Multi-functional reconfigurable antenna using RF-MEMS switches for communication systems

RF-MEMS (Micro-electro-mechanical-system) is an emerging technology that is revolutionizing RF and microwave applications. RF-MEMS switches are basic building blocks for a variety of RF-MEMS circuits. These switches have demonstrated outstanding RF performance with very low insertion loss, and high isolation. In addition they operate at low power with excellent linearity and extremely low signal distortion. Such features make them very attractive for modern communications applications.; The RF-MEMS switches have been integrated for reconfigurable circuits. Using RF-MEMS switches, various RF circuits such as reconfigurable antenna, tunable filters, and phase shifters have been demonstrated with superior performance over conventional semiconductor devices. This re-configurability has highlighted advantages of the RF-MEMS switches. A monolithic fabrication process is proposed to integrate RF-MEMS switches in reconfigurable circuits, directly on printed circuit boards (PCBs). It is essential to develop a manufacturability of RF-MEMS switch on a common substrate housing all essential RF components. Since RF switches are fabricated directly on a PCB, the need for RF wire bonding and impedance matching to external components is eliminated and packaging is simplified, thus yielding a potentially low-cost, fully integrated RF system technology.; In this dissertation, the RF characteristics of capacitive shunt and series switches are analyzed, measured, and compared with coplanar wave-guide (CPW) and microstrip line structures, which are generally used for transmission lines of MEMS reconfigurable circuits. In addition, two reconfigurable antennas are presented for the pattern re-configuration using rectangular spiral antenna and frequency re-configuration using diagonally fed square patch antenna.; A fully integrated solution providing scan-beam capability with a single antenna is presented. The proposed system includes a reconfigurable rectangular spiral antenna with a set of MEMS switches, which are monolithically integrated and packaged onto the same substrate. The system is based on a single-arm rectangular spiral antenna, capable of changing its radiation pattern using RF-MEMS switches. The rectangular spiral and RF-MEMS switches are monolithically integrated on a conventional microwave substrate printed circuit board (epsilon r = 3.27 and tan delta = 0.004) and quartz substrate (epsilon r = 3.78 and tan delta = 0.0002).; Reconfigurable square patch antenna integrated with RF-MEMS switches is presented as well. The proposed antenna radiates circularly polarized wave at selectable dual frequencies, which are 4.7 GHz and 7.5GHz, with high frequency ratio of 1.6:1. The switches are incorporated into the diagonally fed square patch for controlling the operation frequency, and a rectangular stub attached to the edge of the patch acts as the perturbation to produce the circular polarization. Gain of proposed antenna is 5--6dBi. The antenna satisfies the 3dB axial ratio criterion at the both operating frequencies.; The excellent performance of the proposed reconfigurable system emphasizes the importance of being able to integrate MEMS switches into the same low loss substrate for antenna applications. This technology pioneers the design of arbitrarily shaped reconfigurable antennas including the design of reconfigurable antenna arrays.