A 15 GHz-bandwidth 20dBm PSAT power amplifier with 22% PAE in 65nm CMOS

Abstract

Generation of broadband power at mm-wave frequencies with high efficiency is challenging, because of the low gain of CMOS devices and the trade-off between efficiency and gain-bandwidth product (GBW). Power amplifiers (PAs) with multiple paths, leveraging power splitters and combiners are the most popular choice to achieve high output power, but tradeoff between efficiency and GBW still exists. In fact, most of the high-efficiency PAs have a relatively narrow bandwidth, not adequate for applications such as IEEE820.15 or Wigig. Since PAs' bandwidth is limited by the large parasitic capacitors at the input and output of the gain stages, design techniques for power splitters, combiners and interstage networks play a key role in achieving wide bandwidth without sacrificing gain and efficiency. In this work, coupled resonators networks are exploited to achieve more than 2x enhancement of GBW. A design technique to embed the classical coupled resonators networks into power splitters and combiners is presented for the first time. By applying this technique to a 3-stages 2-way power combining PA, measured prototypes show broadband operation from 58.5 to 73.5 GHz with 30dB gain, 20dBm output power and a remarkable 22% PAE.