Abstract

Fragmented spectrum allocations at RF and mm-Wave, increased use of carrier aggregation/MIMO and dense spectrum-reuse in wireless links has led to interest in the design of integrated wideband, high-linearity MIMO RX that provide low noise, blocker tolerance and reconfigurability across signal domains. In this paper, receive architectures for wide operating range and blocker tolerance are presented with a focus on recent developments in reconfigurable N-path receivers. Generalized sequence-mixing architectures that support reconfigurable frequency/spatial/code-domain rejection and filtering are described along with directions of research extending operation to wider bandwidths and higher frequencies.

Highlights

  • Heterogenous networks (Hetnets) that embed small-cells into multi-user(MU) multiple-input multiple-out (MIMO) macrocells (Fig. 1) can achieve orderof-magnitude improvements in overall capacity by increasing spatial frequency-reuse and energy efficiency [1]–[4]

  • RECONFIGURABLE INTERFERER-TOLERANT N-PATH FILTERS AND MIXER-FIRST RECEIVERS Passive switching-mixers in CMOS driven by rail-to-rail LO can provide higher linearity than low noise amplifier (LNA) at the input

  • The following summarizes a correlator-based analysis described in [48]. This approach presents an intuitive explanation for N-path filter or mixer operation where switches are driven by generalized orthogonal sequences

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Summary

INTRODUCTION

Heterogenous networks (Hetnets) that embed small-cells into multi-user(MU) MIMO macrocells (Fig. 1) can achieve orderof-magnitude improvements in overall capacity by increasing spatial frequency-reuse and energy efficiency [1]–[4]. RECONFIGURABLE INTERFERER-TOLERANT N-PATH FILTERS AND MIXER-FIRST RECEIVERS Passive switching-mixers in CMOS driven by rail-to-rail LO can provide higher linearity than LNAs at the input. The reported blocker 1-dB compression at 80 MHz offset OOB blocker is +13 dBm. The RX supports operation from 0.1–2.0 GHz with a noise-figure of 6.3 dBm for operation at LO frequency of 1 GHz. The bottom-plate N-path architecture is further extended in [37] where the bottom plate voltage of the N-path mixer capacitors is connected to NOP-driven switches for readout. The following summarizes a correlator-based analysis described in [48] This approach presents an intuitive explanation for N-path filter or mixer operation where switches are driven by generalized orthogonal sequences. While these results are expected from [33], [46], the correlator-based interpretation suggests that N-path filter operation can be extended to any set of orthogonal sequences, Wk that satisfy (4)

ORTHOGONAL BASIS FUNCTIONS
RECONFIGURABLE SHUNT NOTCH FILTERS FOR INTERFERER-REJECTION
RECONFIGURABLE CODE-DOMAIN RECEIVERS USING WF-SEQ MIXING
CONCLUSION
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