科研之友
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摘要
Multi-phase passive mixer (PM) first RF frontend has regained great concern for its satisfactory noise performance comparable to LNA-first frontend. Moreover, the re-configurable impedance, bi-directional signal transparency and bi-directional impedance translation performance enable a splendid application future for the multi-phase PM-first RF frontend. However, it still suffers from quite a few nonidealities, among which the adjacent Local Oscillator (LO) pulse overlap is the remaining nonideality lacking deep research, and how the LO pulse overlap decays the impedance matching and noise performance of multi-phase PM-first RF frontend remains unclear. In this work, an accurate model is, for the first time, established and analyzed to reveal how the LO pulse overlap decays the impedance matching and noise performance of multi-phase PM-first RF frontend. The analytical and simulation results demonstrate that the impedance matching will be drastically deteriorated because of LO overlap, and when LO pulse overlap exceeds 2% the impedance matching will be collapsed, while the noise figure (NF) is deteriorated by 3.1 dB when LO overlap ranges from 0% to 2%. Moreover, even a chocking inductor technique and a technique by introducing a synchronous phase-shifted signal have been proposed to suppress the LO overlap, the gain and noise performance can be deteriorated or the power and chip area cost are big. To address this question, a LO pulse overlap suppression technique is proposed furthermore by introducing an overlap safeguard factor (OLSF) in this work. The additional impedance smaller than 2 Omega in the main signal path makes the OLSF scheme beneficial for noise and gain improvement, and the proposed OLSF scheme is power, area (0.04 mm(2)) and cost efficient compared with existing LO overlap suppression techniques.
