An ultralow profile, dual-wideband and low passive intermodulation (PIM) in-building ceilingmount antenna for long term evolution (LTE) distributed antenna system (DAS) application is presented. The proposed antenna was designed based on asymmetrical dipole concept having a ground plane with an inclined feeding edge to achieve wideband characteristic and reduced null radiation pattern in the azimuth plane when oriented horizontally. Various dipole and monopole design approaches are presented to give an insight into the typical elevation dipole-liked radiation pattern in the azimuth plane when oriented horizontally to achieve ultralow profile feature. The proposed antenna improves from a simple rectangular monopole to a newly innovated design with off-center feeding location and radiating elements by implementing new design features, e.g. having variation between edges of the radiator and ground plane, slots within monopole radiator and ground plane and inclination of the feeding edge of the ground plane. These additional features enable the proposed design to have a good compromise between the azimuth plane radiation pattern and impedance matching. A production-quality prototype was fabricated to ensure the best PIM performance is achievable. The performance of the prototype was measured. The antenna offers dual-wideband characteristic covering most of the LTE frequency ranges of 698-960MHz and 1350-3800MHz. The passive intermodulation levels that measured for both 700MHz and 1920MHz bands are better than-150 dBc at carrier input of 2 × 20 Watts. INDEX TERMS Broadband antennas, dipole antennas, antenna radiation patterns.

This paper presents an ultralow profile, low passive intermodulation (PIM), and super-wideband in-building ceiling mount antenna that covers both the cellular and public safety ultra high frequency (UHF) band for distributed antenna system (DAS) applications. The proposed antenna design utilizes a modified 2-D planar discone design concept that is miniaturized to fit into a small disc-shaped radome. The 2-D planar discone has an elliptical-shaped disc monopole and a bell-shaped ground plane, a stub at the shorting path, with asymmetrical structure and an additional proximity coupling patch to maximize the available electrical path to support the 350 MHz band range. The proposed design maximizes the radome area with a reduction of about 62% compared to similar concept type antennas. Besides, the proposed design exhibits an improved radiation pattern with null reduction compared to a typical dipole/monopole when lies at the horizontal plane. A prototype was manufactured to demonstrate the antenna performance. The VSWR and radiation pattern results agreed with the simulated results. The proposed antenna achieves a band ratio of 28.57:1 while covering a frequency range of 350–10000 MHz. The measured passive intermodulation levels are better than −150 dBc (2 × 20 Watts) for 350, 700 and 1920 MHz bands.