Design of A 60-GHz Single-ended-to-differential Vector Sum Phase Shifter

In this thesis, a 60-GHz vector sum phase shifter for phased array receiver was designed and fabricated in 90-nm 1P9M CMOS technology. This vector sum phase shifter incorporates a vector generator with a variable gain amplifier (VGA) and a vector modulator to achieve full-360° phase synthesizing. And the vector sum phase shifter is also a single-ended-to-differential converter at the receiver front end.
The vector generator generates the required orthogonal bases for vector interpolation, and is realized by a four-way quadrature power divider which has the advantages of low loss and identical output port impedance over wide operation bandwidth. To synthesize a signal with an arbitrary phase, two quadrature vectors are needed, and the polarities of quadrature-phased signals for vector interpolating are selected by the vector modulator according to the quadrant where the required signal locates. Furthermore, to control the weightings of the quadrature signals, a VGA is needed. The VGA is in a three-stage configuration which is composed of a common-gate amplifier as the input stage for wideband input impedance matching and two stage differential pairs for the orthogonal vector weighted control.
In this design, using active devices and inductors for inter-stage impedance matching and ingenious floor plan substantially reduce the chip size. To achieve good signal balance, all circuits are arranged in symmetric layouts. To the author’s best knowledge, this is the first analysis of symmetry of the circuit layout and the first demonstration of signal balance of the differential outputs in the design of a differential-output vector sum phase shifter.