Deepak Bansal

Abstract: A novel torsional RF MEMS capacitive switch design on silicon substrate is presented. The optimized switch topology such as reduction in up-state capacitance results in insertion loss better than ź0.1 dB till 20 GHz. Off to on state capacitance ratio is also improved by 18 fold and isolation is better than ź43 dB at 9.5 GHz. The achieved on state return loss is ź38 dB as compared to ź21 dB at 9.5 GHz. An optimized reduction in contact area and use of floating metal layer increases the switching speed from 56 to 46 μsec. It also increases the switch reliability by alleviating the stiction.

Abstract: This paper presents a new single pole double throw (SPDT) RF MEMS switch design based on a torsional series capacitive switch. The torsional configuration and use of floating metal reduce the stiction probabilities. Use of a single series capacitive switch compared to the conventional approach of a capacitive and series combination, offers compact size, higher bandwidth and superior reliability. The optimized SPDT topology offers a wider bandwidth of 17 GHz (3---20 GHz) with insertion loss of ?0.3 to ?0.4 dB and isolation ?20 to ?44 dB. The proposed structure actuates at 9 V and the contact force varies in the elastic contact regime from 20 to 68 µN for the bias voltage of 10---15 V.

Abstract: Variation in actuation voltage for RF MEMS switches is observed as a result of stress-generated buckling of MEMS structures. Large voltage driven RF-MEMS switches are a major concern in space bound communication applications. In this paper, we propose a low voltage driven RF MEMS capacitive switch with the introduction of perforations and reinforcement. The performance of the fabricated switch is compared with conventional capacitive RF MEMS switches. The pull-in voltage of the switch is reduced from 70 V to 16.2 V and the magnitude of deformation is reduced from 8 µm to 1 µm. The design of the reinforcement frame enhances the structural stiffness by 46 % without affecting the high frequency response of the switch. The measured isolation and insertion loss of the reinforced switch is more than 20 dB and 0.4 dB over the X band range.

Abstract: A compact radiofrequency (RF) MEMS single-pole double-throw (SPDT) switch based on series capacitive configuration is proposed. The critical process parameters are analyzed to improve the fabrication process. A technique of cold–hot thermal shock for lift-off method is explored. The residual stress in the structure is quantified by lancet test structures that come out to be 51 MPa. Effect of residual stress on actuation voltage is explored, which changes its value from 24 to 22 V. Resonance frequency and switching speed of the switch are 11 kHz and 44 μs, respectively, measured using laser Doppler vibrometer. Measured bandwidth of the SPDT switch is 20 GHz (5 to 25 GHz), which is verified with finite element method simulations in high frequency structure simulator© and an equivalent LCR circuit in advanced design system©. Insertion loss of the switch lies in −0.1 to −0.5 dB with isolation better than −20 dB for the above-mentioned bandwidth.

Abstract: A comparison of dry and wet release methods for surface micromachining of metallic structures, such as RF MEMS switches, test structures, bridges, and cantilevers is presented. The dry release process is opti- mized by varying the concentration of O2 and CF4 plasma and RF power. The plasma ashing of the sacrificial layer typically results in damage to metallic structures or stress-related deformation due to rise in temperature (>80°C). A wet release process using critical point drying (CPD) has been investigated to realize gold-electro- plated structures with reduced residual stress. The CPD, being a low-temperature (31.1°C) process, is more suitable for compliant structures without any deformation. © 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)

Abstract: A novel torsional RF MEMS capacitive switch design on silicon substrate is presented. The optimized switch topology such as reduction in up-state capacitance results in insertion loss better than ź0.1 dB till 20 GHz. Off to on state capacitance ratio is also improved by 18 fold and isolation is better than ź43 dB at 9.5 GHz. The achieved on state return loss is ź38 dB as compared to ź21 dB at 9.5 GHz. An optimized reduction in contact area and use of floating metal layer increases the switching speed from 56 to 46 μsec. It also increases the switch reliability by alleviating the stiction.

Abstract: This paper presents a low insertion loss capacitive shunt RF-MEMS switch. In the presented design, float metal concept is utilized to reduce the capacitance in up-state of the device. Float metal switch shows an insertion loss <0.11 dB, a return loss below 26.27 dB up to 25 GHz as compared to 0.81 dB insertion, 8.67 dB return loss for the conventional switch without float metal. OFF state response is same for the both devices. Further pull-in voltage of 12.75 V and switching time of 69.62 µs have been observed in case of the conventional switch whereas device with float metal have 11.75 V and 56.41 µs. Improvement of around 2.5 times in bandwidth and 4 times in input power has been observed without self actuation, hold down problem. The designed switch can be useful at device and sub-system level for multi-band applications.

Abstract: A new lateral electro-thermally actuated latching RF MEMS switch is presented in this paper. In contrast to conventional electrostatic or electro-thermal MEMS switches which require an actuation voltage to hold the switch in on or off state, this switch has a true mechanical latching design in such a way that there is no power required to hold the switch on or off. The switch structure only consumes power while transition between states. In order to satisfy low voltage operation, electro-thermal actuators are chose as the drive and latching actuators of the switch. The required actuation voltage for drive and latching actuators is 6 V. The switch consumes a power of <99 mW while transition from off to on state and also consumes a power of 46 mW for 0.3 ms in transition from off to on states. FEM simulations show that the return loss of the switch is below ?10 dB up to 140 GHz and is below ?20 dB up to 40 GHz. The insertion loss of the switch is less than ?1 dB up to 150 GHz. The switch isolation when it is off is below ?20 dB up to 160 GHz. The switch has potential applications in low voltage, low power and high performance RF tuning and switching applications.