Inkyu Yang

A Metamaterial-Based 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-composite right- and left-handed(CRLH) configuration-based radiator much smaller than the quarter-guided wavelength adopted a lot 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.

Reducing the Interference in Compact MIMO Antennas of CRLH-TL-Based Broadside-Capacitive and Slot Couplings

We significantly diminish the interference between the radiating elements for a miniature MIMO antenna system on the basis of composite right- and left-handed transmissionline(CRLH-TL). The element radiating structure has capacitively coupled parallel metal parts and slotted ground that correspond to the CRLH-TL to prohibit the volume from growing for an LTE high band. The metal line suspended over the radiating elements is optimally designed to drop the unwanted mutual coupling to -23 dB, as the entire MIMO antenna structure is small and it performs electrically useful. The test case is done for 2.5 GHz.

Miniature Staircase-Shaped Wideband MIMO Antenna with Excellent Isolation, Compliant to the SAR Standard

This paper proposes a novel compact MIMO antenna which has miniaturized radiators and their row correlation coefficient, working for the LTE mobile communication, and its SAR is observed. Each of the proposed radiators has a shape of staircase and the bandwidth is twice larger than the conventional PIFA as 600MHz(21%) in 2.5 GHz - 3.15 GHz. And the area of the radiators is proper for a handheld device. Also, by adding a planar mushroom decoupling structure between the radiators, the isolation is improved. The design has been carried out using the commercial full-wave time-domain EM solver and the finalized MIMO antenna has the return loss less than -10 dB in the LTE band, the isolation better than 20 dB and the efficiency more than 90% with the gain of 4.3 dB. Regarding the SAR of the antenna, it is observed that the average SAR value of 1g is estimated as 1.37W/Kg, which is lower than the SAR standard.

Triple-band spiral antenna array fed by composite right- and left-handed power-divider for gain-enhancement as a flat structure

Summary form only given. Spiral antennas have been adopted a lot over the linear polarization counterparts, since the circular polarizations of their far-field patterns can improve the versatility of wireless communication in multiple-fading and multiple-reflection environment. Nonetheless, there are shortcomings from the conventional spiral antenna systems, which are poor channel selectivity and large physical volumes. Most of the spiral antennas take tapered-shaped metal patterns to have the wideband, since the basic winding of a uniform line to a circle of a growing radius reduces to a narrow-band. The footprint of the aforementioned antenna should be large for a higher gain. With this, because the balanced feed assures the desirable spiral antenna performance, the differential feed or vertical balun is connected to the input port of the antenna, which makes it accompany a cavity beneath the metal pattern. Especially, when the main radiator is above the bottom PEC of the cavity by the quarter-wavelength, the volume of the cavity-backed and balun-fed spiral antenna becomes improper for portable devices and attachment to a vehicle. In this paper, a novel flat spiral antenna array is proposed. It is featured by a triple-band for channel selectivity and gain enhancement as well as a low-profile. To increase the antenna gain, the unit spiral antenna should be expanded to an array. Before this, the array element should have three bands of 2.4 GHz, 4.8 GHz, and 7.2 GHz, not in the form of a bulky cavity-backed geometry, but a planar structure. If the footprint of this element antenna is not enlarged, it has about the gain of 3 dBi. If this is wanted to grow up to 7 dBi, an array is needed. Two elements of planar spiral antennas are needed, and they need to be fed by a powerdivider. Coming up with a planar triple-band spiral antenna is a challenge, but the design of the power-divider to handle the three bands is harder than anything else, considering the existing power-divider technology. A thought can be given that the operational band of a power-divider is wide enough to include the three bands. However, the conventional technique for a wide-band power-divider elongates the physical structure by cascading sections or smooth transition of the branches. To eliminate this problem, a short CRLH(composite rightand left-handed) powerdivider is suggested to be combined with flat spiral antennas for the triple-band array.

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.

Metam aterial-based planar waveguide filters and components for light-weight multi-channel vehicular transceivers

In this paper, it is presented that novel and compact filters and channel combiners are developed for a lighter multi-channel vehicular transceiver working at an X-band and a Ku-band as high frequencies instead of bulky metallic waveguides. The components are in the form of so-called substrate integrated waveguide(SIW) as planar layered structures. For the purpose of reducing the physical sizes of the aforementioned components further from the conventional SIWs for the frequency bands near the millimeter-wave region, the internal parts of the proposed SIWs play the components of the CRLH-line as a metamaterial structure, which turns out much smaller than the SIWs of the same frequency. This is indebted to the phase-lead effect from the LH zone. Firstly, the compact SIW filters are implemented for the channels, particularly, an X-band and a Ku-band in this case, but applicable to millimeter-wave bands, if needed. Secondly, they are combined in another SIW to keep the two channels least distorted as a compact duplexer. The frequency responses of the filters and the channel combiner are given with the photographs of the fabricated versions. The size-reduction effect by the proposed method is mentioned with the conventional waveguide counterparts. It is easy to predict that the design scheme can be adopted for light-weight and low-profile vehicular transceivers.

Design of a Metamaterial-Based Compact Dual-Band 3-way Power Divider for Lighter L-band Military Satellite Transceivers

This paper proposes a compact dual-band 3-way power divider that helps lowering the weight of a transceiver for the L-band or multi-purpose satellite communication. Instead of the multi stages or tapering which ends up with loss accumulation and size-growth, the non-linear dispersive phases from the metamaterial CRLH(composite right and left-handed) properties are obtained by the accurate formulation and implemented by the short transmission line segments. Firstly, the CRLH dual-band two-way unequal power divider and equal power divider are separately designed. And then, the input of the two-way equal power divider is plugged in the output port of the unequal one, and the entire geometry is slightly adjusted for the desirable performance. The circuit analysis and full-wave simulation are used to predict the frequency responses and validated by the measurement of the prototype. Besides, the size-reduction effect is addressed.

A Method to Suppress the Spurious Radiation due to the Current Pulse on the Cable using the Frequency Selective Metamaterial Structure

The spurious electromagnetic radiation is generated due to the RF unbalanced current on a conductive cable connecting an electronic device to another. A metamaterial-based filtering geometry with frequency selectivity is suggested to reduce the radiation with a bandgap structure, where the right-handed inductance and capacitance stem from the transmission-like configuration between the cable and the metal protrusion, and the left-handed components come from the narrow cavities. The effect of the structure on the unbalanced current pulse and its spurious radiation is presented in the FDTD-method frame work.

Design of DNG-type Substrate-Integrated-Waveguide Resonators to Replace the Conventional Metallic Waveguide for the Military Satellite Transceiver

A new and significantly small guided and resonant structure is suggested to take over bulky metallic hollow waveguides used in military satellite transceivers. Below Ku-band, the conventional waveguides resulting in quite heavy transceivers will be replaced by the low profile SIW(substrate integrated waveguide) structures that are distinguished from the others in that the suggested ones have much lower cut-off frequencies by the circuital configuration of DNG(dobule negative) constitutive parameters and become even smaller than the other SIWs. The design scheme is validated by the circuit and full-wave simulations from the guided, resonant, and coupled structures. Besides, a bandpass filter as the suggested coupled structure is fabricated with a cheap substrate in a low-budget fabrication process and its frequency response is measured as verification of the purpose of the design.

Compact duplexer for the UWB system using novel CRLH bandpass filters

In this paper, a miniatuirized duplexer for the lower-half UWB is implemented. Firstly, to reduce the size, novel metamaterial CRLH bandpass filter structures are designed for the duplexer of the 2 channels (3.2GHz ~ 3.7GHz and 4.3GHz ~ 4.7GHz). Secondly, they are further changed to have transmission zeros to improve channel selectivity. Finally, the optimized geometry of the duplexer is obtained to hold the proposed bandpass filters. The presented design methodology is validated through the EM simulation and the measurement. Besides, the performance and size-reduction effect of proposed design is addressed.