Showing papers by "Kamaljit Rangra published in 2015"

Design and investigation of a low insertion loss, broadband, enhanced self and hold down power RF-MEMS switch

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.

Design of compact and wide bandwidth SPDT with anti-stiction torsional RF MEMS series capacitive switch

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.

Performance improvement of RF-MEMS capacitive switch via asymmetric structure design

Abstract: This paper presents a new type of capacitive shunt RF-MEMS switch. In the proposed design, float metal concept has been utilized to make the asymmetric structure on either side of the transmission line to implement the switch. This novel structure is used to inductively tune the isolation in C, X and Ku bands. Isolation peaks of 42.63, 44.22 and 47.75 dB has been observed at 7.2, 8.8 and 16.5 GHz when left, right or both cantilevers are electro-statically actuated in the down-state respectively, whereas conventional switch has peak only in X-band. Switch shows an insertion loss better than 0.10 dB, a return loss below 23.93 dB up to 25 GHz as compared to 0.90 dB insertion loss and 8.02 dB of return loss in case of conventional device. Further, improvement of around 5 times in bandwidth, 50 % in the pull-in voltage and 16.7 % in device area have also been observed. The designed switch can be useful at device and sub-system level for the future multi-band communication applications.

A low insertion loss, multi-band, fixed central capacitor based RF-MEMS switch

Abstract: This paper presents a new type of capacitive shunt RF-MEMS switch. In the proposed design, switch consists of a beam in the form of two symmetric cantilevers anchored at the central conductor of CPW, where they generate a fixed capacitance, whereas the free ends of the cantilevers are hanging over the ground plane of the CPW. The net up-state capacitance thus can be approximately determined from the area of overlap between the ground plane and free ends of cantilevers rather than the central overlap area as in the case of conventional movable bridge based approach. Further, the switch is used to inductively tune the isolation peaks in C and X bands i.e. 44.53 dB at 4.5 GHz and 51.08 dB at 9.8 GHz, when either or both cantilevers are electro-statically actuated to the down-state position. The device with movable bridge has isolation peak only at a single frequency in X band. Device shows an insertion loss less than 0.15 dB, a return loss below 21.38 dB up to 25 GHz as compared to 1.00 dB insertion, 7.67 dB return loss for the equivalent conventional switch with movable bridge. In addition, improvement of around 3.5 times in the bandwidth and 50 % reduction in the pull-in voltage has also been achieved. The designed switch can be useful at device and sub-system level for the future multi-band communication applications.

Design and fabrication of a reduced stiction radio frequency MEMS switch

Abstract: The design, fabrication, and mechanical characterization of a compact-reduced stiction see-saw radio frequency MEMS switch are presented. The switch has a resonance frequency of 9.8 kHz with a corresponding switching speed of 46 μs. Use of a floating metal layer and optimal contact area ensures reduced stiction and smaller capacitive leakage. Overall size of the switch is 0.535 (0.50×1.070) mm2. Reduction in up-state capacitance also results in improvement in self-actuation voltage, insertion, and return loss. The optimized topology has improved the stiction and power handling of the switch.

A Novel Approach for Low Insertion Loss, Multi-band, Capacitive Shunt RF---MEMS Switch

Abstract: This paper presents a novel capacitive shunt RF-MEMS switch. In the proposed design, broadside bridge structure joined with two cantilevers on either side has been used to implement the switch. The transmission line and actuation electrodes under the bridge are designed in the interdigitated form to reduce the area. Switch shows an insertion loss better than 0.11 dB, a return loss below 23.67 dB up to 25 GHz. In down-state, three resonant peaks of 34.71, 34.33 and 40.7 dB at 10.4, 11.0 and 21.4 GHz have been achieved as compared to a single peak in the case of the conventional switch. The proposed device has a bandwidth of 2.2 GHz in X-band and 5.2 GHz in K-band. Bridge structure shows a pull-in voltage of 12.25 V, actuation time of 34.40 µs while cantilevers have 7.5 V and 57 µs. Further, the electrical equivalent model has been presented to represent the switch. The model has been implemented in commercially available software. A good agreement with the 3-D electromagnetic simulated results validates the presented model.

Impact of post deposition annealing in O2 ambient on structural properties of nanocrystalline hafnium oxide thin film

Abstract: In the present work, HfO2 thin film (100nm) has been deposited by sputtering technique and annealed at various temperatures ranging from 400 to 1000\degree (in step of 200 \degree) in O2 ambient for 10 min. The samples have been characterized using XRD, FTIR, EDAX, AFM and Laser Ellipsometer. The impact of annealing temperatures in O2 ambient on structural properties such as crystallite size, phase, orientation, stress have been studied using XRD. The Hf-O phonon peaks in the infrared absorption spectrum are detected at 512, 412 cm^-1 . The stretching vibration modes at 720 cm^-1 and 748 cm^-1 correspond to HfO2. AFM data show mean grain size in the range of 38 nm to 67 nm. The film reveals variation in structural properties, which appears to be responsible for variation in oxygen percentage, refractive index (1.96 to 2.01) at 632 nm wavelength and roughness (6.13nm to 16.40nm). Annealing temperature as well as ambient condition has significant effects on stress, crystal size and thus the arrangement of atoms. For good quality film, annealing temperature larger than 600 \degree is desired.

Design aspect of high power handling applications: metal contact switches

Abstract: This paper outlines the power handling capabilities of metal contact switches The appropriate choice of configuration (inline or offline) reduces the probability of self actuation and allows high input RF power The shape and position of the contact spots decides the current density and accordingly allows the permissible amount of power to flow without causing any failure These two design aspects are taken into consideration and accordingly switch is designed with an insertion: ?01086 dB, isolation: ?325 dB and return loss: ?1807 dB The pull in voltage of the beam is simulated to 19 V Reinforcing of the beam is done to avoid curling of beam, self actuation at high power and to provide optimum contact force (105 µN) in order to reduce contact resistance The power to be handled by the switch is 156 W, when no temperature considerations are taken into account

Design of Reliable Analog DMTL Phase Shifter with Improved Performance for Ku Band Applications

Abstract: An analog phase shifter based on distributed MEMS transmission line (DMTL) is designed for Ku band applications. Traditional RF MEMS phase shifter comprising 6 switches has limited phase shift of 37.75° due to instability region. A new concept of stopper is incorporated to achieve high phase shift. In the present paper, optimisation of the analog phase shifter is done to increase its phase shift upto 88.63°. Phase shift is a strong function of capacitance ratio which is increased from 1.75 to 2.95. The maximum operating voltage and mechanical resonant frequency for the phase shifter are 16 V and 8.3 KHz, respectively. The switching time is calculated to 56 μs. The simulated insertion loss of the phase shifter is -1.75 dB with return loss of -20.49 dB at 17 GHz. The simulated results are verified with analytical modelling which are in close match.

Performance improvement of a reconfigurable series-shunt switch via asymmetric structure based RF-MEMS capacitive switch

Abstract: This paper presents a series combination of metal to metal contact and capacitive RF-MEMS switches for multi-band wireless applications. For performance improvement a novel capacitive shunt switch is used and the response has been compared with a conventional shunt device. The proposed design shows the insertion loss better than 0.35 dB and return loss below 13.96 dB up to 30 GHz as compared to 1.64 dB insertion loss and 6.14 dB of return loss with conventional device. Isolation peaks of 75.33, 71.58 and 72.98 dB has been observed at 8.2, 7.3 and 15.5 GHz when left, right or both cantilevers are electro-statically actuated in the down-state respectively, whereas conventional device has peak only at 7.3 GHz. Further, a reduction of about 60 % in the pull-in voltage of capacitive switch and 17.5 % in device area has also been observed. The proposed design can be used as a building block for multiple throw switches and switch matrices for the future reconfigurable RF front end applications.

Low temperature bonding techniques for MEMS devices

Abstract: Conventional bonding techniques like fusion, glass frit, soldering, eutectic, and anodic bonding, have been used in packaging for micro-electro-mechanical systems (MEMS). These bonding techniques require high temperature which results in bending/buckling of MEMS devices especially in case of hanging structures. In this work, low temperature and low cost bonding techniques with commercially available epoxy 320 NC and photoresist SU-8 2010 are done. Bonding with commercially available epoxy 320 NC at room temperature leads to spreading of epoxy in device region and affects the device performance. To define bonding ring dimensions, photoresist SU 8 2010 is used as an adhesive. Sharp dimensions of SU 8 2010 bonding ring are achieved using lithography. Top silicon cap is fabricated using TMAH etching. The bonds made with these techniques gave good shear strength, as measured with an indigenous setup.