Traditional antenna pattern measurements involve minimizing the impact of multipath propagation in the measurement environment. In contrast, this work introduces a measurement approach that uses rather than mitigates multipath propagation. This is referred to as the Multipath-Enhanced Antenna Pattern (MEAP) Measurement technique. In this respect the approach has some kinship with Multiple-Input Multiple-Output (MIMO) systems. The advantage in the case of MIMO systems is increased capacity; in the MEAP approach the advantage is elimination of the need for creating an anechoic environment. The approach uses measurements with reference antennas to calibrate the multipath channel matrix, and vector spherical harmonics for efficient pattern representation. After presenting the mathematical details of the method, numerical calculations illustrating the approach are presented. Experimental results are described in a companion paper.

A quantum computing circuit is presented that approximates a single spin wave quantum on a linear chain of spin 1/2 particles described by a Heisenberg Hamiltonian. The circuit is a product state where each qubit represents a spin. The spin wave motion is represented by opening the cone angle using Y rotations and then adding progressive Z rotations along the chain to represent wave propagation. We show analytically that this product state yields the correct dispersion relation in the limit of an unbounded chain. This observation is confirmed using both a simulator and various quantum processors. The use of the quantum computing paradigm in this case does not lead to a computational advantage, but rather leads to a novel conceptual connection between classical and quantum descriptions of spin waves, and may also be useful for characterizing the error in quantum processors.

Excited states of spin-chains play an important role in condensed matter physics. We present a method of calculating the single magnon excited states of the Heisenberg spin-chain that can be efficiently implemented on a quantum processor for small spin chains. Our method involves finding the stationary points of the energy vs wavenumber curve. We implement our method for 4-site and 8-site Heisenberg Hamiltonians using numerical techniques as well as using an IBM quantum processor. Finally, we give an insight into the circuit complexity and scaling of our proposed method.

Magnetostatic Waves.Major additions include quantum mechanical treatments of angular momentum, exchange, and spin waves; nonlinear phenomena such as solitons and chaos; and applications such as the generation of spin waves using current-induced spin torques.This book has been fun to write.We hope you find it to be an interesting and useful introduction to spin waves and their applications.

Controlled-NOT (CNOT) gates are commonly included in the standard gate set of quantum processors and provide an important way to entangle qubits. For fixed-frequency qubits using the cross-resonance entangling technique, using the higher-frequency qubit to control the lower-frequency qubit enables much shorter entangling times than using the lower-frequency qubit as the control. Consequently, when implementing a CNOT gate where logical control by the lower-frequency qubit is needed, compilers may implement this functionality by using an equivalent circuit such as placing Hadamard gates on both qubits before and after a CNOT gate controlled by the higher-frequency qubit. However, since the implementation is different depending on which qubit is the control, a natural question arises regarding the relative performance of the implementations. We have explored this using quantum processors on the IBM Q network. The basic circuit used consisted of operations to create a Bell State, followed by the inverse operations so as to return the qubits to their initial state in the absence of errors (Hadamard + CNOT + barrier + CNOT + Hadamard). The circuit depth was varied using multiples of this basic circuit. An asymmetry in the error of the final state was observed that increased with the circuit depth. The strength and direction of the asymmetry was unique but repeatable for each pair of coupled qubits tested. This observation suggests that the asymmetry in CNOT implementation should be characterized for the qubits of interest and incorporated into circuit transpilation to obtain the best accuracy for a particular computation.

Negative refractive index metamaterials (MMs) have found widespread interest in shaping electromagnetic waves. One attractive area is energy transfer using low frequency magnetic waves or wireless power transfer (WPT). Previous reports have presented an isotropic metamaterial with μr = −1 as a “perfect lens” to focus energy and enhance WPT efficiency. In this work, we show that, while the perfect lens condition does enhance efficiency, anisotropic MMs with μr ≠ −1 can provide a larger enhancement in efficiency. These “non-perfect” lenses offer higher efficiency by enhancing the coupled field while incurring lower losses in the magnetostatic waves excited in or on the materials.

Measurements of Ra-226 activity from eight HPGe gamma ray detectors at the NC State University PULSTAR Reactor were analyzed for evidence of periodic variations, with particular attention to annual variations. All measurements were made using the same reference source, and data sets were of varying length taken over the time period from September 1996 through August 2014. Clear evidence of annual variations was observed in data from four of the detectors. Short time periodograms from the data sets suggest temporal variability of both the amplitude and frequency of these variations. The annual variations in two of the data sets show peak values near the first of February, while surprisingly, the annual variations in the other two are roughly out of phase with the first two. Three of the four detectors exhibited annual variations over approximately the same time period. A joint statistic constructed by combining spectra from these three shows peaks approximating the frequencies of solar r-mode oscillations with νR = 11.74 cpy, m = 1, and l = 3, 5, 6. The fact that similar variations were not present in all detectors covering similar time periods rules out variations in activity as the cause, and points to differing sensitivities to unspecified environmental parameters instead. In addition to seasonal variations, the modulation of environmental parameters by solar processes remains a possible explanation of periodogram features, but without requiring new physics.

The next generation of intelligent vehicle systems will use wireless communication to connect a car and its passengers. It is therefore important to understand the in-cabin propagation characteristics of an automobile. This paper investigates the wireless channel native to these cabin enclosures. We present detailed, polarization dependent field measurements over a plane of interest in the cabin, and show that a simple analytical model gives reasonable agreement with our measurements.

Recounts the career and contributions of Dr. Donald Robert Rhodes.

This ellipsoidal surface is called the index ellipsoid, or indicatrix.In the coordinate system in which (1/n 2 ) ij is diagonal, Equation 12.3 reduces to This surface has a simple geometric interpretation.The principal axes of the ellipsoid cor respond to directions in the crystal for which D is parallel to E, and the refractive indices for waves polarized along these directions are n x , n y , and n z .

In this work we characterize the magnetoquasistatic waves in an anisotropic, indefinite metamaterial used in wireless power applications. We show that the magnetic resonances in the metamaterial are volume mode waves and calculate the expected complex wave number, which represents the wavelength and attenuation, versus frequency from the complex permeability of the metamaterial. We then compare the calculated wavenumber to an experimentally extracted number. Our results show that the loss of the metamaterial increases with frequency due to the shortening of the wavelength even though the imaginary part of μ̂ is lower at these frequencies.

An antenna measurement facility has been constructed that can be remotely controlled over the Internet. The primary purpose of the facility is to make it easier for instructors to include antenna construction and measurement projects in courses on antennas, RF systems, and electromagnetic fields. The facility is capable of measuring gain, patterns, and return loss for antennas of the type used in personal electronic devices in the 800 MHz to 6.5 GHz range. Experience with remotely supporting courses at Carnegie Mellon University, Georgia Institute of Technology, and Worcester Polytechnic Institute showed that both students and instructors felt that use of the remote laboratory added value to the students' experiences.

In-cabin wireless networks are attractive in that they enable the passengers to use their own personal equipment during road trips. It is therefore important to obtain information about the wave propagation in the vehicle cabin. This paper presents preliminary results of ray-tracing simulations of the in-vehicle radio channel. The simulations have been performed with respect to the passenger cabin of a Pontiac Montana (a minivan).

An American football was tracked using a long-range magneto-quasistatic position and orientation measurement system. A low-weight emitter that emitted a low-frequency quasistatic magnetic field was embedded within an American football. The emitter weighed a total of 26.5 g, which was within the manufacturing tolerance of an American football, and did not alter the dynamics of the ball. Measurements of a person carrying the football along the goal line of an American football field are described, along with a description of the construction of the magneto-quasistatic tracking system. The technique demonstrated measurements with a distance accuracy of 15 cm and an azimuthal orientation accuracy of 2.45° for measurements conducted along the goal line of an American football field.

Remote experience and visualization in sporting events can be significantly improved by providing accurate tracking information of the players and objects in the event. Sporting events such as American football or rugby have proved difficult for camera- and radio-based tracking due to blockage of the line-of-sight, or proximity of the ball to groups of players. Magnetoquasistatic fields have been shown to enable accurate position and orientation sensing in these environments [1]-[3]. In this work, we introduce a magnetoquasistatic tag developed for tracking an American football during game-play. We describe its integration into an American football and demonstrate its use in game-play during a collegiate American football practice.