Xun-jun He

A novel design of RF-MEMS phase shifter based on bridge-like coplanar waveguide

In this paper, a novel RF-MEMS phase shifter based on a rectangle bridge-like coplanar waveguide (BCPW) structure is proposed. The signal line of the coplanar waveguide (CPW) has symmetrical saw-shaped structures under the MEMS bridges above which covers the BCPW bridge. The CST software is used for the modeling, simulation and optimization the model of phase shifter from 30 to 40 GHz. Simulation and optimization results show that the proposed design with a 35 GHz central resonant frequency has a return loss less than -10 dB within about 2 GHz bandwidth range and for each RF MEMS switch-type bridge, as high as 75 degrees phase shift is realized. Compared with MEMS phase shifters without a BCPW bridge, S11 performance can be improved by up to 10 dB, and interference among the adjacent components can be decreased.

Time response and dynamic behavior of electrostatic driven RF MEMS capacitive switches for phase shifter applications

This paper analyzes the effects of the materials, the driven voltage, the switch height, the width of the CPW signal line and the quality factor on the switching time and the dynamic behavior of electrostatic driven RF MEMS capacitive switches for the microwave distributed MEMS shifters to reduce the switching time and the impact velocity, and increase the capacitive ratio

RF characteristics investigation of MEMS phase shifter with CPW discontinuities

The operating principle of the RF MEMS phase shifter is described. Two improved design approaches based on the CPW discontinuities to decrease the return loss are proposed. By using network theory and CST microwave studio simulation tool, the proposed RF MEMS phase shifters are modeled. Simulation results for the two designs are compared and discussed based on the analysis. Simulation results show that less than -10 dB return loss and more than -2 dB insertion loss is achieved for over 1 GHz bandwidth range for the proposed models. At least 6 dB return loss decrease is realized compared with the conventional MEMS phase shifter design methods.

Wafer Level Micropackaging for Distributed MEMS Phase Shifters

A novel packaging structure which is performed using wafer level micropackaging on the thin silicon substrate as the distributed MEMS phase shifters wafer with vertical feedthrough is presented. The RF performances of proposed structure are investigated using Microwave Studio (CST). The results show that the insertion loss (S21) and return loss (S11) was -0.4-1.84 dB and under -10 dB at 1-50 GHz. respectively. And especially, the phase shifts of 360deg are obtained at 48 GHz. Tins indicate that the proposed packaging structure for the distributed MEMS phase shifters can provide the maximum amount of phase shift with the minimum amount of insertion loss and with return loss of less than -10 dB.

On-wafer level packaging of RF MEMS devices for Ka-band applications

In this paper, on-wafer level packaging technology for RF MEMS is described, and then a novel packaging design for RF MEMS devices with different fabrication technology at millimeter-wave band is presented. The discussed RF MEMS devices on naked wafer includes a MEMS filter and a distributed MEMS transmission line (DMTL) phase shifter, which are fabricated using LIGA and micromachined technology, respectively. In order to realize the integration of those devices into a system at millimeter wave band, the packaged devices are embedded in a substrate. After incorporating the parasitic parameters into the equivalent circuit for the phase shifter, it is found that the bandwidth of predicted packaging increases about 8 GHz, moreover, the predicted packaging area is only about 40% larger than the naked device.

Numerical simulation and analysis of an electroactuated MEMS capacitive switch using finite element method

The MEMS capacitive switch based on fixed-fixed microbeam have garnered significant attention due to their geometric simplicity and broad applicability, and the accurate models should be developed to predict their electromechanical behaviors. The improved macromodel of the fixed-fixed microbeam of MEMS capacitive switch is presented in this paper, the numerical analysis of mechanical characterizations of the MEMS capacitive switches under electric actuation are performed by the finite element discretization method, and the performances of static and dynamic of MEMS capacitive switch are obtained. The numerical results show that, with only a few nodes used in the computation, the finite element discretization method gives the identical results to other numerical methods, such as the shooting method and experiments. Moreover, the proposed model can offer proper and convenient approach for numerical calculations, and promote design of MEMS devices.

Vibration investigation of clamped-clamped microbeam of MEMS capacitive switch under mechanical shock

A numerical analytical method based on multi-mode Galerkin discretization is presented to investigate the nonlinear response of the clamped-clamped microbeam of the MEMS capacitive switch under the different mechanical shock loads. The results show that using five or more modes can be sufficient to capture the nonlinear dynamic response of clamped-clamped microbeam, and the microbeam experiences a mechanical shock load as a quasi-static load or a dynamic load depending on the ration between the natural periods of the structure and the period or requency of the shock load. Moreover, the proposed method gives the identical results to other numerical methods in the literature, and is straightforward to implement and could save computation efforts while not losing accuracy.

Analysis and design of MEMS capacitive switch for microwave distributed phase shifter

A novel low-driven MEMS capacitive switch structure for microwave distributed phase shifter is presented based on the analysis of the operation principle. The driven voltage, response time, release time and vibration modes of the capacitive switch are analyzed using the Intellisuitetrade software. The simulation results show the driven voltage of 2.5 V, the response time less than 30 us, the release time high than 40 us and vibration frequency high than 15 KHz. The microwave distributed phase shifter based on the novel MEMS capacitive switch structure takes on superior electromechanical performance and rapid response time by comparing with other phase shifters based on the common MEMS beam structure switches.

Effects of Structure Parameters and Stress for Capacitive Switches MEMS Bridge on Time Response

In this paper, a novel method for analyzing the switching time of the electrostatic driven RF MEMS capacitive switches is presented. The effects of the structure parameters which mainly include the width, length and thickness and stress for capacitive switches MEMS bridge on time response are investigated using the SYNPLE module of IntelliSuitetrade tool. The result shows that the width of MEMS bridge and the stress in bridge indistinctively affect on time response, while the length and thickness of MEME bridge distinctively effect on time response.

Packaging and Feedthrough Modes of Wafer Level for RF MEMS Switches

This paper reports on the methods, feedthrough modes and RF performance of wafer level packaging for RF MEMS switches. By analyzing the effects of packaging methods and feedthrough modes on the cost, weight, size, loss, RF performance and function of switches, a novel wafer level packaging structure which is performed using the wafer-level microencapsulation on the thin silicon substrate as the RF MEMS switches wafer with the vertical feedthroughs is presented. This structure has some advantages, such as low thickness, low parasitic capacity, short electric path, lightweight, no real ring and compatibility with the devices fabrication processes. Therefore, for RF applications, the packaging structure obviously reduces electric path loss and fabrication cost, and provides better RF performance of RF MEMS switches