Research Of Omnidirectional Circular Polarized Antenna Based On Compact Low-Profile Wideband

Omnidirectional circularly polarized(OCP)antenna can provide a wider signal coverage and avoid polarization mismatch compared with directional antenna,so it can be used in radio frequency energy collection technology,UAV,Beidou satellite system,remote sensing and telemetry and other fields.Due to the increasing market demand for it,it is not only to meet its basic characteristics,but also put for forward higher performance and design requirements.So compact,low-profile and broadband OCP antenna has become a social research hotspot.In this paper,an OCP antenna is constructed based on a disk microstrip antenna,and introduces the distribution of electric field and current on the patch of the disk dielectric substrate in different modes.This paper develops the research from two aspects:on the one hand,the TM₀₁ mode is used to realize the compact low-profile omnidirectional circular polarization antenna;on the other hand,using capacitive feed technology and TM₀₁ mode and top-loaded monopole mode to realize compact wideband omnidirectional circularly polarized antenna.Based on the aforementioned methods,the research results of this paper are as below:1.A compact low-profile OCP antenna is proposed operating TM₀₁ mode.The antenna consists of six short-circuit probes along the Z axis six arcs etched on the patch along the Z axis,and the antenna is fed by coaxial probe in the center of the structure.To achieve compact,there is no additional branch around the antenna to realize the far-field horizontal radiation E_?.To generate far-field radiation E_?,the circular current can be realized on the horizontal plane by etching six arcs on the patch.Meanwhile the proposed antenna can achieve a relatively low profile by using microstrip antenna.The circular current can be realized on the horizontal plane by etching arcs,and the radiation E_?in the far field horizontal direction can be realized.The radiation E_?in the vertical direction of far field can be realized by using the TM₀₁ mode in the vertical electric field.Overall structure size is 0.37?₀×0.37?₀×0.03?₀(?₀ is the minimum operating frequency in free space).Through simulation,the impedance bandwidth is 2.9%(5.70-5.87 GHz),and the axial-ratio bandwidth is 4.5%(5.68-5.94 GHz).2.A compact wideband OCP antenna operating in TM₀₁ mode and top-loaded monopole mode is proposed.The proposed OCP antenna consists of two dielectric plates separated by air,a feed structure composed of coaxial probe and copper sheet,and eight short-circuit probes connecting the upper and lower patches.For the sake of achieving wide impedance bandwidth,TM₀₁ mode and top-loaded monopole mode resonance is realized by adjusting the effective electric length of monopole.For the sake of realizing compact,the resonant frequency of TM₀₁ mode is reduced as much as possible under the condition of ensuring circular polarization.At the same time,the far-field vertical radiation E_?is generated by the copper sheet,so there are no redundant branches around the patch.The measured impedance bandwidth of OCP antenna is 57%(2.08–3.74 GHz),the axial ratio bandwidth is 32.4%(2.04–2.83 GHz),and the whole size of the structure is 0.41?₀×0.41?₀×0.1?₀(?₀ is the minimum operating frequency in free space).