M.-C. Tang

A Dual-Band Epsilon-Negative Material Design Using Folded-Wire Structures

A novel design of epsilon-negative (ENG) material which can exhibit negative permittivity at two nearby bands is presented in this paper. With the unit shape as an unsealed rectangle frame, the components of this ENG material are two folded wires with different dimensions. Each folded-wire structure can achieve electric resonance at a certain frequency band by appropriately adjusting its dimensions. Its electromagnetic properties are then retrieved to demonstrate that the dual-band electric resonances can be obtained in our sample. With the aid of numerical simulation, the transmission property of the proposed dual-band epsilon-negative material is further investigated. And the result shows that the stop band for each folded wire (permittivity ε < 0) is easily adjusted by changing the designing parameters, without influence on the other nearby resonance frequency. It provides an advancement of dual-band and low mutual coupling resonances design. It is also promising that our approach will be effective to make this kind of dual-band ENG material applied into the areas of reconfigurable antennas and their arrays.

Novel folded single split ring resonator and its application to eliminate scan blindness in infinite phased array

In this letter, a simple electric metamaterial is proposed based on grounded folded single split ring resonator (SRR). The grounded SRR results in a compacter size. The proposed metamaterial exhibits a negative effective permittivity ∊e and positive effective permeability μe under electric excitation, and its electric resonant frequency is easily changeable from 4.5GHz to 5.7GHz by adjusting the length of the folded arms. It is used to suppress the mutual coupling between elements in microstrip array by blocking the propagation of the excited surface waves in microstrip substrate, and eliminate the scan blindness in the infinite microstrip phased array. The results indicate its excellent application potential to improve the scanning performance of microstrip array. More interestingly, compared with the reported techniques, such as electromagnetic band-gap (EBG) structures and defected ground structures (DGSs), the new metamaterial almost has nearly zero thickness as an isolation wall, which means that it is very suitable for constructing the high-density array.

A Compact Planar Negative Permittivity ZOR Antenna

In this paper, a compact planar zeroth-order resonator (ZOR) antenna based on epsilon negative (ENG) transmission line is presented. Thanks to the zeroth-order resonance with the aid of virtual ground, we accomplish this proposed antenna with the size of only 0.053λ0 × 0.157λ0 × 0.0096λ0 at 3.580 GHz without destroying the overall substrate. The ZOR characteristic has been analyzed using provided Bloch and Floquet theory. The measured (simulated) bandwidth is about 15 MHz (10 MHz), and the measured (simulated) peak gain is about 2.60 dBi (2.68 dBi), respectively.

The Feasibility of Envelope-Based Time Reversal

This paper proposes the conception of envelope time reversal (TR). Using different frequencies for signal modulation and demodulation, we give the theoretic derivation of one novel frequencydifference method, which demonstrates excellent TR focusing characteristic for envelope signal. In the following experiment, we carry out envelope TR on 100 MHz, 300 MHz and 500 MHz baseband signals separately. Being consistent with theoretic derivation, the experiment result verifies the feasibility of envelope TR.

A novel compact dual-band monopole antenna for slim internal mobile phone application

Compact wideband dual-band antenna suitable for thin internal mobile phone application is presented. This antenna has a simple structure and is formed by a printed monopole closely-coupled with a chip-inductor-loaded shorted strip. The antenna occupies a small board space of only about 180 mm2 on the system board and has negligible thickness, making it suitable for thin internal mobile phone. With the aid of embedding of a 15-nH chip inductor, the longer radiating strip has a length of about 39mm only (about 12% wavelength in free space at 900MHz), yet supports a resonant mode at about 900MHz for the lower frequency band to cover GSM900 operation (890–960MHz). The shorter radiating strip has a length of about 23 mm only (about 14% wavelength in free space at 1800MHz) and provides a resonant mode for wide frequency operation centered around 1800MHz for the antenna upper band to cover GSM1800/1900/UMTS operation (1710–2170MHz).

Ultra wide-band slot antenna based on liquid crystal polymer material for millimeter wave application

A millimeter wave ultra-wide band (UWB) tapered slot antenna is presented based on a multilayer liquid crystal polymer (LCP) circuit process. The multilayer circuit board consists of eight copper layers and seven LCP layers. In order to enhancing the bandwidth, two overlapped tapered slots with different flare angle are applied in the 3rd and the 5th copper layers, respectively. A low backward radiation characteristic is achieved due to using the ground-backed structure. A simple design guideline is detected and the dimension is optimized. The designed results indicate that the millimeter wave UWB slot antenna can work in the frequency band of 33GHz-60GHz (a relative bandwidth of 58%). The radiation patterns are calculated at three typical frequencies and the analysis demonstrates that an elliptical polarization performance is obtained within the total operation frequency band. The study also demonstrates that the LCP process is suitable for developing lightweight and high performance millimeter wave antennas.

Folded arrowhead-shaped wideband patch antenna

In this letter, a patch antenna with folded arrowhead-shaped structure is proposed to extend impedance bandwidth, decrease size and enhance gain. The antenna is optimized, fabricated and measured. The measured results indicate that an impedance bandwidth of 85% with Sll<−10 dB (5.1 GHz to 12.6 GHz) is obtained and the antenna gain fluctuates from 4.4dBi to 6.6dBi over the whole bandwidth. The designed antenna is suitable for IEEE 802.11a, HiperLAN/2 and high band of UWB. Moreover, parametric studies are provided for antenna design.

Improved 2-D FDTD model for analyzing uniform lossy transmission lines

In this paper, an improved two-dimensional finite-difference time-domain (2-D FDTD) model has been proposed for extracting the attenuation constant of the uniform lossy transmission line. Compared with the reported methods, the developed model is reliable and precise and the precise result can be achieved fast. As an example, the attenuation constant of a lossy microstrip line is extracted to perform the proposed method. The unique characteristic comes from the automatic convergence ability of the improved 2-D FDTD model.