Integrated-antenna push-pull power amplifiers

In this paper, the integrated-antenna concept is applied to push-pull power amplifiers (PAs). In this approach, the antenna serves as an out-of-phase power combiner and tuned load for higher harmonics. This new architecture effectively has a near-zero loss output hybrid, and results in a high-efficiency PA. The first example is a narrow-band push-pull amplifier integrated with a dual-feed patch antenna. At an operating frequency of 2.5 GHz, a maximum measured power-added efficiency (PAE) of 55% is achieved. The second example is a broadband push-pull amplifier integrated with a dual-feed slot antenna amplifier operating at 2.46 GHz which has a peak PAE of 63%, and PAE better than 55% in an 8% bandwidth. Additionally, 48% PAE is achieved with code-division multiple-access modulation and adjacent-channel power ratio better than -42 dBe at a 1.25-MHz offset     

From post-distortion to pre-distortion for power amplifiers linearization

This letter presents a new method of digital adaptive pre-distortion for linearization of power amplifiers (PA). The method is derived from a post-distortion approach which identifies the PA inverse function. This approach leads to the minimization of a quadratic function of the polynomial coefficients in the case of a polynomial predistorter form and a least square criterion. We have compared our solution to a method previously proposed by Ghaderi (1996) that was also based on the transformation of a post-distortion into a pre-distortion system. We have tested our predistorter (along with a baseband adaptation of Ghaderi's) on OFDM Hiperlan signals. Both methods significantly reduced the signal distortion and the spectral regrowth. Our less complex approach proved to be even better for small peak back off values.     

Parametric amplifiers for high sensitivity receivers sensitivity receivers

The characteristics of parametric amplifiers, including effective input noise temperature, bandwidth, stability, and gain compression are discussed. Two specific amplifiers, a liquid nitrogen cooledL-band unit for a radio astronomy observatory, and a three-channel unit for a satellite vernier auto track systems are described, and the characteristics of these amplifiers are presented.     

Improved SC amplifiers with low sensitivity to op-amp imperfections

Two novel SC amplifiers using predictive correlated double sampling are proposed. They exhibit very low sensitivity to most non-ideal op-amp effects     

Spectral hole burning in erbium-doped fiber amplifiers

A new theoretical/numerical model of the spectral hole burning (SHB) effect in erbium-doped fiber amplifiers (EDFAs) is suggested. A new measurement technique for SHB measurement is developed. Experiments are conducted to identify the particular mechanism of SHB. A computer simulation program is developed using this approach. The shape and depth of the spectral hole are in accordance with the suggested theory.     

Saturation power in GaAs amplifiers

The results of an experimental investigation of the saturation power level of GaAs amplifiers are reported. It is found that there is an optimum range of applied voltages and electron density-length products to achieve the maximum saturation power. The largest saturation effciency observed was 4 percent.     

System characteristics of quasi-optical power amplifiers

Quasi-optical (QO) amplifiers have advanced to the point where they are competitive with other solid state and vacuum-based power amplifier technologies in the upper microwave and millimeter-wave bands. While still trailing in power-added efficiency, the QO amplifiers have advantages over traditional system architectures because of superior linearity, low noise, high spurious-free dynamic range, and added functionality (e.g., electronic beam steering). These advantages are stated in the present paper through a set of scaling laws that describe the behavior of fundamental amplifier properties versus the number n of elements in the QO array. It is known that the gain and power-added efficiency are scale independent, so that the output power scales as n ¹. Here we find that the white noise figure is scale independent and the 3rd order intercept point increases as n^3/2 . Hence, the spurious-free dynamic range (SFDR) should scale as n ¹.. This makes QO amplifiers attractive as "robust" low-noise amplifiers (LNAs) in traditional superheterodyne receivers. An analysis is carried out to predict the improvement in total SFDR of a superheterodyne receiver having a QO LNA at the front end     

Design technique for microwave-transistor power amplifiers

A design technique has been developed which yields the added-power circuit efficiency of a microwave-transistor power amplifier with arbitrary output termination. Good agreement between theory and experiment has been achieved with a 1 W bipolar junction transistor operating at 1.3 GHz.     

Spectral properties of amplified spontaneous emission insemiconductor optical amplifiers

We present a theoretical investigation of the spectral properties of spontaneous emission in semiconductor optical amplifiers. We use an extended (3×3) transfer matrix formalism to derive in the spectral domain an expression for the total longitudinally averaged internal field, which is valid regardless of the levels of optical input and bias current. The material parameters are saturated not only by the monochromatic signal, but also by the amplified spontaneous emission, filtered into the resonance modes of the structure, and integrated over its whole spectral range     

Transformer coupled stacked FET power amplifiers

The development of high-power linear ultrahigh-frequency amplifiers is made difficult by the low impedance of the devices used in the output stage, which causes matching difficulties and high radio-frequency current levels. A stacked field-effect transistor (FET) configuration is shown to reduce these problems with its increased output impedance and lower current required for a given output power. A linear analysis of the stacked FET configuration is given. Two class A monolithic microwave integrated circuit amplifiers are developed and subjected to one- and two-tone tests to demonstrate the performance of the stacked FET as a power amplifier at 900 MHz     

On power distribution in additive amplifiers

An analysis of the linear power distribution in amplifiers employing the additive amplification principle has been made. It reveals the wide spread of the active devices' contributions to the output power at any one frequency and exposes the band-sharing nature of the additive amplification process in multioctave amplifiers. Reversals in the direction of the energy flow over parts of the frequency band converting active into passive devices were observed. The flat gain response of these amplifiers is found to be the result of a sophisticated process in balancing the active devices' output powers. The computed and measured performance parameters of a 6-18-GHz 2×2 matrix amplifier with emphasis on its experimental multilinear behavior are briefly discussed     

Novel W-band monolithic push-pull power amplifiers

Monolithic W-band push-pull power amplifiers have been developed using 0.1-μm AlGaAs/InGaAs/GaAs pseudomorphic T-gate power HEMT technology. The novel design approach utilizes a push-pull topology to take advantage of a virtual ground between the device pair, eliminating the series feedback of the via hole inductance, and thus improving the performance of the power amplifier at millimeter-wave frequencies. For a two-stage design presented in this paper, the measurement results show a small signal gain of 13 dB and a saturated output power of 19.4 dBm at 90 GHz. The best power added efficiency of 13.3% has been achieved at an output power of 18.8 dBm under a lower bias condition. The gain and efficiency results represent state-of-the-art performance. These are the first reported monolithic push-pull amplifiers at millimeter-wave frequencies     

Application of GaInP/GaAs DHBTs to power amplifiers for wirelesscommunications

Next-generation power amplifiers must operate at lower supply voltages without sacrificing linearity or efficiency. GaInP/GaAs double-heterojunction bipolar transistors with GaInP collectors can improve over GaAs single-heterojunction bipolar transistors (HBTs) in power-amplifier applications, based on lower offset voltage, increased breakdown electric field, and absence of saturation charge storage. To best exploit these characteristics, amplifier architectures that employ HBTs in switching mode can be used     

Low pump power photonic crystal fibre amplifiers

Designs of low pump power optical amplifiers, based on photonic crystal fibres are presented. The potential of these fibre amplifiers is investigated, and it is demonstrated that such amplifiers may deliver gains of more than 15 dB at 1550 nm with less than 1 mW of optical pump power. We focus on the design of erbium-doped photonic crystal fibre amplifiers operated at very low pump powers. We achieve this by using PCFs with large air holes and thereby large index contrasts. With such high index contrast fibres, we may obtain very small mode field diameters.     

High-efficiency class-A power amplifiers with a dual-bias-controlscheme

A new scheme for power amplifiers is proposed, which can provide both high efficiency and linearity. The proposed amplifier operates in a virtual class-A mode under dual-bias control to maximize the power-added efficiency along with its inherent class-A linearity. The dynamic dual-bias control involves controlling both bias current and voltage of the amplifier with a varying envelope of input RF signals. The efficiency of the proposed amplifier is theoretically evaluated and compared with that of other conventional amplifier schemes. Based on theoretical analyses, several promising schemes for dual analog and digital bias control are proposed and discussed     

A power re-use technique for improved efficiency of outphasingmicrowave power amplifiers

An improved power re-use technique is introduced for application to outphased microwave power amplifiers. The technique allows a significant portion of the wasted out-of-phase components of the signal to be returned to the power supply, resulting in substantial improvements in overall power-amplifier efficiency. A peak re-use RF-to-DC efficiency of 63% was obtained at 1.96 GHz