A 4-Element MIMO Baseband Receiver with >35dB 80MHz Spatial Interference Cancellation

Abstract

Next-generation communication systems with wide bandwidths need to operate in interference-limited networks. A discrete-time delay (TD) technique in a baseband receiver array is proposed for canceling wide modulated bandwidth spatial interference and reducing the ADC dynamic range requirements. The proposed discrete TD technique first aligns the interference using non-uniform sampled phases followed by uniform cancellation using a Truncated Hadamard Transform implemented with antipodal binary coefficients. A digital timeinterleaver with 5 ps resolution spanning 15 ns implements a scalable discrete TD to compensate the inter-element delay, while the multiply-accumulate in the signal path is simplified by implementing a 1-bit differential truncated Hadamard matrix. Measured results demonstrate greater than 35 dB cancellation over 80 MHz modulated bandwidth in 65 nm CMOS with a 592x improvement over prior-art demonstration of wide modulated bandwidth interference cancellation.