Showing papers on "Amplifier published in 2011"

Towards ultrasensitive optical links enabled by low-noise phase-sensitive amplifiers

Abstract: Optical phase-sensitive amplifiers (PSAs) are known to be capable, in principle, of realizing noiseless amplification and improving the signal-to-noise-ratio of optical links by 3 dB compared to conventional, phase-insensitively amplified links. However, current state-of-the-art PSAs are still far from being practical, lacking e.g. significant noise performance improvement, broadband gain and modulation-format transparency. Here we demonstrate experimentally, for the first time, an optical-fiber-based non-degenerate PSA link consisting of a phase-insensitive parametric copier followed by a PSA that provides broadband amplification, signal modulation-format independence, and nearly 6-dB link noise-figure (NF) improvement over conventional, erbium-doped fiber amplifier based links. The PSA has a record-low 1.1-dB NF, and can be extended to work with multiple wavelength channels with modest system complexity. This concept can also be realized in other materials with third-order nonlinearities, and is useful in any attenuation-limited optical link.

Memristor Applications for Programmable Analog ICs

Abstract: This paper demonstrates that memristors can be used to implement programmable analog circuits, leveraging memristor's fine-resolution programmable resistance without causing perturbations due to parasitic components. Fine-resolution programmable resistance is achieved by varying the amount of flux across memristors. The resistance programming can be achieved by controlling the input pulsewidth and its frequency. For demonstration, a memristor is designed for a pulse-programmable midband differential gain amplifier with fine resolution.

Linearization Techniques for CMOS Low Noise Amplifiers: A Tutorial

Abstract: This tutorial catalogues and analyzes previously reported CMOS low noise amplifier (LNA) linearization techniques. These techniques comprise eight categories: a) feedback; b) harmonic termination; c) optimum biasing; d) feedforward; e) derivative superposition (DS); f) IM2 injection; g) noise/distortion cancellation; and h) post-distortion. This paper also addresses broadband-LNA-linearization issues for emerging reconfigurable multiband/multistandard and wideband transceivers. Furthermore, we highlight the impact of CMOS technology scaling on linearity and outline how to design a linear LNA in a deep submicrometer process. Finally, general design guidelines for high-linearity LNAs are provided.

High-energy pulse synthesis with sub-cycle waveform control for strong-field physics

Abstract: Over the last decade, control of atomic-scale electronic motion by non-perturbative optical fields has broken tremendous new ground with the advent of phase-controlled high-energy few-cycle pulse sources1. The development of close to single-cycle, carrier-envelope phase controlled, high-energy optical pulses has already led to isolated attosecond EUV pulse generation2, expanding ultrafast spectroscopy to attosecond resolution1. However, further investigation and control of these physical processes requires sub-cycle waveform shaping, which has not been achievable to date. Here, we present a light source, using coherent wavelength multiplexing, that enables sub-cycle waveform shaping with a two-octave-spanning spectrum and a pulse energy of 15 µJ. It offers full phase control and allows generation of any optical waveform supported by the amplified spectrum. Both energy and bandwidth scale linearly with the number of sub-modules, so the peak power scales quadratically. The demonstrated system is the prototype of a class of novel optical tools for attosecond control of strong-field physics experiments. Researchers present a waveform synthesis scheme that coherently multiplexes the outputs from two broadband optical parametric chirped-pulse amplifiers. The technique provides control at the sub-cycle scale and generates high-energy ultrashort waveforms for use in strong-field physics experiments.

Ultra compact 45 GHz CMOS compatible Germanium waveguide photodiode with low dark current

Abstract: We present a compact 13 × 4 μm2 Germanium waveguide photodiode, integrated in a CMOS compatible silicon photonics process flow This photodiode has a best-in-class 3 dB cutoff frequency of 45 GHz, responsivity of 08 A/W and dark current of 3 nA The low intrinsic capacitance of this device may enable the elimination of transimpedance amplifiers in future optical data communication receivers, creating ultra low power consumption optical communications

An Overview of Solid-State Integrated Circuit Amplifiers in the Submillimeter-Wave and THz Regime

Abstract: We present an overview of solid-state integrated circuit amplifiers approaching terahertz frequencies based on the latest device technologies which have emerged in the past several years. Highlights include the best reported data from heterojunction bipolar transistor (HBT) circuits, high electron mobility transistor (HEMT) circuits, and metamorphic HEMT (mHEMT) amplifier circuits. We discuss packaging techniques for the various technologies in waveguide modules and describe the best reported noise figures measured in these technologies. A consequence of THz transistors, namely ultra-low-noise at cryogenic temperatures, will be explored and results presented. We also present a short review of power amplifier technologies for the THz regime. Finally, we discuss emerging materials for THz amplifiers into the next decade.

Fiber chirped-pulse amplification system emitting 3.8 GW peak power.

Abstract: We report on the experimental demonstration of a fiber chirped- pulse amplification system capable of generating nearly transform-limited sub 500 fs pulses with 22 mJ pulse energy at 11 W average power The resulting record peak power of 38 GW could be achieved by combining active phase shaping with an efficient reduction of the acquired nonlinear phase Therefore, we used an Ytterbium-doped large-pitch fiber with a mode field diameter of 105 µm as the main amplifier

Design of Highly Efficient Broadband Class-E Power Amplifier Using Synthesized Low-Pass Matching Networks

Abstract: A new methodology for designing and implementing high-efficiency broadband Class-E power amplifiers (PAs) using high-order low-pass filter-prototype is proposed in this paper. A GaN transistor is used in this work, which is carefully modeled and characterized to prescribe the optimal output impedance for the broadband Class-E operation. A sixth-order low-pass filter-matching network is designed and implemented for the output matching, which provides optimized fundamental and harmonic impedances within an octave bandwidth (L-band). Simulation and experimental results show that an optimal Class-E PA is realized from 1.2 to 2 GHz (50%) with a measured efficiency of 80%-89%, which is the highest reported today for such a bandwidth. An overall PA bandwidth of 0.9-2.2 GHz (84%) is measured with 10-20-W output power, 10-13-dB gain, and 63%-89% efficiency throughout the band. Furthermore, the Class-E PA is characterized through measurements using constant-envelop global system for mobile communications signals, indicating a favorable adjacent channel power ratio from -40 to -50 dBc within the entire bandwidth.

Microwave amplification with nanomechanical resonators

Abstract: Use of nanomechanical resonators has the potential to offer microwave amplification with the minimum possible added noise, namely that due to quantum fluctuations In order to compensate for energy losses, the radio signals used in telecommunications and detection technologies require occasional electrical amplification For specific applications, sensitive amplifiers have been demonstrated that operate near the quantum limit — where the only noise added is due to fundamental quantum fluctuations This paper describes a new concept for amplifying weak electrical signals close to this fundamental limit, using a nanomechanical resonator The system uses a resonator irradiated with microwave light of a frequency tuned so that it sets the resonator in motion with tiny vibrations; these amplify the signal In this proof-of-principle study, signal amplification of 25 decibels is demonstrated, with only 20 fundamental noise quanta added This mechanical amplification approach has the attraction that it is conceptually simple and could feasibly be used in integrated electrical circuits The sensitive measurement of electrical signals is at the heart of modern technology According to the principles of quantum mechanics, any detector or amplifier necessarily adds a certain amount of noise to the signal, equal to at least the noise added by quantum fluctuations1,2 This quantum limit of added noise has nearly been reached in superconducting devices that take advantage of nonlinearities in Josephson junctions3,4 Here we introduce the concept of the amplification of microwave signals using mechanical oscillation, which seems likely to enable quantum-limited operation We drive a nanomechanical resonator with a radiation pressure force5,6,7, and provide an experimental demonstration and an analytical description of how a signal input to a microwave cavity induces coherent stimulated emission and, consequently, signal amplification This generic scheme, which is based on two linear oscillators, has the advantage of being conceptually and practically simpler than the Josephson junction devices In our device, we achieve signal amplification of 25 decibels with the addition of 20 quanta of noise, which is consistent with the expected amount of added noise The generality of the model allows for realization in other physical systems as well, and we anticipate that near-quantum-limited mechanical microwave amplification will soon be feasible in various applications involving integrated electrical circuits

A high-fidelity noiseless amplifier for quantum light states

Abstract: Researchers demonstrate a probabilistic noiseless linear amplifier based on photon addition and subtraction. The technique enables coherent states to be amplified to the highest levels of effective gain and final-state fidelity, and could become an essential tool for applications in quantum communication and metrology.

Frequency Response Analysis and Bandwidth Extension of the Doherty Amplifier

Abstract: A complete frequency response analysis of the Doherty amplifier is presented with the conventional output combining network consisting of two quarter-wavelength (λ/4) transmission lines at a center frequency f0 . Expressions for output power and efficiency were derived over the whole dynamic range and at any frequency f. The analysis shows that the amount of efficiency enhancement, as well as the maximum output power, reduce as the deviation from f0 increases. For instance, the derived expressions show that a conventional Doherty amplifier has a drain efficiency of η ≥ 52.7%, which represents at least 13.4% efficiency enhancement over a class B amplifier, and up to 33.3% fractional bandwidth. A modified output combining network, using λ/4 lines with reduced impedance transformation ratio, is also analyzed, which results in a bandwidth extension of the Doherty amplifier when compared to the conventional design. To verify the derived analyses, three unsymmetrical GaN Doherty power amplifiers (DPAs) were designed and characterized; the first DPA was based on the conventional output combining network, while the second DPA was based on the proposed network. Measurements showed that the first DPA had, at 5-6-dB back-off, a drain efficiency of η ≥ 44% and over 28% fractional bandwidth (1.7-2.25 GHz), while the DPA with the proposed output combining network had a better wideband performance than the third reference conventional DPA, with a back-off drain efficiency of η ≥ 41%, and over 42% fractional bandwidth (1.7-2.6 GHz). To the best of authors' knowledge, the designed DPAs have the highest bandwidths reported thus far.

A Switched-Capacitor RF Power Amplifier

Abstract: A fully integrated switched-capacitor power amplifier (SCPA) utilizes switched-capacitor techniques in an EER/Polar architecture. It operates on the envelope of a nonconstant envelope modulated signal as an RF-DAC in order to amplify the signal efficiently. The measured maximum output power and PAE are 25.2 dBm and 45%, respectively. When amplifying an 802.11g 64-QAM orthogonal frequency-division multiplexing (OFDM) signal, the measured error vector magnitude is 2.6% and the average output power and power-added efficiencies are 17.7 dBm and 27%, respectively.

THz Monolithic Integrated Circuits Using InP High Electron Mobility Transistors

Abstract: In this paper, background describing THz monolithic integrated circuits using InP HEMT is presented. This three-terminal transistor technology has been used to realize amplifiers, mixers, and multipliers operating at 670 GHz. Transistor and processing technology, packaging technology, and circuit results at 670 GHz are described. The paper concludes with initial results from a 670-GHz InP HEMT receiver and trends for InP HEMT components.

Semiconductor memory device

Abstract: A semiconductor memory device includes a pre-charger configured to pre-charge a first pair of differential bus lines SIO and SIOb to a target voltage level, an amplifier configured to amplify a signal loaded on the first pair of the differential bus lines SIO and SIOb based on a drain bias voltage Vb and transfer an amplified signal to a second pair of differential bus lines LIO and LIOb, and a drain bias voltage generator configured to generate the drain bias voltage Vb.

Multimode fiber amplifier with tunable modal gain using a reconfigurable multimode pump.

Abstract: We propose a method for controlling modal gain in a multimode Erbium-doped fiber amplifier (MM-EDFA) by tuning the mode content of a multimode pump. By adjusting the powers and orientation of input pump modes, modal dependent gain can be tuned over a large dynamic range. Performance impacts due to excitation of undesired pump modes, mode coupling and macro-bending loss within the erbium-doped fiber are also investigated. The MM-EDFA may potentially be a key element for long haul mode-division multiplexed transmission.

Wireless power transmission system and associated devices

Abstract: A wireless power transmission system comprises: a power transmitter, which includes a power amplifier that provides a sinusoidal waveform in the frequency range of about 20 to 500 kHz; a first loop antenna producing an alternating magnetic field within a selected area; a power receiver, which includes a second loop antenna located at least partially within the alternating magnetic field of the first antenna; and an electricity-consuming device connected to the output of the power receiver. Both transmitter and receiver preferably contain a capacitive circuit element to optimize tuning, which may be discrete capacitors or may rely on the self capacitance of the antenna(s). Applications of the system include: wirelessly powered lights for fans, boats, aquariums, display cases, etc.; wirelessly powered sensors and other devices for use with captive animals; and systems for transmitting useful power through construction materials to devices on the other side of walls or other structures.

Parallel Reservoir Computing Using Optical Amplifiers

Abstract: Reservoir computing (RC), a computational paradigm inspired on neural systems, has become increasingly popular in recent years for solving a variety of complex recognition and classification problems. Thus far, most implementations have been software-based, limiting their speed and power efficiency. Integrated photonics offers the potential for a fast, power efficient and massively parallel hardware implementation. We have previously proposed a network of coupled semiconductor optical amplifiers as an interesting test case for such a hardware implementation. In this paper, we investigate the important design parameters and the consequences of process variations through simulations. We use an isolated word recognition task with babble noise to evaluate the performance of the photonic reservoirs with respect to traditional software reservoir implementations, which are based on leaky hyperbolic tangent functions. Our results show that the use of coherent light in a well-tuned reservoir architecture offers significant performance benefits. The most important design parameters are the delay and the phase shift in the system's physical connections. With optimized values for these parameters, coherent semiconductor optical amplifier (SOA) reservoirs can achieve better results than traditional simulated reservoirs. We also show that process variations hardly degrade the performance, but amplifier noise can be detrimental. This effect must therefore be taken into account when designing SOA-based RC implementations.

High frequency graphene Voltage amplifier

Abstract: While graphene transistors have proven capable of delivering gigahertz-range cutoff frequencies, applying the devices to RF circuits has been largely hindered by the lack of current saturation in the zero band gap graphene. Herein, the first high-frequency voltage amplifier is demonstrated using large-area chemical vapor deposition grown graphene. The graphene field-effect transistor (GFET) has a 6-finger gate design with gate length of 500 nm. The graphene common-source amplifier exhibits ∼5 dB low frequency gain with the 3 dB bandwidth greater than 6 GHz. This first AC voltage gain demonstration of a GFET is attributed to the clear current saturation in the device, which is enabled by an ultrathin gate dielectric (4 nm HfO(2)) of the embedded gate structures. The device also shows extrinsic transconductance of 1.2 mS/μm at 1 V drain bias, the highest for graphene FETs using large-scale graphene reported to date.

A $160~\mu {\rm W}$ 8-Channel Active Electrode System for EEG Monitoring

Abstract: This paper presents an active electrode system for gel-free biopotential EEG signal acquisition. The system consists of front-end chopper amplifiers and a back-end common-mode feedback (CMFB) circuit. The front-end AC-coupled chopper amplifier employs input impedance boosting and digitally-assisted offset trimming. The former increases the input impedance of the active electrode to 2 GΩ at 1 Hz and the latter limits the chopping induced output ripple and residual offset to 2 mV and 20 mV, respectively. Thanks to chopper stabilization, the active electrode achieves 0.8 μVrms (0.5-100 Hz) input referred noise. The use of a back-end CMFB circuit further improves the CMRR of the active electrode readout to 82 dB at 50 Hz. Both front-end and back-end circuits are implemented in a 0.18 μm CMOS process and the total current consumption of an 8-channel readout system is 88 μA from 1.8 V supply. EEG measurements using the proposed active electrode system demonstrate its benefits compared to passive electrode systems, namely reduced sensitivity to cable motion artifacts and mains interference.

Realization of a nonlinear interferometer with parametric amplifiers

Abstract: We construct an interferometer with parametric amplifiers as beam splitters. Because of the gain in the parametric amplifiers, the maximum output intensity of the interferometer can be much bigger than the input intensity as well as the intensity inside the interferometer (the phase sensing intensity). We find that the fringe intensity depends quadratically on the intensity of the phase sensing field at high gain. This type of nonlinear interferometer has better sensitivity than the traditional linear interferometer made of beam splitters with the same phase sensing intensity.

Physically Inspired Neural Network Model for RF Power Amplifier Behavioral Modeling and Digital Predistortion

Abstract: In this paper, a novel two hidden layers artificial neural network (2HLANN) model is proposed to predict the dynamic nonlinear behavior of wideband RF power amplifiers (PAs). Starting with a generic low-pass equivalent circuit of the PA, several circuit transformations are applied in order to build an appropriate artificial neural network structure and improve the modeling accuracy. This approach culminates in the development of a real-valued and feed-forward 2HLANN-based model. The parameters (number of neurons, memory depth, etc.) of the proposed model and the back propagation learning algorithm (learning rate, momentum term, etc.) used for its training were carefully studied and thoughtfully chosen to ensure the generality of the constructed model. The validation of the proposed models in mimicking the behavior of a 250-W Doherty amplifier driven with a 20-MHz bandwidth signal is carried out in terms of its accuracy in predicting its output spectrum, dynamic AM/AM and AM/PM characteristics, and in minimizing the normalized mean square error. In addition, the linearization of the Doherty PA using the 2HLANN enabled attaining an output power of up to 46.5 dBm and an average efficiency of up to 40% coupled with an adjacent channel power ratio higher than 50 dBc.

High average power spectral beam combining of four fiber amplifiers to 8.2 kW.

Abstract: We report on the incoherent beam combination of the four narrow-linewidth fiber amplifier chains running at different wavelengths Each main amplifier stage consists of a large-mode-area photonic crystal fiber delivering more than 2 kW of optical power The four output beams are spectrally combined to a single beam with an output power of 82 kW using a polarization-independent dielectric reflective diffraction grating mainly preserving the beam quality of the individual fiber amplifiers

On the Extension of the Continuous Class-F Mode Power Amplifier

Abstract: The extended continuous class-F mode RF power amplifier (PA) is presented for the first time. The introduction and experimental validation of this novel PA mode demonstrates a new design space over a wide band of frequencies. This paper will show that high output power and drain efficiency, equivalent to the class-F mode, can be maintained by varying the reactive components of fundamental and second harmonic impedances in accordance with the new formulation of the voltage waveform. Additionally it will be shown that, by varying both phase and magnitude of the fundamental and second harmonic impedances, a yet wider design space can be achieved, where the efficiency is maintained at a level greater than a certain target value. For the validation of this new theory, an experimental investigation was carried out on GaAs pseudomorphic HEMT devices and demonstrates that high output power and drain efficiency between 75%-83% can be achieved over a wide range of fundamental and second harmonic loads.

Design and Linearization of Concurrent Dual-Band Doherty Power Amplifier With Frequency-Dependent Power Ranges

Abstract: A design methodology for a concurrent dual-band Doherty power amplifier (PA) with frequency-dependent backoff power ranges is presented in this paper. Based on a dual-band T-shaped network and a coupled line network, different dual-band components needed in Doherty PA topology, including a 3-dB branch-line coupler, an offset line, and a quarter-wavelength transformer, are developed. Two prototypes with balanced and imbalanced backoff power range modes are implemented to verify the feasibility. Continuous wave signal test results show that the proposed dual-band PA successfully achieves a power-added efficiency of 33% and 30% at the 6-dB backoff point from the saturated output power at 880 and 1960 MHz, respectively. To meet linearity requirements, the PA nonlinear behavior is characterized by using digital multitone signals, which categorize the distortions of a concurrent dual-band PA into intermodulation and cross-modulation. Finally, a 2-D digital predistortion technique is used to compensate for the nonlinearity of PA in dual bands. Two two-tone signals are applied to the dual bands for linearization, and the experimental results show that this technique achieves improvements of better than 19.1 and 24.6 dB for the intermodulation and cross-modulation in the dual bands, respectively.

Active 220- and 325-GHz Frequency Multiplier Chains in an SiGe HBT Technology

Abstract: A 325-GHz ×18 frequency multiplier chain implemented in a fτ/fmax = 250 GHz/380 GHz evaluation SiGe heterojunction bipolar transistor technology is presented. The chain achieves a peak output power of -3 dBm and consists of a balanced doubler driven by two cascaded tripler stages. It operates from 317 to 328 GHz with a 0-dBm 18-GHz input signal and a 1.5-W power consumption. Additionally, 220- and 325-GHz doubler breakout circuits with integrated driver amplifiers are presented. The doublers reach an output power of -1 dBm at 220 GHz and -3 dBm at 325 GHz with a power dissipation of 630 and 420 mW, respectively.

Supercontinuum generation from ~19 to 45 μmin ZBLAN fiber with high average power generation beyond 38 μm using a thulium-doped fiber amplifier

Abstract: A mid-IR supercontinuum (SC) fiber laser based on a thulium-doped fiber amplifier (TDFA) is demonstrated. A continuous spectrum extending from ∼1.9 to 4.5 μm is generated with ∼0.7 W time-average power in wavelengths beyond 3.8 μm. The laser outputs a total average power of up to ∼2.6 W from ∼8.5 m length of ZrF4─BaF2─LaF3─AlF3─NaF (ZBLAN) fiber, with an optical conversion efficiency of ∼9% from the TDFA pump to the mid-IR SC. Optimal efficiency in generating wavelengths beyond 3.8 μm is achieved by reducing the losses in the TDFA stage and optimizing the ZBLAN fiber length. We demonstrate a novel (to our knowledge) approach of generating modulation instability-initiated SC starting from 1.55 μm by splitting the spectral shifting process into two steps. In the first step, amplified approximately nanosecond-long 1.55 μm laser diode pulses with ∼2.5 kW peak power generate a SC extending beyond 2.1 μm in ∼25 m length of standard single-mode fiber (SMF). The ∼2 μm wavelength components at the standard SMF output are amplified in a TDFA and coupled into ZBLAN fiber leading to mid-IR SC generation. Up to ∼270 nm SC long wavelength edge extension and ∼2.5× higher optical conversion efficiency to wavelengths beyond 3.8 μm are achieved by switching an Er:Yb-based power amplifier stage with a TDFA. The laser also demonstrates scalability in the average output power with respect to the pulse repetition rate and the amplifier pump power. Numerical simulations are performed by solving the generalized nonlinear Schrodinger equation, which show the long wavelength edge of the SC to be limited by the loss in ZBLAN.

A Low-Power 32-Channel Digitally Programmable Neural Recording Integrated Circuit

Abstract: We report the design of an ultra-low-power 32-channel neural-recording integrated circuit (chip) in a 0.18 μ m CMOS technology. The chip consists of eight neural recording modules where each module contains four neural amplifiers, an analog multiplexer, an A/D converter, and a serial programming interface. Each amplifier can be programmed to record either spikes or LFPs with a programmable gain from 49-66 dB. To minimize the total power consumption, an adaptive-biasing scheme is utilized to adjust each amplifier's input-referred noise to suit the background noise at the recording site. The amplifier's input-referred noise can be adjusted from 11.2 μVrms (total power of 5.4 μW) down to 5.4 μVrms (total power of 20 μW) in the spike-recording setting. The ADC in each recording module digitizes the a.c. signal input to each amplifier at 8-bit precision with a sampling rate of 31.25 kS/s per channel, with an average power consumption of 483 nW per channel, and, because of a.c. coupling, allows d.c. operation over a wide dynamic range. It achieves an ENOB of 7.65, resulting in a net efficiency of 77 fJ/State, making it one of the most energy-efficient designs for neural recording applications. The presented chip was successfully tested in an in vivo wireless recording experiment from a behaving primate with an average power dissipation per channel of 10.1 μ W. The neural amplifier and the ADC occupy areas of 0.03 mm2 and 0.02 mm2 respectively, making our design simultaneously area efficient and power efficient, thus enabling scaling to high channel-count systems.

Tunable wireless energy transfer systems

Abstract: Described herein are improved configurations for a wireless power transfer. A power source for driving a resonator includes a switching amplifier. The duty cycle of the switching amplifier may be adjusted as well as optionally inductors and/or capacitors of the circuit to improve the efficiency of power transfer from the power source to the resonators when the parameters of the resonant load change.

Echo detection and self-excitation elimination method for electromagnetic wave common-frequency amplifying repeater system

Abstract: The invention relates to an echo detection and self-excitation elimination method for an electromagnetic wave common-frequency amplifying repeater system. By using the method, a relationship among grains of an amplifier, a phase when returned electromagnetic wave signals reach a receiving antenna and the output power of the amplifier in the electromagnetic wave common-frequency amplifying repeater system is discovered. According to the relationship, the magnitude of echo signals can be detected effectively, the output power of the amplifier is improved, the self-excitation of the amplifier resulting from the echo signals is avoided, the requirements on isolations of a forward antenna and a backward antenna are reduced, the system grains are improved, and the coverage area is increased. The method is suitable for all electromagnetic wave common-frequency amplifying repeater systems, such as communication repeaters, data television repeaters and the like.