Lossless Multiway Power Combining and Outphasing for High-Frequency Resonant Inverters

A lossless multi-way power combining and outphasing system have recently been proposed for high-frequency inverters and power amplifiers that offers major performance advantages over traditional approaches. This paper presents outphasing control strategies for the proposed power combining system that enable output power control through effective load modulation of the inverters. It describes a straightforward power combiner design methodology and enumerates various possible topological combiner implementations. Moreover, this study presents the first-ever experimental demonstration of the proposed outphasing system. The design of a 27.12 MHz, four-way power combining and outphasing system is described and used to experimentally verify the power combiner's characteristics. The proposed outphasing law is shown to be effective in controlling the output power over a 10-100 W (10:1) power range

A linear high-efficiency millimeter-wave CMOS Doherty radiator leveraging on-antenna active load-modulation

This thesis presents a Doherty Radiator architecture that explores multi-feed antennas to achieve an on-antenna Doherty load modulation network and demonstrate high-speed high-efficiency transmission of wideband modulated signals. On the passive circuits, we exploit the multi-feed antenna concept to realize compact and high-efficiency on-antenna active load modulation for close-to-ideal Doherty operation, on-antenna power combining, and mm-Wave signal radiation. Moreover, we analyze the far-field transmission of the proposed Doherty Radiator and demonstrate its wide Field-of-View (FoV). On the active circuits, we employ a GHz-bandwidth adaptive biasing at the Doherty Auxiliary power amplifier (PA) path to enhance the Main/Auxiliary Doherty cooperation and appropriate turning-on/-off of the Auxiliary path. A proof-of-concept Doherty Radiator implemented in a 45nm CMOS SOI process over 62-68GHz exhibits a consistent 1.45-1.53× PAE enhancement at 6dB PBO over an idealistic class-B PA with the same PAE at P1dB. The measured Continuous-Wave (CW) performance at 65GHz demonstrates 19.4/19.2dBm PSAT/P1dB and achieves 27.5%/20.1% PAE at peak/6dB PBO, respectively. For single-carrier 1Gsym/s 64-QAM modulation, the Doherty Radiator shows average output power of 14.2dBm with an average 20.2% PAE and -26.7dB EVM without digital predistortion. Consistent EVMs are observed over the entire antenna FoV, demonstrating spatially undistorted transmission and constant Doherty PBO efficiency enhancement.M.S

Diseño e implementación de combinadores de potencia para amplificador LINC @ 868MHz

The ISM is a free band generally used in the environmental scientific and medical study. The regulation depends on the government of each country. This study is focused on the European¡¯s level frequency of 868 MHz, this frequency does not require standards or permissions, as long as they do not exceed the regulations. The project was based on the realization of a LINC transmitter with class E amplifiers made of passive matching networks. Also, the design and production of three combiners: Hybrid 90¨¬, Wilkinson and Chireix. In this project we have seen the different existing types of amplifiers (Class A, Class B ...) and the two main transistors that we can find in the market (BJT and FET). The amplifier¡¯s design was done using the ADS program from Agilent, and to characterize matching networks we have used the Smith Chart and ADS LineCalc. The first thing was find the polarization voltages, to characterize the S parameters of the transistor. The stability calculations have been made as theoretical as graphically (ADS). Matching networks are realized with passive elements such as coils and capacitors, that has been the difference of previous studies. At this point of the project the tunning tool was used to refine the results. The Bias Network were designed with shock coils and decoupling capacitors. The last step was the design of the layout with ADS software and then assembled. The other branch of the study has been the design and implementation of three combiners, for the simulation of both the ADS program was also used and finally took the design to a board. The results obtained for the amplifier with matching networks made of passive elements were good only for one channel. For this reason we have had to continue the combiners study with a project implemented earlier by another student, made with ¥ë / 4 lines. As we have seen in the laboratory, the Chireix combiner is positioned as the most efficient and which allows the maximum gain. Future studies may try to improve the performance of a class E type LINC amplifier with stable matching networks made of passive elements, as well as, improve the efficiency of the Chireix combiner and open new ways of study.La banda ISM es una banda libre que generalmente se usa en el estudio medioambiental, científico y médico. La normativa depende del gobierno de cada territorio. Este estudio se ha centrado en el ámbito europeo a la frecuencia de 868 MHz. Esta frecuencia no requiere de estándares ni permisos siempre que no supere la normativa

Advanced Doherty power amplifier design for modern communication systems

Mobile communication technologies are becoming increasingly sophisticated and have experienced rapid evolution over the last few decades, and this is especially true for the base station transmitter. In response to the ever increasing demand in communication traffic and data throughput, largely driven by video based social media platforms, both spectral and power efficient device and systems are needed to fulfil the requirements. In terms of energy consumption, the power amplifier is an important component, and although developing efficient technologies for handset equipment is important, it is the base station element of the communications system that poses the greater challenge, having to deal with many channels simultaneously, resulting in the need to linearly and efficiently amplify highly dynamic phase and amplitude modulated signals possessing very large peak-to-average power ratios, at high power levels. This unique set of challenges has led to continuous research to improve the efficiency of amplifiers that can accommodate such signals, and the Doherty architecture has now become the architecture-of-choice. However, most of the previous research studies demonstrate Doherty performance enhancement through a ‘conventional’ design approach that uses one input source and a passive power splitter to deliver power to each half of the Doherty structure. They do not emphasize the additional efficiency and other performance improvements that are possible in Doherty amplifiers when using two different, independent and phase coherent input sources, attached to the input path of both main and auxiliary amplifiers. IV The novel research work presented in this thesis introduces an optimised design approach for Doherty amplifier architectures with individual input sources, as well as detailing a measurement architecture that is necessary to characterise such structures, using separate, phase-coherent input sources in a realistic measurement scenario. Finally, following extensive characterisation of a number of promising architectures, investigations around efficiency enhancement are focused around the adaption of gate bias applied to the auxiliary amplifier device, and identifying, for the first time, what is possible by generating different shaping functions that relate bias voltage to the magnitude of the input signal. One completely new area of research and novelty introduced in this work for example shows how choosing the right shaping function can give improved linearity and importantly linearisability by producing a flat gain over dynamic range. Note that linearisability is important, and is defined here as the term used to describe the ease with which the non-linearities of a device or power amplifier can be corrected. It is often assumed in power amplifier design that efficiency and power are the most important parameters, and that modern digital pre-distortion (DPD) techniques can easily correct any non-linearity that may result. Industry is now finding that this is not the case however, and the type and nature of the non-linearity in terms to AM-AM and AM-PM distortion is very important in determining of the degree of linearization possible

RF Power Amplifier and Its Envelope Tracking

This dissertation introduces an agile supply modulator with optimal transient performance for the envelope tracking supply in linear power amplifiers. For this purpose, an on-demand current source module, the bang-bang transient performance enhancer (BBTPE), is proposed. Its objective is to follow fast variations in input signals with reduced overshoot and settling time without deteriorating the steady-state performance of the buck regulator. The proposed approach enables fast system response through the BBTPE and an accurate steady-state output response through a low switching ripple and power efficient dynamic buck regulator. Fast output response with the help of the added module induces a slower rise of inductor current in the buck converter that further assists the proposed system to reduce both overshoot and settling time. To demonstrate the feasibility of the proposed solution, extensive simulations and experimental results from a discrete system are reported. The proposed supply modulator shows 80% improvement in rise time along with 60% reduction in both overshoot and settling time compared to the conventional dynamic buck regulator-based solution. Experimental results for a PA using the LTE 16-QAM 5 MHz standard shows improvement of 7.68 dB and 65.1% in ACPR and EVM, respectively. In a polar power amplifier, the input signal splits into phase and amplitude components using a non-linear conversion operation. This operation broadens the spectrum of the polar signal components. The information of amplitude and phase contains spectral images due to the sampling operation in non-linear conversion operation. These spectral images can be large and cause out-of-band emission in the output spectrum. In addition, during the recombination process of phase and amplitude, a delay mismatch between amplitude and phase signals, which can occur due to separate processing paths of amplitude and phase signals, causes out-of-band emissions, also known as spectral regrowth. This dissertation presents solutions to both of the issues of digital polar power amplifier: spectral images and delay mismatch. In order to reduce the problem of spectral images, interpolation of phase and amplitude is proposed in this work. This increases the effective sampling frequency of the amplitude and phase, which helps to improve the linearity by around 10 dB. In addition, a novel calibration scheme is proposed here for the delay mismatch between phase and amplitude path in a digital polar power amplifier. The scheme significantly reduces the spectral regrowth. The scheme uses the same path for phase and amplitude delay calculation after the recombination that allows having a robust calibration. Furthermore, it can be executed during the empty transmission slots. The proposed scheme is designed in a 40 nm CMOS technology and simulated with a 64-QAM IEEE 802.11n wireless standard. The scheme achieved 7.57 dB enhancement in ACLR and 84.35% improvement in EVM for a 3.5 ns mismatch in phase and amplitude path

Device level characterization of outphasing amplifiers

The outphasing technique proposed by Chireix in 1935 is one of the classical methods of addressing power amplifier (PA) efficiency degradation caused by operating in output back-off (OBO) conditions, where PA efficiency is typically low. Essentially, the envelope from the input signal is eliminated, and two CW signals are constructed; these have constant amplitude, while their relative phase offset holds the original information contained by amplitude modulation. Consequently, efficiency improvements are achieved by amplifying signals with constant amplitude using PAs operating in saturation, where efficiency typically peaks. The envelope is restored at the output by means of a vector summation of both signals, using a non-isolating combiner at the output stage The main focus of the work described in this thesis was placed on extending bandwidth of the inherently narrowband technique of outphasing and then adopting this method to modern telecommunication standards. Two prototype PAs were designed to investigate whether bandwidth improvements can be achieved by adopting a broadband balun as a combining structure in the outphasing PA. Two baluns were designed and fabricated to be used in the demonstrator circuits; one using a section of semirigid coaxial cable and the other, a planar balun realized on 10 mil thick Alumina substrate. A novel method of fabrication was proposed for the former structure, which achieved more than double octave bandwidth, from 1.25 GHz to 4.7 GHz with losses lower than 1dB, an amplitude imbalance (trace separation) below 0.75 dB and phase imbalance within ±5 degrees. The measured CW performance of the prototype circuits produced results comparable with the state-of-the-art solutions available in literature. Moreover, this work demonstrated that a balun with sufficient bandwidth allows load modulation to be prescribed at fundamental and second harmonic frequencies, opening the possibility of waveform engineering to implement continuous PA modes such as class J in outphasing PAs. The desired harmonic load termination was achieved without any specialized matching networks, and solely by means of load modulation provided through active device interaction. The thesis concludes with the formulation, analysis and description of the novel concept derived from Chireix outphasing. Several outdated assumptions still prevalent in outphasing analysis included in literature today are challenged and reformulated for modern semiconductor devices such as GaN HEMTs. Through this process, a new concept of Current Mode Outphasing (CMOP), is proposed and described in detail. One of the significant advantages of the proposed approach is it allows the elimination of the combiner structure, which typically dominates the size of the final outphasing circuit, due to the presence of λ/4 transmission lines. Consequently, the demonstrator MMIC circuit, containing DC bias, stability elements and pre-matched to 50 Ω on input and output, has been deployed on an area of 2.3 mm x 2.8 mm. The CMOP circuit was fabricated using 0.25 µm GaN technology and achieved a bandwidth of 1.6 GHz centered at 3.35 GHz, whereas the maximum CW output power remains within 43 dBm ± 0.5 dB. A total gain of more than 12 dB is reported from 2.95 to 3.95 GHz, while a maximum Power Added Efficiency was measured as 68.5% at 3.25 GHz and remains greater than 60% from 2.85 to 3.8 GHz, and above 50% for almost the entire frequency range. The output back-off (OBO) efficiency peaks at 3.25 GHz with 53.5% and 45.6% for 6 dB and 8 dB back-off, respectively, and remains above 30% and 23.7% for the entire frequency range. To the best of the authors’ knowledge, this is the largest fractional bandwidth achieved in an outphasing PA, that has been reported in literature

RF Power Amplifier and Its Envelope Tracking

This dissertation introduces an agile supply modulator with optimal transient performance for the envelope tracking supply in linear power amplifiers. For this purpose, an on-demand current source module, the bang-bang transient performance enhancer (BBTPE), is proposed. Its objective is to follow fast variations in input signals with reduced overshoot and settling time without deteriorating the steady-state performance of the buck regulator. The proposed approach enables fast system response through the BBTPE and an accurate steady-state output response through a low switching ripple and power efficient dynamic buck regulator. Fast output response with the help of the added module induces a slower rise of inductor current in the buck converter that further assists the proposed system to reduce both overshoot and settling time. To demonstrate the feasibility of the proposed solution, extensive simulations and experimental results from a discrete system are reported. The proposed supply modulator shows 80% improvement in rise time along with 60% reduction in both overshoot and settling time compared to the conventional dynamic buck regulator-based solution. Experimental results for a PA using the LTE 16-QAM 5 MHz standard shows improvement of 7.68 dB and 65.1% in ACPR and EVM, respectively. In a polar power amplifier, the input signal splits into phase and amplitude components using a non-linear conversion operation. This operation broadens the spectrum of the polar signal components. The information of amplitude and phase contains spectral images due to the sampling operation in non-linear conversion operation. These spectral images can be large and cause out-of-band emission in the output spectrum. In addition, during the recombination process of phase and amplitude, a delay mismatch between amplitude and phase signals, which can occur due to separate processing paths of amplitude and phase signals, causes out-of-band emissions, also known as spectral regrowth. This dissertation presents solutions to both of the issues of digital polar power amplifier: spectral images and delay mismatch. In order to reduce the problem of spectral images, interpolation of phase and amplitude is proposed in this work. This increases the effective sampling frequency of the amplitude and phase, which helps to improve the linearity by around 10 dB. In addition, a novel calibration scheme is proposed here for the delay mismatch between phase and amplitude path in a digital polar power amplifier. The scheme significantly reduces the spectral regrowth. The scheme uses the same path for phase and amplitude delay calculation after the recombination that allows having a robust calibration. Furthermore, it can be executed during the empty transmission slots. The proposed scheme is designed in a 40 nm CMOS technology and simulated with a 64-QAM IEEE 802.11n wireless standard. The scheme achieved 7.57 dB enhancement in ACLR and 84.35% improvement in EVM for a 3.5 ns mismatch in phase and amplitude path