In this letter, a microstrip-fed dual-polarized stepped-impedance (SI) slot antenna element with a low profile is firstly proposed. The antenna is composed of two pairs of SI slots excited by two orthogonal stepped microstrip feedlines. The broadband characteristic is achieved by combining the fundamental and spurious resonances of the SI slot resonators, while the good cross polarization is mainly due to the introduction of the shorting pins. Secondly, based on the proposed antenna, a four-element antenna array is designed, constructed and measured for base-station applications. Measured results demonstrate the bandwidths (return loss > 10 dB) of the antenna array are 46.9% (1.55-2.5 GHz) and 38.7% (1.69-2.5 GHz) for Port 1 and Port 2, respectively. The isolation between the two ports is greater than 35 dB whereas the cross polarization level maintains lower than -27 dB across the entire operating band. In addition, the antenna array prototype achieves average gains of 13.5 dBi and 13.9 dBi for horizontal polarization and vertical polarization, respectively.Index Terms-Dual-polarized slot antenna, low profile, high isolation, wide band, antenna array, stable gain.
Abstract-A compact polarization reconfigurable wideband omnidirectional circularly polarized (CP) antenna is presented in this paper. This design is based on a low profile omnidirectional CP antenna which consists of a microstrip antenna working on TM01/TM02 modes with slots etched on the ground plane. Vias are introduced between the patch and the ground plane, in order to excite the TM01 and TM02 modes which generate vertically polarized electric field within a wide frequency band. Sequential bended slots are introduced on the ground plane to radiate horizontally polarized electric field. As the result of the combined radiations from both the patch antenna and the sequential slots, left hand circularly polarized (LHCP) omnidirectional radiation pattern is obtained. The polarization reconfigurable is realized by introducing PIN diodes on the slots and through controlling the states of the PIN diodes, the effective orientation of the slots on ground plane can be adjusted and the polarization of this antenna can be altered between LHCP and RHCP (right hand circularly polarization). To verify this design concept, one LHCP and one polarization reconfigurable prototypes at 2.4GHz band were designed and fabricated. Experimental results show good agreement with the simulation results. The LHCP antenna exhibits a wide impedance bandwidth of 18.4% from 2.12 to 2.57 GHz and 3dB-axial ratio (AR) bandwidth of 450MHz. For the polarization reconfigurable antenna, 19.8% (2.09 GHz -2.55 GHz) overlapped 3 dB AR and 10 dB impedance bandwidths is obtained. The present design has thickness of only 0.024 and exhibit stable CP omnidirectional conical-beam radiation patterns within the operating frequency band with good circularly polarization.
In this paper, a method to reduce the inevitable mutual coupling between antennas in an extremely closely spaced two-element MIMO antenna array is proposed. A suspended meta-surface composed periodic square split ring resonators (SRRs) is placed above the antenna array for decoupling. The meta-surface is equivalent to a negative permeability medium, along which wave propagation is rejected. By properly designing the rejection frequency band of the SRR unit, the mutual coupling between the antenna elements in the MIMO antenna system can be significantly reduced. Two prototypes of microstrip antenna arrays at 5.8 GHz band with and without the metasurface have been fabricated and measured. The matching bandwidths of antennas with reflection coefficient smaller than −15 dB for the arrays without and with the metasurface are 360 MHz and 900 MHz respectively. Using the meta-surface, the isolation between elements is increased from around 8 dB to more than 27 dB within the band of interest. Meanwhile, the total efficiency and peak gain of each element, the envelope correlation coefficient (ECC) between the two elements are also improved by considerable amounts. All the results demonstrate that the proposed method is very efficient for enhancing the performance of MIMO antenna arrays.
Abstract-In this paper, a novel coplanar waveguide (CPW) fed dual band-notched ultra-wideband (UWB) antenna with circular slotted ground is proposed. In order to achieve two notched bands at 3.3-3.7 GHz for worldwide interoperability for microwave access (WiMAX) and 5.15-5.825 GHz for wireless local area network (WLAN) respectively, a pair of bended dual-L-shape branches are attached to the slotted ground. By optimizing the lengths and positions of the branches, the desired notch-bands of WLAN and WiMAX can be achieved. The prototype of the proposed antenna was fabricated and tested. The simulated and measured results show good agreement over the ultra-wideband. Besides these mechanical features, such as compact in size, easy in fabrication, the proposed antenna also shows good characteristics in its radiation patterns and time-domain behaviors. So it is a nice candidate for modern UWB communication systems.
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