Power Amplifier Characterization/Automation for Digital Predistortion (DPD) Metrics and Algorithm Validations
Tuesday, 24 January — 1:30pm – 2:30pm
Anis Ben Arfi
The imminent deployment of 5G networks combined with challenging technical specifications requires new and agile methods to optimize and validate the RF solutions. Particularly, developers of 5G RF Power Amplifiers (PAs) and front-end module technology often face difficult trade-off between device linearity and efficiency. To address the increased bandwidth and power efficiency requirements of 5G systems, today’s Small Cell and MIMO PAs are pushed to operate at non-linear regions. Hence, the need for Digital Pre-Distortion (DPD) to correct for the non-linearity and preserve the highly-efficient PA operation. The design of these efficient PAs needs to follow critical criteria to ensure linearizability (i.e the PA’s ability to be linearized by applying predistortion). For this reason, at ADI, we perform a thorough PA characterization to verify the aforementioned criteria. However, PA characterization is a delicate and lengthy routine which needs to be automated. In fact, we are looking to evaluate significant number of PAs provided by ADI costumers and partner PA vendors. The PA characterization’s main purpose is to ensure that ADI DPD algorithms can handle the large set of PAs used by our customers. With the increasing number of new PAs to be tested, an automation of the PA characterization process becomes necessary in order to perform this characterization in shorter time periods.
The first part of this short course, will lay the foundation of the PA behavior and the DPD metrics used to evaluate its linearizability. Afterwards, the PA characterization process will be presented along with examples of PA reports provided by ADI to customers.
The second part of the short course will touch on the automated test-bench solution developed to perform power and frequency sweeps. The setup was developed using LabView to automate the test equipment and perform RF pulsed and modulated measurements. Similarly, the KeySight PNA-X automation work will be introduced. The PNA-X is used to measure the PA gain flatness over frequency, AM/AM, AM/PM and two-tone response. Finally, the short course will showcase the performance obtained using ADI transceiver boards linearizing various PAs and will discuss the best practices to obtain accurate results.
Linearization of Power Amplifiers used in Radio Frequency (RF) Transmitters
Wednesday, 25 January — 1:30pm – 2:30pm
R. Neil Braithwaite
This short course reviews techniques used to linearize nonlinear power amplifiers (PAs) used in wireless transmission. It begins with an overview of wireless communications including data throughput and the key components within a transmitter. The primary focus is on the power amplifier, which often behaves in a nonlinear fashion.
Compensation for PA nonlinearities, referred to as linearization, is covered in more detail. This includes the measurement of PA nonlinearities, models of nonlinearities (referred to as behavioral modelling), as well as digital and analog linearization. Digital predistortion is discussed along with estimator structures that make the compensation adaptive. Analog techniques reviewed include feedforward compensation and analog predistortion. Comparisons are made between the linearization approaches.
Wave-Matter Interaction at Millimeter-Wave Frequencies
Wednesday, 25 January — 3:30pm -4:30pm
Prof. Abbas Omarr
University of Magdeburg, Germany
Millimeter Wave mobile communication (5G and beyond) is associated with much lower radiation power and much shorter communication range. Millimeter Wavelengths suffer from very strong attenuation in water-rich substances limiting penetration into biological objects (e.g., human and animal bodies and plants) to just few tenths of a millimeter. Deeper inside the body the intensity is negligible making for greater safety compared to early mobile standards (3G and 4G). However, the safety of millimeter-wave radiation for 5G and beyond remains a public concern.
The physical concepts underlying the wave-matter interaction, particularly at millimeter-wave frequencies, are reviewed and discussed in this talk. Health hazard associated with electromagnetic wave exposures are then discussed. These can generally be categorized in ionizing and non-ionizing effects. Health impact of millimeter-wave exposures belong to the latter, and therefore can be either the direct increase in the body temperature or the indirect overloading of the biological processes responsible for the body thermal regulation.
Ionizing radiations are best described by quantizing the related electromagnetic field and dealing with the wave-matter interaction as collisions between highly localized photons and the material atoms, molecules, and/or chemical bonds. On the other hand, at wavelengths that are much larger than the atomic/molecular scale, a continuous spatial distribution of the electromagnetic wave is an adequate mathematical representation. The wave power-density is described by the Poynting vector, and the power transfer from the wave to the biological substances can be calculated with high precision using the concept of constitutive parameters (conductivity, permittivity, and permeability). These are macroscopic spectral quantities (moving spatial averages), which cannot account for special treatment of specific molecular-scale structures similar to that of, e.g., DNA strand. Millimeter Waves and even Tera-Hertz Waves belong to this category.