Power Amplifier Output Research Articles

Двухполяризационное усиление оптического излучения на эффекте Рамана для передатчика лидара.

A comparison is made of the spectral distortions of the output radiation of a Raman amplifier in the case of one and two-polarization amplification of modulated radiation in an extended optical fiber. With an output power of 3.5 W at a wavelength of 1649 nm, the spectral distortions for bipolarization amplification are lower, which makes it possible to increase the amplifier output power to ~ 4 W, and the level of spectral distortions at the amplifier output makes possible to carry out lidar measurements of methane concentration by a remote method with high accuracy. Simulation of bipolarization Raman amplification was carried out along with experimental verification. For this simulation, the coefficient of depolarization of radiation propagating in an extended single-mode fiber was introduced. The experimental results and the results of theoretical modeling are in good agreement. An increase in the amplifier power also makes it possible to increase the methane sensing range in an open atmosphere with lidars using Raman amplifiers as transmitters.

Combined Sidelobe Reduction and Omnidirectional Linearization of Phased Array by Using Tapered Power Amplifier Biasing and Digital Predistortion

Power amplifier (PA) efficiency and linearity are among the key drivers to reduce energy consumption while enabling high data rates in the fifth-generation (5G) millimeter-wave phased array transmitters. Analog per-branch phase and amplitude control is used to steer the beam, suppress the sidelobes, and form zeros to the desired spatial directions. The amplitude control of individual PA inputs makes nonlinearity vary from antenna to antenna, which challenges the common digital predistortion (DPD) used to linearize the array. In this article, we implement an amplitude control for beamforming by tuning the PA gate bias. Varying the output powers via PA biasing makes the nonlinear characteristics observed at the individual PA outputs similar that helps the array DPD to linearize also individual PAs. The technique is validated by both simulations and measurements. As a measurement platform, we use a 28-GHz phased array transceiver equipped with 64 antenna elements and 16 radio frequency chains. The desired beam shape is synthesized by controlling the per-antenna over-the-air-power with PA gate bias. Then, the system is linearized by training DPD with a reference antenna. The DPD is demonstrated with 100-MHz-wide 5G new radio modulated waveform. The best example case showed −23.5-dB maximum sidelobe level (SLL) with 4.9% error vector magnitude and −40.8-dB total radiated adjacent channel power ratio with DPD. The proposed approach enables simultaneous reduction of beam pattern SLL, achieves good linearity in all directions, and maintains the PA efficiency.

All-fiber transient phase noise characterization of polarization maintaining Yb-doped fiber amplifiers

We demonstrated an all-fiber phase noise measurement technique to detect transient phase variation of polarization maintaining Yb-doped fiber amplifier based on active phase locking of an optical heterodyne detection system. The root mean square, power spectral density, and drift velocity in the phase noise were analyzed for both core-pumped single clad fiber amplifier and clad-pumped double-clad fiber amplifier. The phase noise was further analyzed in terms of the seed laser power, amplifier output power, and fiber optic component configurations. The phase drift velocity measurements at various amplifier output powers indicated the optical phase were closely related to the temperature variations.

A comprehensive design analysis of a cost-effective WPT system with a class-E power amplifier and a T-matching network

Magnetically-coupled resonant wireless power transfer systems (WPTs) operating in the megahertz range is well-suited for mid-range transmission of moderate power levels. The class-E power amplifier (PA) is attractive for the MHz WPT applications due to the high-efficiency and soft-switching properties. However, since the output power and the efficiency of the class-E PA strongly depends on the output load, any change in the mutual inductance of coupling coils, which leads to the PA load variation, results in a dramatic loss in the overall performance of WPT system. This paper provides a comprehensive design analysis to analytically and numerically mimic the PA behavior to conveniently adapt any variation of the input impedance of the coupled coils to the PA optimum load using a T-type matching network. An equivalent circuit analysis followed by the design theory for the class-E PA, coupled coils, and the T-network has been presented. For validation purposes, the class-E PA implemented by the cost-effective IRF640 MOSFET was first fabricated and its performance was measured for different load values. The PA efficiency and output power was measured as high as 96.7% and 25.8 W, respectively, for the optimum load value of 9 Ω, which was closely predicted from the theory. A 1 MHz WPT system was then built for the operating range up to 27 cm, showcasing its behavior in presence and absence of the proposed T-type matching circuits at two arbitrary 10 cm and 25 cm distances between the coupling coils; the input impedance of the WPT system for those separation distances were 4 Ω and 0.2 Ω, respectively. Results demonstrate power transfer efficiencies of 88% and 15% at distances of 10 cm and 25 cm with the T-network, respectively, improved by 33% and 12% to the non-matching state, respectively. The overall DC output power achieved using a full-bridge rectifier are 21.9 W and 6.8 W at 10 cm and 25 cm, respectively.

Deep Neural Network Behavioral Modeling Based on Transfer Learning for Broadband Wireless Power Amplifier

The behavior model based on the artificial neural network has been widely used in the broadband power amplifier (PA). Although the deep neural network (DNN) performs well in the PA modeling with high-dimensional inputs, the training time of the DNN model is still long. This letter proposes a PA modeling method based on transfer learning to reduce training time without sacrificing modeling performance. In the proposed method, the model can be divided into two parts. The first part is defined as a predesigned filter that can extract the features of PA, and the second part is defined as adaptation layers that can be used to fit the real PA output. Experimental results show that the proposed method can effectively reduce the training time and ensure good modeling performance compared with the traditional DNN model.

Experimental Evaluation of the Generalized Signal Droop Model With SNR Measurements Including Transponder Implementation Penalty

We experimentally assess the accuracy of a constant output power generalized droop (COP-GD) model combined with transponder implementation penalty to predict transmission performance for single-core long-haul optical transmission systems operating at low channel launch powers and high baud rates. The droop model includes Guided Acoustic Waveguide Brillouin Scattering (GAWBS) and nonlinear interference (NLI) effects along with amplifier noise for signal-to-noise ratio (SNR) calculation in the context of long-haul systems with constant output power amplifiers. We show how the model accuracy is decreased if one of the modeling components is removed, namely, either the droop effect, GAWBS or the transponder implementation penalty. We show that inclusion of implementation penalty and GD is important for accurate performance evaluation, moreover, the transponder implementation penalty has impact both at low and high SNR ends. We compare the model including both effects to experimental transmission data over a wide link SNR range for the first time and demonstrate excellent agreement between modeling predictions and experimental results.

Long term stability of 1.3 GHz high power RF amplifier

Turkish accelerator and radiation laboratory (TARLA) is an accelerator based oscillator mode free electronlaser (FEL) facility under construction. The acceleration beamline includes a fundamental buncher (FB) in order to confine the electron beam into a compressed bunch. In this study, we demonstrate the commissioning tests of 500 W RF amplifier powering FB and present the phase stability dependence on the pressure and temperature of the water cooling line under long time run conditions.As the disturbing effects break down the synchronization between the particle and RF power during acceleration, the reasons disquieting the stability of the RF amplifier are investigated. One reason which causes disturbance in the stability is the variation in the phase of the output power. Phase variation of the output power of the RF amplifier which was measured as $\sim$10 deg/$^{\circ}$C in average initially, which was beyond permitted variation levels by the controller electronics, namely the low level RF system (LLRF), is decreased to less than $\sim$0.45 deg/$^{\circ}$C by incorporating a phase shifter. In addition, this phase variation reduction is accompanied with a reflected power at the output of the RF amplifier decline from 4.3 W (~36.33 dBm) down to 3 mW (~4.7 dBm) by utilizing a circulator, which is also important and desirable in terms of protection of the electronics in the long term run. As ensuring phase stability in the output power is very important, this work may serve as a guide since the documentation regarding the output power dependence of the water cooling line for long term run is very limited.

A compact low-noise frontend for interleaved Rx/Tx arrays at K-/Ka-Band

AbstractThis contribution deals with a frontend for interleaved receive (Rx)-/transmit (Tx)-integrated phased arrays at K-/Ka-band. The circuit is realized in printed circuit board technology and feeds dual-band Rx/Tx- and single-band Tx-antenna elements. The dual-band element feed is composed of a substrate-integrated waveguide (SIW) diplexer with low insertion loss, a low-noise amplifier (LNA), a bandpass filter, and several passive transitions. The compression properties of the LNA are identified through two-tone measurements. The results dictate the maximum allowable output power of the power amplifier. The single band feed consists of a SIW with several transitions. Simulation and measurement results of the individual components are presented. The frontend is assembled and measured. It exhibits an Rx noise figure of 2 dB, a Tx insertion loss of ~ 2.9 dB, and an Rx/Tx-isolation of 70 dB. The setup represents the unit cell of a full array and thus complies with the required half-wave spacing at both Rx and Tx.

Термодеформационная модель субмодуля выходного усилителя мощности Х-диапазона

The results of 3D modeling in the Comsol Multiphysics software environment and calculation of temperature and thermal deformation fields of GaAs crystals of monolithic integrated circuits (MIS) of microwave amplifiers as part of the submodule of the X-band output power amplifier (VUM) and their contact connections with the substrate in pulse modes of operation with different duty cycles are presented. It is shown that the maximum temperature and thermomechanical stresses in the MIS crystal in the dynamic mode of operation significantly exceed the calculated values for the stationary mode and strongly depend on the pulse duty cycle of the power dissipated by the MIS. Thermomechanical stresses take the maximum value in some narrow region near the boundary of the adhesive connection of the MIS crystal with the mounting plate; this maximum value strongly depends on the temperature coefficient of expansion (TCR) of the adhesive and takes the lowest value when the TCR of the adhesive is equal to the TCR of the GaAs crystal.

Analysis of Electrothermal Effects in Devices and Arrays in InGaP/GaAs HBT Technology

In this paper, the dc electrothermal behavior of InGaP/GaAs HBT test devices and arrays for power amplifier output stages is extensively analyzed through an efficient simulation approach. The approach relies on a full circuit representation of the domains, which accounts for electrothermal effects through the thermal equivalent of the Ohm’s law and can be solved in any commercial circuit simulator. In particular, the power-temperature feedback is described through an equivalent thermal network automatically obtained by (i) generating a realistic 3-D geometry/mesh of the domain in the environment of a numerical tool with the aid of an in-house routine; (ii) feeding the geometry/mesh to FANTASTIC, which extracts the network without performing simulations. Nonlinear thermal effects adversely affecting the behavior of devices/arrays at high temperatures are included through a calibrated Kirchhoff’s transformation. For the test devices, the thermally-induced distortion in I–V curves is explained, and the limits of the safe operating regions are identified for a wide range of bias conditions. A deep insight into the electrothermal behavior of the arrays is then provided, with particular emphasis on the detrimental nonuniform operation. Useful guidelines are offered to designers in terms of layout and choice of the ballasting strategy.

Next generation electronics on the ultrawide-bandgap aluminum nitride platform

Gallium nitride high-electron-mobility transistors (GaN HEMTs) are at a point of rapid growth in defense (radar, SATCOM) and commercial (5G and beyond) industries. This growth also comes at a point at which the standard GaN heterostructures remain unoptimized for maximum performance. For this reason, we propose the shift to the aluminum nitride (AlN) platform. AlN allows for smarter, highly-scaled heterostructure design that will improve the output power and thermal management of III-nitride amplifiers. Beyond improvements over the incumbent amplifier technology, AlN will allow for a level of integration previously unachievable with GaN electronics. State-of-the-art high-current p-channel FETs, mature filter technology, and advanced waveguides, all monolithically integrated with an AlN/GaN/AlN HEMT, is made possible with AlN. It is on this new AlN platform that nitride electronics may maximize their full high-power, high-speed potential for mm-wave communication and high-power logic applications.

Recent Progress on High Output Power, High Frequency and Wide Bandwidth GaN Power Amplifiers

Recent Progress on High Output Power, High Frequency and Wide Bandwidth GaN Power Amplifiers

A High-Isolation 26.5–36.2-GHz T/R Duplexer Module on 0.18-μm BiCMOS for 5G Systems

A high-isolation fully integrated 26.5–36.2-GHz frequency-division duplex (FDD) transmit–receive (T/R) duplexer (DUX) front-end module, containing DUX, power amplifier (PA), and low-noise amplifier (LNA), for fifth-generation (5G) wireless systems is demonstrated on a single 0.18- $\mu \text{m}$ BiCMOS Si chip. The isolation between the PA output and LNA input is generally better than 40 dB from 15 to 60 GHz. The DUX module has a 20.8-dB gain with a 13.5-dB minimum noise figure at 28 GHz for the entire receive path. It provides about 12-dB gain with better than an 11-dBm maximum output power across 23.5–36.2 GHz for the transmit path. Leakage of the transmit signal through Si substrate is considered and suppressed using PA with deep-n-well structure and p-type/n-type grounding guard rings. The entire module only occupies an active area of 2.1 mm2.

A −28.5-dB EVM 64-QAM 45-GHz Transceiver for IEEE 802.11aj

This article presents a fully integrated IEEE 802.11aj direct-conversion transceiver system in a 120-nm SiGe:C BiCMOS technology. The system includes a transmitter, a receiver, and two onboard substrates integrated waveguide-fed Yagi-Uda antennas. In the millimeter-wave frequency band, the common-mode (CM) signal in a transformer-based balun is a limiting factor for the linearity of differential devices. In this work, we analyze the cause of the CM effect and provide fast impedance equalization with a passive component compensation method to resolve this problem, which improves the linearity of the transmitter. A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T$ </tex-math></inline-formula> -type second-order harmonic termination method is applied at the power amplifier (PA) output to further improve the linearity of the transmitter. The self-mixing method-based power detector is adopted at the output of the transmitter to have an accurate image signal and local oscillator (LO) leakage calibration. The transmitter reaches an output 1-dB compression point (OP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1dB</sub> ) of 14.6–16.4 dBm and a conversion gain (CG) higher than 24 dB in the IEEE 802.11aj frequency band, operating from 42.3 to 48.4 GHz. The receiver achieves a 3.8–4.1-dB noise figure, −18.7- to −22-dBm input 1-dB compression point, and a CG better than 43.8 dB in the IEEE 802.11aj frequency band. In the system wireless data transmission test, the transceiver is fully compliant with the error vector magnitude (EVM) requirement of the IEEE 802.11aj standard up to the 64-quadrature amplitude modulation (QAM) operating mode, and the measured transmitter-to-receiver EVM is better than −28.5 dB at a 1-m distance over the IEEE 802.11aj frequency band. Compared to other states of the art, the transmitter’s OP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1dB</sub> is the highest, and the demonstrated transceiver system delivers the highest performance in the IEEE 802.11aj wireless link.

Widely-Linear Nyquist Criteria for DFT-Spread OFDM of Constellation-Rotated PAM Symbols

In this paper, the Nyquist criteria for ordinary linear modulation are generalized to the discrete-Fourier transform-spread (DFT-spread) orthogonal frequency-division multiplexing (OFDM) of constellation-rotated PAM symbols. Unlike the conventional Nyquist criteria with a linear receiver, the new criteria are to remove intersymbol interference in the output of a widely-linear (WL) receiver. It is shown that not only the folded spectrum, but also the shifted and reverse-folded spectrum is crucial in the criteria, where the shift offset is determined by the rotation angle. As a design example, combinations of a constellation rotation angle and a square-root raised cosine pulse are proposed. It is shown that the proposed design can achieve better performance both in spectral efficiency and in peak-to-average power ratio than the conventional DFT-spread OFDM of π/2-BPSK symbols. The optimal one-tap frequency-domain equalizer is also derived under the WL zero-forcing (ZF) constraint. It is shown that, when the rotation angle is properly chosen, the proposed one-tap WL-ZF equalizer significantly outperforms the one-tap linear ZF equalizer in output signal-to-noise ratio. The proposed equalizer also outperforms the conventional equalizer in error vector magnitude measured at the output of a nonlinear power amplifier.

Nonlinear distortion of angle modulation signal in output power amplifiers

The output power amplifier is operated in nonlinear mode to increase its efficiency, at which the signal is distorted more. The goal is to analyze effects of nonlinearity on the modulating signal of angle-modulated signal distortions for single-ended and push-pull output power amplifiers with memory and without it. The amplifier characteristic ic(vBE) is preset by the cubic polynomial. The output voltage of memoryless amplifier uout(t) is found by Ohm's law. And in case with amplifier with memory, the output voltage uout(t) is found by Complex amplitude method with a Fourier series of function ic(t). The output voltage uout(t) is represented as the narrowband process with envelope of the waveform U1(t) and initial phase Ф1(t) to determine the angular modulation law Ф1(t) at the amplifier output. The function U1(t) is defined as combination of in-phase А(t) and quadrature В(t) components. The distortion estimate based on Total Harmonic Distortion (THD). The measurement of THD is defined as the ratio of the RMS amplitude of a set of higher harmonic frequencies to the RMS amplitude of the first harmonic. The spectrum of function Ф1(t) is represented a Fourier series. In single-ended memoryless amplifier and non-cutoff mode, the THD decreases as m increases and THD of modulating signal is {37.6; 18.8; 6.3%} at m {0.5; 1; 3}. In cutoff mode, the smallest THD is {15.18; 5.13%} at m {1; 3} as θ = 140o. In push-pull memoryless amplifier and θ = 90o, the THD is {22.2; 11.1; 3.7%} at m {0.5; 1; 3} which is 1.7 times less than in a single-ended amplifier without cutoff. This is due to compensation even-order harmonic of amplified signal at the output of a pushpull amplifier. In this case of memoryless amplifier, the transistor load is a parallel RLC circuit. The distortion decreases under m increases at first (up m is 1.5), but then rapidly increases (from m is 1.7). This is due to increase of the parasitic harmonics level caused by the nonlinearity of the phase-frequency characteristic of RLC circuit. The calculations show that THD of modulating signal is 3.35, 9.02 and 22.88 % at Q = 10 and m {0.5; 1; 3}, respectively. In cutoff mode, the smallest THD is at θ = 90o and it does not depend on θ at large values of m. In push-pull amplifier with memory, the THD is 2.8, 2.5 and 3.0 times less than for a singleended amplifier without cutoff at Q {2.5; 5; 10}, respectively. The results of this paper can be used for the design of signal processing systems.

Sum-Rate of Cell Free Massive MIMO Systems With Power Amplifier Non-Linearity

Cell free (CF) massive multiple input multiple output (mMIMO) has been suggested as a key solution to meet the high data rate demands of future wireless communications. Studying the performance of these systems in practical scenarios such as in the presence of hardware impairments is of vital importance. In this paper, we study the effect of power amplifier non-linearity on the uplink and downlink sum-rate of CF mMIMO systems. We derive closed form expressions for the uplink and downlink achievable sum-rates of orthogonal frequency division multiplexing (OFDM) based CF mMIMO systems. Our results show that in the uplink the sum-rate does not increase unlimitedly as the number of access points (AP) increases, being upper bounded, contrarily to the ideal linear case. In fact, the rate of each user is limited by the distortion signal of its power amplifier. However, in the downlink, the sum-rate of the system with non-linear power amplifiers is not bounded and increases unlimitedly with the number of APs. Our results also indicate that for the same signal to distortion ratio (SDR) at the power amplifier output or the same normalized saturation level of the power amplifiers, the relative downlink sum-rate degradation is lower than the relative uplink sum-rate degradation (both with respect to their corresponding values in the ideal linear case). In fact, our results confirm that the user side power amplifier non-linearity has higher impact on the system performance than the power amplifier non-linearity on the AP antennas.

A Simple and Adjustable Technique for Effective Linearization of Power Amplifiers Using Harmonic Injection

A simple and effective method for linearization of power amplifiers (PAs) is proposed. The method is based on the second harmonic injection into the input of the PA. The second harmonic is generated in a feedback path by taking the low-power transistors of a pseudo-differential pair amplifier to their nonlinear regime. The amplitude and phase of the second harmonics are controlled by tunable matching networks of the pseudo-differential pair which include trimmer capacitors. Using a theoretical analysis, we show that the proposed method is capable of canceling the third-order intermodulation signal at the PA output. As a proof of concept, a 10-W PA in a frequency band of 1.4 - 1.6 GHz is designed and linearized. By fabricating both the reference and linearized PAs and performing measurements under several conditions, it is experimentally demonstrated that applying the proposed scheme, thanks to its adjustability, highly linearizes the PA in a wide bandwidth and a wide range of output power.

A 50-Gb/s Compact RadCom E-Band Transmitter With Phase-Controlled Push–Push Quadrupler and Stacked-FET Power Amplifier

We present a 66–79-GHz transmitter (TX) in 40-nm CMOS technology for radar and communication (RadCom) systems. To accommodate the technical requirements for RadCom systems, such as wideband operation with high linearity, a compact TX was implemented with a stacked-FET power amplifier (PA), upconverting passive mixer, and a phase-controlled push–push frequency quadrupler. The TX exhibits OP1dB and bandwidth of 13.0 dBm and 13 GHz or more, respectively, which are suitable for mid-range sensing up to 100 m with the minimum range resolution of 0.15 m or less and several tens of Gb/s short-range data transmission. In a back-to-back test, the rms error vector magnitude of −21.4 dB was achieved for 50-Gb/s 32-QAM signals occupying 13-GHz bandwidth with an output power of 4 dBm at the PA output. The total core area of the TX is 0.19 mm2.

Ku-band 500W Amplitude-phase Coherence Pulsed MPM for Ocean Exploration

The spatial high-resolution synthetic aperture radar (SAR) for ocean exploration puts forward higher requirement for output power and amplitude-phase consistency of the pulsed TWT amplifier. The kW class pulsed TWT amplifier based on broadband power combining is the key technology for space SAR applications. In this paper, the factors affecting the amplitude and phase consistency of MPM are studied, and a phase consistency compensation circuit was designed to improve the phase consistency of multiple sets of products. A microwave power model (MPM) with dual TWTs output integrated architecture was proposed which consists of two short travelling wave tubes (TWT), two solid-state power amplifiers (SSPA), and an electronic power conditioner (EPC). More than 45% efficiency is achieved in 15% duty cycle within 600 MHz bandwidth, and the phase consistency was less than ± 5 degrees.With the improvement of synthesis efficiency, higher synthesis power and higher sensitivity of ocean wide scanning and detection can be obtained