A Compact Dual-Polarized Low-Pass Filtering Antenna With Wideband Out-of-Band Rejection

Abstract

A compact dual-polarized base-station antenna with filtering characteristics is proposed in this letter. The antenna is composed of a reflector, two balun structures, and two orthogonal half-wavelength radiation arms. The radiation arm mainly consists of multiple transmission lines of different widths, which can be equated to inductance or capacitance. The elaborately designed radiation arm not only ensures a wideband operation but also helps to achieve low-pass filtering characteristics, without using an extra parasitic structure. For demonstration, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm 45^\circ$</tex-math></inline-formula> dual-band dual-polarized antenna array operating at 690–960 MHz and 1710–2690 MHz are fabricated and measured. The implemented array (690–960MHz) achieves stable half-power beamwidth (HPBW) of 65 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> and polarization isolation of 27 dB. Due to the filtering performance of the proposed antenna, stable high gain (17.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 1 dBi) and HPBW of 65 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> also can be realized at 1710–2690 MHz. The proposed antenna is suitable for the base-station application.