Radio Frequency Stability Research Articles

On diagnostics of annular-shape radio-frequency plasma jet operating in argon in atmospheric conditions

One of the driving forces behind the development of cold plasma sources at atmospheric pressure is their application in the biomedical field. In this respect, radio-frequency (RF) plasma jets are of particular importance due to their possible safe operation on humans and the generation of the high amount of reactive species. For this reason, we designed an RF plasma jet in co-axial geometry with the possibility of aerosol introduction, where its characteristics were evaluated by electrical diagnostics, optical emission and laser scattering spectroscopy. The RF plasma jet operation and stability of diffuse mode were analysed based on energy balance. It was observed that α-mode diffuse discharge characterised by an effluent length up to 5 mm was sustained at a power density below 30 W cm−3. The gas and rotational temperature were determined by means of spectroscopy methods and compared with the results of direct laser scattering. It was established that the gas temperature obtained from N2 emission of transition C3Пu → B3Пg (0, 2) is highly overestimated whereas the gas temperature estimated from OH transition A2Σ+ → X2Пi (0, 0) gave a reasonable agreement with both Rayleigh and Raman spectroscopy. Based on the Rayleigh scattering method, uniform gas temperature distribution in the discharge effluent was found at a power below 15 W with the average temperature below 340 ± 15 K. The low gas temperature of argon plasma jets would allow use of this source in temperature-sensitive material applications including skin treatments.

Optimization of the geometry of a charge plasma double-gate junctionless transistor for improved RF stability

The radiofrequency (RF) stability of a charge plasma double-gate junctionless transistor (DG-CPJLT) is reported based on the stability factor (K) obtained from the Y-parameters of the device. The impact of variation of geometrical parameters, voltage biases, temperature, and interface traps on the stability of the DG-CPJLT is studied. Based on the results, an optimized DG-CPJLT device is designed and its RF figures of merit obtained. S-parameter values are also computed to study the high-frequency behavior of the device. Moreover, parameters for evaluation of the linearity, such as the third-order transconductance coefficient (gm3) and third-order voltage intercept point (VIP3), are also obtained for the optimized device. It is found that the DG-CPJLT shows significantly improved stability without affecting the RF figures of merit.

Impact of high k spacer on RF stability performance of double gate junctionless transistor

AbstractIn this paper, radio frequency (RF) stability performance of double gate junctionless transistor for different spacer material, the width of spacer, and bias conditions is reported. The impact of gate oxide thickness and gate work function on RF performance of double gate junctionless transistor is also presented. The analog and RF figure of merit, namely, intrinsic gain, unity gain cut‐off frequency, stern's stability factor, critical frequency, maximum attainable gain, and maximum stable gain, are investigated with the help of numerical simulation. The result shows that the fringing fields of high k spacers have a major impact on the gate to source and gate to drain capacitance. The device design guideline along with bias and geometrical parameters are reported for the optimized structure. The optimized device structure exhibits better RF stability.

RF stability performance of SOI junctionless FinFET and impact of process variation

In this paper we investigate the impact of process parameter variations such as temperature (T), channel doping concentration (ND), Fin height (Hfin) and Fin width (Wfin) on Radio Frequency (RF) stability performance of 20nm Silicon on Insulator Junctionless FinFET (SOI JLFinFET). The developed RF stability model provides relation between critical frequency (fk) and small signal parameters which can be optimized for improved stability. Results shows as temperature increases (27–200°C) cutoff frequency (fT) and maximum oscillation frequency (fmax) reduced by 12% and 8% respectively also stability factor (K) decreases by 20% at high frequency. Increasing ND, Hfin and Wfin increases fT and fmax but degrades stability performance. The result also provides optimized design guideline for operating SOI JLFinFET under RF range.

Performance comparison between the free running oscillator and 50Ω radio frequency systems

Abstract Two common kinds of radio frequency (RF) systems (free running oscillator and 50 Ω) are widely applied in industry and research. However, their unclear performances based on different operational mechanisms influence effective implementations of the two systems. The purpose of this research was to explore advantages and disadvantages of the two systems by experimental comparison. The results showed that heating rates and energy efficiency of the free running oscillator RF system were higher than those of the 50 Ω RF system under the same conditions (e.g. powers, electrode gaps, sample sizes and moisture contents), but control accuracy of the 50 Ω RF system was better than that of the free running oscillator RF system since its RF power could be adjusted under the same electrode gap. The RF heating uniformity and stability of the 50 Ω RF system were also better than those of the free running oscillator RF system. These comparison results may provide detailed performance information of the two RF systems and help to promote further practical applications of the two RF systems in food processing industry.

An optoelectronic oscillator based on series resonance cavity

Commercial and military applications of microwave and millimeter-wave sources in aerospace, radar, navigation, and communication system require high spectrum purity and low phase-noise oscillators. The optoelectronic oscillator (OEO) emerges as an excellent low noise source that has attracted great attention in recent years. In this paper, a novel technique is proposed for single-mode selection in an optoelectronic oscillator, which uses a microwave cavity as the mode selector. It consists of a pump laser and a feedback circuit including an intensity modulator, an optical fiber delay lines, a photodetector, an amplifier, a filter and two drilling cables. The drilling cable is fabricated by drilling open holes on a coaxial cable using a drilling machine. By changing the radius of the drilling holes, the designed reflection coefficient can be obtained. By simulation, the constructed microwave resonator that consists of a filter and two drilling cables has a higher Q value and only the modes that satisfy the oscillation conditions of the loop will be selected. The basic principle is analyzed theoretically and experimentally. By comparing with traditional structure of OEO, it is shown that the novel structure can effectively improve the side-mode suppression ratio. In addition, the stability of the oscillation frequency is easier to control than the parallel structure. In this experiment, the output of a 10 GHz single-mode signal with a side-mode suppression ratio of 72 dB and a phase noise of -122 dBc/Hz@10 kHz from the carrier is obtained. Meanwhile, phase-lock techniques are used to compensate the drift of cavity length. Then the radio frequency (RF) stability of the oscillation frequency is measured using an RF spectrum analyzer, and the RF stability over 3 hours for the OEO is less than 4 Hz. This scheme has the advantages of traditional OEO with low noise since no extra active devices are needed, and it suppresses the side-mode noise also effectively. In addition, this system is promising for the development of compact, high frequency, low cost and low noise OEOs.

Impact of parameter fluctuations on RF stability performance of DG tunnel FET

This paper presents the impact of parameter fluctuation due to process variation on radio frequency (RF) stability performance of double gate tunnel FET (DG TFET). The influence of parameter fluctuation due to process variation leads to DG TFET performance degradation. The RF figures of merit (FoM) such as cut-off frequency (ft), maximum oscillation frequency (fmax) along with stability factor for different silicon body thickness, gate oxide thickness and gate contact alignment are obtained from extracted device parameters through numerical simulation. The impact of parameter fluctuation of silicon body thickness, gate oxide thickness and gate contact alignment was found significant and the result provides design guidelines of DG TFET for RF applications.

Stability performance of optimized symmetric DG-MOSFET

This article presents the bias and geometry optimization procedure for the radio frequency (RF) stability performance of nanoscale symmetric double-gate metal-oxide semiconductor field-effect transistors (DG-MOSFETs). The stability model can provide hints for optimizing the DG-MOSFET under an RF range. The device parameters are extracted for different bias and geometry conditions through numerical simulation, and the RF figures of merit such as cut-off frequency (ft) and maximum oscillation frequency (fmax), along with stability factor, are calculated for an optimized structure. The proposed structure exhibits good RF stability performance.

Joint RF and large-signal stability optimization of MMIC power combining amplifiers

In this paper, authors report on an enhanced approach for the design of monolithic microwave integrated circuit (MMIC) power combining amplifiers. Commonly used techniques for the stabilization of such circuits are empirical and too conservative. This leads very often to a non-desired degradation of the radio frequency (RF) performances that are inherent to the physical properties of such stabilization networks at the fundamental frequency of operation. The methodology proposed here is based on the use of large-signal optimization processes that combine RF and stability analyses from the early stages of the design. This approach results in an improvement of the RF performances while sufficient stability margins are preserved. The optimization procedure is explained on a Ku-band MMIC power amplifier for space-borne communications.

Bias and geometry optimization of silicon nanowire transistor: Radio frequency stability perspective

AbstractThis article presents structure and bias optimization techniques for the radio frequency (RF) stability of silicon nanowire transistor. The RF parameters are extracted using device simulation. The device stability is obtained for various bias conditions and geometry, and observed that the proposed device structure shows good stability response. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2114–2117, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27016