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Beam switching reflectarray with rf mems technology

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2007
Bayraktar, Ömer
In this thesis 10x10 reconfigurable reflectarray is designed at 26.5 GHz where the change in the progressive phase shift between elements is obtained with RF MEMS switches in the transmission lines of unit elements composed of aperture coupled microstrip patch antenna (ACMPA). The reflectarray is illuminated by a horn antenna, and the reflected beam is designed to switch between broadside and 40° by considering the position of the horn antenna with respect to the reflectarray. In the design, the transmission line analysis is applied for matching the ACMPA to the free space. The full wave simulation techniques in HFSS are discussed to obtain the phase design curve which is used in determining two sets of transmission line lengths for each element, one for the broadside and the other for switching to the 40° at 26.5 GHz. The switching between two sets of transmission line lengths is sustained by inserting RF MEMS switches into the transmission lines in each element. Two types of RF MEMS switches, series and shunt configurations, are designed for the switching purpose in the reflectarray. The phase errors due to nonideal phase design curve and type of the RF MEMS switch are reduced. The possible mutual coupling effects of the bias lines used to actuate the RF MEMS switches are also eliminated by the proper design. To show the validity of the design procedure, a prototype of 20x20 reflectarray composed of ACMPA elements is designed at 25GHz and produced using Printed Circuit Board (PCB) technology. The measurement results of the prototype reflectarray show that the main beam can be directed to the 40° as desired. The process flow for the production of the reconfigurable reflectarray is suggested in terms of integration of the wafer bonding step with the in-house standard surface micromachined RF MEMS process.