Research

A modem-agnostic Line-of-Sight (LoS) MIMO system, which performs MIMO processing in analog domain, can be retrofitted to any kind of single-input-single-output (SISO) digital modems to further increase spectral efficiency and data- rate. We show that two of the enabling technologies for broadband analog MIMO processing over several GHz bandwidth are: (1) precise signal delay compensation using continuously tunable delay line and (2) operating analog MIMO equalization at high RF intermediate frequency. Based on these two principles, we design and implement a 2×2 LoS MIMO system that supports MIMO processing of up to 1.6 Gbaud 64-QAM signal. The channel interference can be reduced lower than -25 dB over the entire signal spectrum after MIMO equalization. We demonstrate an indoor 2×2 LoS MIMO link of 16.7 Gbps with each channel carrying 1.6 Gbaud 64 QAM and an outdoor MIMO link of 11.1 Gbps over the range of 13 km with each channel carrying 1.6 Gbaud 16-QAM signal at millimeter-wave (MMW) frequency of 85 GHz.