Single-band Power Amplifier Research Articles

Dual-Band Class J Power Amplifier at 2.45 and 5.8 GHz for UAVs Communications

A hybrid dual-band power amplifier (PA) prototype working at two Industrial, Scientific and Medical (ISM) bands, 2.4-2.5 GHz and 5.725-5.875 GHz, was designed for Unmanned Aerial Vehicles (UAVs) communication applications in Spain. Initially, two single-band PA prototypes centered at each band were designed to evaluate the single-band achievable RF performance. In all the PAs, the Gallium Nitride (GaN) Qorvo HEMT TGF2977-SM was used, as well as microstrip transmission lines technology. To achieve wideband, good linearity and efficiency, the PAs were designed in class J. The measured results for the dual-band PA prototype at the 2dB compression point at the lower and higher bands, respectively, are 14.8 dB and 11.2 dB of Transducer Power Gain (GT ), 35.7 dBm and 34.8 dBm of RF output power (Pout) and 59.2% and 43.5% of Drain Efficiency (η). At 3dB compression the respective lower and higher bands results are 37.9 dBm and 37 dBm of Pout and 73.9% and 55% of η.

Volterra series-based model for concurrent dual-band power amplifier using dynamic memory depth

In this article, a dynamic dual-band baseband equivalent Volterra (DDBE) model is proposed to compensate the nonlinear distortions of the concurrent dual-band power amplifier (PA). The DDBE model is obtained by improving the discretized dual-band baseband equivalent Volterra model which can describe the output characteristics of concurrent dual-band PA completely in theory but is lack of practicability. Three simplification rules are proposed in the article, and the relevance between in-band intermodulation and in-band cross modulation is employed to simplify the establishment complexity of the model. Then the dynamic kernels are categorized into three groups, and based on this, DDBE models with different level dynamical kernels are derived. In addition, draw on the experience of single-band PA behavioral model, even-order kernels are introduced into DDBE models. Digital predistortion performances of a wideband PA, which works in concurrent dual-band mode, are evaluated to verify the feasibility and advantages of the proposed model.

Low Complexity Coefficient Estimation for Concurrent Dual-Band Digital Predistortion

Dual-band or multi-band RF power amplifiers (PAs) have attracted a lot of attention in recent years as they rise to the challenge of segmented spectrum allocation in wireless systems. Adaptive digital predistortion (DPD) for concurrent dual-band PAs evolves from existing DPD for single-band PAs. In this paper, we derive the baseband dual-band Volterra model from the corresponding passband model. In addition, the computational complexity of the DPD estimation algorithm increases dramatically as the number of coefficients for dual-band DPD is much larger than that for single-band DPD. In this paper, we propose a low complexity DPD coefficient estimation algorithm for concurrent dual-band PAs based on polar decomposition of the general Volterra model. By dividing complex-valued coefficient estimation into amplitude estimation and phase estimation separately, the proposed algorithm achieves at most 75% computational complexity reduction. Moreover, the proposed algorithm can achieve similar performance with the conventional coefficient estimation method. Simulation and measured results validate performance of the proposed algorithm for a solid-state PA.

A Harmonic Termination Technique for Single- and Multi-Band High-Efficiency Class-F MMIC Power Amplifiers

This paper presents a harmonic termination technique for single- and multi-band high-efficiency class-F monolithic microwave integrated circuit (MMIC) power amplifiers (PAs). The harmonic termination network (HTN), realized with the minimum possible number of elements, can be used to terminate an arbitrary number of harmonics in a single-band PA or harmonics of multiple frequencies in a concurrent multi-band PA. The drain and gate bias lines are embedded in the HTNs to obviate the need for RF chokes and reduce the chip area. A single- and a dual-band MMIC PA are designed using the proposed technique and implemented in a 0.25- μm AlGaAs-InGaAs pHEMT technology. The single-band 5.5-GHz PA provides 27.5 dBm of output power with 70% power-added efficiency (PAE). This PAE level is achieved by terminating the first five harmonics at the output as well as the first three harmonics at the input of PA. The dual-band PA, operating at 5 and 12 GHz, delivers the output power of 28.0 and 26.7 dBm with PAE of 58% and 51%, at the two frequency bands, respectively.

Behavioral modeling for concurrent dual-band power amplifiers using 2D hammerstein/wiener models

Behavioral modeling for the concurrent dual-band power amplifier (PA) is a critical problem in practical applications. The nonlinear distortion in the concurrent dual-band PA is quite different from that in the conventional single-band PA. This article analyzes the nonlinearities in the concurrent dual-band PA and reveals that both input signals in the dual bands are important for the behavioral modeling. The 2D Hammerstein model and 2D Wiener model are proposed for the first time for the concurrent dual-band PA. They are extended versions of conventional Hammerstein and Wiener structures used in the single-band PA by including the cross-band intermodulation in the static nonlinearity block. The proposed 2D models require much less coefficients than the original work of the 2D-DPD model. Experiments were carried out for an 880 MHz/1960 MHz concurrent dual-band Doherty PA to demonstrate the effectiveness of the proposed models. The results clearly show that less than −40 dB normalized mean square errors (NMSEs) are obtained in the dual bands in the behavioral modeling. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23: 646–654, 2013.

A Multiband Reconfigurable Power Amplifier for UMTS Handset Applications

A new practical reconfigurable output network for a multiband reconfigurable power amplifier (PA) is proposed for universal mobile telecommunications system (UMTS) handset applications. The proposed reconfigurable network can reconfigure the output power and the output path, as well as the frequency. It consists of a power-reconfigurable network, a frequency-reconfigurable network, and a path-selection network. In this paper, its reconfiguration principle is described to extract key design parameters for the reconfigurable PA implementation. To demonstrate the performance of the proposed structure, a 5 mm × 6 mm multiband reconfigurable PA module is developed for UMTS high- and low-frequency band application. The fabricated PA module can cover any three bands out of five popular high- and low-frequency UMTS bands. To enhance the efficiency during low output power operation, the authors' stage-bypass technique is also employed. The fabricated PA module showed adjacent channel leakage ratios better than -39 dBc up to the rated linear output power and power-added efficiencies of higher than 39% at <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</sub> =28 dBm over all the UMTS frequency bands. Efficiency degradation was limited to less than 2% compared to the single-band PA. Measured RF performance of the reconfigurable PA validates the usefulness of the proposed reconfigurable structure for multiband UMTS applications.

Compact 1.5GHz to 2.5GHz multi-band multi-mode power amplifier

This paper presents a compact multi-band/multi-mode power amplifier (PA) for mobile terminals. The PA is reconfigurable within the size of 6.2 x 8.05mm2 and covers the frequency bands for mobile communications from 1.5GHz to 2.5GHz. The experimental results in terms of gain, output power, and adjacent channel leakage ratio are very close to those of actually-used single-band PAs in mobile terminals. To the best of our knowledge, this is the first time that a compact PA is presented that is less than 50mm2 and covers the 1.5, 1.7, 1.8, 1.9, 2.3, and 2.5-GHz bands for GSM, W-CDMA, and LTE modes.

Design of Dualband Class-F PAs for Cellular and WLAN Applications

In this paper, highly efficient class-F power amplifiers(PAs) with harmonic-controlling transmission lines(TLs) were built for cellular and WLAN applications at 840 MHz and 2.4 GHz each. Also, based on these single-band PAs, a dualband class-F PA was designed after a careful investigation into the harmonics of the two frequencies. The harmonic-controlling TL was designed for the class-F operation at dualband by switching the length of the shunt <TEX>$\lambda$</TEX>/4 TL part, while the series <TEX>$\lambda$</TEX>/4 TL is optimized for both frequencies. To verify the performance, two class-F PAs optimized at each frequency and a dualband class-F PA at the corresponding frequencies were built with the secondand the third-harmonic control circuits at each frequencies. As a result, the PA#1 at 840 MHz has a peak drain efficiency of 81.2 % with an output power of 24.4 dBm, while the PA#2 at 2.35 GHz shows a drain efficiency of 94.5 % with an output of 22.8 dBm. Finally, the dualband class-F PA#3 showed 60.5 % and 50.9 % drain efficiencies at 840 MHz and 2.4 GHz, with powers of 23.8 dBm and 19.62 dBm, respectively.

Helix on Pad-Type Ultra Small-Size Power Amplifiers for WCDMA Handset Applications

Ultra small-size power amplifier (PA) modules were developed for WCDMA handset applications. To reduce the size of the PA modules, the bulky transmission lines and lumped surface mountable chip elements of the conventional output matching network (OMN) were replaced with the proposed helix-on-pad (HoP) and an integrated passive device (iPD), respectively. Three 2 mm times 2 mm single-band PA modules were developed using the proposed OMNs for UMTS Band-5, Band-1, and Band-2 applications. No RF performance degradation was observed from the size-reduced PA modules. For the demonstration of ultimate size reduction, a dual-band PA for UMTS Band-2/ Band-5 application was developed in a 3 mm X 3 mm form-factor. The PAs exhibited adjacent channel leakage ratios (ACLRs) better than -38 dBc over the entire output power range together with power-added efficiencies (PAEs) in excess of 39 % at 28.5 dBm. Besides, the PAs showed good low-power efficiency of 16% at P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</sub> = 16 dBm due to the stage-bypass architecture. The proposed method can be applied in a variety of wireless Tx applications requiring small form-factors and high efficiencies.

Novel Band-Reconfigurable High Efficiency Power Amplifier Employing RF-MEMS Switches

A novel scheme for a multi-band power amplifier (PA) that employs a low-loss reconfigurable matching network is presented and discussed. The matching network basically consists of a cascade of single-stub tuning circuits, in which each stub is connected to a transmission line via a Single-Pole-Single-Throw (SPST) switch. By controlling the on/off status of each switch, the matching network works as a band-switchable matching network. Based on a detailed analysis of the influence of non-ideal switches in the matching network, we conceived a new design perspective for the reconfigurable matching network that achieves low loss. A 900/1900-MHz dual-band, 1 W class PA is newly designed following the new design perspective, and fabricated with microelectro mechanical system (MEMS) SPST switches. Owing to the new design and sufficient characteristics of the MEMS switches, the dual-band PA achieves over 60% of the maximum power-added efficiency with an output power for each band exceeding 30dBm. These results are comparable to the estimated results for a single-band PA. This shows that the proposed scheme provides a band-switchable highly efficient PA that has superior performance compared to the conventional multi-band PA that has a complex structure.