There has been little research considering both broadbanding and miniaturisation of thin substrate patch antennas simultaneously. The use of loading slots in the ground plane has also been reported to reduce the antenna size and increase the gain. But these miniaturisation techniques can reduce the bandwidth of the patch antenna. Techniques such as using shorting pins/walls in combination with high dielectric constant substrates have been reported. Miniaturisation is also extremely important for modern wireless communications. However, these antennas are generally fabricated on thicker substrates. Other techniques involve employing multilayer structures with parasitic patchs of various geometries such as E, V and H shapes, which excite multiple resonant modes. To increase the bandwidth of the microstrip patch antenna, many different techniques have been used, such as using a thicker substrate with lower relative permittivity, or using a T-shape feed probe. However, one of the main limitations of microstrip patch antennas fabricated on a relatively thin substrate is the narrow bandwidth, typically about 5% bandwidth with respect to the centre frequency. Introduction: Microstrip patch antennas have found extensive application in wireless communication systems owing to their advantages such as low-profile, conformability, low-cost fabrication and ease of integration with feed networks. Simulated and measured results indicate that a 53% fractional impedance bandwidth is achieved with respect to the centre frequency of 1.409 GHz and the size of the antenna is reduced by 50% compared to the conventional circular patch antenna with respect to a given frequency. An additional ring-slot in the ground plane is used to produce the wideband characteristics of the antenna. The performance is achieved by employing a combination of annular-ring loading on the patch radiator and the use of a crossed-slot for miniaturisation. Small patch/slot antenna with 53% input impedance bandwidthĪ small microstrip patch/slot antenna, which achieves a very large bandwidth on a relatively thin substrate (about 0.01A0), is presented.
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