Performance Analysis of an Integrated Multi-Channel Power Amplifier Incorporating an IC-to-Waveguide Transition

This paper studies the power combiner efficiency of multiple Power Amplifier (PA) output signals that are combined within a low-loss contactless transition, intrinsically having low isolation characteristics. Since the PA performance is sensitive to load impedance variations, poor isolation may affect each PA performance, thereby reducing the overall power combiner efficiency. Load impedance variations can e.g. be due to process, supply-voltage and temperature variations. A four-way spatial power combiner (SPC) design is compared to an on-chip Wilkinson Power Combiner (WPC) implemented in 0.13 µm SiGe BiCMOS technology incorporating a 50 Ω impedance matching net-work. The WPC occupies 84% more area than the non-isolating SPC. Moreover, the non-isolating SPC has an average efficiency 14% larger than the WPC. For physically realistic variations, simulated results show a σ-variation of 2.81 mW in P out and 0.87 % in PAE for the non-isolating SPC, and 2.34 mW in P out and 0.45 % in PAE for the WPC (@1 dB compression).