Background: Growing attentions have been paid to Micro-Electro-Mechanical Systems
(MEMS) phase shifters in recent years. Compared with the traditional phase shifters, the MEMS phase
shifters have a number of advantages including small size, low loss, low cost, high precision, wide frequency
band and easy integration. Furthermore, the MEMS phase shifters are the key parts of the
Phased Array Radars (PARs) and the core devices of future communication systems.
Objective: This paper mainly focused on the performance parameters of the MEMS phase shifters. Numerous
recent academic researches and patents were also presented and discussed.
Method: Firstly, the working principles and the classifications of the MEMS phase shifters were introduced.
The MEMS phase shifters could be grouped into three categories: the distributed MEMS phase
shifters, the switched-line MEMS phase shifters and the reflection-type MEMS phase shifters. Secondly,
the research status of the MEMS phase shifters was presented, the problems of the existing
MEMS phase shifters and the corresponding solutions were summarized.
Results: In this paper, the affecting factors of the performances of the MEMS phase shifters were summarized.
These factors were mainly observed in: 1) the number of Radio Frequency (RF) switches of
the distributed MEMS phase shifters; 2) the transmission line length of the switched-line MEMS phase
shifters; 3) the couplers of the reflection-type MEMS phase shifters. The following improved methods
were proposed: 1) the structural changes of the membrane bridges, the paralleling Metal-Insulator-
Metal (MIM) or Metal-Air-Metal (MAM) capacitors, the material changes of the substrates and the
membrane bridges; 2) the wiring mode changes of the transmission line, the structural optimization of
the RF MEMS switches; 3) the improvement of processing level of the couplers.
Conclusion: There are good prospects for development of MEMS phase shifters. For further enhancement,
a growing number of MEMS phase shifters will be utilized.