Mitsuhiro Amano

A method of effective use of ferrite for microwave absorber

To meet the demands of various types of EM-wave absorber, a method of effective use of conventional ferrites for microwave absorber applications is investigated both by FDTD analysis and experiments. The effects of various kinds of parameters are clarified, particularly for permeability. A new matching characteristic is realized simply by punching out small holes in the conventional rubber ferrite without producing a new ferrite material in the region of the microwaves.

A novel microwave absorber with surface-printed conductive line patterns

A novel microwave absorber with surface-printed conductive line patterns is proposed. The advantage of this absorber is to be able to control the matching frequency both toward a higher frequency or a lower frequency region and to offer twin-peaks characteristic using a conventional single material. The matching characteristics are investigated particularly for making a slim absorber by FDTD analysis and experiments. A slim absorber of 2 mm thickness at 2.45 GHz is presented by computer-aided design.

Novel Right-Handed Metamaterial Based on the Concept of “Autonomous Control System of Living Cells” and Its Absorber Applications

A novel right-handed metamaterial similar to an “autonomous control system of a living cell” and capable of responding to electromagnetic waves is proposed with its fundamental configurations. Using microwave absorbers as an example, the possibility of equivalently controlling their material constants are investigated both theoretically and empirically. These absorbers are composed of unit cells based on the concept of an autonomous controllable metamaterial (ACMM). The theoretical approaches used to obtain ACMM-based absorber design data are revealed. In order to improve the absorber matching characteristics, the principle of obtaining the broadband matching characteristics with an absorption band of 1.3 GHz at 4.25 GHz is clarified. In addition, the methods for improving the matching degradation of the oblique incidence of a TM wave are investigated. For the TM wave oblique incidence, a new ACMM-based absorber configuration comprising unit cells with inductive fins is proposed. At an incident angle of 45°, a matching characteristic of -30 dB is achieved in the case of the TM wave. These ACMMs are controlled by using only two bias feeder wirings for PIN diodes.

Broadband EM-wave absorber based on integrated circuit concept

A broadband EM-wave absorber based on the structural concept of microwave integrated circuit is proposed. Following the fundamental principle and construction, the method of converting the actual microwave circuit into the integrated circuit type absorber is clarified. The problem of fine control of the resistance on the circuit is resolved by changing the configuration of a unit circuit element in a cross shape. Broadband matching characteristics with an absorption band 1.9 times as broad as a conventional Salisbury screen absorber with resistance and capacitance, and 2.6 times as a typical Salisbury absorber are obtained. The thickness of the present absorber is further reduced by introducing a ferrite material, while keeping almost the same broadband matching frequency.

A new concept for functional electromagnetic cell material for microwave and millimeter use

Proposed is a new concept for functional electromagnetic cell material (EMCM) for microwave and millimeter wave, capable of responding to an electromagnetic field. The fundamental concept of EMCM is described. This EMCM is capable of realizing various kinds of characteristics, including an anisotropic characteristic by switching on and off an active micro-circuit element. To examine the capabilities of this new material, FDTD analysis for the model of a microwave absorber with three dimensional active circuits is conducted. The microwave absorber is offered as concrete example of EMCM. Good dynamic matching characteristics are obtained around 1.5GHz. If the EMCM is embedded into certain kinds of material, the original material constant can be changed equivalently. This characteristic is verified experimentally, using a rubber ferrite absorber.

Detailed Investigations on Flat Single-Layer Selective Magnetic Absorber Based on the Equivalent Transformation Method of Material Constants

The effectiveness of equivalent transformation method of material constants (ETMMCs) is introduced through an example of the matching characteristics of a flat single-layer selective magnetic absorber (FSLSMA) with periodic conductive line frames (PCLFs). First, the matching characteristics of magnetic absorbers mounted on conductive line lattice, cross, square-frame, and double-layered PCLFs are simply introduced. Using finite-difference time-domain analysis and experimentations, the detailed matching characteristics focused on the FSLSMA with PCLFs are investigated. In particular, parametric investigations of the matching characteristics are conducted, which are related to the PCLF distributions, frame size, and material constants of the absorbers. Further, the present matching mechanisms and the design principles are clarified on the basis of the behavior of normalized input admittance in a Smith chart. The effectiveness of ETMMCs is demonstrated by designing a thin magnetic absorber with a thickness of 2 mm in the Industry, Science, and Medical frequency band of 2.45 GHz.