An Ultra Low Power 180-Degree, 1-Bit Phase Shifter using MOSFETS

Approved for public release; distribution is unlimited. Abstract: An ultra low power 180-degree , 1-bit phase shifter has been designed using Agilent's Advanced Design Software (ADS) co-simulation. Silicon-on-Insulator (SOI). MOSFETs were used as the switching elements because of their low current draw and low capacitance. A 1-bit 0, 180-degree phase shift has been realized with only two MOSFETs, simplifying manufacture and decreasing power. I. Introduction A phase shifter switchable between 0 and 180 degree is useful for many applications, especially phase modulators for BPSK modulation. Low power is desired to minimize size, weight and space of systems that require batteries and long persistence. Design of switched transmission line phase shifters usually requires two single-pole, double-throw (SPDT) switches. SPDT switches can be realized in a wide variety of ways, using FET, diode, or MEM (micro-electro-mechanical) switches. GaAs MESFETs, HEMTs, P-HEMTs or P-IN diodes have been used to realize phase shifters [3.], but suffer from high current draw and depletion-mode behavior, requiring negative voltages or DC biasing of the transmission lines to turn off. MEM switches either require high voltages to actuate or are difficult to integrate. Although reflection-type phase shifters using hybrid couplers and two switching elements have been reported, this type was discarded after insertion loss of designs using this architecture was found to be too high. Single switch type transmission line phase shifters can also be designed, but are limited to phase angles of smaller than 45 degrees [3.]. MOSFETs are the ideal choice for low-power designs because they do not draw any DC current through their gate, and the only power used is CV 2 f. Limitations of MOSFETs for this application are the capacitance of the MOS structure, its relatively high resistance, and its limited power handling capability. This paper describes a switched line phase shifter using only two MOSFETs to realize an ultra low power, bi-directional, 1-bit, 180-degree phase shifter.