Speed-of-light limitations in passive linear media

We prove that well-known speed of light restrictions on electromagnetic energy velocity can be extended to a new level of generality, encompassing even nonlocal chiral media in periodic geometries, while at the same time weakening the underlying assumptions to only passivity and linearity of the medium (either with a transparency window or with dissipation). As was also shown by other authors under more limiting assumptions, passivity alone is sufficient to guarantee causality and positivity of the energy density (with no thermodynamic assumptions). Our proof is general enough to include a very broad range of material properties, including anisotropy, bianisotropy (chirality), nonlocality, dispersion, periodicity, and even delta functions or similar generalized functions. We also show that the "dynamical energy density" used by some previous authors in dissipative media reduces to the standard Brillouin formula for dispersive energy density in a transparency window. The results in this paper are proved by exploiting deep results from linear-response theory, harmonic analysis, and functional analysis that had previously not been brought together in the context of electrodynamics.Comment: 19 pages, 1 figur

High-Throughput Signal Component Separator for Asymmetric Multi-Level Outphasing Power

Abstract—This paper presents an energy-efficient highthroughput and high-precision signal component separator (SCS) chip design for the asymmetric-multilevel-outphasing (AMO) power amplifier. It uses a fixed-point piece-wise linearfunctional approximation developed to improve the hardware efficiency of the outphasing signal processing functions. The chip is fabricated in 45 nm SOI CMOS process and the SCS consumes an active area of 1.5 mm. The new algorithm enables the SCS to run at a throughput of 3.4 GSamples/s producing the phases with 12-bit accuracy. Compared to traditional low-throughput AMO SCS implementations, at 0.8 GSamples/s this design improves the area efficiency by 25 and the energy-efficiency by 2.Thisfastest high-precision SCS to date enables a new class of high-throughput mm-wave and base station transmitters that can operate at high area, energy and spectral efficiency. Index Terms—Application specific integrated circuits (ASIC), asymmetric multi-level outphasing (AMO) power amplifier, baseband, energy efficiency, linear amplification by nonlinear component (LINC), Signal component separator (SCS), throughput. I

Rigorous sufficient conditions for index-guided mode in microstructured dielectric waveguides

We derive a sufficient condition for the existence of index-guided modes in a very general class of dielectric waveguides, including photonic-crystal fibers (arbitrary periodic claddings, such as ``holey fibers''), anisotropic materials, and waveguides with periodicity along the propagation direction. This condition provides a rigorous guarantee of cutoff-free index-guided modes in any such structure where the core is formed by increasing the index of refraction (e.g. removing a hole). It also provides a weaker guarantee of guidance in cases where the refractive index is increased ``on average'' (precisely defined). The proof is based on a simple variational method, inspired by analogous proofs of localization for two-dimensional attractive potentials in quantum mechanics.Comment: 15 page

Computation and visualization of photonic quasicrystal spectra via Blochs theorem

Previous methods for determining photonic quasicrystal (PQC) spectra have relied on the use of large supercells to compute the eigenfrequencies and/or local density of states (LDOS). In this manuscript, we present a method by which the energy spectrum and the eigenstates of a PQC can be obtained by solving Maxwells equations in higher dimensions for any PQC defined by the standard cut-and-project construction, to which a generalization of Blochs theorem applies. In addition, we demonstrate how one can compute band structures with defect states in the higher-dimensional superspace with no additional computational cost. As a proof of concept, these general ideas are demonstrated for the simple case of one-dimensional quasicrystals, which can also be solved by simple transfer-matrix techniques.Comment: Published in Physical Review B, 77 104201, 200

Sufficient conditions for two-dimensional localization by arbitrarily weak defects in periodic potentials with band gaps

We prove, via an elementary variational method, 1d and 2d localization within the band gaps of a periodic Schrodinger operator for any mostly negative or mostly positive defect potential, V, whose depth is not too great compared to the size of the gap. In a similar way, we also prove sufficient conditions for 1d and 2d localization below the ground state of such an operator. Furthermore, we extend our results to 1d and 2d localization in d dimensions; for example, a linear or planar defect in a 3d crystal. For the case of D-fold degenerate band edges, we also give sufficient conditions for localization of up to D states.Comment: 9 pages, 3 figure

Realization and approximation of stationary stochastic processes

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.Bibliography: leaves 82-84.by Yehuda Avniel.Ph.D

Compact Modeling of Nonlinear Analog Circuits using System Identification via Semi-Definite Programming and Robustness Certification

This paper presents a system identification technique for generating stable compact models of typical analog circuit blocks in radio frequency systems. The identification procedure is based on minimizing the model error over a given training data set subject to an incremental stability constraint, which is formulated as a semidefinite optimization problem. Numerical results are presented for several analog circuits, including a distributed power amplifier, as well as a MEM device. It is also shown that our dynamical models can accurately predict important circuit performance metrics, and may thus, be useful for design optimization of analog systems.United States. Defense Advanced Research Projects Agency (Grant N66001-09-1-2068)Interconnect Focus Center (United States. Defense Advanced Research Projects Agency and Semiconductor Research Corporation)Massachusetts Institute of Technology. Center for Integrated Circuits and System