exhibits an output power at its 1 dB compression point of 22 dBm with a corresponding power added efficieny (PAE) of 25 %. Within a 6dB-backoff the PAE is still 20 %, which among the highest reported for Doherty amplifiers fully integrated in silicon. The input reflection coefficient is less than -15 dB while the maximum forward transmission is 12.5 dB. This Doherty amplifier shows a low phase variation of only 16° over an input dynamic range of 30 dB. To verify the performance the DPA is measured with an orthogonal frequency divison multiplexed (OFDM) signal with 52 carriers using 16 QAM modulation scheme and a carrier frequency of 5.6 GHz. Error vector magnitudes are measured for different input power levels. The circuit is implemented in IHP 250nm-SiGe-BiCMOS technology and needs a 2.5 V supply. The chip area is 1.54 mm² × 0.85 mm² including the pads and eleven integrated inductors.