A Compact 5 GHz Lumped-Element Wilkinson Power Combiner on 28 nm Bulk CMOS

A novel lumped-element Wilkinson power combiner designed at 5 GHz on a 28 nm bulk CMOS process is presented. The core circuit requires only three components with two additional capacitors used to implement a second harmonic trap, further reducing the circuit area and output distortion. The circuit uses a single coupled coil to provide two series inductances used in the combiner. Additionally, the coil parasitics provide the isolation resistance, removing the need for a discrete resistor. Design equations and methodology for the coupled coil are given along with integrated circuit (IC) measurement results. Return losses (RL) and isolation are greater than 10.1 dB from 4.3 GHz to 5.3 GHz with the insertion loss (IL) lower than 1.2 dB. The active circuit dimensions are 261 μm ×346 μm giving an area of 0.09 mm
²
.