High resolution phase shifter for a mm-wave adaptive null-forming array

In future dense 60 GHz wireless environments, cochannel interference (CCI) is a potential problem that degrades the link quality. In a previous paper, a genetic algorithm (GA) assisted analog adaptive array was proposed for 60 GHz applications to mitigate the CCI. The array optimizes the leastsignificant-bits of the discrete weights on each receiver path, so that the nulls in the array pattern are adjusted to the interference direction and results in an improved signal-to-interference-plusnoise ratio (SINR). To facilitate the adaptive null forming, high resolution phase shifter is required. This paper presents a high resolution LO-path phase shifter implemented in 40-nm lowpower CMOS technology. The phase shift tuning is implemented by a tunable transmission line for fine tuning, in combination with a coarse tuning available from the frequency divider-by-4 operation in a sliding-IF front-end. The measured phase shift resolution is 5.4¿ between 44 GHz and 54 GHz, which offers about 6-bit resolution, with a total power consumption of 16.9 mW.