Reconfigurable Impedance Matching Networks Based on RF-MEMS and CMOS-MEMS Technologies

Reconfigurable impedance matching networks are an integral part of multiband radio-frequency (RF) transceivers. They are used to compensate for the input/output impedance variations between the different blocks caused by switching the frequency band of operation or by adjusting the output power level. Various tuning techniques have been developed to construct tunable impedance matching networks employing solid-state p-i-n diodes and varactors. At millimeter-wave frequencies, the increased loss due to the low quality factor of the solid-state devices becomes an important issue. Another drawback of the solid-state tuning elements is the increased nonlinearity and noise at higher RF power levels. The objective of the research described in this thesis is to investigate the feasibility of using RF microelectromechanical systems (RF-MEMS) technology to develop reconfigurable impedance matching networks. Different types of tunable impedance matching networks with improved impedance tuning range, power handling capability, and lower insertion loss have been developed. Another objective is to investigate the realization of a fully integrated one-chip solution by integrating MEMS devices in standard processes used for RF integrated circuits (RFICs). A new CMOS-MEMS post-processing technique has been developed that allows the integration of tunable RF MEMS devices with vertical actuation within a CMOS chip. Various types of CMOS-MEMS components used as tuning elements in reconfigurable RF transceivers have been developed. These include tunable parallel-plate capacitors that outperform the available CMOS solid-state varactors in terms of quality factor and linearity. A tunable microwave band-pass filter has been demonstrated by employing the proposed RF MEMS tunable capacitors. For the first time, CMOS-MEMS capacitive type switches for microwave and millimeter-wave applications have been developed using TSMC 0.35-µm CMOS process employing the proposed CMOS-MEMS integration technique. The switch demonstrates an excellent RF performance from 10-20 GHz. Novel MEMS-based reconfigurable impedance matching networks integrated in standard CMOS technologies are also presented. An 8-bit reconfigurable impedance matching network based on the distributed MEMS transmission line (DMTL) concept operating at 13-24 GHz is presented. The network is implemented using standard 0.35-µm CMOS technology and employs a novel suspended slow-wave structure on a silicon substrate. To our knowledge, this is the first implementation of a DMTL tunable MEMS impedance matching network using a standard CMOS technology. A reconfigurable amplifier chip for WLAN applications operating at 5.2 GHz is also designed and implemented. The amplifier achieves maximum power gain under variable load and source impedance conditions by using the integrated RF-MEMS impedance matching networks. This is the first single-chip implementation of a reconfigurable amplifier using high-Q MEMS impedance matching networks. The monolithic CMOS implementation of the proposed RF MEMS impedance matching networks enables the development of future low-cost single-chip RF multiband transceivers with improved performance and functionality

Modeling, design and fabrication of MEMS filters for RF applications

Currently, micro electro mechanical systems (MEMS) technology has been used in the fabrication and development of several micro devices which cover a broad range of applications. One of these application areas is the telecommunication industry. Current multi-band communication systems depend on off-chip components for frequency selection stages. Since the fabrication of these off-chip components are not compatible with IC fabrication, the electrical connection has to be in the board level, increasing the cost, size and system complexity. Recently MEMS technology has been used in constructing tunable IC components for RF and wireless transceivers, such as resonators, variable capacitors and inductors. These on-chip components can be utilized to implement system on chip (SOC) transceiver architectures with a better performance. This project is focused on modeling, design, and fabrication of band-pass filters for RF applications using MEMS components. The first class of filters is based on MEMS resonators covering a frequency range from 1MHz to 10MHz and the second class of filters use RF MEMS tunable capacitors. The project has two main parts; the first part is dedicated to the behavioral modeling and generating macro models for MEMS resonators that will be used in system level simulation of the final filter, and the second part discusses the design, fabrication, and post processing of both the MEMS resonators and MEMS variable capacitor, besides the experimental results