A linear assisted switching envelope amplifier for a UHF polar transmitter

Spectrally efficient wireless communication standards impose stringent linearity specifications, which would require traditional IQ transmitters to operate with back-offed and power inefficient linear RF power amplifiers (PAs). In order to overcome such a significant limitation, alternative architectures have been proposed, as those based on the envelope elimination and restoration technique. An example of the application of this technique is the polar transmitter. In this paper, a UHF polar transmitter is presented, combining switching and linear stages in the envelope amplifier as to achieve both wide bandwidth and high efficiency, when drain modulating a GaN HEMT Class E RF PA. Several tests, using EDGE, TETRA, and WCDMA standards have been performed with good results.This work was supported by the Spanish Ministries MICINN and MINECO through the FEDER cofunded Project TEC2011-29126-C03-01, Consolider Project CSD2008-00068, Consolider Project RUECSD2009-00046, and Project DPI2010-21110-C02-01

Estudio de modelos para la caracterización del canal de radio en comunicaciones móviles de 2.5G y 3G

In this paper, a comparative study of the models usually employed in the radio channel characterization is developed. After introducing the criteria for their classification, the vectorial model is deeply described. Emphasis is made in the circular, elliptic, and gaussian approximations, taking into account the Doppler effect. Finally, the systems’ behaviour is simulated in different scenarios, validating the corresponding models and evaluating several situations of practical interest for the introduction of intelligent antennas

Antenas resonadoras dieléctricas cilíndricas para sistemas MIMO: fundamentos y evaluación

The analysis and preliminary evaluation of different configurations provided by slot-coupled cylindrical dielectric resonator antenna arrays at one side of ground plane for MIMO systems is the main purpose of this paper. Appropriate envelope correlation values are obtained, and therefore spatial diversity, especially when cross polarization is used

An unbiased dual-mode mixing antenna for wireless transponders

A zero-bias dual-mode mixing antenna for wireless transponders is proposed in this paper. Designed over an Enhancement-mode Pseudomorphic HEMT (E-PHEMT), the mixer takes advantage of the device nonlinear characteristics around cold operation. Simple closed form expressions, obtained from time-varying circuit analysis, predict good conversion efficiency in two different operating modes without requiring DC bias. For validation, a lab prototype has been implemented and tested, to be finally integrated in a compact active printed antenna suitable for wireless sensor networks or other radio frequency identification (RFID) applications.This work was supported by Ministerio de Ciencia e Innovación through projects TEC2008-06684-C03-01 and CSD2008-00068. The authors also thank the support provided by AECID through action D/018607/08

Rectificador síncrono clase E a E-pHEMT para aplicaciones de transmisión inalámbrica y reciclado de energía

In this paper, advantage is taken from the particular characteristics of Enhancement-mode Pseudomorphic High Electron Mobility Transistor (E-pHEMT) devices for the design of synchronous rectifiers with an unbiased gate. Based on one of them, the design of a class E synchronous rectifier working in the 900 MHz frequency band, is proposed. A lumped-element multi-harmonic class E amplifier was first designed, exploiting the time-reversal dualily, to then introduce a drain-to-gate feedback and operate it in the desired synchronous rectifying mode. Competitive efficiency figures are demonstrated over a significant input power, frequency and load resistance range. An efficiency peak of 83% has been measured at 17 dBm, staying above 70% for a 14 dB input power range, a distinguishing characteristic when compared to Schottky diode based alternatives. The verified AM-AM conversion linearity would also allow using the rectifier for the efficient extraction of a time-varying excitation envelope without significant distortion

Transmisor polar en UHF integrando un modulador de envolvente conmutado asistido por etapa lineal y un amplificador clase E a GaN HEMT

Spectrally efficient wireless communication standards impose stringent linearity specifications, which would require traditional IQ transmitters to operate with back-offed and power inefficient linear RF power amplifiers (PAs). In order to overcome such a significant limitation, alternative architectures have been proposed, as those based on the Envelope Elimination and Restoration (EER) technique. In this paper, a UHF polar transmitter is presented, combining switching and linear stages in the envelope amplifier as to achieve both great bandwidth and high efficiency, when drain modulating a GaN HEMT class E RF PA. Several tests, using EDGE, TETRA, and WCDMA standards have been performed with good results

A low-complexity memoryless model for envelope tracking RF power amplifiers

This paper presents a new kind of behavioral model structure for characterizing static nonlinearities in dynamically supplied RF power amplifiers. The proposed architecture is based on the combination of several basic cells and it is focused to simplify the real-time design and implementation of adaptive shaping functions devoted to improve the efficiency in systems controlled by digital signal processors with tight computational capabilities, such is the case of handsets and small-cells.This work was supported by the Spanish Ministry MINECO under projects TEC2011-29126-C03 (-01 and -02)

Conjugador de fase EER para sistemas retrodirectivos

A simple retrodirective solution based on a heterodyne technique, without requiring a complex local oscillator (LO) distribution network, is presented in this paper. The system employs the TM₂₀ mode of an orthogonal dual-feed square patch to receive a spatially distributed LO, containing the amplitude and phase components of the spectrally efficient wireless modulation format to be automatically retransmitted back to the interrogation position. The core of this solution is a phase conjugator, which employs the Envelope Elimination and Restoration (EER) principle, taking advantage oh the conversion gain modulation capability of drain-controlled active gate mixers

Class-E amplifier and rectifier for a wireless link with secure signal and simultaneous power transmission

In this paper, the design and implementation of a GaN HEMT class-E power amplifier and a Schottky diode classE rectifier are described. Based on the widely known Linear Amplification with Nonlinear Components technique (LINC), and taking advantage of the spatial power combining capability of a dual-fed square patch, the highly efficient amplifier and rectifier may be incorporated at both sides of a wireless link, proposed for the simultaneous transmission of signal and power to a remote receiver.This work has been supported by the Spanish Ministry of Economy and Competitiveness (MINECO) through the TEC2014-58341-C4-1-R project with FEDER co-funding. David Vegas also thanks the support provided by the predoctoral grant BES-2015-072203

A dual-band outphasing transmitter using broadband class E power amplifiers

In this paper, a dual-band outphasing transmitter (able of operating either at 770 MHz or 960 MHz frequency bands) is presented. Two broadband RF power amplifiers (PAs) have been designed over packaged GaN HEMT devices, switching close to the nominal zero-voltage and zero-voltage-derivative class E conditions. A reactive combiner, using transmission lines of appropriate electrical lengths at both bands, together with compensating reactances, allows positioning the drain impedance loci to produce high efficiency and good dynamic range profiles. Average drain efficiency figures over 68% and 38% have been measured for WCDMA signals with a peak-to-average power ratio (PAPR) of 5.1 dB and 8.4 dB, respectively.This work was supported by MINECO through projects TEC2011-29126-C03 (-01, co funded with FEDER, and -02), and Consolider CSD2008-00068