Dual-Band Vertically Polarized Omnidirectional Patch Antenna With Low Profile

A dual-band vertical polarization omnidirectional antenna is proposed with the same three substrates in a low profile. The design is configured with four horizontal layers, a wheel-shaped patch (Patch 1) with an outer loop strip on the upper of the top printed circuit board (PCB) (Sub1), a fan-shaped patch (Patch 2) on the top of the mid PCB (Sub2), a four-sector patch on the upper of the bottom PCB (Sub3), and a ground with a ring slot on the lower of Sub3. The four vertical layers are a central coaxial probe from Sub3 to Patches 1 and 2, four inner posts from Patch 1 to Patch 2, four mid posts from the ground to Sub1, and four outer posts from the ground to Patch 1. Based on the new structure, five resonant modes in the passband and one stopband are produced for omnidirectional radiation with vertical polarization. The measured results demonstrate that the impedance bandwidths are 1.62–2.8 GHz (53.4%) and 3.18–4.3 GHz (30%). Therefore, the dual-band operation with a profile as low as 0.053λ_L (λ_L is the wavelength at the lowest frequency of operation) makes the proposed antenna suitable for indoor mobile communications in the bands of DCS1800/PCS1900/UMTS2000/LTE2300 /LTE2500 and 5G NR n77.

I. Introduction

Vertically polarized omnidirectional antennas are a popular choice for indoor mobile communications because they offer all-around coverage in the horizontal plane and minimal signal attenuation [1], [2], [3], [4], [5]. The 2G/3G/LTE (1.71–2.70 GHz) bands and 5G New Radio (NR, 3.3–4.2 GHz) coexist in multiple mobile communication systems for a long time in the future. Therefore, with the rapid development of 5G technology, designing an antenna capable of multiband operation to serve multiple systems is essential. Furthermore, indoor base station antennas should have low-profile characteristics to facilitate antenna integration with the indoor environment.