Omar M. Ramahi

A novel power plane with integrated simultaneous switching noise mitigation capability using high impedance surface

A novel technique for suppressing power plane resonance at microwave and radio frequencies is presented. The new concept consists of replacing one of the plates of a parallel power plane pair with a high impedance surface or electromagnetic band gap structure. The combination of this technique with a wall of RC pairs extends the lower edge of the effective bandwidth to dc, and allows resonant mode suppression up to the upper edge of the band-gap. The frequency range for noise mitigation is controlled by the geometry of the HIGP structure.

Electromagnetic interference (EMI) reduction from printed circuit boards (PCB) using electromagnetic bandgap structures

As digital circuits become faster and more powerful, direct radiation from the power bus of their printed circuit boards (PCB) becomes a major concern for electromagnetic compatibility engineers. In such multilayer PCBs, the power and ground planes act as radiating microstrip patch antennas, where radiation is caused by fringing electric fields at board edges. In this paper, we introduce an effective method for suppressing PCB radiation from their power bus over an ultrawide range of frequencies by using metallo-dielectric electromagnetic band-gap structures. More specifically, this study focuses on the suppression of radiation from parallel-plate bus structures in high-speed PCBs caused by switching noise, such as simultaneous switching noise, also known as Delta-I noise or ground bounce. This noise consists of unwanted voltage fluctuations on the power bus of a PCB due to resonance of the parallel-plate waveguiding system created by the power bus planes. The techniques introduced here are not limited to the suppression of switching noise and can be extended to any wave propagation between the plates of the power bus. Laboratory PCB prototypes were fabricated and tested revealing appreciable suppression of radiated noise over specific frequency bands of interest, thus, testifying to the effectiveness of this concept.

Mutual Coupling Reduction Between Microstrip Patch Antennas Using Slotted-Complementary Split-Ring Resonators

A novel structure based on complementary split-ring resonators (SRRs) is introduced to reduce the mutual coupling between two coplanar microstrip antennas that radiate in the same frequency band. The new unit cell consists of two complementary SRR inclusions connected by an additional slot. This modification improves the rejection response in terms of bandwidth and suppression. The filtering characteristics of the band-gap structure are investigated using dispersion analysis. Using the new structure, it was possible to achieve a 10-dB reduction in the mutual coupling between two patch antennas with a separation of only 1/4 free-space wavelength between them. Since the proposed structures are broadband, they can be used to minimize coupling and co-channel interference in multiband antennas.

Metamaterial Particles for Electromagnetic Energy Harvesting

Antennas developed for electromagnetic field energy harvesting, typically referred to as rectennas, provide an alternative electromagnetic field energy harvesting means to photovoltaic cells if designed for operation in the visible frequency spectrum. Rectennas also provide energy harvesting ability or power transfer mechanism at microwave, millimeter and terahertz frequencies. However, the power harvesting efficiency of available rectennas is low because rectennas employ traditional antennas whose dimensions is typically proportional or close to the wavelength of operation. This invention provides a device for electromagnetic field energy harvesting that employs a plurality of electrically-small resonators such as split-ring resonators that provide significantly enhanced energy harvesting or energy collection efficiency while occupying smaller footprint. The invention is applicable to electromagnetic energy harvesting and to wireless power transfer.

Electromagnetic Coupling Reduction in High-Profile Monopole Antennas Using Single-Negative Magnetic Metamaterials for MIMO Applications

Single-negative magnetic metamaterials are used in order to reduce mutual coupling between high-profile antennas used in multiple-input multiple-output systems. The magnetic permeability of the developed single-negative inclusions have negative effective response over a specific frequency band. The inclusions considered here are composed of broadside coupled split-ring resonators. The single-negative magnetic inclusions are inserted between closely-spaced high-profile monopole antenna elements. It is shown that mutual coupling between the antenna elements can be reduced significantly by incorporating such magnetic inclusions. Effective response of the constitutive parameters of the developed magnetic inclusions are incorporated within the numerical models. Good agreement is obtained between the experimental and numerical results.

Material Characterization Using Complementary Split-Ring Resonators

A microwave method based on complementary split-ring resonators (CSRRs) is proposed for dielectric characterization of planar materials. The technique presents advantages such as high measurement sensitivity and eliminates the extensive sample preparation procedure needed in resonance-based methods. A sensor in the shape of CSRRs working at a 0.8-1.3 GHz band is demonstrated. The sensor is etched in the ground plane of a microstrip line to effectively create a stopband filter. The frequencies at which minimum transmission and minimum reflection are observed depend on the permittivity of the sample under test. The minimum transmission frequency shifts from 1.3 to 0.8 GHz as the sample permittivity changes from 1 to 10. The structure is fabricated using printed circuit board technology. Numerical findings are experimentally verified.

Modeling Graphene in the Finite-Difference Time-Domain Method Using a Surface Boundary Condition

An effective approach for finite-difference time-domain modeling of graphene as a conducting sheet is proposed. First, we present a new technique for implementing a conducting surface boundary condition in the FDTD method; then, the dispersive surface conductivity of graphene is imposed. Numerical examples are presented to show the stability, accuracy, applicability, and advantages of the proposed approach. Validation is achieved by comparison with existing analytic methods.

Near- and far-field calculations in FDTD simulations using Kirchhoff surface integral representation

Kirchhoffs surface integral representation (KSIR) is used to calculate the near and far fields from the finite difference time domain (FDTD) simulation. The KSIR is very simple to implement and its distinct advantage is that the calculation of any of the six field components depends on the value of the same field component over a closed surface. This avoids interpolation errors when using the popular Yee scheme for FDTD. In addition to its efficiency and simplicity of implementation, the KSIR leads to highly accurate near fields that reduce absorbing boundary condition (ABC) errors.

Design and modeling of high-impedance electromagnetic surfaces for switching noise suppression in power planes

This paper presents a detailed design and modeling approach for power planes with integrated high-impedance electromagnetic surfaces (HIS). These novel power planes, which were introduced recently, have the unique ability of providing effective broadband simultaneous switching noise (SSN) mitigation. Full-wave electromagnetic simulation is used to study the impact of the geometry on the performance of these novel power planes. It is demonstrated that power planes using inductance-enhanced HIS can be designed for broadband mitigation of the SSN from the upper hundred megahertz to the gigahertz frequencies. Physics-based compact models for the unit cell of power planes with integrated HIS are developed and several of them connected in a two-dimensional array to build full models for large and multilayer power planes. The compact model offers fast analysis of power planes. As an example, we show that the full-wave simulation time of a 10/spl times/10 cm power plane with integrated HIS can be dramatically reduced from 24 to 48 h using a commercially available three-dimensional full-wave solver to less than 1 min when using the compact circuit model developed here.

Enhanced-Gain Microstrip Antenna Using Engineered Magnetic Superstrates

This letter presents a novel engineered magnetic superstrate designed to enhance the gain and efficiency of a microstrip patch antenna without any substantial increase in the profile of the whole structure (the antenna with the superstrate). The modified split ring resonator (MSRR) inclusions are used in the design of the engineered magnetic superstrate. Numerical full-wave simulations as well as analytical models are used to analyze the entire radiating system. Considering as an example a microstrip antenna operating within the UMTS band, the broadside gain of the antenna was improved by 3.4 dB and the efficiency was improved by 17% when using the engineered superstrate. The total height of the proposed structure, antenna with superstrate, is lambda0/7, where lambda0 is the free-space wavelength at the resonance frequency of the antenna.