Showing papers on "Radio frequency published in 2008"

Efficient Far-Field Radio Frequency Energy Harvesting for Passively Powered Sensor Networks

Abstract: An RF-DC power conversion system is designed to efficiently convert far-field RF energy to DC voltages at very low received power and voltages. Passive rectifier circuits are designed in a 0.25 mum CMOS technology using floating gate transistors as rectifying diodes. The 36-stage rectifier can rectify input voltages as low as 50 mV with a voltage gain of 6.4 and operates with received power as low as 5.5 muW(22.6 dBm). Optimized for far field, the circuit operates at a distance of 44 m from a 4 W EIRP source. The high voltage range achieved at low load current make it ideal for use in passively powered sensor networks.

RF Imperfections in High-rate Wireless Systems

Abstract: Wireless communication systems are persistently applying wider bandwidths, larger signal dynamics and higher carrier frequencies to fulfill the demand for higher data rates. This results in an ever increasing demand on the performance of low-cost and power-efficient radio frequency (RF) front-ends. Since the RF technology is, consequently, pushed to its operation boundaries, the intrinsic imperfections of the RF IC technology are more and more governing the system performance of wireless modems. "RF Imperfections in High-rate Wireless Systems" therefore presents a new vision on the design of wireless communication systems. In this approach the imperfections of the RF front-ends are accepted and digital signal processing algorithms are designed to suppress their impact on system performance. To illustrate this approach, this book focuses on multiple-antenna orthogonal frequency division multiplexing (MIMO OFDM), which will be applied as basis for the majority of near-future high-rate wireless systems. The basics of MIMO OFDM are introduced and the typically required signal processing in the implementation of such systems is elucidated. This book treats several of the front-end impairments that seriously affect the performance of MIMO OFDM systems: carrier frequency offset, phase noise, IQ imbalance and nonlinearities. To provide an in-depth understanding of the impact of these RF imperfections, analytical performance results are presented in the book. These results are then used to design different compensation approaches based on digital baseband processing. "RF Imperfections in High-rate Wireless Systems" is of interest to wireless system designers, who want to familiarise with the digital compensation of RF imperfections. For researchers in the field of wireless communications this book provides a valuable overview of this emerging research topic.

CMP network-on-chip overlaid with multi-band RF-interconnect

Abstract: In this paper, we explore the use of multi-band radio frequency interconnect (or RF-I) with signal propagation at the speed of light to provide shortcuts in a many core network-on-chip (NoC) mesh topology. We investigate the costs associated with this technology, and examine the latency and bandwidth benefits that it can provide. Assuming a 400 mm2 die, we demonstrate that in exchange for 0.13% of area overhead on the active layer, RF-I can provide an average 13% (max 18%) boost in application performance, corresponding to an average 22% (max 24%) reduction in packet latency. We observe that RF access points may become traffic bottlenecks when many packets try to use the RF at once, and conclude by proposing strategies that adapt RF-I utilization at runtime to actively combat this congestion.

Resistor Emulation Approach to Low-Power RF Energy Harvesting

Abstract: This paper presents an approach and associated circuitry for harvesting near maximum output power from electromagnetic waves in the RF/microwave region of the spectrum with variable incident power densities in the range of tens of muW/cm2. It is shown that open loop resistor emulation at the input port of a power converter is a suitable solution for tracking the peak power point of a low-power rectifying antenna source over a wide range of incident RF power densities. A boost converter with a simple low-power control approach for resistor emulation is presented. A hardware design example with detailed efficiency analysis is given using commercially available discrete circuitry. Experimental results are presented for a system harvesting 420 muW to 8 muW from a 6 cm times 6 cm rectifying antenna with incident RF power ranging from 70 muW/cm2 to 30 muW/cm2, respectively. The results demonstrate that resistor emulation is a simple and practical approach to energy harvesting with variable low-power radiative RF sources.

Radio frequency analog electronics based on carbon nanotube transistors

Abstract: The potential to exploit single-walled carbon nanotubes (SWNTs) in advanced electronics represents a continuing, major source of interest in these materials. However, scalable integration of SWNTs into circuits is challenging because of difficulties in controlling the geometries, spatial positions, and electronic properties of individual tubes. We have implemented solutions to some of these challenges to yield radio frequency (RF) SWNT analog electronic devices, such as narrow band amplifiers operating in the VHF frequency band with power gains as high as 14 dB. As a demonstration, we fabricated nanotube transistor radios, in which SWNT devices provide all of the key functions, including resonant antennas, fixed RF amplifiers, RF mixers, and audio amplifiers. These results represent important first steps to practical implementation of SWNTs in high-speed analog circuits. Comparison studies indicate certain performance advantages over silicon and capabilities that complement those in existing compound semiconductor technologies.

System and method for powering vehicle using radio frequency signals and feedback

Abstract: A system and method are described for powering a vehicle using radio frequency (“RF”) signals. For example, a method according to one embodiment of the invention comprises: positioning an antenna array beneath or on the road surface of a roadway, the antenna array configured to transmit RF signals responsive to RF processing logic and/or circuitry; coupling a rectenna array to a vehicle, the rectenna array configured to receive the RF signals transmitted from the antenna array and to generate power from the RF signals; providing feedback signals from the vehicle to the RF processing logic and/or circuitry, the feedback signals including channel state information (CSI) defining a current state of the channels between the antenna array and the rectenna array, the RF processing logic and/or circuitry using the channel state information to adjust the RF signal transmissions from the antenna array to improve the efficiency of the power generated by the rectenna array; and using the power generated by the rectenna array to power the vehicle.

Magnitude least squares optimization for parallel radio frequency excitation design demonstrated at 7 Tesla with eight channels.

Abstract: Parallel excitation offers a means of designing multidimensional radio frequency (RF) pulses using accelerated gradient trajectories resulting in a short pulse duration compared with single-channel excitation. Accelerations of four- to sixfold have been shown using an eight-channel transmit system (1), potentially enabling several important applications, including flexibly shaped excitation volumes, and mitigation of RF field inhomogeneity at high field. Various methods have been proposed for the design of such RF and gradient waveforms (2–5), primarily in the low flip domain (6), and successfully implemented on multichannel hardware (1,7). In this work, we propose an extension to the spatial domain parallel excitation pulse design method introduced by Grissom et al. (5), where we apply magnitude least squares optimization to improve excitation magnitude profile and reduce the required RF power at a cost of increased phase variations in the excitation pattern. However, for many excitation applications, such as when magnitude images are recorded, low-order spatial phase variations do not impose a significant penalty. In fact, they can potentially decrease the dynamic range requirements of the imaging (which can be extensive for high field three-dimensional [3D] acquisitions) by reducing the amplitude at the center of k-space. We, therefore, developed a method for pulse calculation with an adjustable regularization parameter de-emphasizing the excitation phase profile and study the potential benefits in magnitude profile fidelity and SAR, which can accompany this relaxed constraint. The idea of permitting phase variation in the excitation profile has previously been exploited in several applications, including the design of quadratic-phase RF pulses (8,9), RF shimming (10–13), and frequency-sweep pulses (14), with benefits such as improved magnitude transition bands for saturation pulses, homogeneity for RF shimming, and reduced RF peak power for frequency-sweep pulses. In this work, we propose a method that allows us to take advantage of relaxed constraints on the phase profile for parallel excitation design. Our approach is based on a variant of a local optimization method used for solving general magnitude least square problems (15). We demonstrate the method using a 2D spiral excitation with R = fourfold acceleration over the Nyquist sampling and a uniform in-plane slice-selective spoke excitation (1,16) on an eight-channel excitation system at 7 Tesla (T). Recently, at the ISMRM’07 conference, Katscher el al. (17) demonstrated the significant improvement gained in RF shimming when a magnitude least square approach is used. Kerr et al. (18) also proposed an approach for magnitude least square optimization for the design of parallel RF excitation and demonstrate the method using a spiral trajectory. The approach in this work differs in that it takes into account intravoxel dephasing and enables the designer to systematically trade off the allowed spatial phase variation for the improvement in magnitude profile and reduction in RF power. Furthermore, the work provides an extensive simulation and experimental study on the possible benefit of the algorithm on both spiral and spoke k-space trajectory excitations at high magnetic field strength.

Impedance matching and emission properties of optical antennas in a nanophotonic circuit

Abstract: An experimentally realizable prototype nanophotonic circuit consisting of a receiving and an emitting nano antenna connected by a two-wire optical transmission line is studied using finite-difference time- and frequency-domain simulations. To optimize the coupling between nanophotonic circuit elements we apply impedance matching concepts in analogy to radio frequency technology. We show that the degree of impedance matching, and in particular the impedance of the transmitting nano antenna, can be inferred from the experimentally accessible standing wave pattern on the transmission line. We demonstrate the possibility of matching the nano antenna impedance to the transmission line characteristic impedance by variations of the antenna length and width realizable by modern microfabrication techniques. The radiation efficiency of the transmitting antenna also depends on its geometry but is independent of the degree of impedance matching. Our systems approach to nanophotonics provides the basis for realizing general nanophotonic circuits and a large variety of derived novel devices.

Frequency-Selective I/Q Mismatch Calibration of Wideband Direct-Conversion Transmitters

Abstract: The current trend in building low-cost yet flexible radio transceivers is to use the so-called direct-conversion principle, which is based on complex (I/Q) up- and down conversions. Such transceivers are, however, sensitive to mismatches between the I and Q branches. These mismatches are unavoidable in any practical implementation, and result in finite attenuation of the mirror frequencies. In addition to the mirror-frequency interference problem, I/Q mismatches can severely compromise the performance of power amplifier linearization techniques based on pre-distortion. The effects of these impairments are becoming more pronounced as higher order modulated waveforms and/or more wideband multichannel signals are used. This brief focuses on digital-signal-processor-based I/Q mismatch calibration in wideband direct-conversion transmitters, assuming the challenging case of frequency-dependent I/Q mismatch. First, a novel widely linear (WL) calibration structure is introduced, suitable for frequency-dependent calibration. Then, two alternative principles for calibration parameter estimation are proposed. The first estimation approach stems from second-order statistics of complex communication signals, while the second technique is based on WL least-squares model fitting. Both estimators are shown by simulations to yield very good calibration performance. The obtainable performance is further assessed using laboratory RF signal measurements.

Near-field imaging of optical antenna modes in the mid-infrared.

Abstract: Optical antennas can enhance the coupling between free-space propagating light and the localized excitation of nanoscopic light emitters or receivers, thus forming the basis of many nanophotonic applications. Their functionality relies on an understanding of the relationship between the geometric parameters and the resulting near-field antenna modes. Using scattering-type scanning near-field optical microscopy (s-SNOM) with interferometric homodyne detection, we investigate the resonances of linear Au wire antennas designed for the mid-IR by probing specific vector near-field components. A simple effective wavelength scaling is observed for single wires with λeff=λ/(2.0± 0.2), specific to the geometric and material parameters used. The disruption of the coherent current oscillation by introducing a gap gives rise to an effective multipolar mode for the two near-field coupled segments. Using antenna theory and numerical electrodynamics simulations two distinct coupling regimes are considered that scale with gap width or reactive near-field decay length, respectively. The results emphasize the distinct antenna behavior at optical frequencies compared to impedance matched radio frequency (RF) antennas and provide experimental confirmation of theoretically predicted scaling laws at optical frequencies.

Microwave repeater system for wireless network

Abstract: A microwave repeater system for a wireless network is disclosed. The microwave repeater system includes a donor system having a donor RF unit and a donor M/W unit, a remote system having a remote M/W unit and a remote RF unit, and microwave antennas to convert and restore an IF or RF signal into a microwave band frequency. The microwave repeater system includes a VSWR measuring unit provided in the donor M/W unit or the remote M/W unit and checking coupling of a microwave antenna and operation of an antenna circuit, and a current detecting unit interrupting an electric current flowing in a concentric cable connecting the donor RF unit and the donor M/W unit or the remote M/W unit and the remote RF unit.

Experimental demonstration of a μ=−1 metamaterial lens for magnetic resonance imaging

Abstract: In this work a μ=−1 metamaterial (MM) lens for magnetic resonance imaging (MRI) is demonstrated. MRI uses surface coils to detect the radio frequency (rf) energy absorbed and emitted by the nuclear spins in the imaged object. The proposed MM lens manipulates the rf field detected by these surface coils so that the coil sensitivity and spatial localization are substantially improved. Beyond this specific application, we feel that the reported results are the experimental confirmation of a new concept for the manipulation of rf field in MRI, which paves the way to many other interesting applications.

RF MEMS Actuated Reconfigurable Reflectarray Patch-Slot Element

Abstract: This paper describes the design of a reconfigurable reflectarray element using commercially available radio frequency micro-electromechanical system (RF MEMS) switches. The element consists of a microstrip patch on the top surface and a slot with an actuated variable length in the ground plane. RF MEMS switches are mounted on the slot to electronically vary the slot length by actuating the switches and thus obtaining the desired phase response. Waveguide measurements and high frequency structure simulator (HFSS) simulations are used to characterize the reflectarray element. The four MEMS switches element gives 10 independent states with a phase swing of 150 deg and a loss variation from 0.4 dB to 1.5 dB at 2 GHz (more switches can provide larger phase shift). The loss is mainly attributed to the dielectric loss and the conductor loss, which occur due to the relatively strong electric fields in the substrate region below the patch and the large currents on the top surface of the patch, respectively, close to the patch resonance. Detailed analysis is performed to characterize the effect of the switches by taking into consideration the switch model and wire bonding effects.

Displaced feed parallel plate antenna

Abstract: A displaced feed antenna, operating at UHF, microwave, millimetre wave and tetrahertz frequencies, of mostly spaced conducting plate construction that incorporates electronically selectable feed points with associated antenna beam positions, which displaced feed antenna comprises: (i) a set of one or more beamforming configurations means (6) composed of layered, interlinking spaced conducting plates (1 ) and conducting boundaries that are separated by cavities containing dielectric material or free space; (ii) a set of one or more internal focusing means for each beamforming configuration to route radio frequency energy to or from the displaced feed points on receive and transmit respectively; (iii) a linear or curved array of displaced feed means for each beamforming configuration for coupling radio frequency energy into, or from, the cavity between the plates (2); (iv) a selection means (4) to allow definable overlapping regions of the focussing means to be illuminated for each beamforming configuration, by routing radio frequency energy via either selectively reflective elements or adjacent elements, or combinations of both, to create a displaced feed, controllable in extent and position, within the array of displayed feeds; and (v) a radio frequency transition means (3, 5) for each beamforming configuration between spaced conducting plates to free space, allowing either single polarisations or dual polarisation operation.

86-km optical link with a resolution of 2 × 10-18 for RF frequency transfer

Abstract: RF frequency transfer over an urban 86 km fibre has been demonstrated with a resolution of 2×10-18 at one day measuring time using an optical compensator. This result is obtained with a reference carrier frequency of 1 GHz, and a rapid scrambling of the polarisation state of the input light in order to reduce the sensitivity to the polarisation mode dispersion in the fibre. The limitation due to the fibre chromatic dispersion associated with the laser frequency fluctuations is highlighted and analyzed. A preliminary test of an extended compensated link over 186 km using optical amplifiers gives a resolution below 10-17 at 1 day.

Modular wireless communications platform

Abstract: A modular wireless communications platform is provided. The modular wireless communications platform has a modular host unit and a modular remote unit in communication with the modular host unit. The modular host unit has a serial radio frequency communicator configured to convert serial digital data into RF sampled data and configured to convert RF sampled data into serial digital data. The modular host unit also has an interface coupled to the serial radio frequency communicator and configured to allow transfer of the RF sampled data from the serial radio frequency communicator to a digital to analog radio frequency transceiver module. Likewise, the modular remote unit has a serial radio frequency communicator configured to convert serial digital data into RF sampled data and configured to convert RF sampled data into serial digital data. The modular remote unit also has an interface coupled to the serial radio frequency communicator and configured to allow transfer of the RF sampled data from the serial radio frequency communicator to a digital to analog radio frequency transceiver module.

Retarding field analyzer for ion energy distribution measurements at a radio-frequency biased electrode

Abstract: A retarding field energy analyzer designed to measure ion energy distributions impacting a radio-frequency biased electrode in a plasma discharge is examined. The analyzer is compact so that the need for differential pumping is avoided. The analyzer is designed to sit on the electrode surface, in place of the substrate, and the signal cables are fed out through the reactor side port. This prevents the need for modifications to the rf electrode—as is normally the case for analyzers built into such electrodes. The capabilities of the analyzer are demonstrated through experiments with various electrode bias conditions in an inductively coupled plasma reactor. The electrode is initially grounded and the measured distributions are validated with the Langmuir probe measurements of the plasma potential. Ion energy distributions are then given for various rf bias voltage levels, discharge pressures, rf bias frequencies—500kHzto30MHz, and rf bias waveforms—sinusoidal, square, and dual frequency.

Multi-band and multi-mode radio frequency front-end module architecture

Abstract: A multi-band, multi-mode radio frequency (RF) front-end module is capable of operating in widely different frequency bands, including at least one of the following frequency ranges: 700 megahertz (MHz), 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, 2.1 gigahertz (GHz) or 2.4 GHz. The multi-band, multi-mode RF front-end module is also capable of operating according to different mobile communication standards, including at least one of the following standards: GSM, WCDMA, EDGE or LTE. The multi-band, multi-mode RF front-end module includes a plurality of broadband amplifiers, a plurality of transmit (TX) paths selectively connectible to respective broadband power amplifiers; and a plurality of switches. One switch is selectively operable to couple one plurality of TX paths to one broadband power amplifier operable to amplify TX signals within one range of frequencies. A second switch is selectively operable to couple a second plurality of TX paths to a second broadband power amplifier operable to amplify TX signals within a second range of frequencies.

High Dynamic Range Microwave Photonic Links for RF Signal Transport and RF-IF Conversion

Abstract: Two different techniques were used to extend the dynamic range of analog optical links operating at microwave frequencies. The link noise figure was reduced by adjusting the bias point of an external Mach-Zehnder intensity modulator. The link distortion was reduced by linearizing the transfer function of the intensity modulator. Frequency conversion was implemented using an additional optical modulator and electrical local oscillator rather than a conventional electronic mixer. A microwave frequency signal transport link was demonstrated with a spur-free dynamic range (SFDR) of 71 dB in a 500-MHz noise bandwidth. A link with down-conversion from a microwave frequency to an intermediate frequency was demonstrated with an SFDR of 64 dB in a 500-MHz noise bandwidth.

Quickest spectrum sensing in cognitive radio

Abstract: Quickest detection is applied to frequency spectrum sensing in cognitive radio systems. Distribution change in frequency domain is detected for vacating secondary radio networks from licensed frequency band. A successive refinement based quickest detection is proposed to tackle the problem of unknown parameters of primary radio signal. Cooperative quickest detection is used to enhance the performance of quickest spectrum sensing in secondary radio systems without data fusion centers. Performance is evaluated using theoretical analysis and numerical simulations.

Testing the inverse-Compton catastrophe scenario in the intra-day variable blazar S5 0716+71, III. Rapid and correlated flux density variability from radio to sub-mm bands

Abstract: Context. Some intra-day variable, compact extra-galactic radio sources show brightness temperatures severely exceeding 10 12 K, the limit set by catastrophic inverse-Compton (IC) cooling in sources of incoherent synchrotron radiation. The violation of the IC limit, actually possible under non-stationary conditions, would lead to IC avalanches in the soft-γ-ray energy band during transient periods. Aims. For the first time, broadband signatures of possible IC catastrophes were searched for in a prototypical source, S5 0716+71. Methods. A multifrequency observing campaign targetting S5 0716+71 was carried out during November 06−20, 2003. The observations, organized under the framework of the European Network for the Investigation of Galactic nuclei through Multifrequency Analysis (ENIGMA) together with a campaign by the Whole Earth Blazar Telescope (WEBT), involved a pointing by the soft-γ-ray satellite INTEGRAL, optical, near-infrared, sub-millimeter, millimeter, radio, as well as Very Long Baseline Array (VLBA) monitoring. Results. S5 0716+71 was very bright at radio frequencies and in a rather faint optical state (R = 14.17−13.64) during the INTEGRAL pointing; significant inter-day and low intra-day variability was recorded in the radio regime, while typical fast variability features were observed in the optical band. No obvious correlation was found between the radio and optical emission. The source was not detected by INTEGRAL, neither by the X-ray monitor JEM-X nor by the γ-ray imager ISGRI, but upper limits to the source emission in the 3−200 keV energy band were estimated. A brightness temperature Tb > 2.1 × 10 14 K (violating the IC limit) was inferred from the variability observed in the radio regime, but no corresponding signatures of IC avalanches were recorded at higher energies. Conclusions. In the most plausible scenario of negligible contribution of the interstellar scintillation to the observed radio variability, the absence of the signatures of IC catastrophes provides either a lower limit δ > 8 to the Doppler factor affecting the radio emission or strong constraints for modelling of the Compton-catastrophe scenario in S5 0716+71.

A Broadband CMOS Amplitude Detector for On-Chip RF Measurements

Abstract: This paper presents a CMOS RF amplitude detector as a practical integrated test device and demonstrates its application for on-chip testing. The proposed circuit performs full-wave rectification and generates a dc voltage proportional to the amplitude of an RF signal over a wide frequency range. The design considerations and analysis of operation for the employed class-AB rectifier are described. Fabricated in a standard 0.35-mum CMOS process, the RF detector uses only 0.031 of area and presents an equivalent input capacitance of 13 fF. Measurements show that this RF test device has a detection dynamic range of 30 dB from 900 MHz to 2.4 GHz. Experimental results for the application of the RF amplitude detector in the built-in measurement of the gain and compression of a 1.6-GHz low-noise amplifier fabricated in the same chip are also presented.

Method and apparatus for network managed radio frequency coverage and mobile distribution analysis using mobile location information

Abstract: A system and method for identifying geographical areas which distribute poor radio frequency coverage is provided. The method includes measuring a radio frequency signal of a mobile unit in response to a trigger. The method continues with mapping the location data of the radio frequency signal which represents the positioning of the mobile unit at a given time. The method continues with recording the location data of the mobile unit and storing the location data in a database. The trigger, which prompts the radio frequency measurement, may be a timer expiring, a dropped call, or a mobile power increase signaling a weak signal. In any form, a post processing module may be configured in order to record, store and organize the location data into a report, such as a coverage map. Embodiments of this disclosure will display geographic areas that have poor radio frequency and allow for an administrator to identify trouble spots by a geographical region.

1.52-GHz micromechanical extensional wine-glass mode ring resonators

Abstract: Vibrating polysilicon micromechanical ring resonators, using a unique extensional wine-glass-mode shape to achieve lower impedance than previous UHF resonators, have been demonstrated at frequencies as high as 1.2 GHz with a Q of 3,700, and 1.52 GHz with a Q of 2,800. The 1.2-GHz resonator exhibits a measured motional resistance of 1 MOmega with a dc-bias voltage of 20 V, which is 2.2 times lower than the resistance measured on radial contour- mode disk counterparts at the same frequency. The use of larger rings offers a path toward even lower impedance, provided the spurious modes that become more troublesome as ring size increases can be properly suppressed using methods described herein. With spurious modes suppressed, the high-Q and low-impedance advantages, together with the multiple frequency on-chip integration advantages afforded by capacitively transduced mumechanical resonators, make this device an attractive candidate for use in the front-end RF filtering and frequency generation functions needed by wireless communication devices.

Power supplies for rf power amplifier

Abstract: Switched-mode power supplies (SMPSs) and their control methods for radio frequency (RF) power amplifiers in bat- tery-powered wireless transmitter devices. According to embodiments of the invention, a Boost-type SMPS and a Buck-type SMPS in cascade connection are controlled so that high efficiency is maintained for various loads and transmission power levels. The Boost SMPS and the Buck SMPS can be controlled based on the mode of operation of the transmitter, such as the actual battery voltage, the needed output power, the selected frequency band, the selected RF power amplifier (PA), the selected modulation method of the transmission signal, and/or the selected PA voltage control method, such as the envelope elimination and restoration (EER) technique, the envelope tracking (ET) technique, or the power-level tracking (PT).

Analysis of an Electromagnetic Mitigation Scheme for Reentry Telemetry Through Plasma

Abstract: During hypersonic reentry flight, the shock heated air generates a weakly ionized plasma layer. Because the weakly ionized plasma layer has a high plasma number density, it causes an important systems operation problem that is known as a communication, or radio, blackout. The radio blackout occurs when the plasma frequency of the plasma layer is higher than a radio wave frequency. In this case, the radio wave signals to and from the vehicle are reflected or attenuated so that the vehicle loses voice communication, data telemetry, and Global Positioning System navigation. The radio blackout problem can be solved by reducing the plasma number density of the plasma layer because the plasma frequency is mainly related to the plasma number density of the plasma layer. To reduce the plasma number density of the plasma layer, an electromagnetic E ? B layer approach is proposed. The proposed ExB layer is analyzed by a two-dimensional model. It suggests that an E ? B layer can be used to allow transmission of the communication signals through the plasma layer. We also propose an alternative to reduce the plasma density, based on an electrostatic plasma sheath.

Interrupted particle source

Abstract: A synchrocyclotron includes magnetic structures to provide a magnetic field to a cavity, a particle source to provide a plasma column to the cavity, where the particle source has a housing to hold the plasma column, and where the housing is interrupted at an acceleration region to expose the plasma column, and a voltage source to provide a radio frequency (RF) voltage to the cavity to accelerate particles from the plasma column at the acceleration region.

Lifetime Measurements on a High-Reliability RF-MEMS Contact Switch

Abstract: Radio frequency microelectromechanical systems (RF MEMS) cantilever contact switches have been tested for lifetime. The mean cycles-to-failure measured on an ensemble of switches was 430 billion switch cycles. The longest lifetime exhibited without degradation of the switch was 914 billion switch cycles. The devices were switched at 20 kHz with an incident RF frequency of 10 GHz and an incident RF power of 20 dBm. Testing was performed continuously over a period of approximately 18 months. The switches were operated in a cold-switched mode.

Phononic band-gap crystals for radio frequency communications

Abstract: We report on the experimental and theoretical observation of a phononic band-gap crystal operating in the megahertz regime. Our experimental data show over 25dB suppression of bulk acoustic waves, and our theoretical models predict almost linear scaling to the gigahertz frequencies, thus laying the foundation for the implementation of such devices in radio frequency communications. We further argue that cavities in such systems offer a unique opportunity to couple acoustic energy into a resonator utilizing piezoelectric materials, while at the same time allowing the realization of a resonance cavity in high-Q materials such as silicon oxide, silicon, and tungsten.

Miniature and multi-band RF coil design

Abstract: A near field apparatus comprises a Radio Frequency (RF) coil including at least one of a shorting bridge from a first point to a second point along an electrical path of the RF coil and/or a discontinuity in the electrical path of the RF coil.