577 results about "Amplifier gain" patented technology

An envelope tracking radio frequency (RF) power amplifier having an adaptive envelope signal processing circuit is disclosed. An RF input voltage is sampled by the adaptive envelope signal processing circuit which provides control signals to the power supply which supplies voltages to RF power devices in order to simultaneously satisfy two operating conditions: a) provide best possible efficiency of the power amplifier stages depending on the input signal characteristics and b) provide compensation for RF transistor AM-AM and AM-PM distortion compensation across the power range. In particular, the voltage control provides for constant power amplifier gain across the input signal dynamic range, thus minimizing power amplifier amplitude distortions and extending the useful power amplifier linear dynamic range up to saturation point. The power amplifier thus exhibits better linearity and efficiency than offered by conventional techniques and topologies.

An automated identification and configuration system for use with an implantable medical device (IMD) is disclosed. The system includes a first communication circuit that is attached to, or otherwise carried by, a detachable component associated with the IMD such as a medical lead. The communication circuit stores data such as model numbers, serial numbers, technical data, and / or calibration information that describes the additional component. This information may be transferred by the first communications circuit to a second communications circuit that is external to the additional component. This transferred data can be used to automatically configure the internal circuitry and connection functions of the IMD to properly interface with, and support, the additional component. For example, the data can be used to automatically adjust amplifier gains or other sensor circuitry, or to configure a connector block to properly couple to the component. The data may further be entered into a patient record on an external programmer, or may be transferred to a central storage location to be generally accessible to health care providers. In one embodiment, the first communication circuit is a passive RF transponder. This first communication circuit may include a receiver as well as a transmitter to allow the circuit to programmably receive data at the time of component manufacture.

Frequency-independent and frequency-dependent pre-distortion is implemented using look-up tables to retrieve pre-distortion parameters. To compensate for changes in amplifier operating characteristics over time, fixed pre-distortion tables can be used by appropriately offsetting the index values used to retrieve the pre-distortion parameters. The overall amplifier gain as well as the biases applied to one or more amplifier stages are also preferably controlled. In addition, the frequency-independent and / or frequency-dependent pre-distortion tables can be updated either periodically or as needed, by mapping a measure (e.g., average input signal power) to one or more parameters using equations (e.g., piecewise linear curves), where the parameters are applied to one or more polynomials to update the tables.

A method to program a microcontroller using a software program. First a user selects a module from a catalog of available modules. The module may be for implementing an amplifier, timer, pulse width modulator, etc. This causes information related to the selected module to be displayed. For example, a schematic and data sheet for the selected module may be displayed. Next, the user requests a position and places the selected module in a graphical user interface, which represents the resources available to implement the available modules. For example, the resources may be programmable system blocks. Additional user modules may then be selected and placed. The user then configures the circuit by selecting circuit parameters for the user modules (e.g., amplifier gain), pin configurations, and interconnections between programmable system blocks. The user may then edit source code used to cause the user modules to perform their functions.

A power control system and method including a plurality of point-of-load regulators (POL) providing corresponding regulated output voltages; a manager for communicating control signals and operational parameters with said point-of load regulators; a digital bus to carry control signals therebetween; and an analog bus to carry operational parameters therebetween. Analog sensing circuits and a mutliplexer on the POL communicate operational parameters to and from the manager via the analog bus and are controlled via the digital bus. The operational parameters include output voltage, output current, over voltage, temperature, amplifier or comparator offset, and amplifier gain. The analog sensing circuits are calibrated by trim registers on the POL under digital control by the manager.

A translinear amplifier is disclosed. A loop amplifier drives the bases of the input and output transistor pairs from the differential collector voltage of the input pair. The loop amplifier contains a third differential pair (a gain pair). The tail current of the gain pair is inversely related to the tail current of the input pair, such that loop amplifier gain remains stable when the transconductance of the input pair changes (due, e.g., to input gain changes). In one embodiment, a linear-in-dB interface is provided that adjusts input pair tail current exponentially (and gain pair tail current exponentially and inversely) to linear voltage changes at a gain input.

A phase-based TOF system preferably generates an optical waveform with fast rise and fall times, to enhance modulation contrast, notwithstanding there will be many high order harmonics. The system is preferably operated with an odd number of phases, to reduce system bias error due to the higher order harmonics, while maintaining good modulation contrast, without unduly increasing system memory requirements. Preferably the system can dynamically calibrate (and compensate for) higher order harmonics in the TOF generated optical energy waveform, over time and temperature. Within the optical energy transmission channel, or within the optical energy detection channel, detection amplifier gain may be modified, and / or detector signal integration time may be varied, and / or digital values may be employed to implement calibration and error reduction The resultant TOF system can operate with improved phase-vs-distance characteristics, with reduced calibration requirements.

A radio frequency amplifier system is disclosed in which the amplifier bias supply and power supply voltages are >instantaneously modulated with signals derived from the envelope voltage of the input signal. Separate non-linear mapping functions are used to derive the supply and bias voltages. The two mapping functions are optimised jointly to achieve particular system performance goals, such as optimum efficiency, constant gain, constant phase, or minimum spectral spreading. An optimisation of >particular interest is that which achieves best RF amplifier power added efficiency subject to achieving constant amplifier gain. In this way the need for pre-distortion linearization may be reduced or eliminated.

A low power IF strip architecture suitable for Zero-IF (ZIF) or low-IF (LIF) radio receivers for filtering and amplifying a received signal. The apparatus includes a plurality of sequentially connected complex filter / amplifier stages. Each stage includes a complex filter having one or more poles and an automatic gain controlled amplifier (AGC). Each AGC may be feedback or feedforward with fixed minimum and maximum gains. Each stage further includes a control circuit that produces a gain control signal for controlling the amplifier gain within the fixed minimum and maximum gains as a function of a projected amplitude level. The received signal passes through multiple stages of filtering and controlled amplification to attenuate the interfering signal and amplify the desired signal. This is done at a restricted level in each stage such that the circuits in the stages operate at efficient power saving levels. The individual gain control signals from each stage are summed in a received signal strength indicator to provide the overall gain of the apparatus. The overall gain when taken with the amplitude of the apparatus output signal determines the original strength of the desired received signal.

A current sensor includes a shunt and at least one resistant element. The shunt conveys an electric current, and has a resistance which varies with the shunt's temperature. A resistant element, which has a resistance that varies with its own temperature, is electrically connected between the shunt and an output terminal of the current sensor. At least a portion of the resistant element is in thermal contact with a predetermined location on the shunt, so that the resistant element's resistance varies in accordance with the shunt temperature. The current sensor may be connected to an amplifier whose gain varies in accordance with the resistance of the resistant element. The variation in the resistance of the resistant element causes a change in the amplifier gain, which compensates for changes in the shunt resistance due to change's in the shunt's temperature. In some embodiments, a second resistant element is connected between the shunt and a second output terminal.

A gain compensation device for adjusting gain of an amplifier over temperature is disclosed. The gain of the amplifier is controlled by signals on a gain control end of the amplifier. The gain compensation device comprises a temperature compensation generator, an adder, and a temperature sensor. The temperature compensation generator is for generating an additional gain parameter according to a reference temperature, a current temperature, and a temperature coefficient. The adder comprises a first input end, coupled to the temperature compensation generator for receiving the additional gain parameter, a second input end for receiving a default gain parameter, and an output end coupled to the gain control end of the amplifier for outputting sum of the additional gain parameter and the default gain parameter. The temperature sensor is for providing the current temperature.

A system and method are provided for maintaining a consistent operating condition of a power amplifier power amplifier across a range of operating temperatures. The power amplifier is provided with an input bias voltage (Vbias) that adjusts with temperature to compensate for the temperature dependent change of the power amplifier's base-emitter voltage drop Vbe. This maintains a consistent operating condition in the power amplifier, which reduces temperature-dependent changes in the amplifier's gain.

Dynamic range of a differential pixel is enhanced by injecting, synchronously or asynchronously, a fixed compensating offset (ΔV) into a differential signal capacitor whenever magnitude of the differential signal across the capacitor exceeds a predetermined value. The number (N) of ΔV offsets made is counted. Effective differential signal capacitor voltage V(t)=Vo+N·ΔV, where Vo is capacitor voltage. Differential pixel signal / noise ratio is increased by dynamically maximizing operational amplifier gain AG for each differential pixel.

An envelope tracking radio frequency (RF) power amplifier having an adaptive envelope signal processing circuit is disclosed. An RF input voltage is sampled by the adaptive envelope signal processing circuit which provides control signals to the power supply which supplies voltages to RF power devices in order to simultaneously satisfy two operating conditions: a) provide best possible efficiency of the power amplifier stages depending on the input signal characteristics and b) provide compensation for RF transistor AM-AM and AM-PM distortion compensation across the power range. In particular, the voltage control provides for constant power amplifier gain across the input signal dynamic range, thus minimizing power amplifier amplitude distortions and extending the useful power amplifier linear dynamic range up to saturation point. The power amplifier thus exhibits better linearity and efficiency than offered by conventional techniques and topologies.

A method and system enhances the gain of a propagation path of a radio frequency (RF) signal while utilizing an envelope tracking (ET) mechanism to provide power to a power amplifier within the propagation path. An envelope tracking (ET) controller detects using the ET mechanism an RF envelope of the RF signal being propagated towards the power amplifier. The ET controller applies envelope pre-distortion to the RF signal. The ET controller initiates a function for shaping the supply voltage of the power amplifier by selecting a shaping table that can provide a specific level of increasing amplifier gain at higher signal drive level. The ET controller shapes the supply voltage for the power amplifier by adjusting values corresponding to the detected RF envelope. As a result, RF signals are propagated from the transceiver to the power amplifier output port across high and low transceiver drive levels with net constant gain.

An amplifier gain control circuit for the wireless transceiver comprises at least one amplifier, an analog to digital converter (ADC), a digital to analog converter (DAC) and a bias circuit, wherein the ADC is used for receiving an analog gain control voltage to generate a digital control signal that can be used for controlling the gain of the amplifier, the DAC is used for receiving the digital signal to generate an analog signal, and the bias circuit is used for receiving the analog signal and the analog gain control voltage to further fine-tune the gain of the amplifier by the analog process for correcting the least bit error during the digital process, therefore, the amplifier during the gain adjustment will be prevented to operate in the nonlinear area.

A gain boost circuit and methodology are described for providing improved gain boosting with tuned amplifier circuits, such as differential low noise amplifier circuits having output resonant tank circuits. By selectively controlling the current source for a negative transconductance stage coupled between the differential amplifier output and the output resonant tank circuits, the amplifier gain may be adjusted to compensate for temperature variations. In addition, the amplifier gain boost may be selectively added, removed or even incrementally adjusted by using a current source control circuit in the negative transconductance stage to adjust the negative transconductance value generated by the negative transconductance stage.

A dual loop feedforward power amplifier. A dual loop feedforward power amplifier, comprising an input that provides a multicarrier signal; a first feedforward power amplifier; and a second feedforward power amplifier, wherein the first feedforward power amplifier serves as a main amplifier gain block in the second feedforward power amplifier, wherein the first feedforward power amplifier comprises a carrier cancellation loop and a first error amplifier loop, and wherein the second feedforward power amplifier comprises a third loop and a fourth loop that cancel small signal distortions that are not reduced by the first feedforward amplifier.

The invention relates to a method for calibrating sensitivity of a microphone, comprising the following steps: receiving a power supply voltage signal and a sound input signal; judging whether the power supply voltage signal meets a preset condition or not, if so, entering a calibrating mode to continue, and otherwise, stopping; restoring a clock signal from a sound signal; restoring a data signal from the power supply voltage signal; and regulating the amplifier gain and / or microphone bias voltage according to the clock signal and the data signal. A microphone calibrating circuit applying the method comprises a clock restoring module, a data signal restoring module, a gain regulating and controlling and register interface module and a storage, wherein the clock restoring module is used for restoring the clock signal from an output signal of a sound / electricity switching assembly; the data signal restoring module is used for restoring the data signal from the power supply voltage signal, the gain regulating and controlling and register interface module is used for writing amplifier gain regulating data into the storage according to the output of the clock restoring module and the data signal restoring module, and the storage is used for receiving the amplifier gain regulating data from the gain regulating and controlling and register interface module and is used as the grain arrangement when an amplifier normally operates.

A system for a fast, closed power control loop that quickly adjusts the output power of a power amplifier in a non-constant amplitude modulation format. Embodiments of the invention allow fast and precise closed loop power control in a communication system that has a transmit signal that includes a phase modulated component and an amplitude modulated signal component. By detecting the level of the transmit signal before and after the power amplifier, the invention ignores changes in the amplitude of the transmit signal, resulting in an accurate measure of the power amplifier gain. The difference between the level of the transmit signal before and after the power amplifier provides a signal that represents the gain of the power amplifier. The gain signal is compared with a reference signal to develop an error signal. The error signal is used to control the output of the power amplifier.

The invention provides automated systems and methods for measuring ORL of fibers under test. A computer-based test instrument using OTDR tests fibers with the help of a STFM having predefined characteristics that are recorded in a machine-readable memory. The information recorded in the memory is accessible to the computer-based instrument and is used to calibrate a power level of an illumination source in real time using the reflectance response of the STFM. The calibrated illumination power allows the instrument to automatically determine the ORL of the fiber being tested with precision, and without requiring the intervention of an operator. The instrument also has the capability to automatically sense the presence of a test fiber, and to automatically attenuate the reflectance signal to remove a saturation condition by controlling at least one of the illumination, the detector gain, an amplifier gain, and an optional in-line optical attenuator.

An echo canceler circuit (10) and method attenuates at least post-echo canceler uplink data (90) to produce attenuated uplink data (100) in response to uplink echo return loss based attenuation data (40). The echo canceler circuit (10) includes an echo return loss based attenuation data generator (20) and at least an uplink data attenuator (30). The echo return loss based attenuation data generator (20) produces the uplink echo return loss based attenuation data (40) in response to echo return loss data (70). The echo return loss data (70) is based on at least one of: attenuated downlink data (50), pre-echo canceler uplink data (60), and / or amplifier gain data (80). The uplink data attenuator (30) attenuates the post-echo canceler uplink data (90) to produce attenuated uplink data (100) based on the uplink echo return loss based attenuation data (40).

Automatic gain control (AGC) methods and apparatus suitable for use in orthogonal frequency division multiplexing (OFDM) receivers are described. One AGC method includes the steps of repeatedly performing a first AGC process which adjusts amplifier gain based on determining that a signal level of multiple time sample values is outside a limit set by a first predefined threshold; and repeatedly performing a second AGC process which adjusts the amplifier gain based on determining that a signal level of multiple frequency sample values associated with a plurality of pilot tones is outside a limit set by a second predefined threshold. Preferably, the first AGC process is performed repeatedly at a first rate and the second AGC process is performed repeatedly at a second rate that is less than the first rate.

To effect power control of a power amplifier 2 having three amplifier stages 3, 4 and 5 used to amplify input signals modulated in accordance with a variable envelope modulation scheme, there is used a power amplifier 2 having a gain which reduces as the supply voltage to the power amplifier 2 reduces, and the output power POUT of the power amplifier 2 is controlled by regulation of the supply voltage VS. Taking advantage of the reduction in gain of the power amplifier 2, it is ensured that, in respect of each respective amplifier stage 3, 4 and 5 and at each respective value of the supply voltage in the voltage control range, the output power POUT of the respective amplifier stage 3, 4 and 5 is less than the saturation output power PSAT of the respective amplifier stage 3, 4 and 5. As a result, distortion of the signal is reduced. The power control technique improves efficiency over known techniques of backing off the output power and using a variable gain amplifier stage to control the output power.

A radio-frequency (RF) transmitter power amplifier circuit provides for practically linear performance by predistorting the amplifier input signals to compensate for amplifier distortion at high power levels, and provides a fine degree of control of amplifier power needed to handle complex modulation schemes with widely and rapidly varying power requirements. A predistortion database (20) contains gain and phase corrections for various transmission types and a separate automatic gain control database (38) contains fine amplifier gain corrections. A real-time processor (26) combines the two types of corrections and applies them to the amplifier input signals, and a background processor (16) continually updates both databases in accordance with a programmable priority scheme. Integration of predistortion and amplifier power control is achieved in a manner that minimizes adverse effects of one type of control on the other. One feature of the invention provides for rapid convergence of the predistortion correction.

A gain control circuit that permits a variable gain amplifier circuit to operate with high input linearity and low power consumption is disclosed. The variable gain amplifier includes a standard differential bipolar transistor input circuit and a pair of degeneration transistors connected to a current source transistor. The gain control circuit provides a variable degeneration control voltage to vary the effective resistance of the degeneration transistors and a variable bias voltage to vary the current of the current source transistor. The input linearity of the variable gain amplifier is controlled independently of gain by adjusting the effective resistance and the current in an inverse relationship such that at maximum gain the current is at a maximum while the degeneration resistance is at a minimum, and at minimum gain the current is at a minimum while the degeneration resistance is at a maximum. Therefore the variable gain amplifier can be controlled to operate with high input linearity and low power at lower ranges of gain.

A radiofrequency (RF) receiver circuit and method offer one or more performance improvements, such as an increased input compression point through better out-of-band interference suppression. In one example, an RF receiver circuit includes a low-noise amplifier (LNA) circuit and a mixer. The mixer output signal serves as negative feedback to the LNA circuit for improved compression point performance at interferer frequencies in or out of band with respect to a frequency of interest. Compression point performance is further improved for interferer signal components away from the frequency of interest by including at least one frequency-dependent circuit in the LNA circuit that is configured to reduce amplifier gain for such frequencies. The frequency-dependent circuit(s) may be tunable for different frequencies of interest. Additional improvements may be obtained by including a broadband input matching circuit and / or by including active mixer loads to increase the voltage conversion gain of the RF receiver circuit.

The invention provides automated systems and methods for measuring ORL of fibers under test. A computer-based test instrument using OTDR tests fibers with the help of a STFM having predefined characteristics that are recorded in a machine-readable memory. The information recorded in the memory is accessible to the computer-based instrument and is used to calibrate a power level of an illumination source in real time using the reflectance response of the STFM. The calibrated illumination power allows the instrument to automatically determine the ORL of the fiber being tested with precision, and without requiring the intervention of an operator. The instrument also has the capability to automatically sense the presence of a test fiber, and to automatically attenuate the reflectance signal to remove a saturation condition by controlling at least one of the illumination, the detector gain, an amplifier gain, and an optional in-line optical attenuator.

An RFID transponder having an analog front end receiver having an attenuator coupled to receive an RF-signal from an antenna and to attenuate the RF-signal, an amplifier having a fixed amplifier gain and being coupled to receive and to amplify the attenuated RF-signal and a control unit coupled to control a gain of the attenuator, wherein the control unit is configured to control the attenuator gain in response to a level of the amplified RF-signal, the control unit is configured to have a plurality of predetermined states causing the attenuator to increase (step-up) or to decrease (step-down), its gain by a predefined step size.