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Mohammed N. Islam – One of the best experts on this subject based on the ideXlab platform.

  • Raman Amplifiers for telecommunications
    IEEE Journal on Selected Topics in Quantum Electronics, 2002
    Co-Authors: Mohammed N. Islam
    Abstract:

    Raman Amplifiers are being deployed in almost every new long-haul\nand ultralong-haul fiber-optic transmission systems, making them one of\nthe first widely commercialized nonlinear optical devices in\ntelecommunications. This paper reviews some of the technical reasons\nbehind the wide-spread acceptance of Raman technology. Distributed Raman\nAmplifiers improve the noise figure and reduce the nonlinear penalty of\nfiber systems, allowing for longer amplifier spans, higher bit rates,\ncloser channel spacing, and operation near the zero-dispersion\nwavelength. Lumped or discrete Raman Amplifiers are primarily used to\nincrease the capacity of fiber-optic networks, opening up new wavelength\nwindows for wavelengthdivision multmultiplexing such as the 1300 nm, 1400\nnm, or short-wavelength S-band. As an example, using a cascade of S-band\nlumped Amplifiers, a 20-channel, OC-192 system is shown that propagates\nover 867 km of standard, single-mode fiber. Raman Amplifiers provide a\nsimple single platform for long-haul and ultralong-haul amplifier needs\nand, therefore, should see a wide range of deployment in the next few\nyears

Hans Gaunholt – One of the best experts on this subject based on the ideXlab platform.

  • a numerical design approach for single amplifier active rc butterworth filter of order 5
    International Symposium on Circuits and Systems, 2007
    Co-Authors: Hans Gaunholt
    Abstract:

    A design method is presented for the design of all pole lowpass active-RC filters applying operational Amplifiers. The operational amplifier model used is the integrator model: omegat/s where omegat is the unity gain frequency. The design method is used for the design of a fifth order Butterworth filter applying just one operational amplifier coupled as a unity gain amplifier. It is shown that the influence from the real operational amplifier may be reduced by trimming just one resistor in the circuit. The unity gain Amplifiers have the advantage of providing low powepower consumption, yielding a large dynamic range, sometimes simplifying the amplifier design and being usable over a larger frequency range than conventional constant gain Amplifiers. The Schoeffler sensitivity index is used as a basis for a sensitivity comparison with other similar filters reported in the literature.

  • ISCAS – A numerical design approach for single amplifier, Active-RC Butterworth filter of order 5
    2007 IEEE International Symposium on Circuits and Systems, 2007
    Co-Authors: Hans Gaunholt
    Abstract:

    A design method is presented for the design of all pole lowpass active-RC filters applying operational Amplifiers. The operational amplifier model used is the integrator model: omegat/s where omegat is the unity gain frequency. The design method is used for the design of a fifth order Butterworth filter applying just one operational amplifier coupled as a unity gain amplifier. It is shown that the influence from the real operational amplifier may be reduced by trimming just one resistor in the circuit. The unity gain Amplifiers have the advantage of providing low powepower consumption, yielding a large dynamic range, sometimes simplifying the amplifier design and being usable over a larger frequency range than conventional constant gain Amplifiers. The Schoeffler sensitivity index is used as a basis for a sensitivity comparison with other similar filters reported in the literature.

P M Asbeck – One of the best experts on this subject based on the ideXlab platform.

  • a combined series parallel hybrid envelope amplifier for envelope tracking mobile terminal rf power amplifier applications
    IEEE Journal of Solid-state Circuits, 2012
    Co-Authors: Muhammad Hassan, L E Larson, Vincent W Leung, P M Asbeck
    Abstract:

    An improved envelope amplifier architecture for envelope tracking RF power Amplifiers is presented, consisting of two switching Amplifiers and one linear amplifier. The first switching amplifier and the linear amplifier provide wideband and high-efficiency operation, while the second switching amplifier provides a reduced bandwidth variable supply to the linear amplifier to further reduce power loss. The first switching amplifier and the linear amplifier are fabricated together in a 150 nm CMOS process, while the second switching amplifier is external. Measurements show a maximum average efficiency of 82% for a 10 MHz LTE signal with a 6 dB PAPR at 29.7 dBm output power and an SFDR of 63 dBc for a single tone of 5 MHz driving an 8 Ω load.

  • wideband high efficiency digitally assisted envelope amplifier with dual switching stages for radio base station envelope tracking power Amplifiers
    International Microwave Symposium, 2010
    Co-Authors: Chin Hsia, Donald F Kimball, Sandro Lanfranco, P M Asbeck
    Abstract:

    This paper presents a novel envelope amplifier architecture to improve the overall efficiency of wideband high linearity envelope tracking power Amplifiers (PAs). We show here a technique to increase the efficiency of the envelope amplifier while maintaining the amplifier’s bandwidth. The technique utilizes digital signsignal processing (DSP) control in conjunction with analog hysteretic feedback. Two high efficiency buck switching stages are coordinated to provide the wideband envelope power to the RF stage; a wide bandwidth linear regulator is also used at low power to maintain the envelope signal accuracy. The technique improves the efficiency of the envelope amplifier, especially for applications requiring high peak-to-average power ratio (PAPR) with wide bandwidth signals. The overall system was demonstrated using a GaAs high voltage HBT PA. For a variety of signals ranging from 6.6dB to 9.6dB PAR and up to 10MHz bandwidth, the overall system PAE reached above 50%, with a normalized power RMS error below 5% and ACLR1 of −50dBc with memory-less digital predistortion, at an average output power above 19W and gain of 10dB. The efficiencies obtained are the best ever reported, to our knowledge, for envelope tracking base station Amplifiers for these signals.

Youngoo Yang – One of the best experts on this subject based on the ideXlab platform.

  • optimized current of the peaking amplifier for two stage doherty power amplifier
    IEEE Transactions on Microwave Theory and Techniques, 2017
    Co-Authors: Jinhee Kwon, Hyunuk Kang, Keum Cheol Hwang, Cheonseok Park, Youngoo Yang
    Abstract:

    This paper presents a method of improving efficiency for the two-stage Doherty powepower amplifier (DPA) using the optimized current of the peaking amplifier. The DPA has a two-stage structure for both the carrier and peaking Amplifiers. The first stage of the peaking amplifier has an adjusted bias condition for a near Class-B operation, while the first stage of the carrier amplifier has a higher Class-AB operation. The gain expansion of the first stage due to its lower gate bias helps the second stage of the peaking amplifier to be biased for light Class-C operation and to have steeper turn-ON characteristics, which leads higher peak output power and higher back-off efficiency. The two-stage DPA was designed for the 2.655-GHz band. Using a downlink long-term evolution signal with a signal bandwidth of 10 MHz and a peak-to-average power ratio of 6.5 dB, the overall power gain of 25 dB and a peak output power of 54.2 dBm are experimentally obtained. Using an optimized shape of the peaking amplifier’s current, a drain efficiency (DE) of 53% and an adjacent channel leakage power ratio of -30 dBc were obtained at an average output power of 47.8 dBm. A DE of 56.8% and an adjacent channel leakage power ratio of -25 dBc were also obtained at an average output power of 49.5 dBm.

  • analysis and experiments for high efficiency class f and inverse class f power Amplifiers
    IEEE Transactions on Microwave Theory and Techniques, 2006
    Co-Authors: Young Yun Woo, Youngoo Yang, Bumman Kim
    Abstract:

    This paper presents analytic and experimental comparisons for high-efficiency class-F and inverse class-F Amplifiers. The analytic formula of the efficiencies, output powers, dc power dissipations, and fundamental load impedances of both Amplifiers are derived from the ideal current and voltage waveforms. Based on the formula, the performances are compared with a reasonable condition: fundamental output power levels of class-F and inverse class-F Amplifiers are conditioned to be identical. The results show that the inverse class-F amplifier has better efficiency than that of class-F Amplifiers as the on-resistance of the transistor increases. For experimental comparison, we have designed and implemented the class-F and inverse class-F Amplifiers at I-GHz band using a GaAs MESFET and analyzed the measured performances. Experimental results shows 10% higher power-added efficiency of the inverse class-F amplifier than that of the class-F amplifier, which verifies the waveform analysis.

  • analysis and experiments for high efficiency class f and inverse class f power Amplifiers
    IEEE Transactions on Microwave Theory and Techniques, 2006
    Co-Authors: Youngoo Yang
    Abstract:

    This paper presents analytic and experimental comparisons for high-efficiency class-F and inverse class-F Amplifiers. The analytic formula of the efficiencies, output powers, dc power dissipations, and fundamental load impedances of both Amplifiers are derived from the ideal current and voltage waveforms. Based on the formula, the performances are compared with a reasonable condition: fundamental output power levels of class-F and inverse class-F Amplifiers are conditioned to be identical. The results show that the inverse class-F amplifier has better efficiency than that of class-F Amplifiers as the on-resistance of the transistor increases. For experimental comparison, we have designed and implemented the class-F and inverse class-F Amplifiers at I-GHz band using a GaAs MESFET and analyzed the measured performances. Experimental results shows 10% higher power-added efficiency of the inverse class-F amplifier than that of the class-F amplifier, which verifies the waveform analysis.

Liu Yong-ning – One of the best experts on this subject based on the ideXlab platform.

  • Design and Experimental Research on C-band Solid State Power Amplifiers
    Modern Radar, 2005
    Co-Authors: Liu Yong-ning
    Abstract:

    Basing on two kinds of newly developed power Amplifiers, design principles and methods of C-band solid state power Amplifiers are introduced. Simulation and optimization of the bias and divider/combiner circuits are carried out using microwave simulation software. Simulation results and circuits layout are presented. The feasibility of this design is verified by making and testing of two kinds of Amplifiers. The Amplifiers’ pictures and test data are presented. The Amplifiers are used at 5.3~5.9 GHz of C-band, the output power is 30 W and 50 W respectively. They can operate in CW or pulse mode, as single amplifier or basic amplifying unit of power amplamplifier module in a radar.