Showing papers on "RF power amplifier published in 1993"

Large suspended inductors on silicon and their use in a 2- mu m CMOS RF amplifier

Abstract: Large spiral inductors encased in oxide over silicon are shown to operate beyond the UHF band when the capacitance and loss resistance are greatly reduced by selective removal of the underlying substrate. Using a 100-nH inductor whose self-resonance lies at 3 GHz, a balanced tuned amplifier with a gain of 14 dB centered at 770 MHz has been implemented in a standard digital 2- mu m CMOS IC process. The core amplifier noise figure is 6 dB, and the power dissipation is 7 mW for a 3-V supply. >

Dual mode amplifier with bias control

Abstract: A dual mode transmitter with bias control is described wherein an RF signal from a system modulator is fed to a gain control circuit, which can be either a voltage controlled amplifier or attenuator. The ultimate transmitter output power level depends on the attenuation/gain of the gain control circuit. The output signal from the gain control circuit is fed to a driver amplifier which amplifies the signal and feeds it to a power amplifier circuit, which may be comprised of several stages of bipolar transistors or GaAs FETs. The modulated signal to be transmitted is then fed from the power amplifier circuit through a coupler to an antenna terminal. The coupler is connected to an RF detector and is used for RF level monitoring. The Rf level signal from the RF detector is applied to a comparator circuit. An improved combination is provided by incorporating a bias control circuit. A Vpwr signal is applied as one input to the bias control circuit and a mode signal is applied as the other input. When the mode signal is "on" or present it signifies that the digital transmission mode is to be employed. When the mode signal is " off" or at zero level, it indicates that the analog transmission mode is to be employed. The bias control circuit provides three bias signal outputs, Vb1 applied to the driver amplifier, and Vb2 and Vb3, applied to the power amplifier. The levels of Vb1, Vb2 and Vb3 are varied for the analog and digital transmission modes.

Automatic calibration of the quadrature balance within a cartesian amplifier

Abstract: A Cartesian amplifier in which an input signal is pre-processed and split into two quadrature components. Both quadrature components are passed, in parallel, through an error amplifier (4), after which they are re-combined and up-converted to RF. The output of the amplifier is used to provide a feedback signal. This feedback is downconverted from RF to baseband and resolved into two quadrature components which are fed to the respective inputs of the error amplifier (4). Periodically the pre-processor (3) is switched into a calibration mode in which test signals are applied to the amplifier instead of the input signal. At these times the signal strength of the output of the power amplifier is measured and used to provide pre-distortion factors in the signal preprocessor (3) to improve amplifier linearity.

Operating characteristics of a high-power monolithically integrated flared amplifier master oscillator power amplifier

Abstract: High-power monolithically integrated flared amplifier master oscillator power amplifiers (MFA-MOPAs) that operate up to 2 W continuous wave (CW) in a single diffraction-limited lobe have been fabricated. The spectral output of the MFA-MOPA is single longitudinal mode with a side-mode suppression ratio greater than 25 dB. Several operating characteristics of the MFA-MOPA, including the beam astigmatism, amplifier gain saturation, linewidth, far-field extinction ratio, and beam quality metrics are investigated and discussed. >

Spread spectrum communication system particularly suited for rf network communication

Abstract: The transceiver (10) receives data for transmission via a microprocessor (14) by means of an interface (15) under the control of application software (16). The data are transformed into chip sequences by the data encoder (12) and the waveform generator (13). The data then pass through a bandpass filter (18), a baseband amplifier (20), a mixer (22) connected to a local oscillator (24), an RF amplifier (26), and antenna (28). Similarly, the received signal goes through an RF bandpass filter (30), an RF amplifier (32), a mixer (34) connected to a local oscillator (38), a bandpass filter (36), a limiter (40), and a correlator (40). The decoded data packets from the receiver are fed back to the microprocessor (15).

2.0 W CW, diffraction-limited operation of a monolithically integrated master oscillator power amplifier

Abstract: The authors fabricated a monolithically integrated master oscillator power amplifier, M-MOPA, with a flared power amplifier region which radiates in a single diffraction limited lobe to an output power in excess of 2 W CW. The radiation pattern is stable with increasing drive current. The spectral output of the M-MOPA is a single longitudinal mode with a side-mode suppression ratio greater than 25 dB. >

Prediction of indoor electromagnetic wave propagation for wireless indoor systems

Abstract: Techniques are disclosed for predicting RF propagation within a structure such as a building. A reference transmitter location and a plurality of reference receiver locations are selected. For each reference receiver location, RF propagation pathways are determined with respect to the reference transmitter location. The RF propagation pathways include a direct path joining the reference transmitter location to a given reference receiver location across a straight-line path, as well as one or more reflection paths joining the reference transmitter location to a given reference receiver location via reflections from one or more reflective surfaces. One or more propagation pathways may pass through an RF obstacle, such as, for example, a lossy dielectric material. Each reflective surface and RF obstacle is associated with a reflection coefficient and a transmission coefficient. These coefficients are computed for each object and surface from a multilayer dielectric model, maintaining angle and polarization dependencies. For each propagation pathway, a propagation component consisting of the propagation loss relative to free-space propagation is calculated as the product of the magnitude squared of the reflection and transmission coefficients. The local mean of received RF power at each of the reference receiver locations is calculated as the scalar sum of the powers of all the propagation pathway components reaching the specified location.

AM-FM transmitter power amplifier

Abstract: A power amplifier used in a portable, radio frequency transmitter is switched between different modes of operation when transmitting differently modulated carriers. The first mode of operation corresponds to amplitude modulation (AM), while a second mode corresponds to angle modulation techniques such as frequency modulation (FM). A switching network alters the impedance of the power amplifier to match network for matching the impedance of the transmitter antenna in order to achieve maximum efficiency in each mode of operation. Various switching methods and impedance matching circuits are disclosed.

Radio frequency power amplifier having variable output power

Abstract: A radio-frequency amplifier (50) has an impedance transformation network (66) with a control input (70) for controlling the transformation characteristic of the transformation network (66). The radio-frequency amplifier (50) amplifies an input signal to produce an amplified radio-frequency output signal to a load (68). The control circuit selects a power level for the output signal, in response to a control signal, by transforming the impedance of the load to a transformed impedance at the output of the radio-frequency amplifier, so that the efficiency of the radio-frequency amplifier is not substantially degraded as the power level for the output signal is changed.

Independent control of ion density and ion bombardment energy in a dual RF excitation plasma

Abstract: A dual RF excited discharge is described. The dual RF excitation system provides a method to control the substrate self-bias without affecting the state of the discharge. The substrate can be RF-biased utilizing an appropriate excitation frequency and power significantly less than the plasma generating RF power. The substrate self-bias dependence on various system parameters, including substrate excitation frequency, pressure, plasma generating upper electrode RF power, substrate material, and process gas compositions, is described. For a simplified model, a linear relationship between self-bias and RF power is derived using the space-charge limited assumption. The effect of substrate bias on the thermal-oxide etch rate has been studied. The results show good correlation between the ion bombardment energy, i.e., the potential difference across the substrate dark space, and the SiO/sub 2/ etch rate. The SiO/sub 2/ etch rate in a CF/sub 4/ plasma increases linearly with the ion bombardment energy, having a threshold etch energy of approximately 19 V. >

Implementation and evaluation of a dual parallel linearization system for AM-SCM video transmission

Abstract: An externally modulated transmitter was linearized for AM subcarrier multiplexing (AM-SCM) video transmission. Linearization was accomplished by combining the outputs of two lithium niobate Mach-Zehnder interferometers which were simultaneously modulated. By controlling the optical and RF power at each modulator, more than 20 dB of third-order distortion cancellation was demonstrated for a multitone video spectrum. Results are presented for both NTSC and PAL B/G frequency plans. The effects of modulator nonideality on system performance are analyzed and confirmed experimentally. In particular, overall system performance is shown to be very sensitive to acoustic effects and to optical and electrical multipath interference. System modeling is used to provide tolerances on various critical parameters.

Rf repeaters for time division duplex cordless telephone system.

Abstract: The object of the invention is to employ a single amplifier for both the transmit signals and also the receive signals in an RF repeater for interfacing with a base station for exchanging transmit and receive signals in a time division duplex cordless telephone system. A multicarrier amplifier (18) having an input and an output and a transfer switch (16) connected to the amplifier output and the amplifier input and having first and second switch states. The operation of the switch is controlled so that the transmit and receive signals are amplified by the amplifier. The other object is to chain RF repeaters so that the handset can roam over a roamer corridor covered by the RF repeaters. The RF repeaters (10A-10E) are provided with a dedicated signal link (42A-42E).

Rf amplifier bias control method and apparatus

Abstract: A bias control circuit (100) for use with an RF amplifier (102) comprises a detector (112) coupled to the RF amplifier (102) for detecting a signal proportional to the RF amplifier's output signal power level (POUT), a comparator (106), coupled to the detector (112) for comparing the detected signal to a reference (Vref), and an adjustment circuit (108), coupled to the comparator (106) and the RF amplifier (102), for adjusting the amplifier's bias voltage (Vbias) as a function of the comparison in order to control the RF amplifier's quiescent operating point (bias current) and thereby optimize the RF amplifier's operation for selected operating performance characteristics like gain performance, intermodulation performance, and efficiency. In accordance with another embodiment (200), the RF amplifier's quiescent operating point is adjusted as a function of the current drawn by the RF amplifier (202). In accordance with yet another embodiment (300), the RF amplifier's quiescent operating point is adjusted as a function of the RF amplifier's (302) detected input power level (PIN).

Radio transmitter with power amplifier and linearization

Abstract: A radio transmitter includes a power amplifier (12); a linearizer (10) for maintaining linearity in the power amplifier; and a feedback path (13) for feeding a signal from an output of the power amplifier to the linearizer. The amplifier, linearizer and feedback path cooperate to form a feedback loop having adjustable loop linearization parameters (for example phase and gain). Further, a look-up table (19) is used to store predetermined loop linearization parameters and cooperates with a microprocessor having an operating condition input.

Spread spectrum communication system and an apparatus for communication utilizing this system

Abstract: The present invention relates to a spread spectrum communication system in which a PN code p(t) is generated from a PN generator, data d(t) is multiplied by the PN code p(t) by a multiplier, and multiplied output is subjected to BPSK modulation by a BPSK modulating block. The PN code p(t) is subjected to BPSK modulation at BPSK modulating block, the result is delayed by at least 1 chip of the PN code by a delay block, combined with a modulated signal from BPSK modulating block, converted to an RF signal, and then it is transmitted from an antenna. The signal received by an antenna is amplified by RF amplifier block, converted to an intermediate frequency signal by frequency converting block, split into two, one of the split signals is directly applied to a multiplier, the other is delayed by a delay block, and then these two split signals are multiplied by a multiplier and thus data d(t) is demodulated and output.

Dual mode power amplifier for analog and digital cellular telephones

Abstract: The present invention relates generally to RF power amplifiers for portable cellular radiotelephones, and more particularly, to dual-mode cellular radiotelephones. A power supply network enables the RF power amplifier in a dual-mode radiotelephone to operate with two separate modes: saturated and unsaturated. Switches in the power supply network, e.g. complementary transistors, are driven to a first set of logic states by a square wave which is synchronized with transmit time slots present in a TDMA frame structure to charge a capacitor from a battery. When the switches are then driven to a second set of logic states, the capacitor is placed in series with the battery to essentially double the supply voltage. When the radiotelephone operates in a digital mode, the increased supply voltage coincides with the transmit time slot and temporarily increases the saturation point of the RF power amplifier to permit linear amplification. When the radiotelephone operates in an analog mode, the switches are fixed at the first set of logic states. The resulting lower supply voltage lowers the saturation point of the RF power amplifier, causing it to operate in a nonlinear but more efficient mode.

An inductive loop power transmission system

Abstract: An inductive loop power transmission system intended primarily for wireless electrosurgical use has a transmitter including a radio frequency power oscillator with a resonant output circuit coupled to a loop antenna, and a receiver with a receiving antenna (L1a) and a power output (L1b) for an electrosurgical appliance. In the receiver, a signalling circuit (Cp, D1, D2, Ct, R3, M1) produces a pulse signal which is representative of the power received by the receiver insofar as the repetition rate of the pulses is generally proportional to the average power level. This pulse signal is used periodically and momentarily to detune a resonant antenna circuit (L1a, Cr, Cd) of the receiver, causing corresponding alterations in the loading of a resonant antenna of the transmitter. These alterations in transmitted power are detected in the transmitter and used to vary the transmitter output power so as to maintain the receiver power level at the receiver substantially constant.

Time-sharing radar system

Abstract: A radar system and method for use in collision avoidance systems. A radar system in accordance with the present invention may comprise a plurality of antennas, an RF power generator, a transmitting unit, a receiving unit, and a direction detector. Each of the antennas is arranged to radiate a beam having substantially the same pattern as the beams radiated by the other antennas. The beam of each antenna is radiated in a slightly different direction from the beams radiated by the other antennas. Each antenna is also arranged to receive return beams, wherein each of the return beams comprises a beam radiated from one of the beam radiating means and reflected by an object. The RF power generator generates RF power of nearly constant amplitude. The transmitting unit distributes the RF power to each of the antennas, and the RF power is radiated successively. The receiving unit generates amplitude detecting signals which are used to detect the amplitudes of the return beams received by the antennas. Each of the amplitude detecting signals is utilized by a pair of antennas. One antenna of each pair radiates a beam and receives a return beam produced therefrom. The other antenna receives a return beam produced by a beam radiated by an adjacent antenna. The direction detecting means detects a direction to the object based on the amplitude detecting signals, the arrangement of the antennas, and a timing of distribution of FM signals to the antennas.

An adaptive digital technique for compensating for analog quadrature modulator/demodulator impairments

Abstract: Analog quadrature modulators and demodulators have three major impairments: gain imbalance, phase imbalance, and dc-offset. A digital technique is presented for compensation of these modulator and demodulator impairments. Part of the RF signal is fed to an envelope detector. The detector output, along with the baseband quadrature components, is used to estimate the impairment values. The estimated impairment values are then used to compensate for the impairments. Simulation results show that spurious signals can be suppressed by more than 30 dB using this technique. The effect of modulator/demodulator impairments on RF power amplifier linearization techniques is also discussed. The quadrature modulator and demodulator impairment compensator can decrease intermodulation distortion products by 12 dB for the complex gain predistorter and by about 5 dB for the Cartesian coordinate negative feedback method of RF power amplifier linearization. >

Implementation of the LINC transmitter using the combined analogue locked loop universal modulator (CALLUM)

Abstract: A novel modulator and transmitter subsystem is presented which provides amplification through RF synthesis. The technique has the potential for 100% DC to RF power conversion efficiency whilst providing a highly linear output. Based on the LINC concept, the modulator employs feedback around the entire transmitter subsystem to maintain linearity and efficiency with practical component tolerances. >

High frequency power amplifier

Abstract: PURPOSE: To reduce current consumption of the high frequency power amplifier at the time of power reduction and to improve a linear modulation wave in distortion at the time of a maximum output, simultaneously and automatically. CONSTITUTION: A directional coupler 19 inserted to an input section of a post- stage amplifier 18 extracts part of input high frequency power of a pre-stage amplifier 17. The extracted power is superimposed onto a signal at a gate terminal of a post-stage FET 12 via a DC voltage generating circuit 28. Then a bias of the FET 12 is automatically controlled to an optimum value in response to an output level required for the power amplifier. COPYRIGHT: (C)1995,JPO

Highpower 0.15-mm V-band pseudomorphic InGaAs-AlGaAs-GaAs HEMT

Abstract: The DC and RF power performance of double heterostructure pseudomorphic InGaAs-AlGaAs-GaAs HEMTs at V-band is reported. A 0.15-mm*400-mm device has demonstrated output power of 225 mW (0.55 W/mm) with 4.5-dB power gain and 25.4% power-added efficiency (PAE) at 60 GHz. A 0.15-mm*320-mm device demonstrated 31.1% PAE with 170-mW (0.53 W/mm) output power and 5.3-dB power gain. These data represent the highest reported combination of output power, power gain and power-added efficiency for a single device at V-band. >

High power solid state r.f. amplifier

Abstract: Although known because of the high packaging inductances and thought to be wholly unsuitable for RF amplifiers, high voltage power switching MOSFETs (11, 12, 41, 42) of the type having coplanar leads having inductances on the order of between 8nH and 15nH are used in an RF amplifier. The individual devices (11, 12, 41, 42) operate on a high impedance load line to render the high inductance of the coplanar leads insignificant. The circuit configuration presents a high impedance to the output (14) via balun (20), eliminating the need for expensive combiners and low inductance packaging.

High dynamic range modulation independent feed forward amplifier network

Abstract: Briefly described the present invention is a feed forward amplifier network (200) employing a frequency swept pilot tone signal (212) in order to reduce the distortion generated by the network's power amplifier (202). Initially a composite input signal (216) comprising either wide (520) and/or narrow (510) bandwidth modulation formats is input into the network (200). In addition, the frequency swept pilot tone (212), generated for example by a variable frequency oscillator (213), is injected into the input path of the power amplifier (202). Thereafter, distortion cancellation is employed to generate an amplified output signal (217) having output components (510, 520) which replicate those within the input signal (216). Thereafter, pilot tone power is detected (by 215) within the amplifier passband where the output components (510, 520) are absent, in order to ascertain the average pilot tone power remaining within the amplified output signal (217). In response to this detection, various amplifier network characteristics are adjusted (by 214, 208 and 209) in order to reduce the amount of pilot tone at the amplifier network output (217).

Power amplifier linearization using cubic spline interpolation

Abstract: An adaptive RF power amplifier linearization technique is presented. The demodulated amplifier output is compared with the baseband input signal to estimate the amplifier's AM-AM and AM-PM characteristics, using cubic spline interpolation. The input signal is predistorted using these estimated characteristics to compensate for the amplifier's nonlinearity. The proposed technique has nearly 14 dB better suppression of the intermodulation products than the complex gain predistortion technique. The out-of-band power emission is about 12 dB lower in the first two adjacent RF channels than is obtained using the Cartesian coordinate negative feedback technique.

Solid state microwave power amplifier module

Abstract: A solid state high power microwave amplifier module. The module incorporates a stacked assembly of integrated low temperature cofired ceramic substrates forming a monolithic structure containing all the microwave circuitry required to combine the output power of a large number of monolithic microwave integrated circuit power amplifier chips, a heatsink and a power supply. One substrate defines an input radial power divider circuit for dividing the input signal into input signals for each power amplifier chip. The second substrate includes the power amplifier chips and a radial combiner circuit. The output of the combiner to coupled to an output waveguide in the heatsink. The module is lightweight and small in size, and of high reliability since the number of wire bonds is greatly reduced since most of the microwave circuitry and connections can be formed as part of the integrated structure.

Planar MESFET transmission wave amplifier

Abstract: The authors present a quasioptical power combining transmission amplifier for increasing the power level available from solid-state circuits. Receiving and transmitting arrays of patch antennas, input/output isolation, MESFETs, bias and matching circuitry are contained on a single substrate, making monolithic millimetre-wave integration possible. The flexibility of selecting input polarisation with respect to the output while maintaining amplifier stability is demonstrated. A 24-MESFET patch antenna amplifier array is presented.

Dual mode portable cellular telephone having switch control of the rf signal path to effectuate power savings

Abstract: A dual mode, portable cellular telephone utilizes an rf switch to control the rf signal path through its rf output stage. A voltage controlled oscillator (VCO) generates an rf signal that is selectively modulated with an fm modulation signal. In an FM modulation mode, the rf signal generated by the VCO is amplified by a first rf amplifier and a second rf amplifier, and then applied to a power amplifier. The power amplifier couples the amplified rf signal to an antenna for broadcasting. A first rf signal path through the rf output stage thus includes the VCO, first rf amplifier, second rf amplifier, and power amplifier, and the resulting rf output signal is FM modulated. In a digital modulation mode, the rf signal generated by the VCO is unmodulated, having a fixed frequency. This is achieved by making the fm modulation signal be a constant signal. The fixed frequency signal is amplified by the first rf amplifier and then applied to a digital modulator as a local oscillator signal. The digital modulator then modulates the local oscillator signal using appropriate modulation signals, and applies the resulting digitally modulated rf signal to the power amplifier. A second rf signal path through the rf output stage thus includes the VCO, first rf amplifier, digital modulator and power amplifier. Control of the rf signal path is achieved by switchably connecting and disconnecting power to the digital modulator and the second rf amplifier.

Broadband linearisation of high-efficiency power amplifiers

Abstract: A feedforward-based amplifier linearization technique is presented which is capable of yielding significant improvements in both linearity and power efficiency over conventional amplifier classes (e.g. class-A or class-AB). Theoretical and practical results are presented showing that class-C stages may be used for both the main and error amplifiers yielding practical efficiencies well in excess of 30 percent, with theoretical efficiencies of much greater than 40 percent being possible. The levels of linearity which may be achieved are required for most satellite systems, however if greater linearity is required, the technique may be used in addition to conventional pre-distortion techniques.

Simulation of field emission microtriodes

Abstract: Vacuum microtriode RF amplifier performance, based upon a unit cell with a conical field emitter tip, gate, and anode, was evaluated using computer simulation. Electron emission was calculated from the Fowler-Nordheim equation. The dependence of emitted current, transconductance, and field enhancement upon geometrical factors, e.g., tip sharpness, tip height, cone half-angle, and gate hole radius, is shown. The device design parameters of transconductance, cutoff frequency, small signal gain, and efficiency have been calculated. Electron streamlines and current flux are shown for time-dependent RF input. Because a compact electron beam source has wide application, the normalized beam emittance, brightness, and beam quality are calculated for a typical case. Potential difficulties with anode power deposition are noted. >