Parylene based low actuation MEMS phase shifters for reconfigurable antenna applications
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Haridas, Nakul Raghavanand
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Wireless networks face ever-changing demands on their spectrum and infrastructure resources such as, increased communication bands, capacity-intensive data applications, and the steady growth of worldwide wireless subscribers. This rapid increase in the use of wireless communication and the dependence on a reliable connectivity leads manufacturers to seek systems which are ever smaller, low power, provide long range, and high bandwidth, whilst giving higher reliable technologies. In modern communication systems MEMS is now finding its way, replacing older more high power and non-linear systems. One of the important components of RF MEMS technology is the implementation of MEMS phase shifters for phased array applications that require better performance than arrays of conventional phase shifters. An important example is where RF MEMS devices can be applied to vary the characteristics of an antenna, such as beam steering or tuning in a multiband antenna. The core of this thesis is the development and fabrication of a novel Parylene based MEMS phase shifter. This is the first novel application of Parylene as the strength member of the MEMS bridge. The implementation provided MEMS devices with lower actuation voltage of < 25 V. The fabricated phases shifters provide higher RF performance such as < 1 dB insertion loss, linearity of > 65 dBm, and return loss of < -15 dB. The reliability of the fabricated devices were tested beyond 2 billion switching cycles. This is higher than competing MEMS capacitive devices with a maximum lifetime of 500 million cycles. The fabricated device provides a maximum phase shift of 16.82° at 2.5 GHz, whilst the nominal value of phase shift was 5.4° at 2.5 GHz within the stable region of operation. The fabricated device provides comparable results with respect to reference DMTL designs. The research carried out in this thesis has lead to a number of international publications and four granted patents. The generic nature of this technology can open new opportunities in the conception and application of new MEMS devices in communication and sensing applications. The ability to deliver miniature, low power and high efficiency MEMS capacitive devices, will revolutionise the next generation of tuneable RF components suitable for mobile and handheld devices of the future.