Abstract
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.
Highlights
With the explosive growth of mobile communication systems in recent years, ultralow profile antennas for indoor distributed antenna system (DAS) have gained increased popularity due to high expectation of aesthetically pleasing profile when integrated into the ceiling design of the building
To further improve the design, a novel design based on asymmetrical dipole that has offset fed monopole radiating element with offset feeding location on an inclined feeding edge of a ground plane was presented
These give more design freedoms that offer a good compromise between the VSWR and the reduced null radiation pattern at the azimuth plane
Summary
With the explosive growth of mobile communication systems in recent years, ultralow profile antennas for indoor distributed antenna system (DAS) have gained increased popularity due to high expectation of aesthetically pleasing profile when integrated into the ceiling design of the building. C. EFFECT OF FEEDPOINT LOCATION AND INCLINATION ANGLE OF FEEDING EDGE OF GROUND PLANE Like antenna type-IV, the feed point, Fp from right edge plays an important role to reduce the null level of the radiation pattern especially for the frequency range 1550-3800 MHz. Fig. The azimuth plane radiation pattern shows degradation with deeper nulls or reduced gain especially for the frequency range of 1350-1850 MHz. As there are parameters that are interdependent, the impedance of the antenna can be matched with various combinations between them. For the mid-frequency range of 1350-1550 MHz, the measured radiation pattern shows slightly deeper null and lower gain at certain angles compared to the simulated result. The proposed antenna has considered the low PIM construction in design to have consistent performance in mass production
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