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mm-Wave Phase Shifters and Switches

Firouzjaei, Ehsan Adabi
Technical Report Identifier: EECS-2010-163
December 16, 2010

Abstract: The ever increasing speed of transistors in mainstream silicon-based technologies made the mm-wave domain open to consumer electronic applications. Solutions that previously had to be implemented in advanced compound (III-V) technologies and were limited to high-end systems due to cost purposes, are now entering the market of low-cost consumer electronic products. Emerging mm-wave market contains various applications from extremely high data rate transceivers in "Personal Digital Assistant (PDA)" devices to automotive radar modules and to point to point links for replacing the fiber connectivity in sparse areas. Chapter one highlights the specific requirements of each application that makes it more compatible with a certain type of technology.

To have a complete mm-wave system suitable for low cost applications, a single chip or a single package solution is preferred. To achieve this goal integrated low loss transmit / receive switching structures that are highly linear should be employed. A miniature transformer-based shunt T/R switch is introduced and implemented in a standard 90nm CMOS technology. Design equations and trade-offs for such a structure are described in this thesis.

Due to a much higher free space path loss of a 60GHz signal compared to its low frequency counterparts (30dB higher loss than WiFi), and lower performances extractable from devices at these high frequencies, phased antenna array structures should be exploited to add passive antenna gains to the transceiver and help meet the link budget requirement. Fundamentals of phased antenna array structures are described and two different implementations, one through true time delay elements and the other one employing phase shifters are presented.

For wideband applications and for very large arrays intended to have a wide field of view, true time delay elements should be employed to steer the array pointing beam. This work investigates true time delay elements, and an "inductance tuning technique" is introduced which enhances the delay tunability of a synthesized transmission line while keeping its characteristic impedance constant. In most mm-wave applications, delay cells in antenna array structures can be approximated and replaced with phase shifters. Hence different types of phase shifters are studied and an active I-Q interpolating phase shifter in the RF-path is designed and implemented at 60GHz.