For all onboard systems applications, it is important to have very low-loss characteristics and low power consumption coupled with size reduction. The controls and instrumentation in defence and aerospace continually calls for newer technologies and developments. One such technology showing remarkable potential over the years is radio frequency microelectromechanical systems (RF MEMS) which have already made their presence felt prominently by offering replacement in radar and communication systems with high quality factors and precise tunability. The RF MEMS components have emerged as potential candidates for defence and aerospace applications. The core theme of this paper is to drive home the fact that the limitations faced by the current RF devices can be overcome by the flexibility and better device performance characteristics of RF MEMS components, which ultimately propagate the device level benefits to the final system to attain the unprecedented levels of performance.Keywords: RF MEMS, microsystems, MEMS in defence, MEMS in aerospace, instrumentation, RF systems, micromechanical components
568Celebrating Sixty Years of Publication
SASTRY: RADIO FREQUENCY MICROELECTROMECHANICAL SYSTEMS IN DEFENCE AND AEROSPACE 569Celebrating Sixty Years of Publication conventional components fall apart 6 . This provides the ability to fine tune the circuits to the best optimum level and achieve the highest performance. Re-configurability is another desirable feature used to reconfigure the same antennas for various frequencies without shifting from one antenna to another. This helps in faster scanning and better directivity of the antennas. The switches, which are characterized by very low loss, low actuation voltages and better reliability are widely used for reconfiguring the antennas, routing networks, tunable filters, etc. The RF MEMS devices have extremely high linearity, which means that these create less harmonics and this feature makes them excellent candidates for broad band communication system applications, especially needing high dynamic range of operation.
Tunable CapacitorsThe standard semiconductor IC technology can provide a fixed capacitance with a sandwiched dielectric layer between two conductive electrodes In this case, the parasitic capacitance and the series resistance will result in losses and reduction
As the requirement for the low loss phase shifter increases, so does the development of RF MEMS as a solution. This paper presents the design & simulation of Switched line MEMS phase shifter for Ku band using GaAs substrate. The phase shift can be achieved by varying the lengths in delay path to the reference path for the same phase velocity. The electromagnetic & electromechanical simulations were carried out with various structural parameters to optimize the design. The novelties like low insertion loss, low actuation voltage with distributed actuation pads for DC and RF are used to make the design unique. The EM simulations are carried out using 3D simulator HFSS and a phase shift of 172.6 deg./dB for a total Phase shift of 348.75deg was achieved with return loss of 15.5dB over a frequency band from 16-18 GHz and a phase shift error less than ±2 degree in the 32 states. The electromechanical simulations are carried to achieve the low actuation voltage of 15.3V. These parameters make these suitable for the Phased array applications [1, 2].
Micro-Opto-Electro-Mechanical (MOEM) accelerometers employing a cantilever beam and anti resonant reflecting optical waveguide (ARROW) on a silicon is analyzed. Two types of MOEM accelerometers and a closed loop operation that can enhance the performance significantly compared to MEMS accelerometer is presented. As a typical example our study shows a MOEM accelerometer with a minimum detectable acceleration of 0.255 µ g/ √ Hz, a dynamic range of 160g, scale factor stability of 1.57 ppm/ o c and shock survivability of more than 1000 g.
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