Negar Reiskarimian
Ph.D. Thesis   

  • Magnetic-free Non-Reciprocity Based on Staggered Commutation:
    Lorentz reciprocity is a fundamental characteristic of vast majority of electronic structures, which can be broken by violating one of the necessary conditions of time invariance, linearity or isotropy. In recent year, exploiting time-variance, specifically spatio-temporal permittivity modulation has been explored in literature. Circuit implementations of permittivity modulation uses varactors which have a low modulation index (ON/OFF ratio) resulting in large form factor, increased loss as well as increased nonlinearity.
    In this work we have demonstrated the world's first CMOS passive magnetic-free circulator. The circulator is based on staggered commutation (phase-shifting N-path filters), a form of spatio-temporal conductance modulation. Since conductivity in semiconductors can be modulated over a wide range (CMOS transistor ON/OFF conductance ratio can be as high as 1000 - 100000), our structure is able to break reciprocity within a compact form factor with very low loss and high linearity. The prototype is implemented in 65nm CMOS technology with approximate overall dimensions of λ/80 x λ/80 at 750MHz, with measured 1.7dB loss for both TX and RX paths and up to 50dB TX-RX isolation. Our implementation also benefits from a linearity improvement technique, which improves the transmitter side linearity performance. Measurements confirm two orders of magnitude IIP3 enhancement when comparing the cases of excitations at the TX port and ANT port (TX-ANT IIP3: +27.5dBm, ANT-RX IIP3: +8.7dBm).

  • Design of All-Passive Higher-Order CMOS N-Path Filters:
    N-path filters are a promising solution to realize highly-linear, high-Q tunable on-chip filters. However, the original topology only results in a second-order filtering profile which may not be sufficient for many applications. Recent research efforts to realize higher-order N-path filter responses have relied on the incorporation of active circuitry in the filter topology. In this work a design methodology for synthesizing all-passive higher-order N-path filters is introduced and demonstrated with a 6th-order 65nm CMOS prototype which achieves 35% tuning range from 600-850MHz and an in-band P1dB of 0dBm.

M.Sc. Thesis Project

  • Variable Bandwidth TIA/Limiter for optical Links with Maximum Sensitivity:
    Design of a variable bandwidth diversity receiver to mitigate the effects of atmospheric turbulence in Free Space Optical (FSO) links by controlling the total noise power. A comprehensive study of various loss factors in an FSO system was done as part of this project as well as a GUI design for calculating loss based on the physical parameters of an FSO system in MATLAB and finally an integrated circuit design for a chain of TIA and limiting amplifier in 0.18um technology in Cadence.