Bias Voltage Of Varactor Research Articles

Reconfigurable Parametric Amplifications of Spoof Surface Plasmons.

Next‐generation inter‐chip communication requires ultrafast ultra‐compact interconnects. Designer plasmonics offers a possible route towards this goal. Further development of the plasmonic technique to circuit applications requires the direct amplification of plasmonic signals on a compact platform. However, significant signal distortions and limited operational speeds prevent the application of traditional MOS‐based amplifiers to plasmonics. Up to day, the amplification of surface plasmons without phase distortion has remained a scientific challenge. In this work, the concept of parametric amplification (PA) is transplanted to the plasmonics and is realized experimentally an ultrathin reconfigurable PA using a spoof surface plasmon polariton (SSPP) waveguide integrated with tunable and nonlinear varactors. The measured parametric gain in the experiment can reach up to 9.14 dB within a short nonlinear propagation length, for example, six SSPP wavelengths, in excellent agreement with the theoretical prediction. By tuning the bias voltage of varactors, the phase‐matching condition can be precisely controlled over a broad frequency band, enabling the authors to realize the multi‐frequency PA of plasmonic signals. Measured phase responses confirm that the plasmonic parametric amplifier can significantly suppress the signal distortions as compared with the traditional MOS‐based amplifier, which is a property highly desired for ultrafast wireless communication systems and integrated circuits.

Design of power-efficient CMOS based oscillator circuit with varactor tuning control

This paper presents a low-power, wide tuning range CMOS voltage-controlled oscillator with MCML (MOS current mode logic) differential delay cell. Voltage controlled oscillator (VCO) circuit is designed in TSMC 0.25 μm CMOS process. To achieve the broad frequency range concept of variable capacitance is employed in the proposed VCO circuit. Source/drain tuning voltage (Vtune) and body bias voltage (Vb) of I-MOS varactor are used to achieve variable capacitance at different I-MOS varactor widths (W). The dual control voltage of I-MOS varactor results in a tuning range from 0.528 GHz to 2.014 GHz. VCO's figure of merit (FoM) is 152.13 dBc/Hz with phase noise of −93.77 dBc/Hz at 1 MHz offset from the oscillation frequency. The proposed VCO dissipates maximum power of 3.127 mW.

Active Compact Wearable Body Area Networks for Wireless Communication, Medical and IoT Applications

The development of compact wearable antennas and transceivers for communication, IoT (Internet of Things), and biomedical systems will be presented in this paper. Development of Compact efficient wearable antennas is one of the major challenges in development of wearable communication, IoT, and medical systems. The main goal of wireless body area networks (BANs), WBANs, is to provide continuously medical data to the physician. Body area network (BAN) antennas should be flexible, lightweight, compact, and have low production cost. However, low efficiency is the major disadvantage of small printed antennas. Microstrip antennas resonant frequency is altered, due to environment conditions, different antenna locations, and different system operation modes. These disadvantages may be solved by using compact active and tunable antennas. A new class of wideband active wearable antennas for medical applications is presented in this paper. Amplifiers may be connected to the wearable antenna feed line to increase the system dynamic range. Small lightweight batteries supply the bias voltage to the active components. An active dual polarized antenna is presented in this paper. The active dual polarized antenna gain is 14 ± 3 dB for frequencies ranging from 380 to 600 MHz. The active transmitting dual polarized antenna output power is around 18 dBm. A voltage-controlled diode, varactor, may be used to control the antenna electrical performance at different environments. For example, an antenna located in patient stomach area has VSWR (Voltage Standing Wave Ratio) better than 2:1 at 434 MHz. However, if the antenna will be placed on the patient back, it may resonate at 420 MHz. By varying the varactor bias voltage, the antenna resonant frequency may be shifted from 420 to 434 MHz. An ultra-wideband passive and active printed slot antenna may be employed in wideband wearable communication systems. The active slot antenna gain is 13 ± 2 dB for frequencies from 800 MHz to 3 GHz.

Experimental validation of active holographic metasurface for electrically beam steering.

In this paper, a holographic metasurface possessing beam scanning capability at fixed frequency is presented. The desired radiation beam is obtained by using a reference wave to excite a sinusoidally-modulated impedance surface, which is equivalent to the interference pattern between the radiation wave and reference wave. By changing the bias voltage of varactor diodes loaded on the sub-wavelength unit cells, the variation range of the modulated impedance can be tuned, resulting in the change of radiation angle. Both the simulation and experimental results demonstrate that the direction of the radiation beam can be tuned in the range from 23° to 50° at 5.5 GHz. The proposed holographic metasurface shows great potential applications in constructing planar beam scanning antenna for integrated microwave system.

Design of a Fixed-Frequency Beam-Scanning Antenna Controlled by Voltage

A microstrip leaky wave antenna with operating frequency 2.5GHz is designed based on composite right/left handed transmission line. The beam scanning of the antenna can be controlled by changing the bias voltage of varactor in the antenna. And the performance, S-parameters and horizontal polarization pattern, of the antenna are investigated by simulation and experimental measurement, respectively. The results show that the designed antenna has better beam scanning, which is proper to be used in wireless local area networks and short-range wireless technology.

Design of a Voltage-Controlled Beam Scanning Antenna Array Based on CRLH TL

The voltage-controlled beam scanning antenna array based on the CRLH transmission line is designed with series power divider and three small antenna. The resonant frequency of the open-termination power divider is 2.5GHz, and the varactor bias voltage of the small antenna is from 8V to 2V. At the operating frequency of 2.5GHz, the horizontally polarized pattern of the antenna array is measured. When the bias voltage of the varactor is changed, the antenna array radiation beam scanning range is up to 96 degrees, and its radiation from backward to forward can be achieved by controlling the varactor bias voltage.

Metamaterial Based Electronically-Scanned Circularly-Polarized LWA

An electronically-scanned circularly-polarized leaky-wave antenna (LWA) designed for ETC system is proposed in this paper. Based on the theory of composite right/left-handed (CRLH) transmission line (TL), the proposed antenna can fulfill the beam-scan from -6° to -21° in the half plane continuously at the fixed frequency of 5.8 GHz by tuning the bias voltage of varactors loaded on the CRLH TL. By loading corner-cut square patches, a circularly-polarized radiation is obtained at the main beam, and the maximum gain in the main beam direction keeps above 11 dB.

A frequency agile active microstrip antenna for CP operation

AbstractA frequency agile microstrip antenna for CP operation is presented. The frequency agility is achieved by symmetrical loading of two identical varactor diodes at the radiating edge of the patch, in which the operating frequency of the square microstrip antenna is electronically controlled by the reverse bias voltage of varactor, whereas circular polarization is achieved by four slits and a pair of truncated corners. Theoretical modal for an antenna is developed using modal cavity model and circuit theory concept. The results are validated with MOM‐based simulator and experimental results. A good agreement between the simulated, calculated, and experimental results is obtained. The tuning range is found to be 660 MHz (40.24%) and shows about 71% reduction in antenna size as compared to the conventional circular polarized antenna. Antenna shows consistent radiation characteristics for entire frequency tuning range. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2205–2209, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27033

Compact, tunable large group delay line

AbstractIn this paper, we present a compact, tunable delay line based on left‐handed nonlinear transmission line (LH NLTL). The widely tunable range of the large group delay is achieved by controlling a reverse bias voltage of series varactors in the LH NLTL. The proposed tunable delay line can be made in a very compact form because its size is dominated by the cascaded varactors. Our experiment shows that the fabricated prototype exhibits tunable group delay between 1.2 and 2.2 ns at a frequency of 1.42 GHz and good return loss. The circuit size is merely 1.6 cm in length. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2893–2895, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24747

A reconfigurable bandpass-bandstop filter based on varactor-loaded closed-ring resonators [Technical Committee

In this article, a novel reconfigurable bandpass-bandstop filter based on the varactor-loaded closed-ring resonators is presented, where the bandpass and bandstop characteristics can be easily controlled by tuning the varactor bias voltage. This reconfigurability results from the perturbation effect on the degenerated even and odd modes of the closed-ring resonator. When the perturbation varactor is at the series resonance, its reactance vanishes, so a bandstop characteristic is formed. When the perturbation varactor is changed to be capacitive, the bandpass characteristic is generated. Additional varactors, incorporated at input and output ports, are tuned along with the perturbation varactors to maintain good return losses.

Nonlinear effects in varactor-tuned resonators

This paper describes the effects of RF power level on the performance of varactor-tuned resonator circuits. A variety of topologies are considered, including series and parallel resonators operating in both unbalanced and balanced modes. As these resonators were designed to produce oscillators with minimum phase noise, the initial small signal insertion loss was set to 6 dB and, hence, QL/Q0 = 1/2. To enable accurate analysis and simulation, S parameter and PSPICE models for the varactors were optimized and developed. It is shown that these resonators start to demonstrate nonlinear operation at very low power levels demonstrating saturation and lowering of the resonant frequency. On occasion squegging is observed for modified bias conditions. The nonlinear effects are dependent on the unloaded Q (Q0), the ratio of loaded to unloaded Q (QL/Q0), the bias voltage, and circuit configurations with typical nonlinear effects occurring at -8 dBm in a circuit with a loaded Q of 63 and a varactor bias voltage of 3 V. Analysis, simulation, and measurements that show close correlation are presented.

Quasi-optical VCOs

Quasi-optical grid voltage controlled oscillators (VCOs) are presented. These VCOs are the first demonstration of a quasi-optical system consisting of several periodic arrays loaded with solid-state devices. A quasi-optical VCO consists of an array of oscillators, a variable capacitance array, and a mirror. The mirror provides feedback for locked power-combining of a large number of MESFET oscillators that load a two-dimensional metal grid on a dielectric substrate. The frequency can be electrically tuned either with gate bias or with another array loaded with varactor diodes. When the varactor bias voltage is changed, the capacitance of the diodes changes, which in turn modulates the frequency of the output power-combined wave. Two types of arrays are presented, one consisting of short dipoles, and the other of bow-tie elements. As expected, the bow-tie VCO has better performance than the dipole VCO, due to its broadband impedance. A 10% tuning bandwidth with less than 2 dB power change was measured in the case of a bow-tie VCO.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Analytic Model for Varactor-Tuned Waveguide Gunn Oscillators (Short Papers)

An analytic model for electronic tuning of an X-band waveguide transferred-electron oscillator is presented. The oscillator is electronically tunable by a varactor, and mechanically tunable by movement of a short circuit. The model is used to predict oscillation frequency, maximum electronic tuning range, and electronic tuning versus varactor bias voltage. Two different methods, the zero reactance theory and the Slater perturbation theory, are used to calculate the electronic tuning. The results of these calculations are compared to experimental results for two different oscillator configurations.