The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Gabriel M Rebeiz - One of the best experts on this subject based on the ideXlab platform.
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a differential dual polarized cavity backed microstrip patch antenna with independent frequency tuning
IEEE Transactions on Antennas and Propagation, 2010Co-Authors: Carson R White, Gabriel M RebeizAbstract:A dual-polarized cavity-backed microstrip patch antenna has been demonstrated with independent tuning of both polarizations from 0.6 GHz to ~1.0 GHz using Varactor diodes (1.2-5.4 pF). The 10-dB impedance bandwidth varies from 0.9% to 1.8% over that range. Differential coaxial feeds and the placement of the tuning Varactors in the appropriate symmetry planes are employed to achieve a differential-mode port-to-port isolation of >28 dB over the tuning range. Accordingly, the cross-polarization level is <; -20 dB at broadside. The antenna is 100 × 100 × 6.4 mm3 and is fabricated on a dielectric substrate (er = 2.2). The feed point and matching circuit for an impedance match to 50 Ω are determined using the transmission line model. This model underestimates the sensitivity of the resonance frequency to the loading capacitance, but leads to a good initial design. To the authors' knowledge, this is the first dual-polarized antenna with independent tuning over a 1.7:1 bandwidth and single-sided radiation.
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compact low loss tunable x band bandstop filter with miniature rf mems switches
IEEE Transactions on Microwave Theory and Techniques, 2010Co-Authors: Isak Reines, Sangjune Park, Gabriel M RebeizAbstract:This paper presents a compact low-loss tunable X-band bandstop filter implemented on a quartz substrate using both miniature RF microelectromechanical systems (RF-MEMS) capacitive switches and GaAs Varactors. The two-pole filter is based on capacitively loaded folded-λ/2 resonators that are coupled to a microstrip line, and the filter analysis includes the effects of nonadjacent inter-resonator coupling. The RF-MEMS filter tunes from 11.34 to 8.92 GHz with a - 20-dB rejection bandwidth of 1.18%-3.51% and a filter quality factor of 60-135. The GaAs Varactor loaded filter tunes from 9.56 to 8.66 GHz with a - 20-dB bandwidth of 1.65%-2% and a filter quality factor of 55-90. Nonlinear measurements at the filter null with Δf = 1 MHz show that the RF-MEMS loaded filter results in > 25-dBm higher third-order intermodulation intercept point and P-1 dB compared with the Varactor loaded filter. Both filters show high rejection levels ( > 24 dB) and low passband insertion loss ( <; 0.8 dB) from dc to the first spurious response at 19.5 GHz. The filter topology can be extended to higher order designs with an even number of poles.
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a Varactor tuned rf filter
IEEE Transactions on Microwave Theory and Techniques, 2000Co-Authors: A R Brown, Gabriel M RebeizAbstract:An electronically tunable filter at 1 GHz is presented in this paper. The filter uses a suspended substrate design and commercially available Varactors for filter tuning. The filter has a 60% tuning range from 700 MHz to 1.33 GHz with a low insertion loss (better than 3 dB from 1 to 1.33 GHz). This paper discusses the effects of the Varactor series resistance and the electrical length of the distributed resonator on the overall resonator quality factor and filter insertion loss. The input third-order intermodulation product intercept point was measured to be better than 17 dBm across the entire tuning range.
Shengfuh Chang - One of the best experts on this subject based on the ideXlab platform.
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a reconfigurable bandpass bandstop filter based on Varactor loaded closed ring resonators technical committee
IEEE Microwave Magazine, 2009Co-Authors: Yiming Chen, Shengfuh Chang, Chengyu Chou, Kunhsing LiuAbstract: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.
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a reconfigurable bandpass bandstop filter based on Varactor loaded closed ring resonators
2009Co-Authors: Yiming Chen, Shengfuh Chang, Chengyu Chou, Kunhsing LiuAbstract: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.
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a full 360 circ reflection type phase shifter with constant insertion loss
IEEE Microwave and Wireless Components Letters, 2008Co-Authors: Shengfuh Chang, Wenchun HsiaoAbstract:A new reflection-type phase shifter with a full 360deg relative phase shift range and constant insertion loss is presented. This feature is obtained by incorporating a new cascaded connection of Varactors into the impedance-transforming quadrature coupler. The required reactance variation of a Varactor can be reduced by controlling the impedance ratio of the quadrature coupler. The implemented phase shifter achieves a measured maximal relative phase shift of 407deg, an averaged insertion loss of 4.4 dB and return losses better than 19 dB at 2 GHz. The insertion-loss variation is within plusmn0.1 and plusmn0.2 dB over the 360deg and 407deg relative phase shift tuning range, respectively.
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design of a reflection type phase shifter with wide relative phase shift and constant insertion loss
IEEE Transactions on Microwave Theory and Techniques, 2007Co-Authors: Shengfuh Chang, Chiachan ChangAbstract:reflection-type phase shifter with constant insertion loss over a wide relative phase-shift range is presented. This important feature is attributed to the salient integration of an impedance-transforming quadrature coupler with equalized series-resonated Varactors. The impedance-transforming quadrature coupler is used to increase the maximal relative phase shift for a given Varactor with a limited capacitance range. When the phase is tuned, the typical large insertion-loss variation of the phase shifter due to the Varactor parasitic effect is minimized by shunting the series-resonated Varactor with a resistor Rp. A set of closed-form equations for predicting the relative phase shift, insertion loss, and insertion-loss variation with respect to the quadrature coupler and Varactor parameters is derived. Three phase shifters were implemented with a silicon Varactor of a restricted capacitance range of Cv,min = 1.4 pF and Cv,max = 8 pF, wherein the parasitic resistance is close to 2 Omega. The measured insertion-loss variation is 0.1 dB over the relative phase-shift tuning range of 237deg at 2 GHz and the return losses are better than 20 dB, excellently agreeing with the theoretical and simulated results.
Xiu Yin Zhang - One of the best experts on this subject based on the ideXlab platform.
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high q factor tunable bandpass filter with constant absolute bandwidth and wide tuning range based on coaxial resonators
IEEE Transactions on Microwave Theory and Techniques, 2019Co-Authors: Lian Yang, Yang Yang, Xiu Yin ZhangAbstract:This paper presents a method for designing low-loss Varactor-based tunable bandpass filters (BPFs) with constant absolute bandwidth (CABW) and wide tuning range based on coaxial resonators. The whole structure consists of a metallic cavity and a piece of printed circuit board (PCB). Varactors and their biasing components are mounted on the PCB, which are connected to the coaxial resonators to enable frequency tuning. The coupling control between coaxial resonators and the nonsynchronous tuning of the resonators are utilized to realize the CABW over a wide tuning range. Moreover, transmission zeros are generated near the passband, resulting in high skirt selectivity. For demonstration, a second-order tunable coaxial BPF with a wide tuning range from 698 to 960 MHz (31.5%) is designed and fabricated. Due to the use of high- $Q$ -factor coaxial resonators, the proposed tunable filter realizes low insertion losses ranging from 0.82 to 2.03 dB under a narrowband specification. The 1-dB bandwidth is measured as 35.3 ± 2.7 MHz, showing excellent CABW responses. Moreover, a third-order tunable coaxial BPF is also designed and implemented with enhanced skirt selectivity and out-of-band rejection. Comparison with other reported tunable BPFs is given, where the proposed designs show excellent performance of wide tuning range, CABW, high selectivity, and high tuning speed.
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tunable bandpass filters with constant absolute bandwidth and high linearity
International Conference on Microwave and Millimeter Wave Technology, 2012Co-Authors: Yi Bin Zhang, Xiu Yin Zhang, Xian Yi WangAbstract:This paper presents a frequency-agile bandpass filter with constant absolute bandwidth and high linearity. The proposed resonator is composed of an open-ended transmission line with back-to-back Varactor diodes loaded at one end. A novel mixed electric and magnetic coupling scheme is proposed to contorll the coupling coefficients in order to keep the bandwidth constant when the frequency is tuned. Moreover, the back-to-back Varactor diodes are used to enhance the linearity of the filter, which is better than that of the single Varactor counterparts. For validation, a demonstration filter is implemented. The design methodology and the experimental results are presented.
Christophe Fumeaux - One of the best experts on this subject based on the ideXlab platform.
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tunable bandpass to bandstop quasi yagi uda antenna with sum and difference radiation patterns
IEEE Transactions on Antennas and Propagation, 2019Co-Authors: Seyedali Malakooti, Seyed Mohammad Hadi Mousavi, Christophe FumeauxAbstract:A design of the double-element E-plane quasi-Yagi–Uda antenna is proposed offering two different radiation patterns and reconfigurable bandpass-to-bandstop frequency-tunable responses. The double-element antenna covers a wide frequency range that is exploited for the realization of the tunable operation modes. This is achieved by the integration of a pair of bandpass-to-bandstop filters, each of which can be reconfigured using two Varactor diodes and one p-i-n diode. The p-i-n diode serves the function of switching between bandpass and bandstop states, and the Varactors facilitate the frequency tunability for both states of operation. The bandpass filter provides a continuous frequency tuning function with a minimum rolloff rate of 57 dB/GHz and out-of-band transmission coefficient −1 dB. Importantly, the reconfigurable filtering functionality of the two-element antenna is preserved when fed by a wideband hybrid coupler to produce both the sum and difference radiation patterns. To obtain a high beam symmetry, the antenna elements are fed by the difference ( $\Delta $ ) signal to produce the directive radiation pattern and they are fed by the sum ( $\Sigma $ ) port to produce the null in the main radiation direction. The experimental results validate this concept with a measured tunability of 50.0% for the bandpass state and 50.4% for the bandstop state.
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planar array of electric lc resonators with broadband tunability
IEEE Antennas and Wireless Propagation Letters, 2011Co-Authors: Withawat Withayachumnankul, Christophe Fumeaux, Derek AbbottAbstract:A planar array of microwave electric- LC (ELC) resonators with broadband tunability of the resonance frequency is presented in this letter. An ELC resonator is typically composed of inductive loops and a capacitive gap, resonant at a wavelength much larger than its physical dimension. Here, the original resonator is modified to accommodate a Varactor and its accompanying dc bias enabling resonance tunability. The wideband operation can be achieved through strategic placement of the Varactor. The robustness of the response for a large array containing hundreds of the Varactor-loaded resonators is considered via a sensitivity analysis. The numerical and experimental results show that the fabricated array possesses a wide tuning range of nearly 32% with no significant resonance broadening, despite the tolerance in Varactor characteristics.
Huei Wang - One of the best experts on this subject based on the ideXlab platform.
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An analysis of miniaturized dual-mode bandpass filter structure using shunt-capacitance perturbation
IEEE Transactions on Microwave Theory and Techniques, 2005Co-Authors: Huei WangAbstract:A dual-mode bandpass ring filter using two pairs of shunt capacitances has been analyzed and designed. The size of the ring resonator can be reduced significantly by increasing the shunt capacitances. Since the resonator size is not an integer multiple of operating frequency, harmonic suppression is easily achieved. Analysis shows that the two pairs of shunt capacitances independently control the even- and odd-mode resonant frequency of the ring resonator. Moreover, the shunt capacitance also allows easier biasing, making tunable filters using Varactors realizable. Various configurations of dual-mode bandpass filters have been reported, and the advantages and disadvantages of each structure are discussed. Several filters of various capacitances have been designed and tested at 1.8 GHz, and show significant size reduction of over 67%. A Varactor-tuned filter has also been designed, and demonstrated a measured tunable center frequency of 20%. This study is a solution to the miniaturization of ring filters, and allows performance tuning, making ring filters more attractive in monolithic microwave integrated circuits and system-on-chip applications.
