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Register a new userBreaking Bandwidth Limit: A Review of Broadband Doherty Power Amplifier Design for 5G
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Added by
Gholamreza Nikandish
Publication date
2019
fields
Electronic Engineering
and research's language is
English
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The Doherty power amplifier (DPA) has been extensively explored in the past and has become one of the most widely used power amplifier (PA) architectures in cellular base stations. The classical DPA suffers intrinsic bandwidth constrains which limit its application in future 5G wireless transmitters. In this paper, we present a comprehensive review of the DPA bandwidth enhancement techniques proposed in literature in order to provide a thorough understanding of the DPAs broadband design for high-efficiency 5G wireless transmitters. We elaborate on the main bandwidth limitation sources and provide circuit design insights. We then follow with an overview of bandwidth enhancement techniques developed for the DPA, including modified load-modulation networks, frequency response optimization, parasitic compensation, post-matching, as well as distributed DPA, dual-input digital DPA, transformer-based power-combining PA, and transformer-less load modulated PA architectures. Furthermore, challenges and design techniques for integrated circuit (IC) implementation of broadband DPAs are discussed, including a review of circuits developed in CMOS, SiGe, and GaN processes, and operating in RF and mm-Wave frequencies.
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Owing to the complicated characteristics of 5G communication system, designing RF components through mathematical modeling becomes a challenging obstacle. Moreover, such mathematical models need numerous manual adjustments for various specification requirements. In this paper, we present a learning-based framework to model and compensate Power Amplifiers (PAs) in 5G communication. In the proposed framework, Deep Neural Networks (DNNs) are used to learn the characteristics of the PAs, while, correspondent Digital Pre-Distortions (DPDs) are also learned to compensate for the nonlinear and memory effects of PAs. On top of the framework, we further propose two frequency domain losses to guide the learning process to better optimize the target, compared to naive time domain Mean Square Error (MSE). The proposed framework serves as a drop-in replacement for the conventional approach. The proposed approach achieves an average of 56.7% reduction of nonlinear and memory effects, which converts to an average of 16.3% improvement over a carefully-designed mathematical model, and even reaches 34% enhancement in severe distortion scenarios.
In this work, the designs of a single-stage and 2-stage 2.4 GHz power amplifier (PA) are presented. The proposed PAs have been designed to provide high gain and improved efficiency using harmonic suppression and optimized impedance matching techniques. There are two harmonic suppression circuits, each stage of the PA consists of 2 capacitors and 2 inductors, which will help to suppress the harmonic frequency for 2.4 GHz. These suppression circuits will help to enhance the overall efficiency of the PAs. Both the PAs are provided with a VCC supply of 4.2V. Input and output impedances are matched to 50 ohms. Simulation and experimental results are presented, where the simulated gain and power added efficiency (PAE) for single stage PA are 17:58dB and 53%, respectively. While the experimental gain and PAE are 16:7dB and 49.5%, respectively. On the other hand, for 2-stages PA, simulated gain comes out to be 34.6dB and PAE is 55%, while the experimental gain and PAE are 30.5dB and 53.1%, respectively. The final design is being fabricated on the Taconic printed circuit board (PCB) with a thickness of 0.79mm and the dielectric constant value of 3.2 and its dimensions are 4.6cm x 3.4cm for single stage and 5.9cm x 3.6cm for 2-stages PA.
We present design and simulation of a Josephson parametric amplifier with bandwidth exceeding 1.6 GHz, and with high saturation power approaching -90 dBm at a gain of 22.8 dB. An improvement by a factor of roughly 50 in bandwidth over the state of the art is achieved by using well-established impedance matching techniques. An improvement by a factor of roughly 100 in saturation power over the state of the art is achieved by implementing the Josephson nonlinear element as an array of rf-SQUIDs with a total of 40 junctions. WRSpice simulations of the circuit are in excellent agreement with the calculated gain and saturation characteristics.
This paper presents a feasibility study for a novel positioning-communication integrated signal called Multi-Scale Non-Orthogonal Multiple Access (MS-NOMA) for 5G positioning. One of the main differences between the MS-NOMA and the traditional positioning signal is MS-NOMA supports configurable powers for different positioning users (P-Users) to obtain better ranging accuracy and signal coverage. Our major contributions are: Firstly, we present the MS-NOMA signal and analyze the Bit Error Rate (BER) and ranging accuracy by deriving their simple expressions. The results show the interaction between the communication and positioning signals is rather limited, and it is feasible to use the MS-NOMA signal to achieve high positioning accuracy. Secondly, for an optimal positioning accuracy and signal coverage, we model the power allocation problem for MS-NOMA signal as a convex optimization problem by satisfying the QoS (Quality of Services) requirement and other constraints. Then, we propose a novel Positioning-Communication Joint Power Allocation (PCJPA) algorithm which allocates the powers of all P-Users iteratively. The theoretical and numerical results show our proposed MS-NOMA signal has great improvements of ranging/positioning accuracy than traditional PRS (Positioning Reference Signal) in 5G, and improves the coverage dramatically which means more P-Users could locate their positions without suffering the near-far effect.
Drones, unmanned aerial vehicles (UAVs), or unmanned aerial systems (UAS) are expected to be an important component of 5G/beyond 5G (B5G) communications. This includes their use within cellular architectures (5G UAVs), in which they can facilitate both wireless broadcast and point-to-point transmissions, usually using small UAS (sUAS). Allowing UAS to operate within airspace along with commercial, cargo, and other piloted aircraft will likely require dedicated and protected aviation spectrum at least in the near term, while regulatory authorities adapt to their use. The command and control (C2), or control and non-payload communications (CNPC) link provides safety critical information for the control of the UAV both in terrestrial-based line of sight (LOS) conditions and in satellite communication links for so-called beyond LOS (BLOS) conditions. In this paper, we provide an overview of these CNPC links as they may be used in 5G and satellite systems by describing basic concepts and challenges. We review new entrant technologies that might be used for UAV C2 as well as for payload communication, such as millimeter wave (mmWave) systems, and also review navigation and surveillance challenges. A brief discussion of UAV-to-UAV communication and hardware issues are also provided.
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