A novel planar monopole antenna with dual‐band circularly polarisation (CP) is presented here. The antenna consists of a modified L‐shaped monopole, an inverted‐L strip, and a modified ground. The utilisation of the modified L‐shaped monopole not only generates dual‐band operation, but also excites CP radiation in the lower band. In order to achieve CP in the upper band, a parasitic inverted‐L strip is added on the top plane of the substrate and a modified ground is designed. The proposed antenna has been fabricated and tested, the measured −10 dB reflection coefficient bandwidths are 370 MHz (2.38–2.85 GHz) in the lower band and 2330 MHz (4.05–6.38 GHz) in the upper band. The measured corresponding 3 dB axial ratio (AR) bandwidths are 610 MHz (2.39–3 GHz) and 850 MHz (5.15–6 GHz), respectively. The overlapped −10 dB reflection coefficient and AR bandwidths can totally cover the WLAN bands, Wi‐Fi bands, Bluetooth band, and partly cover the WiMAX bands. The proposed antenna owns bidirectional radiation characteristic and reasonable gain at both the lower band and the upper band.
Meander lines (MLs) in two configurations are presented to reduce the mutual coupling (MC) between two microstrip patch antenna elements. Inserting a slot in the ground plane between the antenna elements is a simple method to reduce the MC, while adding the MLs in the slot of the ground can further reduce the MC. In the first configuration, one ML is inserted in the slot of the ground and a maximum MC reduction of 39 dB throughout the −10 dB bandwidth is achieved. What’s more, the radiation patterns are not changed compared with the dual-element microstrip antenna array with a slotted ground. For the second configuration, two MLs are added in the slot of the ground. It is found that a maximum isolation of 53 dB can be obtained. However, the radiation patterns are slightly changed compared with the dual-element microstrip antenna array with a slot in the ground. Meanwhile, the measured peak gain and efficiency of the dual-element microstrip antenna array in the two configurations are given. Along with this paper, several prototypes have been fabricated and measured. The simulated results are in good accordance with the measurements, which are presented to verify that MC reduction can be achieved between microstrip antenna elements by adding the MLs in the slotted ground.
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