Experimental demonstration of the origin of photonic bandgap creation and associated defect modes in microwave planar circuits

Abstract

We have measured the relative complex permittivity of epoxy resinous material under changes in temperature. The variation of the temperature of the single-layer absorber has been analyzed using the FDTD-HTE method. As a result, the following three aspects were confirmed:1. If the relative complex permittivity of the sample depends on the temperature, its real part increases from 14.7 to 16.8, and its imaginary part increases from 1.5 to 4.2 under the condition that the temperature increases from 24°C to 160°C. 2. The temperature inside the single-layer absorber increases rapidly with increased irradiation power. It is observed that the heat generated inside the absorber tends to equal to heat radiated from the surface of one after 120 min of irradiation. The stabilization temperatures are about 40°C at 100 W/m 2 , about 110°C at 500 W/m 2 , and about 170°C at 1000 W/m 2 . 3. The absorption of the absorber becomes 25 dB in the initial state. Then the absorption increases gradually, shows a peak value of about 60 dB, and decreases gradually after that.In the near future, we would like to measure the temperature characteristics of various materials for the radiowave absorbers. Moreover, we will also try to examine the absorption characteristics of other types of radiowave absorbers under irradiation power.

Ferromagnetic nanowire-loaded membranes for microwave electronics

“…As explained in Section 3, the presence of the NWs modify both the effective permeability and the permittivity of the composite substrate, as compared to the bulk porous substrate. This induces a periodic contrast in refractive index and associated characteristic (or wave) impedance, that is responsible for a bandgap in the transmission of the microwave signal through the microstrip line lying on the so-called MPBG substrate [13,14]. Hence, measurements of transmission factor S 21 on the prototype of Fig.…”

Investigation of Microwave Absorption Mechanisms in Microcellular Foamed Conductive Composites

“…The technique used to develop the model presented in Section 3.1 for conductive foams is explained with details in references [14,15]. In brief, the foam medium is approximated by a periodical structure, alternating hollow thick sections filled with air, and thin composite sections corresponding to the wall of the foam that are constituted of PC, PP or PCL loaded with conductive charges.…”

“…They link, in matrix formalism, the incoming, transmitted and reflected waves and are helpful to gain precise understanding of the electromagnetic behavior of a multilayered structure, such as that shown in Figure 1. The technique proposed in [14,15] and applied in [16,17] enables us to calculate the transmission of microwave power through a cascade of air and wall sections, by taking the matrix product of their corresponding chain matrices that are formulated as a function of their respective thickness, of the electromagnetic parameters for the conductive polymer forming the wall of the foam and of the frequency of operation of the composite material used as a microwave absorber. As the technique also provides the amount of power reflected by the composite multilayer, the absorbed power can be obtained.…”

Smart Nanocomposites for Nanosecond Signal Control: The Nano4waves Approach

“…[1], artificial or composite materials dedicated to the control of wireless propagation of signals (popularized over the last decade under the term "metamaterials" in the scientific community) are multi-functional materials tailored to display electromagnetic (EM) properties not found in nature, through a nonconventional modification of their macroscopic effective permittivity and/or permeability, sometimes reaching negative values [2]. Superlensing beyond the diffraction limit [3], invisible cloaking of objects [4,5], left-handed propagation reducing the size of devices to one tenth of their operating wavelength [6], frequency selective surface (FSS) [7,8] or electromagnetic bandgap (EBG) structures [9][10][11][12] are some of the outstanding developments in progress over various frequency ranges, going from GHz to optics.…”