Seongryong Yoo

CRLH ZOR ANTENNA OF A CIRCULAR MICROSTRIP PATCH CAPACITIVELY COUPLED TO A CIRCULAR SHORTED RING

In this paper, a novel Metamaterial (MTM) CRLH Zeroth Order Resonance (ZOR) Circular microstrip patch antenna is proposed to have a monopole antenna pattern due to the completely closed loop of a magnetic current around the structure, and reduced proflle and size due to the left-handedness. Difierent from other ZOR antennas of 1D periodic arrays with shorted patches, we suggest 1 circular patch capacitively coupled to 1 circular shorted ring to have ZOR and i1st resonance modes. The antenna is designed and modeled with equivalent circuits for the coaxial-fed central patch and the circular shorted ring and verifled by the comparison with 3D EM simulation of the physical structure. The no-phase variation at the ZOR (2.4GHz) and the i1st resonance mode (2GHz) as the metamaterial properties are proven with electric fleld distributions and far-fleld patterns. The measurement shows there exist the ZOR and the i1 resonance modes despite the frequency shift from the simulation, which is proven by the monopolar radiation pattern and broadside radiation pattern, respectively. So the advantages of the proposed antenna will be addressed with the low-proflle monopole at the ZOR and the size reduction efiect at the i1st resonance.

A novel metamaterial CRLH ZOR circular patch antenna capacitively coupled to a circular ring

In this paper, a novel circular patch antenna is proposed to have Zeroth Order Resonance(ZOR) generated based on the Metamaterial Composite Right- and Left-Handed(CRLH) structure. Making the in-phase electric field over the entire antenna other than a half-wavelength as the fundamental resonance mode of a ordinary microstrip patch or its positive multiple, the metallic patch is suggested to be capacitively coupled with only one surrounding circular ring, different from the previous 1D ZOR antennas commonly having several metal cells in line. The performance of the proposed antenna is simulated by a 3D field solver that inputs the sizes of the physical structure corresponding to the equivalent circuit designed to have ZOR at 2.4 GHz. Consequently, the resonance frequency, the gain and the antenna efficiency are observed 2.4 GHz, 5 dB and 98%, respectively. Besides, the important property of the proposed antenna is addressed as the combination of the low-cost low-profile as an advantage of microstrip patch antennas, and the omni-directional field pattern typical of monopole antennas.

A metamaterial-inspired handset antenna with the SAR reduction

A method to reduce the specific absorption rate(SAR) of the antenna for WiMAX mobile communication is proposed in this paper. The SAR reduction is achieved by miniaturizing the physical size of the antenna for the given resonance frequency by devising a metamaterial-inspired radiator much smaller than the quarter-guided wavelength appearing in the conventional planar inverted F antenna(PIFA) or modified monopole antenna. The proposed antenna is placed near the head-phantom and its SAR is evaluated by the full-wave simulations(SEMCAD X), where the metamaterial-inspired antenna is shown to have the lower value than a modified monopole as the reference in terms of the SAR.

Compact MIMO antenna of the open-loop and meandered-line 1-layer radiators with improved isolation

We propose a compact MIMO antenna with high inter-antenna isolation. It is featured by small radiating elements each of which comprises a meandered line and an open-loop, and a modified T-shaped decoupling structure to lower the interaction between the radiators. For a WiMAX band, the size of the entire MIMO antenna is 0.22λg showing effective miniaturization. And the gain, efficiency and isolation are 3.7dBi, 56% and 17dB, acceptable to the industrial standard.

Flat metamaterial antenna with dual-circular-polarization at the −1st-order-resonance mode, applicable to reconfigurable RF systems

In this paper, a novel compact and dual-circular-polarized antenna is proposed. To be physically small, the electromagnetic wave is radiated at the -1st-order resonance mode of a planar composite right- and left-handed(CRLH) antenna, instead of the +1st resonance mode. To enable two circular polarizations in one structure, the orthogonal coaxial feed points for the 90°-angular difference are decided at the -1st resonance mode, and connected to the output ports of a hybrid branch-line coupler for 90°-phase difference. The functional block diagram is given, and is followed by the steps of full-wave simulations for design and the performance is verified by the measurement of the fabricated antenna with the test frequency of the 2.37-2.40 GHz band. The LHCP and RHCP will be observed with good inter-polarization isolation and axial ratio, and the applicability to a compact reconfigurable RF device will be considered.

Novel common-mode current detector using metamaterial CRLH transmission-line structure

A novel planar common-mode current(Ic) and differential-mode current(Id) detector is designed to provide a quick check of Ic and Id from the differential-mode signalling, size-reduction effect and possibility of lower manufacturing cost. This is made possible by implementing a branch-line balun which has metamaterial Composite Right- and Left-Handed(CRLH) 1-layer microstrip- structure phase shifter as small as approximately λg/14. The proposed balun clearly differs from others who meander the delay line or make slits on the metal ground. When the proposed balun is connected to the output ports of the differential-mode signal lines through its inputs Port U and Port L, Id and Ic are obtained at Port Δ and Port Σ of this compact balun, respectively. The design method is validated by the circuit and full-wave simulations(SEMCAD X) with the dispersion diagram showing metamaterial properties of the structure. Also, the even and odd modes in differential-mode signalling are treated as examples of the Ic and Id Detector. The size-reduction effect is addressed also.

Compact UHF 5th-Order bandpass filter with sharp skirt

We propose a bandpass filter miniaturized by the composite right-handed and left-handed(CRLH) zeroth order resonators(ZORs). A 5th-order bandpass filter form a cascaded triplet(CT) to have a significantly sharp skirt for high frequency selectivity. First, we design an in-line ZOR bandpass filter whose total size is nearly 0.2 of the parallel-edge coupled filter. Second, we create multiple transmission zeros(TZs) by changing the three innermost ZORs of the in-line filter to a CT. As a result, the proposed filter has the insertion loss less than 1.5dB and the return loss less than −15dB. The simulation and measurement validate the proposed design method, and the CRLH ZOR properties are proven by the no-phase variation electric field and dispersion diagram.