Hiroshi Toyao

Design and Characterization of Miniaturized Patch Antennas Loaded With Complementary Split-Ring Resonators

An investigation into the design of compact patch antennas loaded with complementary split-ring resonators (CSRRs) and reactive impedance surface (RIS) is presented in this study. The CSRR is incorporated on the patch as a shunt LC resonator providing a low resonance frequency and the RIS is realized using the two-dimensional metallic patches printed on a metal-grounded substrate. Both the meta-resonator (CSRR) and the meta-surface (RIS) are able to miniaturize the antenna size. By changing the configuration of the CSRRs, multi-band operation with varied polarization states can be obtained. An equivalent circuit has been developed for the CSRR-loaded patch antennas to illustrate their working principles. Six antennas with different features are designed and compared, including a circularly-polarized antenna, which validate their versatility for practical applications. These antennas are fabricated and tested. The measured results are in good agreement with the simulation.

Compact Circularly-Polarized Patch Antenna Loaded With Metamaterial Structures

A metamaterial-inspired low-profile patch antenna is proposed and studied for circularly-polarized (CP) radiation. The present antenna, which has a single-fed configuration, is loaded with the composite right/left-handed (CRLH) mushroom-like structures and a reactive impedance surface (RIS) for miniaturization purpose. The CP radiation is realized by exciting two orthogonally-polarized modes simultaneously which are located in the left-handed (LH) region. The detailed antenna radiation characteristics are examined and illustrated with both simulated and experimental results. The CP performance can be controlled in several different ways. This antenna exhibits an overall size of 0.177λ0 × 0.181λ0 × 0.025λ0 at 2.58 GHz and a radiation efficiency around 72%. Finally, based on the proposed CP patch antenna, a compact dual-band dual linearly-polarized patch antenna has also been designed and fabricated. Promising experimental results are observed.

Open stub electromagnetic bandgap structure for 2.4/5.2 GHz dual-band suppression of power plane noise

A conventional open stub electromagnetic bandgap (EBG) structure has a compact unit cell size. However, each bandgap of this structure may not be controlled independently of the others, making the structure impossible to be used for several predetermined frequency ranges required in wireless communication. In this paper we upgrade the EBG structure by using two open stubs and realize dual-band operation. In present case, unit cell size is 2.3 mm × 2.7 mm almost same as the previously described open stub EBG structure. Through equivalent-circuit analytic calculation and finite element method (FEM) simulation, we estimated bandgaps of the proposed structure. According to obtained data, they cover 2.4- and 5.2-GHz bands used in wireless LAN. Then we confirmed these results by measuring insertion loss of corresponding patterns disposed in a fabricated evaluation board.

“Open-stub electromagnetic bandgap” structures loaded with capacitive transmission line segments for bandgap frequency control

An electromagnetic bandgap (EBG) structure is an effective tool to suppress power plane noise (PPN) in gigahertz region. Here we propose a concept and a new EBG structure enabling to control bandgaps for applications, including multiband wireless communication. The EBG strcture based on an open-end transmission line has such an advantage as its compactness. Also, in this structure voltage distribution along the transmission line is dependent on frequency, and such dependency can provide control of the bandgap by an appropriate selection of a position of a loaded capacitance. In this paper, the capacitance in the EBG structure is obtained by an additional open-end transmission line segment. The proposed structures achieve both the compactness and multiband operation. Here we present results of equivalent circuit analysis and measurement of evaluation boards for developed EBG structures.

Miniaturized zeroth order resonance antenna over a reactive impedance surface

A miniaturized zeroth order resonance (ZOR) antenna designed on a reactive impedance surface (RIS) is proposed and presented. It is essentially a composite right/left-handed (CRLH) structure which enables the miniaturization by pushing down the left-handed (LH) region. This is achieved by increasing the LH inductor using a shorted meander line. The RIS consists of two-dimensional periodic printed metallic patches. It is an inductive surface which can also miniaturize the antenna size and improve the radiation efficiency. The antenna radiates omni-directional waves in the horizontal plane. Simulated and measured results are provided, which show a good consistency.

Compact and Multiband Electromagnetic Bandgap Structures With Adjustable Bandgaps Derived From Branched Open-Circuit Lines

Branched open-circuit lines are introduced for artificial negative-permittivity media, which is a type of metamaterial, to simultaneously achieve compact unit cells and adjustable bandgaps to cover multiband frequencies. Our electromagnetic bandgap (EBG) structures, the unit cells of which are under

Compact antenna using split-ring resonator integrated with bent dipole-like metal pattern

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Band-Selectively Tunable Electromagnetic Bandgap Structures With Open-Circuit Lines and Variable Capacitors

of the wavelength in a substrate, were designed to display characteristic effects, including bandgap-separation control and enhancement of the bandgap width. We analytically and experimentally investigated these effects. The compactness is derived from the length-dependent resonances of the open-circuit line instead of inductance-capacitance resonances, and the adjustable bandgaps originate from the introduction of the branched shape, which destroys the periodic capactive-inductive-impedance alternation of not-branched open-circuit lines. The proposed EBG structures are highly promising for frequency-selective devices, such as for electromagnetic noise suppression in power distribution networks.

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We propose a novel compact antenna using a split-ring resonator (SRR), a common metamaterial structure. By integrating an SRR with a bent dipole-like metal pattern, miniaturization and performance enhancement are achieved. From simulated results, we confirm wide bandwidth and high efficiency close to the theoretical limit. We also designed and evaluated the proposed antenna with a reflector and extended feed line for applications requiring directed radiation.

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We discuss the band-selective tuning of specific bandgaps (BGs) in an electromagnetic BG (EBG) structure. Two variable capacitors (VCs) attached to an open-circuit line (an element of the EBG structure) are selectively excited by voltage standing waves in the open-circuit line, and they can selectively tune the first and second BGs. With the change in a VC by 4.8 pF, the first BG moves from 0.55 to 0.39 GHz with almost no shift of the second one, while the second BG is tuned from 1.61 to 1.29 GHz with a 1.8-pF change in the other VC. This tuning technique can be potentially applied to other microwave devices using resonant phenomena such as antennas and filters.