Proposed Linearization Scheme Research Articles

A 40% PAE and 34dBm Peak OIP3 CMOS Power Amplifier with Integrated Zero Power Consumption Phase Linearizer

In this paper, an Integrated Phase Linearizer (IPL) technique is designed to improve the linearity performance of a CMOS power amplifier (PA). The IPL is integrated at the gate of the PA so that the effect of the parasitic gate-to-source ([Formula: see text]) capacitance of the main transistor is compensated by the linearizer. Thus, it improves the 3rd-order intermodulation point (OIP3) without trading-off the power added efficiency (PAE). The proposed solution is designed and fabricated in an 180[Formula: see text]nm CMOS technology process consuming the chip area of 2.25[Formula: see text]mm2. At the operating frequency of 2.45[Formula: see text]GHz, it exhibits a gain of 11.14[Formula: see text]dB with unconditional stability characteristics from 1[Formula: see text]GHz to 10[Formula: see text]GHz. Biased quiescent current of 19.35[Formula: see text]mA, the IPL-PA delivers a maximum output power of 15.20[Formula: see text]dBm with 40.86% peak PAE, 34.91[Formula: see text]dBm of peak OIP3 and maximum power consumption of 63.65[Formula: see text]mW at 2.45[Formula: see text]GHz with supply voltage headroom of 1.8[Formula: see text]V. The proposed linearization scheme proved to be an excellent solution for low-power transceivers integration.

A Direct Learning Digital Predistortion Method to Compensate for the Power Amplifier Nonlinear Distortion

In this paper, a novel direct learning digital predistortion (DPD) relied on gradient-based algorithm to identify the model of power amplifier (PA) is proposed. Unlike the conventional DPD introducing an inevitable calculation error in model identification, the proposed method accurately calculates the predistortion function by constructing a univariate polynomial and finding its roots to obtain the accurate value of the DPD function, which linearizes the PA more precisely. Simulations show that the proposed linearization scheme outperforms the conventional DPD in the normalized mean square error (NMSE) performance, and the adjacent channel leakage ratio (ACLR) performance as well.

Modeling large-deforming fluid-saturated porous media using an Eulerian incremental formulation

The paper deals with modeling fluid saturated porous media subject to large deformation. An Eulerian incremental formulation is derived using the problem imposed in the spatial configuration in terms of the equilibrium equation and the mass conservation. Perturbation of the hyperelastic porous medium is described by the Biot model which involves poroelastic coefficients and the permeability governing the Darcy flow. Using the material derivative with respect to a convection velocity field we obtain the rate formulation which allows for linearization of the residuum function. For a given time discretization with backward finite difference approximation of the time derivatives, two incremental problems are obtained which constitute the predictor and corrector steps of the implicit time-integration scheme. Conforming mixed finite element approximation in space is used. Validation of the numerical model implemented in the SfePy code is reported for an isotropic medium with a hyperelastic solid phase. The proposed linearization scheme is motivated by the two-scale homogenization which will provide the local material poroelastic coefficients involved in the incremental formulation.

An efficient phase analysis-based wavenumber linearization scheme for swept source optical coherence tomography systems

This letter reports an efficient phase analysis-based direct time domain resampling scheme for swept source-based optical coherence tomography (SS-OCT) systems. The unwrapped phase values, representing non-linear frequency sweeping of the laser, are extracted from the calibration signal generated by a Mach–Zehnder interferometer. Equidistant wavenumber spaces are calculated by normalizing obtained phase values followed by scaling to the maximum number of sampling points. The non-uniform fractional time index values corresponding to the uniformly distributed phase values are computed directly from the linearizer coordinates in order to eliminate the use of the polynomial fitting approach that is used in existing phase-based time domain resampling methods. This proposed linearization scheme shows a significant improvement in performance in terms of accuracy and speed in comparison with the major existing schemes. The robustness of the algorithm, as well as its impact on the resolution and sensitivity, are illustrated using an in-house-developed SS-OCT system and by performing imaging of a human finger nail and an eye model as test samples.

LINEARIZATION OF RF POWER AMPLIFIERS USING ADAPTIVE KALMAN FILTERING ALGORITHM

In this paper, a new linearization algorithm of power amplifier (PA), based on Kalman filtering theory is proposed for obtaining fast convergence of the adaptive digital predistortion. The proposed method uses the real-time digital processing of baseband signals to compensate the nonlinearities and memory effects in radio-frequency power amplifier. To reduce the complexity of computing in classical Kalman filtering, a sliding time-window has been inserted which combines offline measurement and online parameter estimation with high sampling time to track the changes in the PA characteristics. The performance of the proposed linearization scheme is evaluated through simulation and experiments. Using digital signal processing, experimental results with commercial power amplifier are presented for multicarrier signals to demonstrate the effectiveness of this new approach.

Design of a memory polynomial predistorter for wideband envelope tracking amplifiers

Efficiency and linearity of the microwave power amplifier are critical elements for mobile communication systems. A memory polynomial baseband predistorter based on an indirect learning architecture is presented for improving the linearity of an envelope tracing (ET) amplifier with application to a wireless transmitter. To deal with large peak-to-average ratio (PAR) problem, a clipping procedure for the input signal is employed. Then the system performance is verified by simulation results. For a single carrier wideband code division multiple access (WCDMA) signal of 16-quadrature amplitude modulation (16-QAM), about 2% improvement of the error vector magnitude (EVM) is achieved at an average output power of 45.5 dBm and gain of 10.6 dB, with adjacent channel leakage ratio (ACLR) of -64.55 dBc at offset frequency of 5 MHz. Moreover, a three-carrier WCDMA signal and a third-generation (3G) long term evolution (LTE) signal are used as test signals to demonstrate the performance of the proposed linearization scheme under different bandwidth signals.

Linearization of Efficiency-Optimized Dynamic Load Modulation Transmitter Architectures

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, a detailed linearization procedure for dynamic load modulation (DLM) transmitter architectures is proposed for the first time. Compared with the conventional single-input/single-output digital predistortion (DPD) approach used with traditional power amplifiers (PAs), the proposed linearization scheme is based on a regular memory DPD in combination with an efficiency-optimized static one-to-two mapping inverse model, which constructs the predistorted input signals to the DLM transmitter. The time-alignment issue, which is very important to this dual-input architecture, is also considered. The proposed technique is demonstrated by a 1-GHz 10-W LDMOS PA that employs a varactor-based tunable matching network. A normalized mean square error of <formula formulatype="inline"> <tex Notation="TeX">$-{\hbox {35 dB}}$</tex></formula>, and adjacent channel leakage ratio of <formula formulatype="inline"><tex Notation="TeX">$-\hbox{43 dBc}$</tex></formula> is achieved, with an average power-added efficiency of 53% for a single-carrier WCDMA signal with 7-dB peak-to-average ratio. Finally, it is shown that the time-alignment sensitivity is relaxed when the proposed linearization scheme is used. This means that the overall complexity of the transmitter implementation can be reduced. </para>

Linearization of DFB LD by using Cross Gain Modulation of Reflective SOA in Radio-over-Fiber Link

We proposed a novel linearization technique for a DFB LD in the RoF link. The proposed scheme is based on the cross gain modulation(XGM) effect of a reflective semiconductor optical amplifier(RSOA) with light injection. We experimentally demonstrated and evaluated the enhanced CIR performance using the proposed linearization scheme.

A linear method for calculating the electronic structure of metal alloys having arbitrary degrees of long range order

A linear method is developed for calculating the electronic structure of partially ordered alloys based on multiple scattering theory. This method makes it possible to describe the properties of a system (atomic, magnetic, etc.) having various degrees of order within a single approach. The proposed linearization scheme reduces the amount of and increases the speed of the calculations in obtaining the electronic structure of complicated multicomponent systems possessing arbitrary degrees of long range order.