The Experts below are selected from a list of 144 Experts worldwide ranked by ideXlab platform

Fei-yue Wang - One of the best experts on this subject based on the ideXlab platform.

  • Design and simulation of the tire pressure sensor based on the SAW resonator and the tire Capacitor Impedance
    2009 IEEE Intelligent Vehicles Symposium, 2009
    Co-Authors: Xiangwen Zhang, Fei-yue Wang
    Abstract:

    A novel tire pressure sensor based on the SAW resonator and the tire Capacitor Impedance was researched, and the sensor can measure the tire pressure wirelessly and passively according to the relation between the tire pressure and the tire Capacitor Impedance and the relation between the tire Capacitor Impedance and the resonant frequency of the sensor circuit. The novel sensor structure was introduced, and four L type, five T type and five π type sensor circuit structures were analyzed and their frequency characteristics were simulated. The simulation results show that the T1∼T5, π1, π2, π4 and π5 type sensor circuit structures are suitable for the tire pressure sensor, and the performance of the T3 type sensor circuit structure is the best among them. The sensitivities of the sensor were calculated and the best sensor circuit was designed according to the simulation and analysis results.

Andrew Bish - One of the best experts on this subject based on the ideXlab platform.

  • Low-Weight Fixed Ceramic Capacitor Impedance Matching System for an Electrothermal Plasma Microthruster
    Journal of Propulsion and Power, 2014
    Co-Authors: Christine Charles, Roderick Boswell, Andrew Bish
    Abstract:

    OVER the past few years, there has been increasing interest in the development of small-size radiofrequency (rf) plasma sources [1–5] for a variety of applications: portable sources for biological applications, process uniformity using hexagonal close packing of plasma sources, material milling with nonmetallic focused ion beam sources, and plasma thruster development for space use. There are a number of rf-driven thrusters currently being developed that span a large rf power range, i.e., over tens of kW in the VASIMR plasma rocket [6] and only a few tens of W in the Pocket Rocket electrothermal microthruster [5] or in the dielectric capillary rf thruster [7]. Although the use of rf power has some advantages (lower breakdown potential, higher plasma coupling efficiency, wider range of plasma parameters), its implementation on a spacecraft poses a number of challenges (electromagnetic radiation control, thermal control, weight/volume/power restrictions) [8]. Still, remarkable success was achieved with the rf inductive ion gridded thruster Rf Ion Thruster (RIT) flown on the Artemis mission [8,9]. With the emergence of CubeSat satellites and a variety of new remote sensing technologies providing cheaper access to space, there is increasing demand for low-weight, low-power, small-size, lowcost propulsion systems that can be operated with greener or cheaper propellants compared to the toxic propellants (i.e., hydrazine) used in chemical thrusters or to the expensive propellants (i.e., xenon) used in resistojets [8]. A small-size, low-power, rf-driven plasma device called Pocket Rocket has been proposed as a new electrothermal thruster [5,10,11]; its estimated performances are promising and in agreement with analytical studies on gas heating by ion-neutral charge exchange collisions [12] and other experimental charge exchange thruster studies using dc excitation [13]. Neutral gas heating in Pocket Rocket was recently measured by spectroscopy [14] for 10 W operation. However, its current heavy and bulky rf power Impedance matching subsystem strongly limits its development as a low-power plasma thruster for space use on small satellites. Similarly, development studies of inductive or wave-heated rf thrusters in laboratories, whether immersed in avacuumor contiguously attached to large vacuum chambers, are usually carried out using fixed excitation frequency and variablevacuumCapacitors in an Impedance matching network, where the rf antenna plays the role of the inductor in the resonant circuit [6,15–17]. It has recently been shown that efficient rf power transmission can be achieved at low power (a few hundred W) by varying the excitation frequency and using fixed ceramic Capacitors directly mounted on the rf antenna [18]. Here, a low-weight (∼90 g) fixed ceramic Capacitor and inductor Impedance matching system mounted on a printed circuit board (PCB) is developed and used to couple rf power into the electrothermal Pocket Rocket plasma microthruster. The excitation frequency is swept to achieve maximum transmitted rf power to the plasma at the resonant frequency and the system is compared to a standard high-weight (∼ a few kg) variable Capacitor Impedance matching network pretuned at about 13.56 MHz.

  • Variable frequency matching to a radiofrequency source immersed in vacuum
    Journal of Physics D: Applied Physics, 2013
    Co-Authors: Christine Charles, Roderick Boswell, Andrew Bish
    Abstract:

    A low-weight (0.12 kg) low-volume fixed ceramic Capacitor Impedance matching system is developed for frequency agile tuning of a radiofrequency (rf) Helicon plasma thruster. Three fixed groups of Capacitors are directly mounted onto a two loop rf antenna with the thruster immersed in a vacuum chamber. Optimum plasma tuning at the resonance frequency is demonstrated via measurements of the load Impedance, power transfer efficiency and plasma density versus driving frequency in the 12.882–14.238 MHz range. The resonance frequency with the plasma on is higher than the resonance frequency in vacuum. The minimum rf power necessary for ignition decreases when the ignition frequency is shifted downwards from the resonance frequency. This development has direct applications in space qualification and space use of rf plasma thrusters.

T. Ono - One of the best experts on this subject based on the ideXlab platform.

  • Switched-Capacitor Impedance simulation circuits realized with simplified circuit structure
    1997 IEEE International Symposium on Circuits and Systems (ISCAS), 1997
    Co-Authors: T. Ono
    Abstract:

    This paper describes switched-Capacitor (SC) inductor and Frequency Dependent Negative Resistor (FDNR) which use unity gain buffer (UGB) in common with another SC circuit to simplify circuit structure. Though common use of UGB has been reported in many references, UGB is usually connected to the same nodes and it often suffers simplification of SC circuits. In this paper, UGB is used in common with another SC circuit in a different way and SC inductor with simpler structure is obtained. The circuit is controlled by a simple two phase control clock. The Capacitor value spreads and the sum of Capacitor values is small. The number of Capacitors needed is four. Then this SC inductor is modified to introduce SC FDNR. The sum of Capacitor values and number of Capacitors in the SC FDNR are the smallest value in SC FDNR circuits reported so far. To confirm basic operations of circuits proposed, simulation results by SWITCAP are also shown.

Xiangwen Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Design and simulation of the tire pressure sensor based on the SAW resonator and the tire Capacitor Impedance
    2009 IEEE Intelligent Vehicles Symposium, 2009
    Co-Authors: Xiangwen Zhang, Fei-yue Wang
    Abstract:

    A novel tire pressure sensor based on the SAW resonator and the tire Capacitor Impedance was researched, and the sensor can measure the tire pressure wirelessly and passively according to the relation between the tire pressure and the tire Capacitor Impedance and the relation between the tire Capacitor Impedance and the resonant frequency of the sensor circuit. The novel sensor structure was introduced, and four L type, five T type and five π type sensor circuit structures were analyzed and their frequency characteristics were simulated. The simulation results show that the T1∼T5, π1, π2, π4 and π5 type sensor circuit structures are suitable for the tire pressure sensor, and the performance of the T3 type sensor circuit structure is the best among them. The sensitivities of the sensor were calculated and the best sensor circuit was designed according to the simulation and analysis results.

Isak C. Reines - One of the best experts on this subject based on the ideXlab platform.

  • Stress-tolerant and temperature-stable RF MEMS capacitive switches and tunable filters
    2010
    Co-Authors: Isak C. Reines
    Abstract:

    This dissertation presents RF MEMS capacitive switches which are based on a thin-film aluminum circular beam geometry that exhibit reduced sensitivity to both initial residual stress and stress-changes versus ambient temperature. The device symmetry also facilitates low- series-inductance compact device arrays for high-value capacitances. These switches are built in the Raytheon RF MEMS process and show an 8-10x improvement in temperature stability over the standard fixed-fixed beam designs. Also, cascadable RF MEMS switched Capacitors are demonstrated that are suitable for VHF and UHF tunable filters and reconfigurable matching networks. These devices are fabricated in the UCSD and Raytheon RF MEMS processes and result in a near ideal Capacitor Impedance over a 30:1 frequency range. The circular geometry is then used to demonstrate an RF MEMS switched Capacitor with 10 W power handling at 10 GHz under hot-switching conditions that maintains a relatively-low (< 30 V) pull-in voltage. The device consists of separate RF and DC electrodes, which are defined underneath a temperature-stable circular beam, to result in both increased restoring force above the RF electrode and higher RF self-actuation voltage. This thesis also presents a compact low-loss tunable X-Band bandstop filter that is implemented on a quartz substrate using both miniature RF-MEMS capacitive switches and GaAs varactors. The 2-pole filter is based on capacitively loaded folded-[lambda] resonators that are coupled to a microstrip line, and the filter analysis includes the effects of non-adjacent inter-resonator coupling. The RF MEMS loaded filter results in a measured 25 dB improvement in power handling and linearity compared to the GaAs varactor design. Finally, a 1.6-2.4 GHz suspended 3-pole RF MEMS tunable filter is presented. The filter results in an insertion loss of 1.34-3.03 dB over the tuning range and a 3-dB bandwidth of 201-279 MHz. This design results in a tunable Q_u of 50-150 over the frequency range, and to our knowledge, is the first suspended RF MEMS filter with the best Q_u. The Appendix presents in full detail the UCSD RF MEMS capacitive switch process on a high- resistivity silicon substrate

  • Stress-tolerant and temperature-stable RF MEMS capacitive switches and tunable filters - eScholarship
    2010
    Co-Authors: Isak C. Reines
    Abstract:

    This dissertation presents RF MEMS capacitive switches which are based on a thin-film aluminum circular beam geometry that exhibit reduced sensitivity to both initial residual stress and stress-changes versus ambient temperature. The device symmetry also facilitates low- series-inductance compact device arrays for high-value capacitances. These switches are built in the Raytheon RF MEMS process and show an 8-10x improvement in temperature stability over the standard fixed-fixed beam designs. Also, cascadable RF MEMS switched Capacitors are demonstrated that are suitable for VHF and UHF tunable filters and reconfigurable matching networks. These devices are fabricated in the UCSD and Raytheon RF MEMS processes and result in a near ideal Capacitor Impedance over a 30:1 frequency range. The circular geometry is then used to demonstrate an RF MEMS switched Capacitor with 10 W power handling at 10 GHz under hot-switching conditions that maintains a relatively-low (< 30 V) pull-in voltage. The device consists of separate RF and DC electrodes, which are defined underneath a temperature-stable circular beam, to result in both increased restoring force above the RF electrode and higher RF self-actuation voltage. This thesis also presents a compact low-loss tunable X-Band bandstop filter that is implemented on a quartz substrate using both miniature RF-MEMS capacitive switches and GaAs varactors. The 2-pole filter is based on capacitively loaded folded-[lambda] resonators that are coupled to a microstrip line, and the filter analysis includes the effects of non-adjacent inter-resonator coupling. The RF MEMS loaded filter results in a measured 25 dB improvement in power handling and linearity compared to the GaAs varactor design. Finally, a 1.6-2.4 GHz suspended 3-pole RF MEMS tunable filter is presented. The filter results in an insertion loss of 1.34-3.03 dB over the tuning range and a 3-dB bandwidth of 201-279 MHz. This design results in a tunable Q_u of 50-150 over the frequency range, and to our knowledge, is the first suspended RF MEMS filter with the best Q_u. The Appendix presents in full detail the UCSD RF MEMS capacitive switch process on a high- resistivity silicon substrate