M.Sc Thesis

M.Sc StudentZlotnikov Tal Vitaly
SubjectStudy and Design of Microwave Phase Shifters
DepartmentDepartment of Electrical and Computer Engineering
Supervisor PROFESSOR EMERITUS Yael Nemirovsky


Phase shifter is a network where the phase difference between output and input signals can be controlled electrically, magnetically or mechanically. Low insertion loss and its variation over phase states, low control voltage, small chip area are essential for wide range of phase shifter’s applications such as phased array antenna systems. In such systems wave beams are steered in space without physically moving the antenna elements.

In this thesis we consider a RC bridge topology for the phase shifter. This topology has been widely used in low frequency applications for decades, but to the best of our knowledge its applicability for microwave applications is studied for the first time.  

We propose a semi-analytical approach for model optimization resulting in a set of optimal model parameters which is responsible for a number of unique properties of the phase shifter:

·         Maximum feasible phase shift for the given topology

·         Minimal feasible losses for maximum phase shift for the given topology

·         No loss variation with frequency and phase state

·         Nearly linear phase response for wide frequency range

We explore the feasibility of phase shifter realization in RF MEMS technology and present a pre-manufacturing, simulation phase of comb varactor design that can be implemented in this topology.

We present design and characterization of the phase shifter in a commercially available 45nm RF-CMOS process. In addition to the RC bridge phase shifter itself, the fabricated chip includes input and output buffers to isolate the phase shifter circuit from the measurement environment and to provide certain and real source and load impedances. Presented laboratory measurements of the phase shifter are in good agreement with theoretical study and simulations confirming phase shifter’s performances to the extent of uncertainty in the device models. The RC bridge phase shifter occupies area of just 0.05x0.04mm2 which is very small relative to state-of-the-art phase shifter circuits at microwave frequencies.