Symmetric RF Research Articles

Shift-invariant homogeneous classes of random fields

Given an Rd-valued random field (rf) Z(t),t∈T and an α-homogeneous mapping κ we define the corresponding equivalent class of rf's (denoted by Cκ[Z]) which include representers of the same tail measure νZ. When T is an additive group, tractable equivalent classes of interest are the shift-invariant ones, which contain in particular all independent random shifts of Z. This contribution is mainly concerned with the investigation of the probabilistic properties of shift-invariant Cκ[Z]'s. Important objects introduced in our setting are tail and spectral tail rf's. Further, the class of universal maps U acting on elements of Cκ[Z] turns out to be crucial for properties of functionals of Z. Applications of our findings concern max-stable and symmetric α-stable rf's, their maximal indices as well as their random shift-representations.

Quantitative measurements of singlet molecular oxygen in a low pressure ICP

We present measurements of the densities and temperatures (rotational and translational) of the metastable a1Δg (v = 0) state of O2 in a cylindrically symmetric RF driven plasma operating in inductive mode at 100 mTorr total pressure and 300 W applied power. Line-of-sight absorption across the plasma region was determined by diode laser cavity ringdown spectroscopy on the (0, 0) vibrational band of the O2(b1Σg +) ← O2(a1Δg) transition near 1.9 μm. Four rotational quantum states were studied, with a population distribution corresponding to a rotational temperature of 346 ± 38 K. The translational temperature was determined to be 359 ± 16 K from the width of the strongest absorption line, Q(12), and in equilibrium with the rotational distribution. The absolute concentration of O2(a1Δg, v = 0) was measured as (9.5 ± 1.3) × 1013 cm−3, and corresponds to an apparent (3.5 ± 0.45)% contribution to the total number density. Time-resolved CRDS measurements following plasma extinction were used to deduce a wall loss coefficient, γ, of (2.8 ± 0.3) × 10−3 on predominantly Al surfaces. Surmising reasonable concentrations for O2(b1Σg +) and an upper limit for the vibrational temperature places the total contribution of O2(a1Δg) at between 3.6% and 5.85%. The variation of the O2(a1Δg, v = 0) state concentration with RF power shows a clear transition from the E to H mode excitation near an applied power of 150 W. Allan variance analysis yields a minimum measurable concentration of O2(a1Δg, v = 0) of 1.1 × 1012 cm−3 over 100 ringdown events, an order of magnitude more sensitive than previously reported.

RF design of a compact, X-band travelling-wave RF photogun made from halves

This paper presents the RF design, thermal calculations and beam dynamics simulations of a compact, high repetition rate, travelling-wave RF photogun operating at the European X-band frequency of 11.994 GHz. The design is based on a CLIC prototype structure milled from copper halves and proposes to use the unique gap, introduced in the original X-band accelerating structure’s geometry, to couple in the photocathode laser without obstructing the outgoing electron bunches. Operating at an input RF power of 29 MW and combined with a single X-band structure downstream, the non-cylindrically symmetric travelling-wave RF photogun operates as a compact photo-injector able to provide 40 pC bunches with an energy of 34.4 MeV ± 0.07 %, a bunch length of 533 fs and a horizontal and vertical emittance of 0.368 and 0.338 mm mrad, respectively, at a repetition rate up to 1 kHz.

Design of Reconfigurable Tri-Band Antenna for Wireless Communication

The Design is a quotidian rectangular patch antenna which functions on three Different frequency bands. Tri-band antenna is an electronic device that can operate in three different frequency bands. Taking the advantage of antenna parameter modification in to account the tri-band operation is achieved. Reconfigurable antenna is capable of modifying its frequency and radiation properties in a controlled and changeable manner. The antenna is designed with the use of dielectric substrate of 1.6mm thickness with permittivity of 4.6. The design is simulated in HFSS platform. In designed antenna, configuration I engages in three different bands of frequencies 1.3 ∼ 3, 4.1 ∼ 4.7, 6.1 ∼7.6 GHz where the return loss value is around and below -10 dB. The Configuration I is designed to have an enhanced performance over a specified range of frequency (1.5 GHz to 3 GHz). But configuration II is devised to have a subsided performance over all UWB frequency ranges. The return loss of configuration II is -15 dB over 1.25 GHz to 2 GHz range and -12 dB over 4.25 GHz to 5.75 GHz range, -14 dB for 7.5 GHz to 8.5 GHz range. Switching between the frequencies is achieved using three symmetrical ideal RF MEMS switches. The Patch antenna which can be applicable to wireless communication systems like Sensing, RFID, WLAN is presented.

Symmetric Traveling Wave Parametric Amplifier

We developed and experimentally tested a Symmetric Traveling Wave Parametric Amplifier (STWPA) based on Three-Wave Mixing, using the new concept of a Symmetric rf- SQUID. This allows to fully control the second and third order nonlinearities of the STWPA by applying external currents. In this way, the optimal bias point can be reached, taking into account both phase mismatch and pump depletion minimization. The structure was tested at 4.2K, showing a 4GHz bandwidth and a maximum estimated gain of 17dB. STWPA showed also great flexibility, allowing up-down conversion mixer operations and rf-controlled switch.

The effects of electron surface interactions in geometrically symmetric capacitive RF plasmas in the presence of different electrode surface materials

Particle-in-cell/Monte Carlo collision (PIC/MCC) simulations are performed to investigate the asymmetric secondary electron emission (SEE) effects when electrons strike two different material electrodes in low pressure capacitively coupled plasmas (CCPs). To describe the electron-surface interactions, a realistic model, considering the primary electron impact energy and angle, as well as the corresponding surface property-dependent secondary electron yields, is employed in PIC/MCC simulations. In this model, three kinds of electrons emitted from the surface are considered: (i) elastically reflected electrons, (ii) inelastically backscattered electrons, and (iii) electron induced secondary electrons (SEs, i.e., δ-electrons). Here, we examined the effects of electron-surface interactions on the ionization dynamics and plasma characteristics of an argon discharge. The discharge is driven by a voltage source of 13.56 MHz with amplitudes in the range of 200–2000 V. The grounded electrode material is copper (Cu) for all cases, while the powered electrode material is either Cu or silicon dioxide (SiO2). The simulations reveal that the electron impact-induced SEE is an essential process at low pressures, especially at high voltages. Different electrode materials result in an asymmetric response of SEE. Depending on the instantaneous local sheath potential and the phase of the SEE, these SEs either are reflected by the opposite sheath or strike the electrode surface, where they can induce δ-electrons upon their residual energies. It is shown that highly energetic δ-electrons contribute significantly to the ionization rate and a self-bias forms when the powered electrode material is assumed to be made of SiO2. Complex dynamics is observed due to the multiple electron-surface interaction processes and asymmetric yields of SEs in CCPs.

Symmetrical Quasi-Absorptive RF Bandpass Filters

A type of symmetrical RF bandpass filters (BPFs) with quasi-absorptive functionality are presented. They are composed of a bandpass section that is loaded at its input/output ports with nearly complementary resistively terminated bandstop sections. In this manner, the input-signal energy that is not transmitted by the bandpass section is dissipated by the loading resistors of the bandstop sections to attain the quasi-reflectionless behavior. The theoretical analysis of the first-order symmetrical quasi-absorptive BPF stage is detailed. In addition, synthesis examples of higher attenuation and sharper rejection designs based on in-series-cascade arrangements, higher order realizations, and cross-coupling techniques are illustrated. A coupling-matrix-level loss analysis of the devised symmetrical quasi-reflectionless BPF configuration for uniform and nonuniform quality-factor ( ${Q}$ ) distribution is also carried out. Furthermore, for experimental validation, 2.5-GHz microstrip BPF demonstrators consisting of an in-band linear-phase two-stage in-series-cascade circuit and a second-order prototype are manufactured and characterized.

Azimuthal inhomogeneities of axially symmetric rf discharge plasma in arc-shaped magnetic field

An axially symmetrical rf magnetron discharge in argon with a small admixture of air and in air was studied. The plane loaded electrode was equipped with a ring-shaped dielectric insert. Design features of the electrode and of the magnetic system allow the discharge ring to be located in the region where the electric and magnetic field lines are not perpendicular to each other. It has been revealed that in this case the glowing plasma ring is sectionalized. Up to 10 long-living plasma bunches were observed. They equidistantly locate along the discharge ring and may either rotate around the discharge axis or remain motionless. Both the discharge power and the working gas pressure are quite different from those proper to dc and high-power impulse magnetron sputtering discharges with spokes.

On characterization of symmetric type capacitive RF MEMS switches

This paper presents the design, fabrication and characterization of capacitive type MEMS switch for space and terrestrial communication applications. The deviation in measured actuation voltage and RF response of the switches are discussed in terms of the process variation which occurred unintentionally during the fabrication of devices. For example the measured actuation voltage is 15 V, about 20% higher than the designed voltage of 12.25 V. The deviation corresponds to the increase in thickness of the membrane while electroplating. The impact of process parameters on mechanical resonance frequency of the switches, and on/off time is also discussed. Measured S-parameters shows isolation of > − 20 dB for 7–16 GHz and an insertion loss better than − 0.6 dB up to 20 GHz. The capacitance ratio of the fabricated switch is 77, which is 15% lower than the designed capacitance ratio. The switch has been tested for 1 million 65 thousand cycles without switching failure. The deviation of simulated and measured results is discussed in the following sections.

Design of a Broadband Planar RF Structure for a 0.22 THz Travelling Wave Tube

Planar broadband THz travelling wave tube is being designed for ultra broadband high speed data rate communication and imaging. A simplified analytical approach is developed for designing of a planar staggered double vane rectangular waveguide slow-wave structure (SDVSWS) for a broadband 0.22 THz 100W TWT. The structure is inherently compatible for sheet beam operation, and it is designed for an electron beam of voltage 20 kV and current 50 mA. 3D e.m. field simulator code CST-MWS was used for simulating the SDVSWS using the analytical design parameters. It is found that the dispersion characteristic by the analytical method matches well within 5% with the simulated dispersion characteristic of the structure. Effects of various parameters of a double-vane SWS on dispersion and impedance characteristics are evaluated for achieving a planar TWT of bandwidth more than 40 GHz with high gain. It is shown that pitch and vane height are most significant parameters and half-period staggering of double vanes in the structure provides wider bandwidth, high impedance and high symmetric RF electric field for efficient beam-wave interaction.

Results of using the axisymmetric RF focusing by means of field spatial harmonics at 7 MeV proton linac

For several decades, axially symmetric channels with RF focusing by means of nonsynchronous spatial harmonics of the accelerating field are offered as an attractive alternative to proven and reliable RFQ linacs. In a number of works an effectiveness of channels with axially symmetric RF focusing by means of the nonsynchronous harmonics of the field was demonstrated in the proton energy range up to 2 MeV. An effectiveness of discussed channels for protons at energies up to 7 MeV is considered in this paper. Numerical simulation results of proton self-consistent dynamics in a channel with axisymmetric RF focusing are presented and discussed in this article.

Computational Characterization of a New Inductively Coupled Plasma Source for Application to Narrow Gap Plasma Processes

Since the recent advent of serious problems in the plasma fabrication processes (bowing, faceting, notching, and twisting) is related to the polymer control issue. The polymer control on the wafer surface by controlling the radical composition in the plasma has become a major mission in the fabrication industry. This polymer control has been successfully performed in the capacitively coupled plasma (CCP) source. The CCP source can be operated in the small volume condition (narrow gap) without the loss of good uniformity of plasma. Unlike the CCP source, the inductively coupled plasma (ICP) source needs large enough space to make a uniform plasma via the plasma diffusion process. The polyer control in the ICP source has been very difficult for an increased residence time of radicals due to large space. To reduce this problem, we propose a new ICP antenna named quadrupole antenna. It can make a uniform plasma in a narrow gap, compared with the conventional ICP antenna. A comparative electromagnetic simulation study between the quadrupole and the conventional ICP antennas shows that the quadrupole antenna makes better symmetric and uniform RF fields close to the antenna compared with the conventional antenna. The key elements are the perfect symmetric structure and the restricted radiation property of the proposed quadrupole antenna.

Design of experiments based factorial design and response surface methodology for MEMS optimization

This paper presents the application of the design of experiments technique based factorial designs and response surface methodology (RSM) for optimization of MEMS devices. The RSM methodology is used to optimize the geometric parameters of the symmetric toggle RF MEMS switch to minimize the switch pull-in voltage. Fractional factorial based Plackett---Burman screening design is developed and the corresponding pull-in voltage is obtained, through finite element method (FEM) based simulations, for different combinations of the dimensional parameters. Analysis of variance is performed to distinguish the most significant parameters affecting the output response. The significant parameters, obtained using Plackett---Burman screening design, are further investigated using second order Box---Behnken design to obtain the optimal levels of the significant parameters and analyze their interactions. Regression analysis is carried out to check the adequacy of the Box---Behnkan based response surface model for predicting the output response. The effect of the significant parameters and their interactions on the pull-in voltage is analyzed through model based 3D surface and contour plots. The optimal levels of the parameters for a pull-in voltage $$\le$$ ≤ 15 V, with compact device dimensions, are determined and verified through FEM simulations. A comparison is made for the results obtained through RSM with the analytical results presented in the literature. This showed a close agreement, verifying the practicability of this approach for the optimization of MEMS devices.

Accurate geometry scalable complementary metal oxide semiconductor modelling of low‐power 90 nm amplifier circuits

This paper proposes a technique to accurately estimate radio frequency behaviour of low-power 90 nm amplifier circuits with geometry scalable discrete complementary metal oxide semiconductor (CMOS) modelling. Rather than characterising individual elements, the scheme is able to predict gain, noise and reflection loss of low-noise amplifier (LNA) architectures made with bias, active and passive components. It reduces number of model parameters by formulating dependent functions in symmetric distributed modelling and shows that simple fitting factors can account for extraneous (interconnect) effects in LNA structure. Equivalent-circuit model equations based on physical structure and describing layout parasites are developed for major amplifier elements like metal–insulator–metal (MIM) capacitor, spiral symmetric inductor, polysilicon (PS) resistor and bulk RF transistor. The models are geometry scalable with respect to feature dimensions, i.e. MIM/PS width and length, outer-dimension/turns of planar inductor and channel-width/fingers of active device. Results obtained with the CMOS models are compared against measured literature data for two 1.2 V amplifier circuits where prediction accuracy for RF parameters (S 21, noise figure, S 11, S 22) lies within the range of 92–99%. .

Back Cover: Plasma Process. Polym. 5∕2014

Back Cover: Acetone and carbon dioxide are used within a symmetric RF plasma discharge to deposit oxygenfunctional plasma polymer films that are exceptionally stable under aging conditions. Further details can be found in the article by Dirk Hegemann et. al. on page 496.

CMOS Ultra-Wideband Low Noise Amplifier Design

This paper presents the design of ultra-wideband low noise amplifier (UWB LNA). The proposed UWB LNA whose bandwidth extends from 2.5 GHz to 16 GHz is designed using a symmetric 3D RF integrated inductor. This UWB LNA has a gain of 11 ± 1.0 dB and a NF less than 3.3 dB. Good input and output impedance matching and good isolation are achieved over the operating frequency band. The proposed UWB LNA is driven from a 1.8 V supply. The UWB LNA is designed and simulated in standard TSMC 0.18 µm CMOS technology process.

Dynamics and Electronegativity of Oxygen RF Plasmas

AbstractThe capacitively coupled radio frequency plasma at 13.56 MHz in oxygen was systematically studied by 160 GHz Gaussian beam microwave interferometry at high temporal resolution (200 ns) and simultaneous laser photodetachment for electron and negative ion density analysis. Additionally, spatio‐temporally resolved electric probe measurements were performed for comparison with microwave interferometry. A high and low electronegative operation mode was found in the asymmetric rf discharge. In the high electronegative mode it was shown the significant role of the metastable excited oxygen molecules in electron attachment and detachment processes. In particular, a temporary electron density increase is observed in the early afterglow of a pulsed rf plasma. The transition between both modes is driven by the rf power and the self‐bias voltage, respectively. In connection with the phase resolved optical emission spectroscopy and the study of the electron heating mechanisms the transition into the low electronegative mode at higher rf power shows a relation to the alpha to gamma mode transition. Furthermore, electron density fluctuations are measured over a wide field of processing parameters, e.g. due to the attachment‐induced ionization instability. PIC‐MCC simulation and fluid model calculation of a symmetric oxygen rf discharge confirm the different electron heating mechanisms and the dominance of negative atomic oxygen ions (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A numerical and experimental investigation of an axially symmetric RF plasma

The characteristics of an atmospheric pressure, RF discharge in air were determined and compared with a 2D numerical model adapted from that used for a dc glow discharge. For a 15 mm discharge, the RF plasma's electrical and optical characteristics show a close correlation to several equivalent dc plasmas and to the results calculated from the adapted model. For an rms conduction current range of 11–30 mA, the rotational temperature varies between 2800 and 3200 K; the vibrational temperature shows a change of 3500–4000 K with near equilibrium conditions to the rotational state occuring in the central region of the discharge. Spatial measurements and modelling of nitrogen emission spectra identify the changes in the temperatures and dimensions along the vertical z-axis as well as the spatial dependence on the atomic and molecular species generated in the discharge.

A symmetric metamaterial element-based RF biosensor for rapid and label-free detection

A symmetric metamaterial element-based RF biosensing scheme is experimentally demonstrated by detecting biomolecular binding between a prostate-specific antigen (PSA) and its antibody. The metamaterial element in a high-impedance microstrip line shows an intrinsic S21 resonance having a Q-factor of 55. The frequency shift with PSA concentration, i.e., 100 ng/ml, 10 ng/ml, and 1 ng/ml, is observed and the changes are Δf ≈ 20 MHz, 10 MHz, and 5 MHz, respectively. The proposed biosensor offers advantages of label-free detection, a simple and direct scheme, and cost-efficient fabrication.

Magnetic vortex core reversal by rotating magnetic fields generated on micrometer length scales

AbstractUnidirectional switching of the magnetic vortex core can be achieved in micron‐sized ferromagnetic platelets by excitation of the gyrotropic mode of the vortex structure with in‐plane rotating magnetic fields. Circulating fields with a switchable sense of rotation (clockwise, CW or counter clockwise, CCW) have been generated on a micrometer length scale at frequencies up to 1 GHz by two orthogonal electric RF currents with 90° phase shift flowing through crossed but not isolated striplines. Decoupling of these currents is realized by balanced symmetric RF sources. The amplitudes of the rotating magnetic fields and their spatial distributions are calculated and the stripline geometry is discussed. By taking advantage of this technique, unidirectional vortex core reversal by excitation with CW or CCW rotating magnetic fields has been observed by time resolved scanning transmission X‐ray microscopy. An area with reversed magnetization, the “dip,” was observed near the vortex core before vortex core reversal.