Showing papers on "RF power amplifier published in 1998"

Design and experiments of a high-conversion-efficiency 5.8-GHz rectenna

Abstract: A high-efficiency rectenna element has been designed and tested at 5.8 GHz for applications involving microwave-power transmission. The dipole antenna and filtering circuitry are printed on a thin duroid substrate. A silicon Schottky-barrier mixer diode with a low breakdown voltage is used as the rectifying device. The rectenna element is tested inside a waveguide simulator and achieves an RF-to-DC conversion efficiency of 82% at an input power level of 50 mW and 327 /spl Omega/ load. Closed-form equations are given for the diode efficiency and input impedance as a function of input RF power. Measured and calculated efficiency results are in good agreement. The antenna and circuit design are based on a full-wave electromagnetic simulator. Second harmonic power levels are 21 dB down from the fundamental input power.

An IC for linearizing RF power amplifiers using envelope elimination and restoration

Abstract: Efficient power amplifiers (PAs) are desirable because power amplifiers typically dominate the power consumed in portable radio devices. Cellular systems such as the advanced mobile phone system (AMPS) employ modulation schemes that generate constant amplitude RF outputs to use efficient but nonlinear PAs. Modern digital communication standards such as the North American dual-mode cellular (NADC) system require nonconstant amplitude RF outputs to maximize frequency spectral usage, and therefore require linear PAs. The traditional approach to linear RF power amplification is to back-off the output power of a PA until its distortion is reduced to an acceptable level. Power back-off can lead to significant reduction in output power and efficiency. The envelope elimination and restoration (EER) system is an alternative to power back-off, to simultaneously achieve efficiency and linearity in RF PAs.

L-band transmitter using Kahn EER technique

Abstract: This paper describes a 20-W peak-envelope power linear L-band transmitter based upon the Kahn envelope-elimination-and-restoration technique. A double envelope-feedback loop assures high linearity. The radio-frequency (RF) power amplifier employs a two-stage monolithic-microwave integrated-circuit driver amplifier and a 20-W power amplifier biased for class-AB operation. The class-S modulator includes a high-speed comparator and 1/2-/spl mu/m heterojunction field-effect transistors in its output stage. A double envelope-feedback loop assures both high linearity and time-delay equalization for RF bandwidths to 150 kHz. With a two-tone signal, the transmitter achieves an efficiency of 56% at full power (41 dBm), and 35% at 18 dB into back-off. The third-order intermodulation distortions for a two-tone signal vary from -30 to -40 dBc over a 20-dB range of back-off. For quaternary phase-shift keying, the first and second adjacent-channel powers are -48 and -57 dBc.

Power- conserving drive-modulation method for envelope-elimination-and-restoration (EER) transmitters

Abstract: A method and a circuit for high-efficiency linear RF-power amplification over a wide range of amplitudes from zero to peak output includes a final RF-power amplifier operating at or near saturation, an RF driver amplifier, a high-level amplitude modulator for the final amplifier, preferably a high-level amplitude modulator for the driver amplifier, and a means for determining the supply-voltage input to the final amplifier and for controlling the amplitude of the drive. The means for determining the supply-voltage input and for controlling the amplitude acts so that the final amplifier drive varies from a minimum level to peak as the desired transmitter output varies from zero to peak. The transmitter is preferably of the envelope-elimination-and-restoration type or the envelope-tracking type.

TM surface-wave power combining by a planar active-lens amplifier

Abstract: Power combining of TM surface waves by a planar active-lens amplifier is the subject of this paper. An amplifier gain of 11 dB at 8.25 GHz with a 3-dB bandwidth of 0.65 GHz has been demonstrated. Gain is measured from input to output connector to facilitate comparisons with more conventional amplifiers. Measurements of output power versus input power are also presented. The amplifier behaved in a linear manner and no problems with spurious oscillations were encountered. Construction of the amplifier is compatible with planar fabrication technologies. A key component of the combiner is a microstrip-fed Yagi-Uda slot-array antenna for TM surface-wave excitation of a thick dielectric slab. Design and optimization guidelines for the antenna are presented as well as detailed spectral-domain and finite-difference time-domain (FDTD) analysis results. Measured and simulation results show an input return loss and front-to-back ratio better than 10 dB over a 5% bandwidth. Calculated and measured results for the fields radiated by the antenna confirm forward radiation of the dominant TM mode in the thick dielectric slab. Integration of the computed radiated fields shows the antenna has a surface-wave launching efficiency of 85%.

Switched-mode high-efficiency microwave power amplifiers in a free-space power-combiner array

Abstract: A design-oriented analysis of the microwave transmission-line class-E amplifier is presented. Experiments and harmonic-balance circuit simulations verify the theoretical equations which predict class-E-amplifier output power, maximum frequency of operation, and dc-RF conversion efficiency. Experimental results at 0.5, 1,2, and 5 GHz are presented. At 0.5 GHz, 83% drain efficiency and 80% power-added efficiency (PAE) are measured, with an output power of 0.55 W, using the Siemens CLY5 MESFET. These results are compared to a class-A and class-F power amplifier using the same device. At 5 GHz, 81% drain efficiency and 72% PAE are measured, with an output power of 0.61 W, using the Fujitsu FLK052WG MESFET. Finally, the 5-GHz class-E power amplifier is successfully integrated into an active-antenna array, demonstrating power combining of four elements with an 85% power-combining efficiency. At 5.05 GHz, the class-E power-amplifier antenna array delivers a total of 2.4 W of output power, with a dc-RF conversion efficiency of 74% and a PAE of 64%.

Sense amplifier circuit

Abstract: This invention provides a sense amplifier circuit capable of determining an output with small power consumption at high speeds and simplifying a control signal. The sources of a pair of driver nMOS transistors in a first amplifier are connected to VSS via an activation nMOS transistor. An output from the first amplifier is directly input to input/output nodes of a second, latch amplifier. The sources of a pair of nMOS transistors in the second amplifier are connected to VSS via an activation nMOS transistor. The input/output nodes are precharged to VCC by a precharge circuit in a standby state. The activation nMOS transistors are simultaneously controlled by a clock signal, and the first and second amplifiers are simultaneously activated to sense, amplify, and latch the potential difference between input/output nodes.

Power amplifier output module for dual-mode digital systems

Abstract: A power amplifier output module 200 having low insertion loss and self-shielding properties for dual-mode digital systems is provided. Module 200 has a first power amplifier drive circuit comprising a first power amplifier 220 and a first output impedance matching network having integrated suppression of higher order harmonics 222. A second power amplifier drive circuit comprising a second power amplifier 224 and a second output impedance matching network having integrated suppression of higher order harmonics 226 is also provided. Module 200 also comprises a single diplexer 228 coupled to the first impedance matching network and the second impedance matching network. Module 200 also comprises a single broadband directional coupler 230, coupled to the diplexer 228, for coupling both the first power amplifier drive circuit and the second power amplifier drive circuit. Module 200 provides an integrated solution involving greater performance in a smaller package.

Linear high-efficiency microwave power amplifiers using bandpass delta-sigma modulators

Abstract: A novel amplifier configuration is described, in which a bandpass delta-sigma modulator is used to produce a two-level (digital) signal representing an analog radio frequency (RF) input. Subsequently, a switching-mode amplifier and bandpass filter are used to amplify the signal and remove unwanted spectral components. This configuration has the potential of achieving high efficiency (typical of switching mode amplifiers) together with high linearity. A simulated implementation with GaAs heterojunction bipolar transistors (HBT) is shown.

Design and Experiments of a High-Conversion-Efficiency

Abstract: A high-efficiency rectenna element has been designed and tested at 5.8 GHz for applications involving microwave- power transmission. The dipole antenna and filtering circuitry are printed on a thin duroid substrate. A silicon Schottky- barrier mixer diode with a low breakdown voltage is used as the rectifying device. The rectenna element is tested inside a waveguide simulator and achieves an RF-to-dc conversion efficiency of 82% at an input power level of 50-mW and 327- load. Closed-form equations are given for the diode efficiency and input impedance as a function of input RF power. Measured and calculated efficiency results are in good agreement. The antenna and circuit design are based on a full-wave electromagnetic simulator. Second harmonic power levels are 21 dB down from the fundamental input power.

Efficient integrated RF telemetry transmitter for use with implantable device

Abstract: An efficient RF telemetry transmitter system includes a first stage and a second stage. The transmitter system sends power and data to an implant device using pulse-width modulation of a high fixed frequency clock signal, e.g., a 49 MHz clock signal, within the first stage in order to provide efficient generation of an RF output signal in the second stage. Digital logic gates and related circuitry, e.g., implemented in an application specific integrated circuit (ASIC), are used in the first stage to provide pulse-width modulation of the fixed frequency clock signal in order to optimally set the drive level of the output signal of the first stage, or inter-stage signal. ON/OFF keying, or other modulation scheme, further modulates the clock signal with data in the first stage. The second stage includes a Class-E amplifier circuit implemented with a single RF transistor, biased with a temperature-compensated offset voltage set just below the cut-off voltage of the transistor. An LC filter placed in the front end of the second stage filters out all but the fundamental frequency component of the inter-stage signal. The drive level of the inter-stage signal is selected to prevent both overdriving and underdriving of the Class-E amplifier. An adjustable or selectable collector voltage coupled to the single RF transistor allows the amplitude of the output signal to be set to an optimum power level for transmission to the implant device.

Impedance matching circuit for power amplifier

Abstract: An impedance matching circuit for a multi-band power amplifier has an input port for receiving RF signals from an amplifier, a first path for communicating RF signals in a first frequency band to a first output port, and at least one second path for communicating RF signals in a second frequency band to a second output port. The first path includes impedance matching circuitry for matching the impedance of the first output port and the input port in the first frequency band, and the second path includes impedance matching circuitry for matching the impedance of the second output port and the input port in the second frequency band. The first path contains circuitry which blocks RF signals in the second frequency band; and the second path contains circuitry which blocks RF signals in the first frequency band. A multiband power amplifier includes a multi-band amplifier coupled with an impedance matching circuit for a multiband power amplifier.

Frequency selective predistortion in a linear transmitter

Abstract: A system for linearly transmitting an amplified output signal using predistortion is disclosed. The system uses a straight inverse modeling scheme to more easily and accurately determine the inverse of the distortion caused by a power amplifier (1002) of a RF transmitter. The direct inverse modeling scheme of the present invention indexes the LUT (1020) using the modulated input signals instead of the potentially noisier output signals, which helps to increase the accuracy of the predistortion. The predistorter system (1010) stores complex coefficients in the LUT (1020), which are then used as the tap weights of a digital filter implementing the predistorter (1022). Finally, the trainer (1008) uses a modified version of the power amplifier (1002) output signal. The modified power amplifier (1002) output signal has the in-band distortion removed from the power amplifier (1002) output signal.

Power deposited on a dielectric by multipactor

Abstract: We use a simple transmission line model to evaluate the RF power deposited on a dielectric window by a multipactor discharge. The calculation employs Monte Carlo simulation, using realistic secondary electron yield curves as input, and taking into account the distributions in the emission velocities and emission angles of the secondary electrons. Beam loading on the external RF, as well as the evolution of the DC electric field due to dielectric charging, are also accounted for. It is found that the buildup of the multipactor space charge, rather than beam loading, causes saturation. Over a wide range of operating conditions and materials, it is found quite generally that the multipactor delivers on the order of 1 percent, or less, of the RF power to the dielectric. A simple estimate is given in support of this ratio, using the susceptibility diagram that was constructed from kinematic considerations. Comparison with experimental results is given.

A linear rf power amplifier with optically activated switches

Abstract: A linear power amplifier amplifies a linear baseband signal having I and Q components. An up-converting mixer uses optically activated switches to mix the amplified baseband signal with a local oscillator signal at specified carrier frequency. The optically activated switches are activated according to a switching sequence that produces a constant impedance over each carrier frequency cycle. In this way, the optically activated switches prevent introduction of non-linearities during the up-conversion process.

Method and apparatus for secure registration within an in-home wireless network

Abstract: A method for secure registration of a access device (400) having a receiver (418) and a transmitter (420) transmitting at an operational RF power level with a base station (200) having a receiver (218) and a transmitter (216) in which the base station reduces its operational RF power level to a registration RF power level and transmits a registration invitation message (610) to an access device (400), wherein the base station (200) after receiving a registration response message (614) from the access device (400) restores its power level to the operational RF power level

System and methods for stimulating and training a power amplifier during non-transmission events

Abstract: A LINC amplifier of a radio frequency transmitter provides substantially linear amplification from two nonlinear amplifiers by decomposing the original signal into two constant amplitude envelope, phase varying signals, which, when combined, constructively and destructively interfere to re-form the original signal. The output of the LINC amplifier, which is to be transmitted via an antenna, is an amplified form of the original signal. The LINC amplifier uses a digital control mechanism to control and adapt a digital compensation network that directly compensates for the imperfections of the analog RF environment, including the amplifiers. The mechanism monitors the combined amplifier output and adjusts the signal components in order to precisely compensate for any differences in the characteristics of the separate signal paths which would cause the combination not to accurately represent the original signal. The mechanism also corrects the component signals using information which can be applied to the amplifiers independent of the signal to be transmitted.

Compensation system and methods for a linear power amplifier

Abstract: A LINC amplifier of a radio frequency transmitter provides substantially linear amplification from two nonlinear amplifiers by decomposing the original signal into two constant amplitude envelope, phase varying signals, which, when combined, constructively and destructively interfere to re-form the original signal. The output of the LINC amplifier, which is to be transmitted via an antenna, is an amplified form of the original signal. The LINC amplifier uses a digital control mechanism to control and adapt a digital compensation network that directly compensates for the imperfections of the analog RF environment, including the amplifiers. The mechanism monitors the combined amplifier output and adjusts the signal components in order to precisely compensate for any differences in the characteristics of the separate signal paths which would cause the combination not to accurately represent the original signal. The mechanism also corrects the component signals using information which can be applied to the amplifiers independent of the signal to be transmitted.

Digital control of a linc linear power amplifier

Abstract: The inventive LINC amplifier provides substantially linear amplification from two nonlinear amplifiers by decomposing the original signal into two constant amplitude envelope, phase varying signals, which, when combined, constructively and destructively interfere to re-form the original signal. The output of the LINC amplifier, which is to be transmitted via an antenna, is an amplified form of the original signal. The inventive LINC amplifier utilizes a digital control mechanism to control and adapt a digital compensation network that directly compensates for the imperfections of the analog RF environment, including the amplifiers. The mechanism monitors the combined amplifier output and adjusts the signal components in order to precisely compensate for any differences in the characteristics of the separate signal paths which would cause the combination not to accurately represent the original signal. The mechanism also corrects the component signals using information which can be applied to the amplifiers independent of the signal to be transmitted.

High temperature ceramic heater assembly with rf capability

Abstract: The present invention provides techniques for coupling radio-frequency (RF) power to a metal plate in a ceramic pedestal. Perforations in the metal plate allow ceramic-to-ceramic bonding through the metal plate. The power from an RF power feed is distributed to the perforated metal plate via several electrodes that are spaced away from the centerline of the RF power feed, thus splitting power distribution. A ceramic bonding disk between the metal plate and the RF power feed provides mechanical support for the metal plate and a ceramic body to bond to through the perforations, thus reducing cracking of the metal plate and the surrounding ceramic material.

Dual band transmitter for a cellular phone comprising a pll

Abstract: Disclosed is a dual band wireless phone, such as a cellular phone for a mobile communications system, with a dual band transmitter that includes a phase-locked loop (PLL). The dual band transmitter includes first and second power amplifiers and the PLL. The first power amplifier has a first input for a first signal at a first radio frequency band, and a first output for an amplified first signal. The second power amplifier has a second input for a second signal at a second radio frequency band and a second output for an amplified second signal. The outputs of the power amplifiers are connectable to an antenna. The PLL generates two output frequency ranges and includes a voltage-controlled oscillator (VCO) which has a first output connected to the first power amplifier and generates a first signal. A frequency multiplier has an input connected to the first output of the VCO and a second output connected to the second power amplifier. The frequency multiplier receives the first signal and generates the second signal.

Battery life extending technique for mobile wireless applications

Abstract: An operating voltage applied to a transmitter's power amplifier in a mobile wireless transceiver is dynamically controlled so as to improve the efficiency of the transmitter at all output power levels. In one embodiment, the bias current levels within the transmitter are also varied to optimize the efficiency of the transmitter at all output power levels. In a preferred embodiment, a highly efficient switching regulator is controlled by a control circuit to adjust the operating voltage and/or bias current for the power amplifier in the transmitter. The control circuit has as its input any of a variety of signals which reflect the actual output power of the transmitter, the desired output power, or the output voltage swing of the transmitter.

Polynomial Predistortion linearizing device, method, phone and base station

Abstract: A device ( 400 ), method ( 1200 ), phone ( 400 ) and base station ( 400 ) provide predistortion for linearization in a radio frequency RF power amplifier. The method includes the steps of: A) predistorting ( 1201 ) a baseband signal to provide a predistorted baseband signal in accordance with real-time polynomial coefficients; B) modulating ( 1202 ) the predistorted baseband signal to provide an RF signal; C) amplifying ( 1203 ) the RF signal to provide an amplified RF signal; D) demodulating ( 1204 ) the amplified RF signal to provide a demodulated baseband signal; and E) estimating ( 1205 ) the real-time polynomial coefficients to provide a linear amplified RF signal.

Dual band cellular phone with two power amplifiers and a current detector for monitoring the consumed power

Abstract: A transmitter for a cellular phone comprising an antenna and being operable at a first radio frequency band and a second radio frequency band is disclosed. The transmitter comprises a first power amplifier and a second power amplifier. The first power amplifier has a first input for a first signal at the first radio frequency band, a second input for a first control signal and a first output for an amplified first signal. The first output is connectable to the antenna. The second power amplifier has a third input for a second signal at the second radio frequency band, a fourth input for a second control signal and a second output for an amplified second signal. The second output is connectable to the antenna. The transmitter further comprises a single control module which receives a signal indicative of a current an active power amplifier draws. The control module uses this signal indicating the drawn current to generate a control signal to control the active power amplifier.

Tunable slot antenna

Abstract: In order to offer a tunable slot antenna capable of varying an impedance matching center frequency thereof, there is provided a coaxial resonant slot antenna for supplying RF power to a strip conductor placed in a flat conductive cubic with a slot formed in its upper surface and electrically insulated from the flat conductive cubic, wherein a variable capacitor is electrically connected between one point lying in the neighborhood thereof including an end far from a RF power connection point on the strip conductor and a side wall of the flat conductive cubic, and a d.c. voltage to be applied across the variable capacitor is supplied to the connection point.

Controller and associated methods for a linc linear power amplifier

Abstract: A LINC amplifier of a radio frequency transmitter provides substantially linear amplification from two nonlinear amplifiers by decomposing the original signal into two constant amplitude envelope, phase varying signals, which, when combined, constructively and destructively interfere to re-form the original signal. The output of the LINC amplifier, which is to be transmitted via an antenna, is an amplified form of the original signal. The LINC amplifier uses a digital control mechanism to control and adapt a digital compensation network that directly compensates for the imperfections of the analog RF environment, including the amplifiers. The mechanism monitors the combined amplifier output and adjusts the signal components in order to precisely compensate for any differences in the characteristics of the separate signal paths which would cause the combination not to accurately represent the original signal. The mechanism also corrects the component signals using information which can be applied to the amplifiers independent of the signal to be transmitted.

A 95-GHz InP HEMT MMIC amplifier with 427-mW power output

Abstract: We have established a state-of-the-art InGaAs-InAlAs-InP HEMT MMIC fabrication process for millimeter-wave high-power applications. A two-stage monolithic microwave integrated circuit (MMIC) power amplifier with 0.15-/spl mu/m gate length and 1.28-mm output periphery fabricated using this process has demonstrated an output power of 427 mW with 19% power-added efficiency at 95 GHz. To our knowledge, this is the highest output power ever reported at this frequency for any solid-state MMIC amplifier.

Power amplifier saturation prevention method, apparatus, and communication system incorporating the same

Abstract: An apparatus for controlling the power level of an output signal from the output of an electronic amplifier. The electronic amplifier has a control signal input for receiving an amplifier control signal and has a power input for receiving current from a power supply. The apparatus comprises an amplifier output power detector, coupled to the output of the amplifier, used for generating a power measurement signal representing the output power of the amplifier. The apparatus contains a current detector arranged to detect the current received by the amplifier from the power supply and to provide a current measurement signal dependent on the amount of current received from the power supply. The apparatus contains a digital signal processor which receives the current measurement signal and provides a reference signal dependant on the current measurement signal. The apparatus also contains a comparator coupled to receive the reference signal and the power measurement signal which is used for generating the control signal to prevent saturation of the amplifier.

Power saving device for radio communication terminal

Abstract: A power saving device for a radio commmunication terminal reduces current consumption by changing the number of power amplifying stages. A power amplifier in the radio communication terminal includes a first amplifier (300) for high power and a second amplifier (208) for low power. A signal path selector (209) switches an input signal to an input node of the first or second amplifier in response to a switching control signal. An output path selector selects one of output signals from the first and second amplifiers in response to the switching control signal. An RSSI detector (105) detects signal strength of a signal received from a base station. A controller generates the switching control signal of a first state, when the signal strength is low, to enable the signal path selector to switch the input signal to the first amplifier (300) and enable the output path selector to select the output signal of the first amplifier, and generates the switching control signal of a second state, when the signal strength is high, to enable the signal path selector to switch the input signal to the second amplifier (200) and enable the output path selector to select the output signal of the second amplifier. A power supply (107) blocks a first supply voltage to the first amplifier in response to the switching control signal of the second state, and blocks a second supply voltage to the second amplifier in response to the switching control signal of the first state.

Transmission power control system and method for a mobile station

Abstract: A transmission power control system and method is provided that controls the magnitude of transmission power in proportion to the distance between a base station and a mobile station. The transmission power control system provides the exact transmission power by compensating for an error between a real gain and a gain controlled value according to the magnitude of the transmission power. The transmission power control system can be used, for example, in a mobile phone. The transmission power control system can include a transmission part, a mobile station modem, a power detector, a gain difference controlling part and a power amplifier controlling part. The transmission part outputs a transmission power signal in accordance with input signals. The power detector transforms the transmission power signal into a DC voltage. The mobile station modem outputs a first and second gain control values, respectively, based on the DC voltage. The gain difference controlling part generates a gain difference control signal and applies the gain difference control signal to the transmission part in accordance with the first gain control value and an attenuated signal. The power amplifier controlling part outputs a power amplifier gain control value to the transmission part in accordance with the DC voltage and the second gain control value.