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In this communication, a novel filtering antenna is proposed by utilizing active frequency selective surface (FSS), which can simultaneously achieve filtering and beam steering function. The FSS unit is composed of a metallic rectangular ring and a patch, with a pair of microwave varactor diodes inserted in between along incident electric field polarization direction. Transmission phase of the emitted wave can be tuned by changing the bias voltage applied to the varactor diodes. Through different configurations of the bias voltages, we can obtain the gradient phase distribution of the emitted wave along E- and H-plane. This active FSS is then fabricated and utilized as a radome above a conventional horn antenna to demonstrate its ability of steering the beam radiated from the horn. The experimental results agree well with the simulated ones, which show that the horn antenna with the active FSS can realize beam steering in both E- and H-plane in a range of \pm 30^\circ at 5.3 GHz with a bandwidth of 180 MHz. [ABSTRACT FROM PUBLISHER]

ABSTRACT This article presents a new quadrature voltage-controlled oscillator (QVCO). The LC-tank QVCO consists of two first-harmonic injection-locked oscillators (ILOs). The outputs of one ILO are injected to the common nodes of capacitors on the other ILO and vice versa so as to force the two ILOs operate in quadrature. At the supply voltage of 1.1 V, the total power consumption is 5.94 mW. The free-running frequency tuning range is 11.5%, tunable from 6.56 to 7.36 GHz as the tuning voltage is varied from 0.0 to 2 V. The QVCO has been implemented with the TSMC 0.18-μm CMOS technology and the die area is 0.504 × 0.803 mm2. The measured phase noise at 1-MHz offset is −123.01 dBc/Hz at the oscillation frequency of 7.34 GHz and the figure of merit of the proposed QVCO is about −192.5 dBc/Hz. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2528-2531, 2013 [ABSTRACT FROM AUTHOR]

A new frequency agile BST varactor loaded stacked circular microstrip antenna is presented. The antenna is analysed using extended cavity model. One of two bands of antenna is tunable with the help of BST varactor. The upper band is useful for WiMAX and lower band for other wireless communication systems. Various antenna parameters like return loss, resonant frequency, frequency agility etc. have been investigated. The simulated results agree well with the numerical data. A frequency agility of 60.64 % is achieved, which is better than simple Varactor diode loaded antenna. Lowest resonant frequency of 0.866 GHz is obtainable that shows a significant physical area reduction. The group delay of S $$_{11}$$ remains constant for entire band of operation. [ABSTRACT FROM AUTHOR]

ABSTRACT In this article, we present a frequency reconfigurable antenna for digital video broadcasting on handheld devices standard. By loading a printed inverted F antennas with a varactor diode, the resonance frequency can be tuned from 470 to 862 MHz. Furthermore, a magneto dielectric superstrate is used to reduce the dimension of the antenna while keeping a large bandwidth. To study the performance improvement due to the magneto-dielectric resonator,a comparison is performed with a reference antenna without magneto-dielectric superstrate. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2007-2011, 2013 [ABSTRACT FROM AUTHOR]

This paper presents a two-pole dual-band tunable bandpass filter (BPF) with independently controllable dual passbands based on a novel tunable dual-mode resonator. This resonator principally comprises a \lambda/2 resonator and two varactor diodes. One varactor is placed at the center of the resonator to determine the dominant even-mode resonant frequency; the other is installed between two ends of the resonator to control the dominant odd-mode resonant frequency. These two distinct odd- and even-mode resonances can be independently generated, and they are used to realize the two separated passbands as desired. Detailed discussion is carried on to provide a set of closed-form design equations for determination of all of the elements involved in this tunable filter, inclusive of capacitively loaded quarter-wavelength or \lambda/2 resonators, external quality factor, and coupling coefficient. Finally, a prototype tunable dual-band filter is fabricated and measured. Measured and simulated results are found in good agreement with each other. The results show that the first passband can be tuned in a frequency range from 0.77 to 1.00 GHz with the 3-dB fractional-bandwidth of 20.3%–24.7%, whereas the second passband varies from 1.57 to 2.00 GHz with the 3-dB absolute-bandwidth of 120 \pm 8 MHz. [ABSTRACT FROM PUBLISHER]

This article presents the design of a microwave bandpass filter with tunable center frequencies and reconfigurable transmission zeros. The tuning of the center frequencies is realized by loading varactors at the ends of the λ/2 resonator. The reconfiguration of transmission zero is implemented through varactors in combination with tapped λ/4 stubs. The equivalent circuit models of the tunable filters are provided. The transmission zeros can be set to be at the lower side, the upper side, or both sides of the passband. The design concept is demonstrated by measurement results for both one transmission zero case and two transmission zeros case. The tuning frequency ranges are 680-890 MHz and 680-1020 MHz for one zero case and two zeros case, respectively. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1526-1531, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27628 [ABSTRACT FROM AUTHOR]

In this paper, a novel tunable bandpass filter with an improved J-inverter is suggested. In this resonator, as the loading capacitance is increased, the resonant frequency is decreased. Also, the phase of the admittance inverter has characteristics that are variable by series capacitors and parallel varactor diodes. The electrical length of the inverter always maintains 90° at a given physical length of the inverter, which should be changed for different operating frequencies. This new bandpass filter has a tuning range of 1.8 GHz ∼ 2.45 GHz and an insertion loss of less than 2.5 dB. Also, the bandwidth is almost constant within the tuning range. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:852-855, 2013; View this article online at wileyonlinelibrary.com. DOI: 10.1002/mop.27467 [ABSTRACT FROM AUTHOR]

To realize a high-efficiency terahertz signal source, a varactor-based frequency-doubler topology is proposed. The structure is based on a compact partially coupled ring that simultaneously achieves isolation, matching, and harmonic filtering for both input and output signals at f0 and 2f0. The optimum varactor pumping/loading conditions for the highest conversion efficiency are also presented analytically along with intuitive circuit representations. Using the proposed circuit, a passive 480-GHz frequency doubler with a measured minimum conversion loss of 14.3 dB and an unsaturated output power of 0.23 mW is reported. Within 20-GHz range, the fluctuation of the measured output power is less than 1.5 dB, and the simulated 3-dB output bandwidth is 70 GHz (14.6%). The doubler is fabricated using 65-nm low-power bulk CMOS technology and consumes near zero dc power. [ABSTRACT FROM AUTHOR]

Deoxyribonucleic acid (DNA) biopolymer films are fabricated with varying amounts of hexadecyltrimethylammonium chloride (CTMA), which is a surfactant necessary to produce a DNA complex that is soluble in organic solvents. The dielectric constant ( κ) of these films at microwave frequencies as a function of applied static electric field ( E) is investigated. Results show that the dependence of κ on E, which is referred to as the dielectric tunability, is influenced by the amount of CTMA in the complex. Dielectric tunability is suppressed when the amount of CTMA is insufficient and improved when more CTMA is added. However, excessive amounts of CTMA also result in a very rough film surface that causes shorting problems when used in a capacitive structure. A varactor employing a 1- μm-thick DNA biopolymer film as the dielectric is demonstrated. Under 5 V DC bias, which generates E = 5 V/ μm, its capacitance at 15 GHz changes by 0.04 pF. This change corresponds to a relative dielectric tunability of 6.6%. A simple application of this varactor for modulation of the power transmitted through a microwave transmission line is also demonstrated. [ABSTRACT FROM AUTHOR]

A tunable band stop filter is designed in the frequency range of 0.5 GHz to 1 GHz and its performance is simulated with Agilent ADS. The filter is fabricated on FR-4 substrates. The BST parallel plate ferroelectric varactors are fabricated on sapphire substrates by MOD technique with Platinum Electrodes and ion-milling. The ferroelectric capacitors show a tunability over 50% within an applied DC bias of 5 V. The filter response was measured using Agilent Vector network analyzer. For the third order BST varactor tuned band stop filters, the notch frequency can be tuned from 480 MHz to 620 MHz by the application of 5 V tuning voltage with a maximum band attenuation of 20 dB. [ABSTRACT FROM AUTHOR]

This article presents a K-band CMOS voltage controlled oscillator (VCO) using a wide tuning range MOSFET varactor. The proposed varactor consists of a MOSFET in which the source and drain are connected to each other through a large resistor, the body is grounded through another large resistor, and the gate and source are connected through a capacitor. The newly proposed varactor improves the tuning range of the capacitance compared to that in a conventional MOSFET varactor and a resistors-added varactor because two large resistors partially cancels the parasitic capacitances of the MOSFET in the depletion mode, and the external capacitor supplements additional capacitance in the inversion mode. The proposed varactor achieves a capacitance tuning range of ±64.5%. The voltage controlled oscillator using the proposed varactor features a wide tuning range characteristic of 11.7% in the K-Band and shows a good figure-of-merit of −186.5 dBc/Hz. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2751-2754, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27164 [ABSTRACT FROM AUTHOR]

The effective capacitance of variable reactors (varactors) can be modulated by the magnitude of applied RF signals, resulting in troublesome detuning issues in resonators constructed with these devices. In this paper, the fundamental causes behind these issues are investigated through the use of Volterra series. It is concluded that two major distortion mechanisms, namely, compression and blocking, are responsible for this effective capacitance change under RF excitation. In light of this observation, different varactor configurations are proposed and investigated, yielding novel devices with much smaller capacitance variation, typically on the order of \sim \ 0.1\mathchar"707B \0.5\% compared to \sim \ 10\mathchar"707B \50\% for conventional semiconductor-based varactors. With this improvement, the resonance frequency shift of a 2-GHz resonator is decreased from \sim \ 300 to \sim \ 5~\ MHz for worst case conditions, a property essential to tunable high-Q filter applications. Among all analyzed structures, the varactor topology that facilitates cancelation of all important distortion products has been experimentally tested. These measurements demonstrate successful cancellation of both compression and blocking terms, resulting in capacitance variation below 0.5% in worst case scenarios. [ABSTRACT FROM AUTHOR]

Abstract: Two highly compact tunable stopband filters using microstrip transmission lines coupled with split ring resonators (SRRs) and varactor diodes are presented. Frequency or bandwidth tuning capability of each device is demonstrated. The frequency tunable filter, realized by a single stage, shows a wide tuning range of 19.8% with a maximum bandwidth of 5% and an insertion loss of approximately 20dB at 4GHz. The bandwidth tunable filter, realized by double stages, shows a 10-dB bandwidth of 19–34% with a biasing voltage of 0–10V. The implemented frequency tuning and bandwidth tuning devices show a significant area reduction of 60.1% and 53.5%, respectively, in comparison with a similar frequency or bandwidth tunable structure presented by others. Equivalent circuit models are presented. The measured S-parameters are in good agreement with simulated ones. [Copyright &y& Elsevier]

Analysis and design of a novel variable directional coupler based on a parallel line directional coupler using the even-odd mode technique are proposed. In this coupler, the variation of coupling is achieved using a PIN diode, connected to the nominally coupled port of a parallel line directional coupler, while the output is derived from the normally isolated port. To verify the theory, a parallel microstrip line coupler is fabricated on a substrate with ε r = 3.66, h = 762 μm, and tanδ = 0.006 and measured. The measured results show a variation in the transmission coefficient of nearly 20 dB, while at the same time, the change in the direct arm insertion loss is lower than 0.2 dB. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2643-2646, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27151 [ABSTRACT FROM AUTHOR]

A novel symmetric anchor-shaped active frequency selective surface (AFSS) with a wide tuning frequency range is proposed. Varactor diodes are used as the active tuning components at the center of each AFSS unit. The equivalent circuit model of the AFSS unit is extracted. SPICE-based circuit simulation and full-wave simulation are compared to predict the resonant frequency. A wide tunable frequency range from 1.76 to 2.45 GHz with a relative bandwidth of 33% is achieved. A prototype of AFSS is fabricated and tested. The measurement result is consistent with the simulation. The design has low power consumption and is potentially used for selectively shielding or reusing of GSM, TD-SCDMA, or Wi-Fi spectrums. [ABSTRACT FROM PUBLISHER]

A method and device for measuring the bias-voltage dependences of the Q-factor and capacitance for variconds and varactors of different dimensions and structures (two-electrode and three-electrode structures) in the 1-10 GHz frequency band are considered. By placing the devices to be measured outside a closed resonant cavity in a special microstrip holder, the measuring instrument can easily be adapted for rapid automated certification of the components and their mass production. [ABSTRACT FROM AUTHOR]

This paper presents a new low phase-noise microwave oscillator and wideband voltage-controlled oscillator (VCO) based on microstrip combline bandpass filters. For this type of oscillator, the passband filter is embedded into the feedback loop to treat as a frequency stabilization element. Instead of designing the oscillator at the group-delay-peak frequency of the filter to achieve a good phase-noise performance, in this paper, the peak frequency of the complex quality factor Qsc is adopted for oscillator design. To demonstrate the effectiveness of using Qsc-peak frequency, two filter-based oscillators are implemented at the Qsc-peak and group-delay-peak frequencies, respectively. The oscillator designed at the Qsc-peak frequency improves the phase-noise about 10 dB as compared with that realized at the group-delay-peak frequency. The developed oscillator with the three-pole combline filter is experimentally demonstrated at 2.05 GHz with -148.3-dBc/Hz phase noise at 1-MHz offset frequency. Moreover, by attaching a varactor on each resonator of the combline filter, the oscillator can be extended to a wideband VCO. The developed VCO has a frequency tuning range from 1.3 to 2.2813 GHz with a 54.8% bandwidth. Over this frequency range, all the phase noises measured at 1-MHz offset frequency are better than -117.19 dBc/Hz. [ABSTRACT FROM AUTHOR]

This letter presents a new differential active inductor voltage-controlled oscillator (VCO), which uses the complementary cross-coupled pairs to generate differential negative resistance. The active inductor is formed with complementary CMOS. The proposed CMOS low-phase noise VCO has been implemented with the United Manufacture Corp. (UMC) 90nm CMOS technology and the die area is 0.575 × 0.61 mm2. At the supply voltage of 0.9 V, the total power consumption is 4.5 mW. The free-running frequency of VCO is tunable from 1.22 to 1.86 GHz as the tuning voltage is varied from 0.0 to 0.9 V. The measured phase noise at 1MHz offset is −111.56 dBc/Hz at the oscillation frequency of 1.22 GHz and the figure of merit of the proposed VCO is about −166.75 dBc/Hz. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2039-2042, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27030 [ABSTRACT FROM AUTHOR]

A completely wireless detection coil with an integrated parametric amplifier has been constructed to provide local amplification and transmission of MR signals. The sample coil is one element of a parametric amplifier using a zero-bias diode that mixes the weak MR signal with a strong pump signal that is obtained from an inductively coupled external loop. The NMR sample coil develops current gain via reduction in the effective coil resistance. Higher gain can be obtained by adjusting the level of the pumping power closer to the oscillation threshold, but the gain is ultimately constrained by the bandwidth requirement of MRI experiments. A feasibility study here shows that on a NaCl/D2O phantom, 23Na signals with 20 dB of gain can be readily obtained with a concomitant bandwidth of 144 kHz. This gain is high enough that the integrated coil with parametric amplifier, which is coupled inductively to external loops, can provide sensitivity approaching that of direct wire connection. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

This article presents a CMOS millimeter-wave voltage-controlled oscillator (VCO), which provides a wide tuning range using a resistors-added MOSFET varactor.Large resistors connected to the source and bulk allow a MOSFET varactor to lower minimum capacitance and to maintain maximum capacitance compared to a conventional MOSFET varactor. Thus, the total capacitance tuning range of the proposed varactor is expanded to ±46.1%, allowing a VCO with the new varactor to possess a frequency tuning range of 13.4% from 29.3 to 33.5 GHz. The measured phase noise is −97.8 dBc/Hz at a 1-MHz offset at the center frequency of 31.3 GHz. The VCO in a 0.18-μm standard CMOS process dissipates 12.6 mW from a 1.8-V supply voltage. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1777-1783, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26983 [ABSTRACT FROM AUTHOR]

We present a fast radio frequency–capacitance-voltage (RF-CV) method to measure the CV relation of an electronic device. The approach is more accurate, much faster, and more cost effective compared to the existing off-the-shelf solutions. Capacitances are determined using a single-frequency 1-port S-parameter setup constructed from discrete components. We introduce a new way to correct for nonlinearities of the used components, which greatly increases the accuracy with which the phase and magnitude of the reflected signal is measured. The measurement technique is validated on an RF microelectromechanical systems capacitive switch and a barium-strontium-titanate tunable capacitor. Complete CV curves are measured in less than a millisecond, with a measurement accuracy well below 1%. [ABSTRACT FROM PUBLISHER]

Abstract: p-type TlGaSeS single crystal was used to fabricate a Schottky device. Silver and carbon metals were used as the Ohmic and Schottky contacts, respectively. The device which displayed wide RF band at 13.200 and narrow band at 62.517kHz with Q value of 1.4 and of 6.3×104, respectively, is characterized by means of current (I)–voltage (V), capacitance (C)–voltage characteristics as well as capacitance–frequency (f) characteristics. The device series resistance, ideality factor and barrier height are determined from the I–V curve as 35.8MΩ, 1.2 and 0.74eV, respectively. The apparent acceptor density and the build in voltage of the device increased with increasing ac signal frequency. The high Q value, observed at 62.517kHz, indicated a much lower rate of energy loss relative to the stored energy of the device. The energy loss (Q −1) is much less than 0.001% of the stored value. The device was tested and found to remain at the same mode of resonance for several hours. It never switched or ceased unless it was tuned off. [Copyright &y& Elsevier]

Abstract: The temperature effects on the capacitance–voltage characteristics as well as the room temperature capacitance–frequency characteristics of TlGaTe2 crystals are investigated. A very wide range of linearly varying tunable capacitance from 6.0μF to 60pF was recorded. The capacitance–voltage characteristics, being recorded in the temperature range of 290–380K, revealed a linear increase in the build in voltage associated with exponential decrease in the density of non-compensated ionized carriers with increasing temperature. The high temperature (up to 380K) biasing ability, the linear tunability and the high dielectric constant values (∼103) make the TlGaTe2 crystals applicable in microelectronic components. [Copyright &y& Elsevier]

This paper presents a study on reconfigurable transmit-array (TA) antennas based on multilayer tunable elements. The proposed configuration can be referred to as a multilayer antenna–filter antenna (MAFA) and it can be viewed as an extension of the antenna-filter antenna concept. It consists of multiple antenna layers cascaded to form a spatially distributed bandpass filter. Phase agility is achieved by tuning the resonant frequency of each layer. The main objective of this paper is to introduce a new design technique for MAFA TA antennas. As will be shown, the key feature of the proposed approach is that it allows to simultaneously take into account three key design parameters: the phase tuning range, the maximum acceptable losses per unit cell, and the operating bandwidth. Simulations and experimental results for MAFAs based on varactor-loaded slot antennas will be illustrated to prove the validity of the proposed method. In particular, numerical results will demonstrate that MAFA cells can be designed to provide full phase agility over operating bandwidths of up to 10% with maximum insertion losses of 3 dB. Furthermore, a specific example will show how introducing an inter-layer medium with a higher dielectric permittivity it is possible to reduce the array longitudinal size. Finally, experimental results obtained using a waveguide simulator will be presented for a 1\,\times\, 3 five-layer MAFA cell. [ABSTRACT FROM AUTHOR]

Abstract: In this paper the importance of a new design variable for high power anti-serial Schottky varactors, the aluminum composition of the AlGaN barrier layer, is demonstrated. AlGaN/GaN varactors containing either (1) a high-doped/low-doped GaN region or (2) just a low doped GaN region have been compared demonstrating that the selection of the device structure also depends on the amplitude of the input signal being tripled in frequency. Stronger susceptance modulation is exhibited in AlGaN/GaN ASVs made from Ga-face polar material compared to N-face polar material. Results indicate choosing the proper aluminum composition results in 27% conversion efficiency with an input signal of 5GHz and over 7% conversion efficiency with an input signal of 60GHz along with optimization trends. With input voltage amplitudes over 10V an AlGaN/GaN structure with 15% Al provides greater conversion efficiency than one with 5% Al. Power absorbed in the varactor also increases as aluminum percent increases affecting reliability and power transfer. Results of a GaN ASV performing as a frequency tripler for fundamental frequencies up to 110GHz indicate an advantage to using an AlGaN/GaN epi-structure over only a GaN epi-structure. [Copyright &y& Elsevier]

Ag contacts on the surface of the TlGaSeS single crystals are observed to exhibit Schottky characteristics. The ideality factor of the Ag/ TlGaSeS/Ag device decreased from 5.2 to 1.3 by the reduction of series resistance effect on the I-V characteristics. Cheung's model analysis revealed a series resistance and barrier height of 40.6 KΩ and 0.32 V, respectively. The device was run on the passive mode by injection with an alternating ac signal of variable frequency in the frequency range of 0-120 MHz and recoding the device capacitance. Several resonance-antiresonance positions in the range of 27-350 KHz were observed. The tangent loss factor of the passive device was observed to decrease with increasing frequency. It exhibited a very low loss value of the order of 10−5 at 120 MHz. Such property is a characteristic of high performance tunable device being suitable as processor clock controller. [ABSTRACT FROM AUTHOR]

In this paper, the design and use of an in situ tuner (IST) aiming On-Wafer multi-impedance method are presented. The conventional method using Off-Wafer tuner is limited by the frequency range and has high losses between this external tuner and the device under test (DUT). Here, the IST is placed near the DUT to achieve higher \vert\Gamma\vert and to cancel losses between the impedance generator and the device. The architecture of the tuner is based on variable lumped R and C elements fulfilled with cold-field-effect transistor and varactors controlled through biasing and associated to coplanar transmission line for phase shifting. Detailed and dedicated noise de-embedding technique is described to extract the four noise (NF\min,{R}n,{\mmb{\Gamma}}opt) parameters of 65-nm metal-oxide-semiconductor field-effect silicon transistors through the use of this in situ multi-impedance method. The 75–110 GHz noise test bench using cold-noise source method and the noise measurement are described showing transistor capabilities at MMW. [ABSTRACT FROM PUBLISHER]

In this paper, Fourier cosine series are proposed for representing the hard nonlinear dependence of the permittivity and conductance of a ferroelectric material on the DC bias voltage. Using these Fourier series representations closed-form expressions are obtained for the amplitudes of the fundamental and third-order intermodulation products generated when a exposing ferroelectric-based varactor to a DC bias voltage plus an equal-amplitude two-sinusoids signal. The results clearly show the strong and complicated dependence of the third-order intermodulation performance on the DC bias voltage, the temperature and the amplitude of the sinusoid. The results obtained suggest that the DC bias voltage and/or the temperature play an important role in deciding the nonlinear performance of the ferroelectric-based varactors. [ABSTRACT FROM AUTHOR]

In this paper, we present the design and development of a low-power LC-VCO with improved phase noise performance by implementing a new capacitor divider varactor configuration and a 2nd order notch filter. We propose a new time-weighted approach to model the effective capacitance experienced by the oscillating signal over the oscillation period. The modeled effective capacitance is used in the calculation of the oscillation frequency, which agrees well with the simulation results. Two VCOs are designed and fabricated in TSMC 0.18 μm technology. The oscillation frequency is tunable from 759 to 910 MHz with a tuning range of 18%. At 900 MHz carrier, the measured phase noise is −126.1 dBc/Hz at 1 MHz frequency offset with 4.5 mW power consumption. [ABSTRACT FROM AUTHOR]

In this paper, we study an electrical nonlinear medium consisting of voltage-dependent capacitors and inductors to generate sharp pulses from a lower frequency sinusoid. First, we analyze the optimum conditions for maximum harmonic generation in a uniform nonlinear line. Next, we extend the nonlinear line to a two-dimensional nonlinear lattice that is compatible with CMOS technology. Compared with the nonlinear line, the lattice relies on spatial power combining, higher cut-off frequency, and nonlinear wave interaction to enhance the pulse amplitude and sharpness. To show the feasibility of this method, we implement the first CMOS nonlinear lattice in a 0.13-\mum CMOS process, and successfully demonstrate 2.7-Vpp, 6.3-ps pulses from a 22-GHz input signal. [ABSTRACT FROM AUTHOR]

In this paper, we experimentally realized a steering antenna using a type of active metamaterial with tunable refractive index. The metamaterial is realized by periodically printed subwavelength metallic resonant patterns with embedded microwave varactors. The effective refractive index can be controlled by low direct-current (dc) bias voltage applied to the varactors. In-phase electromagnetic waves transmitting in different zones of such metamaterial slab experience different phase delays, and, consequently, the output direction of the transmitted wave can be steered with progressive phase shift along the interface. This antenna has a simple structure, is very easy to configure the beam direction, and has a low cost. Compared with conventional phased-array antennas, the radome approach has more flexibility to operate with different feeding antennas for various applications. [ABSTRACT FROM PUBLISHER]

This paper presents a compact highly linear tunable second-order quasi-elliptic filter with constant 3-dB bandwidth. The proposed filter is thoroughly analyzed to clearly describe the filter equivalent circuit and the tuning mechanism involved. In addition, the tunable resonator configuration employed is shown to improve filter linearity, especially for low bias voltages where distortion is normally stronger. A quasi-elliptic tunable filter was designed, built, and tested for illustration and verification. With a 3-dB bandwidth variation of only 4.6%, the filter had a frequency coverage from 1.45 to 1.96 GHz, an insertion loss better than 2.5 dB, and measured IIP3 > 43 dBm throughout. The experimental results are in excellent agreement to theory and simulations. [ABSTRACT FROM PUBLISHER]

This paper analyzes various aspects of the performance of LC VCOs over temperature with emphasis on the temperature dependence of Kvco. A novel frequency-tuning scheme is proposed which allows wide temperature range operation while keeping the average Kvco low. [ABSTRACT FROM PUBLISHER]

Abstract: TlInSe2 single crystal has been successfully prepared by the Bridgman crystal growth technique. The crystal, which exhibits compositional atomic percentages of 25.4%, 25.2% and 49.4% for Tl, In and Se, respectively, is found to be of tetragonal structure with lattice parameters of a=0.8035 and c=0.6883nm. The crystals were used to design radio frequency sensitive varactor device. The temperature dependence of the current–voltage characteristics of the device allowed the calculation of the room temperature barrier height and ideality factor as 0.87eV and as 3.2, respectively. Rising the device temperature increased the barrier height and decreased the ideality factor. This behavior was attributed to the current transport across the metal–semiconductor interface. The capacitance of the device is observed to increase with increasing voltage and increasing temperature as well. The temperature activation of the capacitance starts above 82°C with a temperature coefficient of capacitance being 1.08×10−3 K−1. Furthermore, the capacitance of the device was observed to increase with increasing frequency up to a maximum critical frequency of 4.0kHz, after which the capacitance decreased with increasing frequency. The behavior reflected the ability of maximum amount of charge holding being at a 4.0kHz. The analysis of the capacitance–voltage characteristics at fixed frequencies reflected a frequency dependent barrier height and acceptors density. The decrease in the barrier height and acceptors density with increasing frequency is mainly due to the inability of the free charge to follow the ac signal. [Copyright &y& Elsevier]

Varactors are key components in the realization of tunable networks, for instance, in high-efficiency power-amplifier architectures. This paper presents a method to measure the varactor quality factor (Q-factor) in the presence of nonlinear distortion. The importance of correctly choosing the loading condition at the second harmonic is illustrated by multiharmonic active source– and load–pull measurements. Furthermore, the method also allows for accurate extraction of the bias-dependent series resistance without the need of area consuming resonant structures. [ABSTRACT FROM PUBLISHER]

This paper presents the design of an ultra-low-power LC quadrature VCO (QVCO). It is designed in a single-poly seven-metal 65-nm CMOS process. Several aspects of state-of-the-art QVCO design are addressed, for example tank design and circuit topologies in nano-meter CMOS technology. To minimize power dissipation, an inductor with a high LQ product of 188 nH at 2.4 GHz, and a self-resonant frequency ( f) of 3.8 GHz, was designed. According to post-layout simulations, the power dissipation is below 300 μW at a 0.6 V supply. At this supply, the simulated tuning range and phase noise at 1 MHz offset are 10.3% (2.26-2.5 GHz) and −109.6 dBc/Hz respectively. The phase noise figure of merit (FoM) is better than 182.5 dB at all supply voltages of interest, which is competitive to other state-of-the-art QVCOs. [ABSTRACT FROM AUTHOR]

An inductively coupled, wireless sensor was fabricated for remote measurement of pH. The sensor consisted of a planar spiral inductor connected to a surface mount varactor, which was a voltage controlled capacitor, forming an inductive-capacitive (LC) resonant circuit. The pH electrodes, made of a thick-film antimony/antimony oxide sensing electrode and a thick-film silver/silver chloride reference electrode, were connected in parallel to the varactor. A voltage change across the electrodes due to the pH variation in the test medium would change the capacitance of the varactor, shifting the resonant frequency of the LC circuit. By inductively coupling the spiral inductor with a detection coil, the resonant frequency of the LC circuit was remotely monitored, allowing measurement of the pH. The advantage of the described pH sensor is its wireless and passive nature, which allows for long-term pH monitoring in inaccessible area. The sensor will be useful for remote monitoring of pH during industrial or food processes. When miniaturized, the sensors can also be used for biomedical applications such as remote tracking of gastric or esophageal pH on patients suffering from gastroesophageal reflux disease. [ABSTRACT FROM PUBLISHER]