Abstract
This paper presents a method for sidelobe level (SLL) reduction, return loss improvement, and bandwidth enhancement in notch-loaded TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> mode rectangular patch antennas. In this method, a fractal-slot is introduced in the center of notch-loaded patch to remove the unwanted out-of-phase current regions. It is shown that a combination of the fractal-slot and notch loading technique can achieve significant improvement in SLL, return loss, and bandwidth of notch-loaded TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> mode without compromising gain or symmetry of radiation patterns. Moreover, the method also gives an additional degree of freedom to improve the impedance matching without changing the feed location. A prototype of the antenna is fabricated to verify the proposed method. The proposed antenna shows a measured gain of 13 dBi with a low SLL of −16 dB. Furthermore, it shows symmetrical patterns in both planes with cross-polarization (X-pol) levels of less than 35 dB. An under-sampled <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times 4$ </tex-math></inline-formula> array of the proposed antenna is also presented by utilizing its low SLL property to simplify the complexity of feed networks in high gain array antennas. The array offers the same directivity and SLL as that of an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times 8$ </tex-math></inline-formula> array of fundamental mode rectangular patch elements in the same area.
Highlights
M ICROSTRIP patch antennas have been extensively used in mobile and satellite communications, Global Positioning Systems and radars due to their attractive features of low profile, ease of fabrication and lightweight
In order to satisfy the resonant condition of half wavelength, rectangular patch antennas are normally operated in their fundamental mode, TM10
In this work, a high gain and low sidelobe level (SLL) TM30 mode patch is presented by combining the fractal-slot with notch-loading technique
Summary
M ICROSTRIP patch antennas have been extensively used in mobile and satellite communications, Global Positioning Systems and radars due to their attractive features of low profile, ease of fabrication and lightweight. To achieve low SLL without compromising X-pol and symmetry of radiation pattern, [18] employed differential feeding for TM30 mode slot loaded rectangular patch antenna. Instead of using slots to reshape the out-of-phase currents, removal of out-of-phase regions was proposed for higher-order TM30 and TM70 mode rectangular patch antennas This removal, known as notchloading, resulted in new in-phase radiating edges and achieved both gain enhancement and SLL reduction. The main contributions and salient features of this work are summarized as follows: 1) It is shown that by combining fractal-slot and notch loading technique, the current distribution of higherorder mode patch antennas can be manipulated to achieve low SLL and X-pol without compromising gain and symmetry of the pattern. 4) An under-sampled high gain, 4x4 array of the proposed antenna is presented to reduce the complexity of conventional array feed networks
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