The Experts below are selected from a list of 165102 Experts worldwide ranked by ideXlab platform
Andrei Grebennikov - One of the best experts on this subject based on the ideXlab platform.
-
design and analysis of class e f _ bf 3 power amplifier with nonlinear shunt capacitance at nonoptimum operation
IEEE Transactions on Power Electronics, 2015Co-Authors: Mohsen Hayati, Akram Sheikhi, Andrei GrebennikovAbstract:This paper presents analytical expressions for the Class-E/F 3 power amplifier with a nonlinear shunt capacitor for satisfying the nonoptimum condition at 50% duty ratio. The design parameters for achieving the nonoptimum condition are expressed as a function of the phase shift and dc supply voltage. The Class-E/F 3 amplifier with nonoptimum condition increases one design degree of freedom compared with the optimum conditions. Because of the increase in the design degree of freedom, one more relationship can be specified as a design specification. The following parameters series reactance, peak switch voltage, output power capability, and maximum Operating Frequency are presented. Based on analytical results, an example of the Class E/F 3 at Operating Frequency of 4 MHz is analyzed. The PSpice simulation and measured results agree with the analytical expressions, which show the validity of our analytical expressions at zero-voltage switching.
-
high efficiency class e f lumped and transmission line power amplifiers
IEEE Transactions on Microwave Theory and Techniques, 2011Co-Authors: Andrei GrebennikovAbstract:The theoretical analysis of a single-ended Class E/F n mode with explicit derivation of the idealized optimum voltage and current waveforms and load-network parameters with their verification by time- and Frequency-domain simulations for a particular case of Class E/F3 mode with a 50% duty cycle are presented. The ideal collector voltage and current waveforms for driving signals with 50% duty cycles demonstrate a possibility of 100% efficiency without overlapping between each other. Two examples of the Class E/F3 GaN HEMT power amplifiers, one with lumped elements at Operating Frequency of 430 MHz and the other with transmission-line elements at Operating Frequency of 2.14 GHz, are described and analyzed based on the simulation results. The test board with implemented transmission-line Class E/F3 GaN HEMT power amplifier has been measured and high-performance results with the output power of 40 dBm, drain efficiency of 76%, power-added efficiency of 73.1%, and power gain of 14.3 dB were achieved at Operating Frequency of 2.14 GHz.
Vincent Fusco - One of the best experts on this subject based on the ideXlab platform.
-
high efficiency harmonic peaking class ef power amplifiers with enhanced maximum Operating Frequency
IEEE Transactions on Microwave Theory and Techniques, 2015Co-Authors: Mury Thian, Ayman Barakat, Vincent FuscoAbstract:The recently introduced Class-EF power amplifier (PA) has a peak switch voltage lower than that of the Class-E PA. However, the value of the transistor output capacitance at high frequencies is typically larger than the required Class-EF optimum shunt capacitance. Consequently, soft-switching operation that minimizes power dissipation during off-to-on transition cannot be achieved at high frequencies. Two new Class-EF PA variants with transmission-line load networks, namely, third-harmonic-peaking (THP) and fifth-harmonic-peaking (FHP) Class-EF PAs are proposed in this paper. These permit operation at higher frequencies at no expense to other PA figures of merit. Analytical expressions are derived in order to obtain circuit component values, which satisfy the required Class-EF impedances at fundamental Frequency, all even harmonics, and the first few odd harmonics as well as simultaneously providing impedance matching to a 50- $\Omega$ load. Furthermore, a novel open-circuit and shorted stub arrangement, which has substantial practical benefits, is proposed to replace the normal quarter-wave line connected at the transistor's drain. Using GaN HEMTs, two PA prototypes were built. Measured peak drain efficiency of 91% and output power of 39.5 dBm were obtained at 2.22 GHz for the THP Class-EF PA. The FHP Class-EF PA delivered output power of 41.9 dBm with 85% drain efficiency at 1.52 GHz.
-
transmission line class e power amplifier with extended maximum Operating Frequency
IEEE Transactions on Circuits and Systems Ii-express Briefs, 2011Co-Authors: Mury Thian, Vincent FuscoAbstract:A novel Class-E power amplifier (PA) topology with transmission-line load network is presented in this brief. When compared with the classic Class-E topology, the new circuit can increase the maximum Operating Frequency up to 50% higher without trading the other Class-E figures of merit. Neither quarterwave line/massive radio-Frequency choke for collector/drain biasing nor additional fundamental-Frequency output matching circuit are needed in the proposed PA, thus resulting in a compact design. Closed-form formulations are derived and verified by simulations with practical design limitations carefully taken into consideration and good agreement achieved.
Ching-yuan Yang - One of the best experts on this subject based on the ideXlab platform.
-
A wide-range delay-locked loop with a fixed latency of one clock cycle
IEEE Journal of Solid-state Circuits, 2002Co-Authors: Hsiang-hui Chang, Ching-yuan YangAbstract:A delay-locked loop (DLL) with wide-range operation and fixed latency of one clock cycle is proposed. This DLL uses a phase selection circuit and a start-controlled circuit to enlarge the Operating Frequency range and eliminate harmonic locking problems. Theoretically, the Operating Frequency range of the DLL can be from 1/(N/spl times/T/sub Dmax/) to 1/(3T/sub Dmin/), where T/sub Dmin/ and T/sub Dmax/ are the minimum and maximum delay of a delay cell, respectively, and N is the number of delay cells used in the delay line. Fabricated in a 0.35 /spl mu/m single-poly triple-metal CMOS process, the measurement results show that the proposed DLL can operate from 6 to 130 MHz, and the total delay time between input and output of this DLL is just one clock cycle. From the entire Operating Frequency range, the maximum rms jitter does not exceed 25 ps. The DLL occupies an active area of 880 /spl mu/m/spl times/515 /spl mu/m and consumes a maximum power of 132 mW at 130 MHz.
Dukju Ahn - One of the best experts on this subject based on the ideXlab platform.
-
optimal design of wireless power transmission links for millimeter sized biomedical implants
IEEE Transactions on Biomedical Circuits and Systems, 2016Co-Authors: Dukju Ahn, Maysam GhovanlooAbstract:This paper presents a design methodology for RF power transmission to millimeter-sized implantable biomedical devices. The optimal Operating Frequency and coil geometries are found such that power transfer efficiency (PTE) and tissue-loss-constrained allowed power are maximized. We define receiver power reception susceptibility (Rx-PRS) and transmitter figure of merit (Tx-FoM) such that their multiplication yields the PTE. Rx-PRS and Tx-FoM define the roles of the Rx and Tx in the PTE, respectively. First, the optimal Rx coil geometry and Operating Frequency range are identified such that the Rx-PRS is maximized for given implant constraints. Since the Rx is very small and has lesser design freedom than the Tx, the overall Operating Frequency is restricted mainly by the Rx. Rx-PRS identifies such Operating Frequency constraint imposed by the Rx. Secondly, the Tx coil geometry is selected such that the Tx-FoM is maximized under the Frequency constraint at which the Rx-PRS was saturated. This aligns the target Frequency range of Tx optimization with the Frequency range at which Rx performance is high, resulting in the maximum PTE. Finally, we have found that even in the Frequency range at which the PTE is relatively flat, the tissue loss per unit delivered power can be significantly different for each Frequency. The Rx-PRS can predict the Frequency range at which the tissue loss per unit delivered power is minimized while PTE is maintained high. In this way, Frequency adjustment for the PTE and tissue-loss-constrained allowed power is realized by characterizing the Rx-PRS. The design procedure was verified through full-wave electromagnetic field simulations and measurements using de-embedding method. A prototype implant, 1 mm in diameter, achieved PTE of 0.56% ( $-$ 22.5 dB) and power delivered to load (PDL) was 224 $\mu{\rm W}$ at 200 MHz with 12 mm Tx-to-Rx separation in the tissue environment.
-
wireless power transmission with self regulated output voltage for biomedical implant
IEEE Transactions on Industrial Electronics, 2014Co-Authors: Dukju Ahn, Songcheol HongAbstract:This paper presents a wireless power transfer (WPT) system for powering implantable biomedical devices; the system is configured to achieve high efficiency even with CMOS switches and printed-circuit-board pattern coils and to maintain constant output voltage against coupling and loading variations without any additional blocks. It is shown that the parallel-resonant transmitter (TX) and receiver (RX) topology is advantageous for high efficiency even with lossy but compact components. In addition, the output voltage of the topology is insensitive to coupling and/or loading variations if the Operating Frequency is automatically adjusted according to coupling variations. A parallel-resonant class-D oscillator TX is developed to track the optimum Operating Frequency for the constant output voltage. The Operating distance for the constant output voltage is also extended using a novel resonator structure, which contains two resonating coils. These proposed schemes allow a compact, efficient, and robust wireless power system. Maximum power of 174 mW can be transmitted with 63% overall efficiency.
P F Sciortino - One of the best experts on this subject based on the ideXlab platform.
-
mode locked hybrid soliton pulse source with extremely wide Operating Frequency range
IEEE Photonics Technology Letters, 1993Co-Authors: P A Morton, Victor Mizrahi, Peter A Andrekson, T Tanbunek, R A Logan, P Lemaire, D L Coblentz, A M Sergent, K W Wecht, P F SciortinoAbstract:The authors report a mode-locked pulse source with extremely wide Operating Frequency range and very stable operation, through the use of a long, linearly chirped Bragg reflector as the output coupler integrated in a fiber external cavity. A 1.55 mu m strained MQW laser diode is used, with one facet high reflectivity (HR) coated for improved cavity Q, and the other antireflection (AR) coated to allow coupling to the external cavity and suppress Fabry-Perot modes. Near-transform-limited pulses are obtained over a Frequency range of 700 MHz around a system Operating Frequency of 2.488 GHz, with pulsewidths of 50 ps, as required for a practical soliton transmission system. >
