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Power Amplifier (power + amplifier)
Kinds of Power Amplifier Selected AbstractsCombined class F monolithic PA designMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2007Paolo Colantonio Abstract Experimental results on two GaAs PHEMT MMIC Class F Power Amplifiers for X-band applications are reported, aimed to validate a novel devices' combination method. In particular, 28.1 dBm output power with 44% power added efficiency and 30.6 dBm output power with 40% of power added efficiency were measured at 9.6 GHz, for single and combined devices amplifiers respectively. Both realised amplifiers exhibit 12% operating bandwidth. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 360,362, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22141 [source] Energy scavenging for energy efficiency in networks and applicationsBELL LABS TECHNICAL JOURNAL, Issue 2 2010Kyoung Joon Kim Telecommunication networks will play a huge part in enabling eco-sustainability of human activity; one of the first steps towards this is to dramatically increase network energy efficiency. In this paper we present two novel approaches for energy scavenging in networks. One involves thermal energy scavenging for improving wireless base station energy efficiency, and the other involves mechanical energy scavenging for powering sensors in sensor networks, for machine-to-machine (M2M) communications, and for smart grid applications. Power amplifier (PA) transistors in base stations waste 30 percent of the total energy used in a wireless access network (WAN) as heat to the environment. We propose a thermoelectric energy recovery module (TERM) to recover electricity from the waste heat of PA transistors. A fully coupled thermoelectric (TE) model, combining thermoelectricity and heat transfer physics, is developed to explore the power generation performance and efficiency as well as the thermal performance of the TERM. The TE model is comprehensively used to determine optimized pellet geometries for power generation and efficiency as a function of PA transistor heat dissipation, heat sink performance, and load resistance. Maximum power generation and efficiency for various parametric conditions are also explored. Untapped kinetic energy is almost everywhere in the form of vibrations. This energy can be converted into electrical energy by means of transducers to power wireless sensors and mobile electronics in the range of microwatts to a few milliwatts. However, many problems limit the efficiency of current harvesting generators: narrow bandwidth, low power density, micro-electro-mechanical system (MEMS) scaling, and inconsistency of vibrating sources. We explore energy scavenger designs based on multiple-mass systems to increase harvesting efficiency. A theoretical and experimental study of two degrees-of-freedom (2-DOF) vibration-powered generators is presented. Both electromagnetic and piezoelectric conversion methods are modeled by using a general approach. Experimental results for the multi-resonant system are in agreement with the analytical predictions and demonstrate significantly better performance in terms of maximum power density per total mass and a wider bandwidth compared to single DOF (1-DOF) generators. © 2010 Alcatel-Lucent. [source] Envelope tracking power amplifier with static predistortion linearizationINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 2 2009Timo Rautio Abstract This paper presents the design method, properties and driving techniques of a linear 0.5,W 1,GHz LDMOS power amplifier used in a supply modulated envelope tracking transmitter with real-time predistortion. Causes of nonlinearities are identified, and various supply voltage drives are experimented. Measured results show that the power efficiency can be improved while maintaining high linearity. Copyright © 2008 John Wiley & Sons, Ltd. [source] Adaptive predistortion of COFDM signals for a mobile satellite channelINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2 2003Nibaldo Rodriguez Abstract In this paper, we consider the optimization of the performance of QPSK and 16-QAM coded orthogonal frequency division multiplexing (COFDM) signals over the non-linear and mobile satellite channel. A high power amplifier and Rician flat fading channel produces non-linear and linear distortions; an adaptive predistortion technique combined with turbo codes will reduce both types of distortion. The predistorter is based on a feedforward neural network, with the coefficients being derived using an extended Kalman filter (EKF). The conventional turbo code is used to mitigate Rician flat fading distortion and Gaussian noise. The performance over a non-linear satellite channel indicates that QPSK COFDM followed by a predistorter provides a gain of about 1.7 dB at a BER of 3×10,3 when compared to QPSK COFDM without the predistortion scheme and 16-QAM COFDM provides a gain of 0.5 dB output back-off and 1.2 dB signal to noise ratio at a BER of 3×10,5 when compared with an adaptive predistorter based on the Harmmerstein model. We also investigate the influence of the guard time interval and Doppler frequency effect on the BER performance. When the guard interval increases from 0 to 0.125T samples and the normalized Doppler frequency is 0.001, there is a gain of 0.7 and 1 dB signal to noise ratio at a BER of 6×10,4 for QPSK and 16-QAM COFDM, respectively. Copyright © 2003 John Wiley & Sons, Ltd. [source] Frequency reconfigurable RF circuits using photoconducting switchesINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 1 2010D. Draskovic Abstract Designs for a frequency switchable dual-band branch-line coupler and a reconfigurable S-band power amplifier input matching network with photoconducting switches are presented. Frequency switching is achieved by increasing the power of the laser applied to the highly resistive silicon wafer and changing the properties of silicon under optical illumination. The advantages of this approach are high-speed switching, electromagnetic transparency (no interference), and thermal and electrical isolation between the device and the control circuit. A branch-line coupler frequency shift of 35% and 10% has been achieved from all switches off to all switches on in lower (900 MHz) and upper (1800 MHz) frequency bands, respectively. Frequency switchable class AB power amplifier with silicon switch in the input matching circuit has obtained the frequency tuning range of 2.5,3.5 GHz with no significant loss in efficiency and linearity. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010. [source] A digital predistorter for wireless transmittersINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 4 2009D. Bondar Abstract A novel digital baseband predistorter with improved reduction of spectral regrowth is proposed and investigated. The improvements are achieved by using a proposed predistortion technique and extended power amplifier (PA) fundamental-frequency modeling. The digital baseband predistortion (DPD), known for its simplicity of realization, low cost and integrability; however, it suffers from poor linearizing performances. We incorporate baseband iterative injection of in-band distortion components into the baseband DPD to enhance the nonlinearity compensation. General formulas for the fundamental-frequency output of a PA with n -order nonlinearity and recursive formulas for calculating the injected components for different number of iterations are developed. The proposed iterative digital baseband predistorter is verified experimentally with a wireless PA and measured results are presented to demonstrate feasibility of the proposed concept. The spectral regrowth suppression of 20 dB is achieved for a 3.5 MHz digitally modulated signal. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009. [source] Multiharmonic manipulation for highly efficient microwave power amplifiersINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 6 2001Paolo Colantonio Abstract Multiharmonic manipulation is presented as the most effective solution to improve power amplifier (PA) efficiency performances. Remarkable improvements in output power, power gain and power-added efficiency (PAE) are demonstrated, properly manipulating the input and output second and third harmonics, as compared to more classical design approaches. Experimental results at 5GHz confirm the feasibility, the validity and effectiveness of the proposed approach, increasing the maximum measured power-added efficiency from 39% to 61% © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 366,384, 2001 [source] Average power handling capability of multilayer microstrip linesINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 6 2001Inder J. Bahl Abstract This article describes the average power handling capability (APHC) of multilayer microstrip lines, including the effect of mismatch at the terminations. The data presented herein are validated by considering an example of a 12-W monolithic microwave integrated circuit power amplifier fabricated using multilayer low-loss microstrip technology. The calculated value of APHC for a 50-, line of a 75-,m-thick GaAs substrate is 1445 W at 10 GHz, whereas the corresponding value for a multilayer microstrip that has 10-,m-thick polyimide is only 44 W. At 40 GHz, these values are reduced by a factor of 2. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 385,395, 2001. [source] An efficient CMOS power-combining technique with differential and single-ended power amplifierMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2010Eunil Cho Abstract This article proposes an efficient power-combining architecture with differential and single-ended power amplifiers (PAs) in a CMOS process. The single-ended amplifier is added for overall efficiency enhancement. To demonstrate this concept, a CMOS PA using the proposed architecture was fabricated with a 0.13-,m CMOS technology that delivers 30.6 dBm of output power with 42% drain efficiency and 38% power-added efficiency at 1.95 GHz. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2214,2217, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25460 [source] Optimization of output matching network for class F power amplifier according to envelope in the envelope elimination and restoration transmitterMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2010Chongmin Lee Abstract This article presents the design and optimization of output matching network according to envelope for class F power amplifier (PA), which is to apply to envelope elimination and restoration (EER) transmitter. In this article, to increase the PAE of class F PA, which applies to EER transmitter, the varactor diode has been used on output matching network. As envelope changes, it optimizes constitution of harmonic trap that is short circuit in second-harmonic and is open circuit in third-harmonic. When drain voltage changes from 25 V to 30 V, some percentage is improved in the PAE. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1890,1893, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25335 [source] Complementary predistorter in CMOS differential power amplifierMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2010Inn-Yeah Oh Abstract For adaptive improvement of linearity above a 12 dB PAPR for 64QAM WiMAX, a complementary feedback loop in a differential amplifier is adopted as a pre-distorter that is realized using an NMOS cell operating in the triode region in order to compensate the gm3, the third order transconductance, of the differential amplifier. The power amplifier has been implemented in 0.18 ,m CMOS technology, and the chip size is 870 ,m × 1050 ,m. The proposed PA obtains the 42% efficiency at P1dB while improving the IMD by more than 10 dB above 15 dBm output power levels. It shows a gain of as much as 14.5 dB, and a return loss below ,12 dB for 2.3,2.4 GHz operation. Finally, the fabricated PA complies with the spurious emission of WiMAX standards up to 22 dBm. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:833,836, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25062 [source] A highly efficient class-F power amplifier for wideband linear power amplifier applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2009Jangheon Kim Abstract In this letter, a highly efficient class-F power amplifier (PA) is developed as a new main block of the wideband base-station linear power amplifier. The class-F PA is implemented using Eudyna EGN010MK GaN HEMT with a 10-W peak envelop power. The nonlinearity and memory effects of class-F PA are explored to apply the wideband application. The maximum power-added efficiency of the implemented PA is 68% at a saturated output power of 40 dBm for the 2.14-GHz CW signal. The PA delivers a good efficiency of 35% at an average output power of 32.3 dBm for wide-band code division multiple access 3FA signal with 15-MHz bandwidth, and the linearity can be improved to about ,48 dBc using the digital feedback predistortion linearization technique. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2323,2326, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24631 [source] Synergistic digital predistorter based on a low memory power amplifier for wideband linearizationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2009Jangheon Kim Abstract We investigate on linearization performance of a digital predistortion (DPD) linearization technique based on the low memory power amplifier (PA) for wideband signals. The low memory PA is implemented using a 90W PEP LDMOSFET at 2.14 GHz, and an envelope short matching topology is applied at the active ports to minimize memory effects. To explore memory effects of the implemented amplifier, the amplifier is tested through two-tone signals (up to 20 MHz tone spacing). The proposed DPD technique is compared with DPD technique based on a PA exhibiting serious memory effects for a forward-link WCDMA 3FA signal with 15-MHz bandwidth. The experimental result shows that the proposed DPD scheme has better linearization performance than the conventional digital predistorter and lower computational complexity over the conventional wideband digital predistorters. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1548,1552, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24357 [source] A 40-W balanced GaN HEMT class-E power amplifier with 71% efficiency for WCDMA base stationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2009Yong-Sub Lee Abstract A balanced class-E power amplifier (PA) using a push-pull GaN HEMT for high power and high efficiency is represented. For validation, a class-E PA is designed and implemented using a push-pull type GaN HEMT and tested for a single tone of 2.14 GHz. The measured results show that the balanced GaN HEMT class-E PA shows a drain efficiency and power-added efficiency (PAE) of 71% and 67.4% at an output power of 40 W with a gain of 13 dB through the significant harmonic suppression of below ,51 dBc. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 842,845, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24150 [source] A reduced-size branch-line coupler for improved LDMOS balanced power amplifiersMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2009Drasko Draskovic Abstract This article discusses the application of a reduced-size branch-line coupler in the design of a LDMOS class-AB balanced power amplifier at a center frequency of 2.14 GHz. In the proposed balanced configuration, at center frequency a size reduction, improved intermodulation distortion level by 7 dB, and power added efficiency by 5% are achieved, comparing with the balanced configuration with Wilkinson couplers. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 445,448, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24058 [source] Compact harmonic control network for Doherty power amplifierMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2009Paolo Colantonio Abstract In this contribution, an innovative design solution to realize small size Doherty power amplifier is presented. The idea consists in the realization of a unique output matching network for both carrier and peaking devices without losing the Doherty behavior. Experimental results performed on uneven Doherty amplifier using GaN HEMT device is given to demonstrate the proposed approach. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 256,258, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23983 [source] A 1-GHz GaN HEMT based class-E power amplifier with 80% efficiencyMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2008Yong-Sub Lee Abstract This article reports a highly efficient 1-GHz class-E power amplifier based on a GaN HEMT. The compensation elements with a series capacitor and a shunt inductor are used to compensate for the internal parasitic components of the packaged transistor. To improve output power and efficiency by suppressing harmonic powers, an output matching circuit using the transmission lines is used. The peak PAE and drain efficiency of 79.2 and 80.4% with a power gain of 18.14 dB is achieved at an output power of 41.14 dBm for a continuous wave. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2989,2992, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23803 [source] 20-W average power, high repetition rate, nanosecond pulse with diffraction limit from an all-fiber MOPA systemMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2008Songtao Du Abstract In this article, we report an all-fiber master oscillator power amplifier (MOPA) system, which can provide high repetition rate and nanosecond pulse with diffraction-limit. The system was constructed using a (2 + 1) × 1 multimode combiner. The Q-Switched, LD pumped Nd:YVO4 solid-state laser was used as master oscillator. The 976-nm fiber-coupled module is used as pump source. A 10-m long China-made Yb3+ -doped D-shape double-clad large-mode-area fiber was used as amplifier fiber. The MOPA produced as much as 20-W average power with nanosecond pulse and near diffraction limited. The pulse duration is maintained at about 15 ns during 50,175 kHz. The system employs a simple and compact architecture and is therefore suitable for the use in practical applications such as scientific and military airborne LIDAR and imaging. Based on this system, the amplification performances of the all-fiber amplifier is investigated. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2546,2549, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23770 [source] Investigation of broadband power amplifier with high power-combining efficiencyMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2008Kaijun Song Abstract A four-device broadband solid-state power amplifier, which is based on radial waveguide power-dividing/combining circuit, has been investigated in this work. The fabricated power amplifier combining four monolithic microwave integrated circuit power amplifiers shows a 12,16.6 dB small-signal gain over a broadband from 6 to 14 GHz. The measured maximum output power at 1 dB compression is 25.6 dBm at 10 GHz, with a high power-combining efficiency of 96%. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2178,2181, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23614 [source] MMIC PAM applied with pre-distorter having independent operation of nonlinear signalMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2008Inn-Yeal Oh Abstract A dynamic pre-distorter with two paths to set nonlinear signal level and phase encourages power amplifier module (PAM) for wireless broadband (Wibro) service to enhance linearity. We proposed a linearizer having a new IM generator, which is made up of the InGaP/GaAs HBT operated at saturation region of a common collector circuit. The targeted Wibro PAM is designed using InGaP/GaAs HBT technology, and the pre-distorter, drive and power amplifier are fully integrated in single chip within 960 × 2400 ,m. Even though PAM is designed to have just a 5-dB back-off, PAM is compatible with linearity standards up to maximum output power 21 dBm, and has a 17.5% efficiency by having a low leakage and improving spurious of 6 dB in the 64QAM form based on IEEE802.16e-2005 standards. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 851,855, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23235 [source] An experimental load matching technique for RF CMOS power amplifierMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2008YunSeong Eo Abstract A load matching method for CMOS PA (power amplifier) design is proposed. The contours for RF power and efficiency can be drawn while considering external L and C as tunable X and Y variables. On the basis of the existence of this contour, the realization of load matching of CMOS PA is easily achieved and optimized. A tested CMOS PA based on 0.18 ,m CMOS technology shows a design example whose P1dB is 17.8 dBm and power efficiency 37%, respectively. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 899,902, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23248 [source] A CMOS power amplifier with an adaptive bias scheme for mobile radio frequency identification reader applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2007Jeonghu Han Abstract A 900-MHz linear power amplifier with an adaptive bias scheme is fabricated using a 0.25-,m CMOS technology. The power amplifier operates over the range of 860,960 MHz, which is the ultrahigh-frequency band for radio frequency identification (RFID). All matching networks and RF chokes are implemented on a chip. The developed power amplifier provides a 1-dB-gain-compression point (P1 dB) of 27 dBm and a power-added-efficiency (PAE) of 28% at the P1 dB. The adaptive bias scheme enables the power amplifier to reduce the quiescent power consumption from 280 to 80 mW by adjusting the gate voltage of power transistors as a function of the input power. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1241,1245, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22435 [source] A high-efficiency class-E power amplifier using SiC MESFETMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2007Yong-Sub Lee Abstract This article reports a high efficiency class-E power amplifier using a SiC MESFET, which is designed and tested at 2.14 GHz. To improve output power and efficiency by suppressing harmonic powers, an output matching circuit using the transmission lines is used. From measured results for a single tone, the harmonic power levels are maintained below ,58 dBc at a whole output power level. The peak power-added efficiency of 72.3% with a power gain of 10.27 dB is achieved at an output power of 40.27 dBm. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1447,1449, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22455 [source] A fully matched 9 W compact PHEMT MMIC high power amplifier for X-band phase array radar applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2007Chen-Kuo Chu Abstract This paper presents a compact X-band, 9 W AlGaAs/InGaAs/GaAs PHEMT MMIC high power amplifier. This amplifier is designed to fully match a 50 , input and output impedance. Based on 0.35 ,m gate-length power PHEMT technology, a two-stage power amplifier is fabricated on a 3-mil thick wafer. While operating under 9 V DC bias condition, the characteristics of 17 dB small-signal gain, an average of 9 W continuous-wave output power, and 34% power added efficiency from 9.0 to 10.5 GHz can be achieved. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 257,261, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22102 [source] Circularly polarized broadband high-efficiency active integrated antennaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2006S. Gao Abstract This letter presents a circularly polarized (CP) broadband high-efficiency active integrated antenna, where the broadband CP antenna is integrated directly with a broadband high-efficiency class-E power amplifier (PA). To achieve CP operation, a series feed using an L-shaped microstrip feed line below the ground plane is used to provide a 90° phase shift between crossed slots. The antenna serves both functions of a broadband CP radiator and a broadband harmonics-termination load network for the class-E PA. Measures results demonstrate both broadband CP radiation and high efficiency. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2145,2148, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21940 [source] A 38-dBm power amplifier using AlGaAs/lnGaAs/GaAs PHEMT for S-band applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2005Hong-Zhi Liu Abstract A high-performance S-band power amplifier fabricated on a low-cost 20-mil-thick FR-4 printed circuit board (PCB) for S-band radar applications is demonstrated. The amplifier consists of a single-ended driver stage and a balanced output power stage utilizing Wilkinson power dividers/combiners with quarter-wave transmission lines. Under 10-V and 2.45-A dc bias condition, the S-band power amplifier with 23-dB small-signal gain, 38-dBm 1-dB gain-compression power with 25.6% power-added efficiency (PAE) and 3.9-dB noise figure can be achieved. In addition, excellent linearity with a 48.73-dBm 3rd -order intercept point is also measured. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 311,313, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20620 [source] Electromagnetic Field Treatment of Nerve Crush Injury in a Rat Model: Effect of Signal Configuration on Functional RecoveryBIOELECTROMAGNETICS, Issue 4 2007Janet L. Walker Abstract Electromagnetic fields (EMFs) have been demonstrated to enhance mammalian peripheral nerve regeneration in vitro and in vivo. Using an EMF signal shown to enhance neurite outgrowth in vitro, we tested this field in vivo using three different amplitudes. The rat sciatic nerve was crushed. Whole body exposure was performed for 4 h/day for 5 days in a 96-turn solenoid coil controlled by a signal generator and power amplifier. The induced electric field at the target tissue consisted of a bipolar rectangular pulse, having 1 and 0.3 ms durations in each polarity, respectively. Pulse repetition rate was 2 per second. By varying the current, the coils produced fields consisting of sham (no current) and peak magnetic fields of 0.03 mT, 0.3 mT, and 3 mT, corresponding to peak induced electric fields of 1, 10, and 100 µV/cm, respectively, at the tissue target. Walking function was assessed over 43 days using video recording and measurement of the 1,5 toe-spread, using an imaging program. Comparing injured to uninjured hind limbs, mean responses were evaluated using a linear mixed statistical model. There was no difference found in recovery of the toe-spread function between any EMF treatments compared to sham. Bioelectromagnetics 28:256,263, 2007. © 2007 Wiley-Liss, Inc. [source] A single magnetic field exposure system for sequential investigation of real time and downstream cellular responsesBIOELECTROMAGNETICS, Issue 1 2004Raj R. Rao Abstract To be able to correlate real time membrane potential or ion flux changes with further downstream gene transcription responses due to extremely low frequency (ELF) electromagnetic field (EMF) exposure, we devised an experimental system consisting of a pair of symmetric circular coils. This system can be used on an inverted microscope stage (real time signaling) as well as inside controlled environment incubators (gene transcription end points). The system includes a unique, custom made switch box for blinding the experimental staff and a power amplifier. We report herein the design and characterization of the system with respect to parameters considered important in in vitro ELF,EMF exposure studies, including linear magnetic field distribution, compensation for microscope objective lens interference, heating effects of the coils, and harmonic content of the signals. Bioelectromagnetics 25:27,32, 2004. © 2003 Wiley-Liss, Inc. [source] Natural gradient algorithm for neural networks applied to non-linear high power amplifiers,INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 8 2002H. Abdulkader Abstract This paper investigates the processing techniques for non-linear high power amplifiers (HPA) using neural networks (NNs). Several applications are presented: Identification and Predistortion of the HPA. Various Neural Network structures are proposed to identify and predistort the HPA. Since a few decades, NNs have shown excellent performance in solving complex problems (like classification, recognition, etc.) but usually they suffer from slow convergence speed. Here, we propose to use the natural gradient instead of the classical ordinary gradient in order to enhance the convergence properties. Results are presented concerning identification and predistortion using classical and natural gradient. Practical implementations issues are given at the end of the paper. Copyright © 2002 John Wiley & Sons, Ltd. [source] Study of the influence of bias and matching networks on the distortion and memory of FET-based power amplifiersINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 6 2008Jon Santiago Abstract A study of the influence of bias and matching networks on the distortion and memory in FET-based power amplifiers has been carried out at the device and amplifier circuit levels. The study includes simulated and experimental results that allow us to identify effects produced by the introduction of particular biasing and matching networks in the power amplifier design. The influence of the bias point, as well as of biasing and matching network topologies on the nonlinear, short- and long-term memory behavior has been studied by means of simulations and measurements, using different power amplifier prototypes. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008. [source] | |||||||||||||