Showing papers on "Output impedance published in 2010"

Resistive Impedance Matching Circuit for Piezoelectric Energy Harvesting

Abstract: A two-stage power conditioning circuit consisting of an AC-DC converter followed by a DC-DC converter is proposed for a vibration-based energy harvesting system. The power conditioning circuit intends to maximize the amount of power extracted from a piezoelectric energy harvester by matching the source impedance with the circuit by adaptively adjusting the duty cycle. An equivalent electrical circuit representation derived from a distributed-parameter piezoelectric energy harvester model is adapted to enable the impedance matching method proposed here. For a given piezoelectric energy harvester, there is a theoretical maximum power output that is determined by the mechanical damping, base acceleration, and the effective mass of the harvester structure under base excitation. Experimental results are given to validate the effectiveness of the proposed resistive impedance matching circuit around the first resonance frequency of a cantilevered piezoelectric energy harvester.

Thermal energy harvesting through pyroelectricity

Abstract: Pyroelectric cells based on fabricated screen-printed PZT and commercial PVDF films are proposed as thermal energy harvesting sources in order to supply low-power autonomous sensors. The cells are electrically modelled as a current source in parallel with output impedance. Heating and cooling temperature fluctuations generated by air currents were applied to the pyroelectric converters. The generated currents and charges were respectively in the order of 10 −7 A and 10 −5 C for temperature fluctuations from 300 K to 360 K in a time period of the order of 100 s, which agrees with the theoretical model. Parallel association of cells increased the generated current. The dependence of the generated current on relevant technological parameters has been also characterized. Finally, current from cyclic temperature fluctuations was rectified and stored in a 1 μF load capacitor. Energies up to 0.5 mJ have been achieved, enough to power typical autonomous sensor nodes during a measurement and transmission cycle.

Virtual Impedance Loop for Droop-Controlled Single-Phase Parallel Inverters Using a Second-Order General-Integrator Scheme

Abstract: This paper explores the impact of the output impedance on the active and reactive power flows between parallelized inverters operating with the droop method. In these systems, a virtual output impedance is usually added to the control loop of each inverter to improve the reactive power sharing, regardless of line-impedance unbalances and the sharing of nonlinear loads. The virtual impedance is usually implemented as the time derivative of the inverter output current, which makes the system highly sensitive to the output current noise and to nonlinear loads with high slew rate. To solve this, a second-order general-integrator (SOGI) scheme is proposed to implement the virtual impedance, which is less sensitive to the output current noise, avoids to perform the time derivative function, achieves better output-voltage total harmonic distortion, and enhances the sharing of nonlinear loads. Experimental results with two 2-kVA inverter systems under linear and nonlinear loads are provided to validate this approach.

Resonance type non-contact charging apparatus

Abstract: A resonance type non-contact charging system is disclosed that includes a resonance system. The resonance system has a primary side resonance coil, a secondary side resonance coil, a power converting section having a DC/DC converter, and a battery. The charging system has a controlling section that controls the DC/DC converter. The controlling section controls the duty cycle of the DC/DC converter such that the input impedance of the resonance system at the resonant frequency and the output impedance of a high-frequency power source match each other.

Load impedance decision device, wireless power transmission device, and wireless power transmission method

Abstract: A load impedance decision device, a wireless power transmission device, and a wireless power transmission method are provided. At least one of a distance and an angle between two resonators may be measured. A load impedance may be determined based on at least one of the measured distance and the measured angle. When the distance between the two resonators changes, a high power transfer efficiency may be maintained without using a separate matching circuit. Where the load impedance is determined, a test power may be transmitted. Depending on a power transfer efficiency of the test power, the load impedance may be controlled and power may be wirelessly transmitted from the source resonator to the target resonator.

Linear Stabilization of a DC Bus Supplying a Constant Power Load: A General Design Approach

Abstract: In this paper, an oscillation compensation technique is proposed to improve the stability margin of an electrical system constituted by a dc power supply, an LC filter, and a constant power load. This is realized here by an actuator (inverter-permanent-magnet synchronous motor). To design the compensator, input impedance of the constant power load and output impedance of the filter are required and derived in this paper. To develop the load input impedance expression, small signal approximation is employed and all dynamics are taken into account except by the inverter ones only, which can often be neglected in practical applications. Then, the control structure of the whole system is slightly modified to implement the oscillation compensation block that increases the stability margin, and thus, permits to reduce the dc-link capacitance value. In this paper, the proposed method is applied to an actuator designed for aerospace applications. The influence of the actuator control parameters and the input filter parameters on the stability of the dc-link voltage is discussed. Simulations and experimentations confirm the validity of the proposed approach.

A Two-Phase Switching Hybrid Supply Modulator for RF Power Amplifiers With 9% Efficiency Improvement

Abstract: A hybrid supply modulator consisting of a parallel operation of a high-drive, low output impedance, wideband class-AB linear amplifier and a high-efficiency, wideband, low-ripple switching amplifier is presented for the application of polar transmitters. At system level, a two-phase switching is employed to lower the inductor current ripple so that both the output ripple and power loss are reduced. On-chip feed-forward bandpass filter is used to extend the tracking bandwidth of the switching amplifier, without hurting the stability of parallel control loop or the need to increase switching frequency. At circuit level, the output impedance of the linear amplifier is lowered by optimizing the design of super source-follower output stage. Inductor current sharing and two-phase ramp generator are implemented for realizing the two-phase switching scheme. Fabricated in a 0.35-μm CMOS process, the prototype chip measures 9 % static efficiency improvement over the conventional single-phase switching design in the back-off power level. Dynamic efficiency is enhanced by 8-12% by enabling the bandpass filter. Successful tracking of a 4 MHz 0.4-2.8 V full-wave rectified sine wave and a WCDMA envelope signal is demonstrated.

Impedance change detection in wireless power transmission

Abstract: Exemplary embodiments are directed to wireless power transfer. Energy from a transmit antenna is coupled to internal signals on a transmitter. An impedance measurement circuit generates an impedance indication signal for indicating an impedance difference between the coupled internal signals by comparing them. A controller samples the impedance indication signal and determines digital signaling values responsive to changes in the impedance indication signal. The impedance measurement circuit measures one or more of magnitude difference of the internal signals, phase difference of the internal signals, and changes in power consumed by an amplifier coupled between the RF signal and the transmit antenna. A transmitter generates the electromagnetic field with a transmit antenna responsive to a Radio Frequency (RF) signal to create a coupling-mode region within a near field of the transmit antenna.

Output-Capacitor-Free Adaptively Biased Low-Dropout Regulator for System-on-Chips

Abstract: A high-precision low-voltage adaptively biased (AB) low-dropout regulator (LDR) with extended loop bandwidth is proposed. The multistage output-capacitor-free LDR is stabilized by Miller compensation and Q-reduction techniques to reduce the required minimum load current. Adaptive biasing is achieved by using direct current feedback from a simple current mirror. The dynamics of both the main feedback loop (MFL) and the adaptive biasing loop are thoroughly analyzed. Tradeoffs between the adaptive biasing factor and the MFL stability are discussed. The AB LDR is designed using a standard 0.35- ?m CMOS technology ( Vtn ? 0.52 V and Vtp ? -0.72 V). The output is 1.0 V, which delivers a maximum current of 100 mA. The minimum input voltage is 1.2 V, and the minimum load current required is reduced to 50 ?A . Extensive simulation results verify that the proposed LDR achieves high loop bandwidth, fast line and load transient responses, high power supply rejection, and low output impedance.

Accurate Extraction of Noise Source Impedance of an SMPS Under Operating Conditions

Abstract: An accurate measurement method to extract the common mode (CM) and the differential mode (DM) noise source impedances of a switched-mode power supply (SMPS) under its operating condition is developed and validated With a proper premeasurement calibration process, the proposed method allows extraction of both the CM and the DM noise source impedances with very good accuracy These noise source impedances come in handy to design an electromagnetic interference filter for an SMPS systematically with minimum hassle

Closed-loop input and output impedances of DC-DC switching converters operating in voltage and current mode control

Abstract: This work derives the closed-loop input and output impedances of three major types of DC-DC converters (Buck, Boost, and Buck-Boost) operating in voltage or current mode control. First, it introduces the small-signal converter model employed to derive the input and output impedances. Next, it reviews open-loop impedances for use in simplifying the expressions developed for closed-loop impedances. It then derives the closed-loop impedances by closing the voltage or current loop (depending on control method) in the converter model. Finally, The validity of the impedances thus derived is verified by simulation.

Design of Doherty Power Amplifiers for Handset Applications

Abstract: In this paper, we analyze the power drive of a Doherty power amplifier (PA), and introduce a technique for proper input dividing without a coupler. For the proper Doherty operation, we place a phase compensation circuit at the input of the carrier amplifier. We also propose an output matching of Doherty PA to reduce the number of matching components, and to match the output impedances to enhance efficiency and linearity in consideration of the uneven input drive. The PA circuit is fabricated using a 2-μm InGaP/GaAs heterojunction bipolar transistor process and combined for Doherty operation using merged lumped components. For the IEEE 802.16e m-WiMAX signal, which has a 9.54-dB crest factor and 8.75-MHz bandwidth, the PA has an error vector magnitude of 3% and a power-added efficiency of 40.2% at an output power of 26 dBm.

Matching network for transmission circuitry

Abstract: The present disclosure relates to transmission circuitry of a wireless communication device. The transmission circuitry includes power amplifier circuitry, an output matching network, and impedance control circuitry. The power amplifier circuitry amplifies a radio frequency (RF) input signal to provide an amplified RF output signal, which is passed through the output matching network and transmitted via one or more antennas. As the center frequency of the RF input signal and conditions of operating parameters change, the impedance control circuitry adjusts the values of one or more variable impedance elements of the output matching network in a desired fashion. The values of the variable impedance elements are adjusted such that the output matching network concurrently and dynamically presents the desired load impedances at the center frequency and at one or more harmonics of the RF input signal to achieve a given performance specification.

Grounded capacitor current mode single resistance-controlled oscillator using single modified current differencing transconductance amplifier

Abstract: This study proposes a current mode canonical single resistance-controlled oscillator (SRCO) circuit based on a single modified current differencing transconductance amplifier. The circuit employs grounded capacitors and provides a current output with high output impedance. The proposed circuit also enables orthogonal control of frequency and oscillation condition. The performance of the proposed SRCO is verified by means of simulation program with integrated circuit emphasis (SPICE) simulations, on-chip experiments and measurements.

Tunable matching circuits for power amplifiers

Abstract: Tunable matching circuits for power amplifiers are described. In an exemplary design, an apparatus may include a power amplifier and a tunable matching circuit. The power amplifier may amplify an input RF signal and provide an amplified RF signal. The tunable matching circuit may provide output impedance matching for the power amplifier, may receive the amplified RF signal and provide an output RF signal, and may be tunable based on at least one parameter effecting the operation of the power amplifier. The parameter(s) may include an envelope signal for the amplified RF signal, an average output power level of the output RF signal, a power supply voltage for the power amplifier, IC process variations, etc. The tunable matching circuit may include a series variable capacitor and/or a shunt variable capacitor. Each variable capacitor may be tunable based on a control generated based on the parameter(s).

A Resistively Degenerated Wideband Passive Mixer With Low Noise Figure and High ${\rm IIP}_{2}$

Abstract: A CMOS mixer whose linearity is maintained for a wide frequency range is presented. Transconductance (Gm) boosting methods, such as input cross-coupling, current reuse complementary input, and back gate connection, are used to improve overall gain and noise performance. A source-degenerated passive mixer is used to improve noise figure (NF) by increasing the equivalent mixer output impedance. The operating frequency is from 1.55 to 2.3 GHz. The measured performance shows less than 9.5 dB double-sideband (DSB) NF, more than 22-dB voltage gain, better than +50 dBm uncalibrated IIP2, and higher than +7 dBm of IIP3, while consuming only 10 mW from a 2-V supply. A 0.18-?m Si CMOS process with metal-insulator-metal capacitors is used.

Electronically tunable multiphase sinusoidal oscillator using translinear current conveyors

Abstract: A new electronically tunable current-mode multiphase sinusoidal oscillator based on translinear current conveyors is presented. The proposed oscillator circuit, which employs only one translinear current conveyor and one grounded capacitor for each phase, can generate arbitrary N output current equal-amplitude signals that are equally spaced in phase (N being even or odd), all at high output impedance terminals. The frequency of oscillation and the condition of oscillation can be controlled electronically and independently through the bias current of the translinear current conveyor. The proposed structure also has simple circuitry, low-component count, and is highly suitable for integrated circuit implementation. The theoretical results were verified by PSPICE simulation. In addition, the modification of the N sinusoidal oscillators to construct a programmable multiphase oscillator is also discussed.

High frequency surgical generator comprising an additional transformer

Abstract: An HF surgical appliance comprising an HF generator having an output circuit, which contains an output transformer and has an output impedance. Output terminals, to which an HF surgical instrument can be connected, are provided, said instrument supplying a high-frequency current with a specific frequency into tissue to treat the same. An additional output circuit containing an additional transformer, which is connected between the output circuit and the output terminals to reduce the output impedance is also provided. In this way, the HF surgical appliance can be operated with a high power output even on loads having low impedance.

Intrinsic Gain in Self-Aligned Polysilicon Source-Gated Transistors

Abstract: Thin-film self-aligned source-gated transistors (SGTs) have been made in polysilicon. The very high output impedance of this type of transistor makes it suited to analog circuits. Intrinsic voltage gains of greater than 1000 have been measured at particular drain voltages. The drain voltage dependence of the gain is explained based on the device physics of the SGT and the fact that a pinchoff occurs at both the source and the drain. The results obtained from these devices, which are far from optimal, suggest that, with a proper design, the SGT is well suited to a wide range of analog applications.

Amplifier module with multiple operating modes

Abstract: An amplifier module with multiple operating modes is described. In an exemplary design, the amplifier module includes an amplifier (e.g., a power amplifier), a switch, and an output circuit. The amplifier receives and amplifies an input signal and provides an amplified signal in a first mode. The switch is coupled to the output of the amplifier and bypasses the amplifier and provides a bypass signal in a second mode. The output circuit is coupled to the amplifier and the switch. The output circuit performs output impedance matching for the amplifier in the first mode. The output circuit also (i) receives the amplified signal and provides an output signal in the first mode and (ii) receives the bypass signal and provides the output signal in the second mode. The amplifier is enabled in the first mode and disabled in the second mode.

A self-powered power management circuit for energy harvested by a piezoelectric cantilever

Abstract: This paper presents development of a self-powered power management circuit for energy harvested by a piezoelectric cantilever A full-wave rectifier followed by a buck-boost converter running in the discontinuous conduction mode rectifies the AC output, matches the source impedance, and generates a regulated DC output provided the input power is sufficient to charge up the load A low power microcontroller unit is used for the maximum power point tracking and the output voltage regulation Experimental results show that the circuit can harvest up to 35 mW with a 50×318 mm2 piezoelectric cantilever under 05g (rms) base acceleration Detailed loss analysis is presented for efficiency enhancement in the future

Runtime Extension of Low-Power Wireless Sensor Nodes Using Hybrid-Storage Units

Abstract: The sensor nodes of wireless sensor networks remain inactive most of the time to achieve longer runtimes. Power is mainly provided by batteries, which are either primary or secondary. Because of its internal impedance, a significant voltage drop can appear across the battery terminals at the activation time of the node, thus preventing the extraction of all the energy from the battery. Additionally, internal losses can also be significant. Consequently, the runtime is reduced. The addition of a supercapacitor in parallel with the battery, thus forming a hybrid-storage device, has been proposed under pulsed loads to increase the power capabilities and reduce both the voltage drop and the internal losses at the battery. However, this strategy has not yet thoroughly been analyzed and tested in low-power wireless sensor nodes. This paper presents a comprehensive theoretical analysis that extends previous works found in the literature and provides design guidelines for choosing the appropriate supercapacitor. The analysis is supported by extensive experimental results. Two low-capacity (< 200 mAh) batteries were tested together with their hybrid-storage unit counterparts when using an electronic load as a pulsed current sink. The hybrid-storage units always achieved a higher runtime. One of the batteries was also tested using a sensor node. The runtime extension was 16% and 33% when connecting the hybrid-storage unit directly and through a dc-dc switching regulator to the sensor node, respectively.

Antenna interface circuits including tunable impedance matching networks, electronic devices incorporating the same, and methods of tuning antenna interface circuits

Abstract: An antenna interface circuit for a wireless communication device includes a tunable matching circuit that is coupleable to an antenna The tunable matching circuit includes a variable impedance element having a variable impedance Ztune The interface circuit further includes a fixed impedance element having a fixed impedance Zmeas, and a switch coupled to the fixed impedance element and configured to controllably switch the fixed impedance element into electrical communication with the tunable matching circuit Related devices and methods are also disclosed

High-output-impedance current-mode multiphase sinusoidal oscillator employing current differencing transconductance amplifier-based allpass filters

Abstract: This article presents a multiphase sinusoidal oscillator using current differencing transconductance amplifier (CDTA)-based allpass filters. The oscillation condition and oscillation frequency can be orthogonally controlled. The proposed circuit provides 2n – phase signals (n≥2) that are equally spaced in phase and of equal amplitude. The circuit requires one CDTA, two resistors and one capacitor for each phase and no additional current amplifier. Owing to high-output impedances, the proposed circuit enables easy cascading in current-mode configurations. The effects of the nonidealities of the CDTA-allpass sections were also studied. The results of PSpice simulations are presented, demonstrating their consistency with theoretical assumptions.

A new CMOS dual-X second generation current conveyor (DXCCII) with an FDNR circuit application

Abstract: In this paper, a new CMOS high performance dual-X second-generation current conveyor (DXCCII) is presented. The proposed DXCCII provides good linearity, high output impedance at Z terminals, and excellent output–input current gain accuracy. Besides the proposed DXCCII circuit operating at a supply voltage of ± 1.5 V . Moreover, a tunable novel lossless frequency-dependent negative resistance (FDNR) circuit employing only a single active element and three passive components is firstly proposed in this study. The applications of the DXCCII and FDNR to realize a current-mode fifth-order elliptic filter are given. The proposed DXCCII and its applications are simulated using CMOS 0.35 μ m technology.

Multilayer acoustic impedance converter for ultrasonic transducers

Abstract: An impedance conversion layer useful for medical imaging ultrasonic transducers comprises a low impedance polymer layer and a high impedance metal layer. These layers are combined with corresponding thicknesses adapted to provide a function of converting from a specific high impedance to specific low impedance, wherein the polymer layer is at the high impedance side and the metal layer is at the low impedance side. The effective acoustic impedance of the polymer and metal layer combination may be adapted to configure an impedance converter in the same way as a quarter wavelength impedance converter, converting from low impedance to high impedance (metal to polymer) or from a high impedance to low impedance (polymer to metal). This structure may be used for front matching with the propagation medium and back matching with an absorber for ultrasonic transducers.

Multi-band high-efficiency doherty amplifier

Abstract: The present invention relates to a Multi-Band Doherty amplifier. Embodiments of the present invention provide an amplifying structure including a main amplifier configured to amplify a first signal, a peak amplifier configured to amplify a second signal, a tunable impedance inverter configured to perform impedance inversion to modulate a load impedance of the main amplifier, and a combining node configured to receive the amplified second signal from the peak amplifier and an output of the tunable impedance inverter. The tunable impedance inverter includes a tuner configured to tune the impedance inversion over at least one broad frequency band. The tuner is (i) at least one capacitor, (i) at least one varactor, or (ii) at least one open stub shunted by a diode.

SIMO type low-input and high-output impedance current-mode universal filter employing three universal current conveyors

Abstract: In this paper, the Universal current conveyor (UCC) is presented. The paper also contains UCC application possibilities and an outline of its internal structure. Real parameters obtained by measurement are also included. This circuit can operate as almost any known type of current conveyor of all three generations and even as some other types of active element. In the paper, the single-input multiple-output (SIMO) universal filter solution employing three UCC elements is also shown. This solution has many beneficial features and offers all kinds of transfer function in both inverted and non-inverted form and that is why this topology is suitable to be included in the library of functional blocks. The paper also contains experimental results, whose goal was to verify real parameters of the designed block.