A New Receiver Architecture for MIMO Beam-Forming Applications

Abstract

Owing to its reduction in hardware complexity and power consumption, hybrid beam-forming has become one of the most promising substitutes for fully digital beam-forming (FDB) in large antenna array systems. In conventional hybrid beam-forming (CHB) architecture, phase shifters are designed to operate at RF band and inaccuracies of the RF phase shifts are unavoidable in practice. Furthermore, these RF phase shifters still consume considerable power if implemented as active devices or a large space/area on dice (form factor) if implemented as passive devices. This issue becomes more critical for massive MIMO systems where lower power consumption and smaller form factor are much desired due to the large number of antenna elements. Aiming at reducing power consumption and form factor of the receiver, we investigate a new method to insert phase shifts via adjusting sampling-offset on sample and hold (S&H) circuit. Based on this method, a new receiver architecture with RF under-sampling technique and adjustable S&H circuit is proposed. We also develop a method to find out the required phase shifts for the beam-forming in the proposed receiver architecture. Performance evaluation at 28 GHz band shows that the proposed technology gives practically the same bit error rate (BER) performance as the CHB architecture but yields advantages in terms of power consumption, chip area, and beam-forming phase errors, which makes it appealing for massive MIMO systems.