This tutorial clarifies the axiomatic definition of (v(α); i(β)) circuit elements via a lookup table dubbed an A-pad, of admissible (v; i) signals measured via Gedanken probing circuits. The (v(α); i(β)) elements are ordered via a complexity metric. Under this metric, the memristor emerges naturally as the fourth element, characterized by a state-dependent Ohm's law. A logical generalization to memristive devices reveals a common fingerprint consisting of a dense continuum of pinched hysteresis loops whose area decreases with the frequency ω and tends to a straight line as ω ~ ∞, for all bipolar periodic signals and for all initial conditions. This common fingerprint suggests that the term memristor be used hence-forth as a moniker for memristive devices.

The Fourth Element.

A novel compact, planar, and coplanar waveguide (CPW)-fed dual-band antenna is designed and proposed using composite metamaterial. Such composite metamaterial consists of an inner split-ring resonator (SRR) and an outer closed-ring resonator (CRR). The composite metamaterial can provide dual-band operation at 2.595-2.654 and 3.185-4.245 GHz with reflection coefficient better than -10 dB by the two resonant modes of SRR and CRR, respectively. A CPW-fed line with trapeziform ground plane and tapered impedance transformer line is employed to improve the impedance matching of the antenna. The uniqueness of this design is that the inner SRR with size much smaller than the resonant wavelength is used for obtaining the lower narrow frequency band, which makes the dual-band antenna very compact. Antenna parameters, including reflection coefficient, radiation pattern, radiation efficiency, and gain, are analyzed with numerical simulation and experimental measurement. Good agreement between the simulation and measurement is observed.

A Compact, Planar, and CPW-Fed Metamaterial-Inspired Dual-Band Antenna

This communication introduces an approach for designing miniaturized single-feed multiband patch antennas. The size reduction is obtained by loading shorting metalized vias on one edge of the radiating patch, while multiband is obtained by etching inverted multiple U-shapes. A dual-band antenna with a large measured frequency ratio of 2.74 is first discussed. Then triple-band, and further quad-band antennas are, respectively, designed. The antennas have sufficient electrical small size when considering the radius of the minimum enclosing sphere to the radiating patch. A radius value of 0.09λ
 0
 is obtained for the quad-band antenna with respect to the lowest operating frequency centered at 3.04 GHz. Simulated and measured results of the antennas' reflection coefficient and radiation patterns are provided. Good agreement between the simulation results and measurement results is achieved. The antennas' measured peak gains and efficiencies vary from 1.43 to 3.06 dBi and 42% to 74%, respectively. Compared with other designs, the proposed antennas exhibit multiband performance by using a simple single-feed structure, realize different combinations of highly isolated frequency bands with wide tunability of frequency ratios, and have directional stable radiation patterns that are compact and of electrically small size. Indeed, they have the potential to meet the practical requirements for wireless applications.

Miniaturized Single-Feed Multiband Patch Antennas

Synaptic devices based neuromorphic computing applications in artificial intelligence

Diverse models have been proposed over the past years to explain the exhibiting behavior of memristors, the fourth fundamental circuit element. The models varied in complexity ranging from a description of physical mechanisms to a more generalized mathematical modeling. Nonetheless, stochasticity, a widespread observed phenomenon, has been immensely overlooked from the modeling perspective. This inherent variability within the operation of the memristor is a vital feature for the integration of this nonlinear device into the stochastic electronics realm of study. In this paper, experimentally observed innate stochasticity is modeled in a circuit compatible format. The model proposed is generic and could be incorporated into variants of threshold-based memristor models in which apparent variations in the output hysteresis convey the switching threshold shift. Further application as a noise injection alternative paves the way for novel approaches in the fields of neuromorphic engineering circuits design. On the other hand, extra caution needs to be paid to variability intolerant digital designs based on nondeterministic memristor logic.

Stochasticity Modeling in Memristors

This paper presents two simple SPICE circuit models of the memristor using two different kinds of integrators. These models expand and simplify the previous methods of solving the memristor's modeling equations presented by Hewlett–Packard Lab. The behaviors of the two memristor models are investigated when they are excited by a sinusoidal voltage source. Both models satisfy the general features of memristive systems such as having a zero-crossing property in the form of an i–v Lissajous figure. In order to explore the unique characteristics and applications of the memristor in microwave devices, first we incorporate the memristor in a microstrip transmission line as a load. We do the analysis using a finite-difference time-domain simulator integrated with a nonlinear SPICE circuit solver. Furthermore, we design a reconfigurable microstrip bandpass filter based on a memristor-loaded resonator, and utilize a memristor as a carrier-wave modulator connecting the microstrip patch antenna to the ground.

Two Memristor SPICE Models and Their Applications in Microwave Devices

In this letter, we present a dual-band electrically small antenna (ESA) operating at 934 MHz and 1.55 GHz. The miniaturized radiation structure consists of a small ring and two concentric split-ring resonators on an FR-4 substrate. The resonant response of the proposed radiation structure is characterized by the coupling among two split-ring resonators and the small ring. A weak electric field interaction between two split-ring resonators is observed. This interaction provides an additional capacitance to further reduce the total dimension of the resonant electrical length. The calculated return loss of the proposed structure agrees well with the measured data. Measured radiation patterns are presented. The planar structure is promising for compact wireless devices and may find applications in wireless electrocardiograph sensors, multiband portable MIMO wireless systems, and RF energy-harvesting systems.

A Dual-Band Printed Electrically Small Antenna Covered by Two Capacitive Split-Ring Resonators

We first theoretically present a magnetic antenna based on a two dimensional DC superconducting quantum filter device. This antenna may detect the dynamical magnetic field instead of the absolute magnetic field. We call it B-antenna since it only responses to the external magnetic field. We show the robustness of 2D SQIF structure when the 2D SQIF chip encounters statistical distributions of the fabrication of individual Josephson junctions. Finally, we find that B-antenna can work properly even though the bias current is smaller than the critical current. Our research opens the dimensions of novel ultra-sensitive antennas by combing superconducting quantum interference filter devices and classic electromagnetic waves.

Meng Qing Yuan

Papers

Two Memristor SPICE Models and Their Applications in Microwave Devices

A Dual-Band Printed Electrically Small Antenna Covered by Two Capacitive Split-Ring Resonators

Magnetic antenna based on two dimensional DC superconducting quantum interference filter