A Frequency Tunable MIMO Antenna Cluster with Transmitter IC

Abstract

This paper demonstrates the feasibility of an transmitter system where a handset MIMO antenna is fed by a 0.5–4.5 GHz integrated transmitter front-end to implement a frequency-tunable antenna cluster. The transmitter implementation performs on-chip amplitude and phase tuning to provide compatible MIMO performance over a wide frequency range in the low bands (700 MHz–960 MHz) and the high bands (1.5 GHz–4.5 GHz). The antenna is built with 8 elements comprising 4 clusters, two for low-band frequencies and two for higher frequencies. The transmitter-IC driving the antenna cluster is implemented in a 28-nm CMOS process with an active chip area of only 0.2 mm2. The proof-of-concept implementation demonstrates enhanced antenna efficiencies from -6.5 dB to -1.5 dB across the frequency bands, and envelope correlation coefficient below 0.4. The measurement results indicate that the antenna cluster technique can be applied with a real integrated transmitter to enhance MIMO operation of mobile antennas.