Showing papers on "Output impedance published in 2001"

An extended Doherty amplifier with high efficiency over a wide power range

Abstract: An extension of the Doherty amplifier, which maintains high efficiency over a wide range of output power (>6 dB), is presented in this paper. This extended Doherty amplifier is demonstrated experimentally with InGaP/GaAs heterojunction bipolar transistors at 950 MHz. Power-added efficiency (PAE) of 46% is measured at P/sub 1dB/ of 27.5 dBm and 45% is measured at 9 dB backed off from P/sub 1dB/. Additionally, PAE of at least 39% is maintained for over an output power range of 12 dB backed off from P/sub 1dB/. This is an improvement over the classical Doherty amplifier, where high efficiency is typically obtained up to 5-6 dB backed off from P/sub 1dB/. Compared to a single transistor class-B amplifier with similar gain and P/sub 1dB/, the extended Doherty amplifier has PAE 2.6 /spl times/ higher at 10 dB back off and 3 /spl times/ higher at 20 dB back off from P/sub 1dB/. Under different bias and output matching conditions, the amplifier was also evaluated with CDMA signals. At the highest measured power of 25 dBm, the extended Doherty amplifier achieves a PAE of 45% with an adjacent channel power ratio of -42 dBc. Generalized design equations are also derived and the consequences of finite device output impedance on amplifier gain and linearity are explored.

Analysis and design of impedance-transforming planar Marchand baluns

Abstract: A technique for designing impedance-transforming baluns is presented in this paper. It is based on the Marchand balun with two identical coupled lines. By varying the coupling factor of the coupled sections, a wide range of impedance transforming ratios can be achieved. In addition, a resistive network added between the balun outputs is proposed to achieve balun output matching and isolation. Microstrip baluns, matched at all ports, for transforming from a 50-/spl Omega/ source impedance to 40-/spl Omega/ as well as 160-/spl Omega/ load terminations are realized to demonstrate the technique.

General design equations, small-sized impedance transformers, and their application to small-sized three-port 3-dB power dividers

Abstract: In this paper, design equations for three-port power dividers have been derived. These design equations are available for both arbitrary power divisions and arbitrary termination impedances, and many sets of design equations are possible. Therefore, the design equations may be called general design equations and an arbitrary design impedance A is introduced to describe them. On the basis of the derived general design equations, a coplanar three-port power divider with a power split ratio (3 dB) terminated by 50, 60, and 70 /spl Omega/ is designed with A=33.33 /spl Omega/, so that a commercially available resistor 100 /spl Omega/ can be used for the isolation resistance. Additionally, to reduce the size of transmission-line impedance transformers, two types of small-sized impedance transformers are designed, named a constant VSWR-type transmission-line impedance transformer (CVT) and a constant conductance-type transmission-line impedance transformer (CCT) and compared with conventional reduced-sized impedance transformers. These impedance transformers are designed in the low-Q region on the Smith chart. Therefore, they show wide-band properties. To make sure that the derived design equations of CVTs and CCTs are reasonable, four 1;6:1 impedance transformers, CVT 20/spl deg/, CVT 30/spl deg/, CCT 15/spl deg/, and CCT 20/spl deg/ have been fabricated in microstrip technology and measured. The measured results show the expected tendency. Based on the CVTs and CCTs, small-sized three-port 3-dB power dividers are constructed and named a constant VSWR-type three-port 3-dB power divider (CVT3PD) and a constant conductance-type three-port 3-dB power divider (CCT3PD). For the CVT3PD and CCT3PD, perfect isolation conditions are derived, and it is shown that the perfect isolation circuit (I.C) must be composed of resistance combined with capacitance or inductance in the case that the length of transmission lines is not /spl lambda//4. These I.Cs are quite different from conventional ones composed of only resistance. Finally, on the basis of the derived perfect isolation impedance, CVT3PD and CCT3PD are designed and simulated, giving the possibility that a CCT3PD can be realized with the electrical length 15.30/spl deg/ of the transmission lines.

Frequency-scalable SiGe bipolar RF front-end design

Abstract: The optimum collector current density, at the global minimum noise figure (NF) point for a bipolar transistor, scales linearly with frequency. The optimum source impedance, on the other hand, remains constant if the device area is scaled inversely with frequency. As a result, transforming the design from one frequency to another can be achieved by simple circuit scaling. Taking advantage of the shallow nature of the NF/sub min/ global minima, it is possible to increase the linearity of the low-noise amplifier (LNA) or decrease its power consumption, which is required for multimode designs, with little degradation in NF. These theoretical results have been applied to LNA and active mixer designs, and verified by constructing a 1.8-GHz frequency-scaled SiGe bipolar test chip. The measured LNA NF is 1.3 dB at 4.5 mA, while the double-balanced mixer achieves a single-sideband (SSB) NF of 6.1 dB for the low-linearity mode and an IIP3 and an SSB NF of +3 dBm and 6.6 dB, respectively, for the high-linearity mode.

Integrated impedance matching and stability network

Abstract: An integrated circuit for intermediate impedance matching and stabilization of high power devices is disclosed. High quality epitaxial layers of monocrystalline materials grown over monocrystalline substrates enables the formation of impedance matching and stability circuits to be placed on the same substrate as the active device. Additionally, by using the manifolds of the active to form plates of a capacitor, an impedance matching network of series inductance and shunt capacitor can be compactly fabricated for increasing the output impedance to intermediate levels. The manifolds of the active device are also used to form capacitors to provide stability to high power active devices.

Output driver circuit with well-controlled output impedance

Abstract: An output driver circuit for driving a signal onto a signal line. The output driver circuit comprises at least one driver circuit and a passive network. The passive network is configured to limit the variation in the output impedance of the output driver circuit. The output driver circuit thus provides an output impedance that closely matches the loaded impedance of the signal line at all times so as to minimize secondary reflections on the signal line.

Bi-directional output buffer

Abstract: A bi-directional output buffer includes active termination and separate driving and receiving impedances. The buffer has at least a driving mode and a receiving mode. In driving mode, the output impedance of the buffer is calibrated to a specified strength. In receiving mode, the buffer is calibrated to another specified impedance as an active termination. In addition, the buffer may be configured such that resistive components are shared in driving and receiving modes.

Active impedance matching in communications systems

Abstract: A signal sensing module senses an RF signal and produces one or more secondary signals representative of the RF signal. An impedance matching control module generates a control signal, based on the one or more secondary signals, which is indicative of an impedance mismatch between a load and a communications device. The control signal is then applied to at least one variable impedance device to adjust the impedance of an impedance matching network and thereby reduce the impedance mismatch between the load and the communications device. In an embodiment, the at least one variable impedance device is a barium strontium titanate, thin film, parallel plate capacitor. In other embodiments, other variable impedance devices such as other types of thin film capacitors or varactor diodes are be used to adjust the impedance of the impedance matching network.

Single output stage power amplification for multimode applications

Abstract: The present invention eliminates the need for complex impedance networks or parallel amplification stages for multi-mode mobile terminals. A wideband power amplifier is configured to amplify signals in different frequency bands corresponding to different operating modes. The supply voltage of the wideband power amplifier is adjusted in light of the load impedance of radiating circuitry to achieve a desired output power for the respective operating modes.

LED driving circuit and optical transmitting module

Abstract: An LED is an element in which when a voltage pulse applied to the intrinsic diode of an electrical equivalent model reaches a peak value, a current suddenly flows to obtain an optical output proportional to the forward current. By utilizing this property, the LED receives a rectangular voltage pulse having a large-current driving ability at a low output impedance, or a voltage pulse having two high levels. The low level of the voltage pulse is set within a voltage range where the extinction ratio of an output signal from the LED can be maintained. Even in an LED having a large internal capacitance, an increase in power consumption can be minimized, the transient response time can be shortened, high-speed modulation can be performed, and output light almost free from pulse waveform distortion can be obtained.

A de-embedding technique for interconnects

Abstract: In general, three parameters are needed to model symmetrical adapters, but not enough equations can be found to solve them. The measurement of through adapters gives two conditions only, but neither open nor short adapter gives any useful condition. The results from lines with length L and length 2L can be used to derive the result for through adapters. This paper proposes one approach with a 2-impedance model, which has one shunt impedance and one series impedance. This model can be used with more complicated structures than the single impedance model.

Robust average current-mode control of multimodule parallel DC-DC PWM converter systems with improved dynamic response

Abstract: This paper presents a novel average current-mode control (ACC) strategy for the control of multimodule parallel pulsewidth modulation DC-DC converters, which represents a drastic improvement over conventional ACC. This new method consists of the addition of an auxiliary controller into the control loop, besides the current and voltage regulators. The reference-model-based auxiliary controller improves the robustness of the ACC dynamics in buck-derived distributed power systems, preserving loop gain crossover frequency and stability margins over significant changes of the number of connected modules, the load and the line voltage. Moreover, this control scheme shows much better disturbance rejection properties, i.e., closed-loop output impedance and audiosusceptibility, than conventional ACC. From a control theory point of view robust performance is achieved, preserving stability. A multimodule buck prototype has been experimentally tested with different numbers of modules on stream, line, and load conditions, including discontinuous conduction mode. Measurements of the small-signal frequency response of the converter have been carried out, showing the improvement achieved by the proposed control scheme. The empirical large-signal response of the converter under load steps is also shown in order to validate the concept.

Programmable logic integrated circuit devices with differential signaling capabilities

Abstract: A programmable logic device is equipped for various differential signaling schemes by providing a differential output buffer on the device that can be configured according to the needs of the particular differential signaling schemes that may be used. The buffer includes a differential output driver, an adjustable current limiting circuit between the supply voltage and the differential output driver, and an adjustable current limiting circuit between the differential output driver and ground. By selectively adjusting the two current limiting circuits, the output impedance and current, as well as the common mode output voltage and the differential output voltage can be controlled.

High-output-impedance transadmittance type continuous-time multifunction filter with minimum active elements

Abstract: A new transadmittance multifunction filter with single input and three outputs employing only three positive-type second-generation current conveyors and five passive elements is presented. The proposed filter realizes three basic filter functions simultaneously, all at high impedance outputs. No component matching is required and all the passive sensitivities are low. Experimental verification is also performed.

Noise filter and electronic device using noise filter

Abstract: A noise filter comprises a magnetic member (32) formed of a laminated magnetic sheets (24, 28, 30, 31), a first impedance element (21) formed in the magnetic body (32), and a second impedance element (25) formed above the first impedance element (21). The first impedance element (21) includes a first normal impedance element part (22) and a first common impedance element part (23). The second impedance element (25) includes a second common impedance element part (26) and a second normal impedance element part (27).

Impedance control circuit

Abstract: An impedance control circuit that reduces the impedance variance when an external impedance generated from an external resistor is matched to internal impedance. In one aspect, an impedance control circuit comprises an external resistor for establishing a first reference voltage; a comparator for comparing the first reference voltage with a second reference voltage and outputting an impedance corresponding to the result of the comparison; and a PMOS current source connected to a constant-voltage source and to the output of the comparator, wherein the PMOS current source generates a current that corresponds to the impedance of the comparator.

Adaptive tuning device and method utilizing a surface acoustic wave device for tuning a wireless communication device

Abstract: An adaptive tuning method for a wireless communication device determines the impedance of a matching circuit relative to an impedance to be matched and adjusts the impedance of the matching circuit accordingly. A passive surface acoustic wave (SAW) device includes multiple terminated interdigital transducers (IDTs) which generate reflected SAWs when excited by incident SAWs, each reflected SAW having magnitude and phase characteristics dependent upon the particular IDT termination. According to the invention, the IDT terminations include the impedance matching circuit and the impedance to be matched. Input IDTs in the SAW device are excited with electrical signals, which are converted to generate the incident SAWs. The resultant reflected SAWs are converted by output IDTs into output electrical signal signals which can then be analyzed to determine magnitude and phase differences between the output electrical signal signals and generate an impedance matching circuit control signal based thereon.

Output buffer circuit

Abstract: An output buffer circuit having a function of accomplishing pre-emphasis, and transmitting a logic signal to a transmission line acting as a distributed parameter circuit, includes (a) a first buffer which receives a first logic signal defining a logical value of a logic signal to be transmitted to the transmission line, and drives the transmission line, and (b) a second buffer which receives a second logic signal having a predetermined logical relation with the first logic signal, and cooperates with the first buffer to drive the transmission line. The second buffer has an output impedance higher than an output impedance of the first buffer as long as attenuation in a signal in the transmission line is improved.

Radio station with optimized impedance

Abstract: A radio station optimizes the impedance. An antenna of a transmitter of the radio station matches an output impedance of a power amplifier by adding an impedance with a variable reactance. A processor adjusts the variable reactance of the impedance according to an output signal of the power amplifier. The impedance with the variable reactance preferably includes either a plurality of inductors and capacitors, variable inductors and capacitors, or a plurality of microstrip lines. The processor calculates an optimum value for the variable reactance according to a measurement of the output signal of the power amplifier and stores those values for those measured values. In this way, a table is created, so that when the output signal is again measured the processor can use this table to determine which variable reactance will lead to impedance matching.

Programmable impedance device

Abstract: A programmable impedance element (204) is implemented using integrated circuit techniques and devices. An impedance of the programmable impedance element is adjusted by appropriately configuring the element. The programmable impedance element has a range of impedance values, and is configurable to be a value within this range. In an embodiment, the programmable impedance element is implemented using a floating gate device (230), and is nonvolatile.

Differential impedance control on printed circuit

Abstract: A new method to control differential signal trace impedance allows flexible use of different signal trace width and spacing while maintaining constant differential impedance in printed circuit boards. Differential impedance of a signal pair is determined by the geometry of individual traces and the spacing between traces. The value of the differential impedance is inversely proportional to signal trace width and directly proportional to signal trace spacing. By decreasing or increasing trace width and spacing simultaneously, a constant differential impedance can be achieved.

An Impedance-Based CT Saturation Detection Algorithm for Bus-Bar Differential Protection

Abstract: This paper presents an algorithm for current transformer (CT) saturation detection based on the measurement of the power system source impedance seen at the relay location. The algorithm estimates this source impedance using a short-data window impedance-estimation algorithm and samples taken from the CT secondary current and bus-bar voltage. Following the changes on the impedance seen at the relay location, the algorithm is able to detect a CT saturation and send a blocking order to a fast tripping bus-bar differential relay.

High output impedance current-mode lowpass, bandpass and highpass filters using current controlled conveyors

Abstract: Three new current-mode second-order filter configurations which employ one or two current controlled conveyors (CCCIIs) and three passive elements are presented. Each proposed filter can realize one of the bandpass, lowpass or highpass responses all at high impedance outputs. The proposed filters offer current-control of pole angular frequency ωo without disturbing the parameter ωo /Q. No component matching is required and all the passive and active sensitivities are low. PSPICE simulation results are given to confirm the theoretical analysis.

Facility to measure solar cell ac parameters using an impedance spectroscopy technique

Abstract: An experimental setup has been developed to measure the solar cell ac parameters using an impedance spectroscopy technique. It consists of an electrochemical interface to set the dc bias voltage and to apply the signal voltage across the solar cell and a frequency response analyzer to generate the excitation signal with varying frequency and analyze the result. The setup is calibrated with a standard RC network and measured an error of ±4% (maximum). Solar cell capacitance, parallel resistance and series resistance are calculated from the measured data.

High frequency MOSFET switch

Abstract: A high-frequency switch circuit having an MOS pass gate or transfer transistor. The switch circuit of the invention includes a first impedance element coupled to the gate of the transfer transistor and, preferably, an alternative second impedance element coupled to the bulk of the transfer transistor. One or both of the impedance elements substantially negates the low-parasitic shunt capacitance associated with the transfer transistor that controls signal attenuation under high frequency operation. The impedance element is coupled in series with that parasitic capacitance to increase substantially the impedance of that pathway, thereby increasing substantially the passable bandwidth. The impedance element may simply be a resistor. The switch circuit is suitable for use in an array of applications, including signal propagation in computing systems, routers, and flat panel screen displays.

Chip-type LTCC-MLC baluns using the stepped impedance method

Abstract: A chip-type low-temperature co-fired ceramic (LTCC) multilayer ceramic (MLC) balun is presented in this paper. This balun is designed using the stepped impedance method. It uses a multilayer structure, meander lines, and multisection coupled lines. The use of multisection couple lines that have various characteristic impedance ratios can shrink the length of a quarter-wavelength coupled-transmission line and makes it very easy to match various impedances of balanced output. The proposed chip-type balun operates over a bandwidth of 2.25-2.65 GHz. The in-band phase and amplitude balances are excellent because of the symmetric structure and transmission-line trimming section. Measured results of the chip-type LTCC-MLC balun match well with the computer simulation.

Current mode signal interconnects and CMOS amplifier

Abstract: This invention provides a structure and method for improved transmission line operation on integrated circuits A first embodiment of this invention provides a current mode signaling technique over transmission lines formed having a lower characteristic impedance than conventional CMOS transmission lines The low impedance transmission lines of the present invention are more amenable to signal current interconnections over longer interconnection lines An interconnection on an integrated circuit is described in which a first end of a transmission line is coupled to a driver The transmission line is terminated at a second end with a low input impedance CMOS technology In one embodiment, the low input impedance CMOS technology is a current sense amplifier which is input impedance matched to the transmission line This minimizes reflections and ringing, cross talk and noise as well as allows for a very fast interconnection signal response A second embodiment of the present invention includes a novel current sense amplifier in which feedback is introduced to lower the input impedance of the current sense amplifier In this embodiment, the novel current sense amplifier is employed together with the current signaling technique of the present invention The novel low input impedance CMOS circuit described here provides an improved and efficiently fabricated technique for terminating low impedance transmission lines on CMOS integrated circuits

Wide-band replica output current sensing circuit

Abstract: An indirect current sensing circuit and method for replicating an output current is disclosed. The present invention is capable of preventing device damage and circuit disruption by maintaining output voltage signal integrity and consuming negligible power as well as optimizing output impedance. Furthermore, the indirect current sensing circuit and method is independent of semiconductor process variations and thus is more reliable over prior art current sensing techniques. The indirect current sensing circuit and its method of current limiting and output impedance optimization, according to the present invention, can reliably drive transmission lines in networking system and communication applications.

Power amplifier (PA) with improved power regulation

Abstract: A circuit for regulating the power provided to a load connected to an output of a power amplifier. The circuit includes an amplitude detector that outputs a voltage corresponding to the amplitude of the signal outputted by the power amplifier. This output voltage is a function of the impedance of the load. Thus, when the impedance of the load changes, the output voltage also changes. Given a constant current into the load, it is the load impedance that determines the power delivered to the load. Therefore, because the output voltage reflects changes in the impedance of the load, the output voltage can be used by a regulator circuit to maintain a constant output power, regardless of changes in the impedance of the load.