mm-Wave Power-Combining Architectures: Current Combining

The millimeter-wave (mm-Wave) frequency band attracts tremendous research interest due to its wide bandwidth and unique features. Silicon-based processes provide high promise of a realization of wide deployment of mm-Wave systems. Among different circuit components, the silicon power amplifier (PA) is one of the key challenging components due to high power efficiency and high energy efficiency requirements. This is very challenging due to the inherent drawbacks of silicon processes, including low device speed, large losses, low supply, and breakdown voltages, etc. To overcome these issues, power-combining techniques are widely adopted to overcome the power limitation from a single-channel PA. Among different combining techniques, transformer power-combining provides good features such as wide bandwidth and compact size, and therefore is widely adopted. This chapter has makes detailed comparison between current combining and voltage combining of transformer-based structures and leads to the conclusion that current combining is more suitable for the mm-Wave power-combining applications due to two major advantages: higher tolerance to parasitic resistance on the efficiency degradation and better symmetricity. To validate the current-combining techniques, this chapter exemplifies a two-way current-combining-based PA design and achieves then-record performance of the saturated output power Psat of 14.8. dBm, peak PAE of 9.4%.