IEEE Circuits and Systems Magazine - Q2 2019 - 1

Circuits
and Systems
IEEE

MAGAZINE

Volume 19, Number 2

Second Quarter 2019

Features

Printed in U.S.A.

L. Xiang, F. Chen, W. Ren, and G. Chen

The last decade has seen an explosion of research in network controllability. The present article
reviews some basic concepts, significant progress, important results and recent advances in the
studies of the controllability of networked linear dynamical systems, regarding the relationship of
the network topology, node-system dynamics, external control inputs and inner dynamical interactions with the controllability of such complex networked dynamical systems. Different approaches
to analyzing the network controllability are evaluated. Some advanced topics on the selection of
driver nodes, optimization of network controllability and control energy are discussed. potential
applications to real-world networked systems are also described. Finally, a near-future research
outlook is highlighted.

Performance, Power, and Area Design Trade-offs in Millimeter-Wave
Transmitter Beamforming Architectures
H. Yan, S. Ramesh, T. Gallagher, C. Ling and D. Cabric

millimeter wave (mmW) communications is viewed as the key enabler of 5g cellular networks due
to vast spectrum availability that could boost peak rate and capacity. Due to increased propagation
loss in mmW band, transceivers with massive antenna array are required to meet a link budget, but
their power consumption and cost become limiting factors for commercial systems. Radio designs
based on hybrid digital and analog array architectures and the usage of radio frequency (RF) signal
processing via phase shifters have emerged as potential solutions to improve radio energy efficiency and deliver performances close to the conventional digital antenna arrays. In this paper, we
provide an overview of the state-of-the-art mmW massive antenna array designs and comparison
among three array architectures, namely digital array, partially connected hybrid array (sub-array),
and fully-connected hybrid array. The comparison of performance, power, and area for these three
architectures is performed for three representative 5g downlink use cases, which cover a range of
pre-beamforming signal-to-noise-ratios (SNR) and multiplexing regimes. This is the first study to
comprehensively model and quantitatively analyze all design aspects and criteria including: 1) optimal linear precoder, 2) impact of quantization error in digital-to-analog converter (DAC) and phase
shifters, 3) RF signal distribution network, 4) power and area estimation based on state-of-the-art
mmW circuits including baseband digital precoding, digital signal distribution network, high-speed
DACs, oscillators, mixers, phase shifters, RF signal distribution network, and power amplifiers. Our
simulation results show that the fully-digital array architecture is the most power and area efficient
compared against optimized designs for sub-array and hybrid array architectures. Our analysis
shows that digital array architecture benefits greatly from multi-user multiplexing. The analysis also
reveals that sub-array architecture performance is limited by reduced beamforming gain due to array
partitioning, while the system bottleneck of the fully-connected hybrid architecture is the excessively
complicated and power hungry RF signal distribution network.

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Advances in Network Controllability

The World of Ripples
Pavel Zahradnik and Miroslav Vlcˇek

Approximation techniques are useful in numerous engineering and non-engineering tasks. In
electrical engineering and in the filter design in particular, approximation techniques allow to
approximate in some sense a desired, usually an ideal, but not feasible frequency response of
a filter. Among various approximations, polynomial approximations are very useful. The design
of feasible linear digital filters with finite impulse response is based on them. There emerge two
unique types among polynomial approximations, a maximally flat approximation and an equiripple
approximation. We review here the polynomial equiripple approximation, its highlights, applications, history, evolution and latest achievements including open questions.

Digital Object Identifier 10.1109/MCAS.2019.2909444

SECOND QUARTER 2019

IEEE CIRCUITS AND SySTEmS mAgAzINE

IEEE Circuits and Systems Magazine - Q2 2019

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