Abstract
Introduction. The multipath resistance of GNSS antennas is largely determined by the gain slope of the amplitude radiation pattern at sliding angles (angles close to the horizon). The gain slope of the antenna radiation pattern is determined by the size of its ground plane. This article investigates the dependence between the gain slope and ground plane radius R of a quadrupole antenna.Aim. To analyse the impact of the radius of conventional and high-impedance ground planes on the backscatter radiation pattern of a quadrupole antenna at sliding angles.Materials and methods. Computer simulations were carried out in CAD CST Studio Suite using the methods of finite element analysis (FEM), finite difference time domain (FDTD) and template based post-processing.Results. Quadrupole antennas with a capacitive high-impedance ground plane and a conventional flat ground plane were simulated. The dependence of the average gain slope at sliding angles on the radius of the ground plane was determined at low fн and upper fв GNSS frequencies. The analysis of the down/up ratio, the rolloff gain and the multipath ratio for R= 1…20 of the wavelength of capacitive high-impedance and ground planes conventional flat was performed. It was established that higher gain slopes can be obtained using different types of ground planes; however, lower backscatter radiation values are achievable only using high-impedance structures. It was observed that the same slope of the radiation pattern (about 1 dB/°) for GNSS lower frequencies can be obtained at different R=12λ0, and, presumably, at 20λ0.Conclusion. A high-impedance ground plane with a diameter of 2R=12λ0 is preferable for a quadrupole antenna at low GNSS frequencies. A further increase in the ground plane size will insignificantly improve its characteristics.
Highlights
The multipath resistance of GNSS antennas is largely determined by the gain slope of the amplitude radiation pattern
The gain slope of the antenna radiation pattern is determined by the size of its ground plane
This article investigates the dependence between the gain slope and ground plane diameter R of a quadrupole antenna
Summary
В [10] показано, что высокоимпедансная поверхность в виде решетки стержней обладает меньшей на 30 % крутизной частотной зависимости поверхностного сопротивления по сравнению с choke ring и может использоваться на всех частотах ГНСС. Поэтому в настоящей статье представлены результаты исследований высокоимпедансных и проводящих экранов как малых, так и больших электрических размеров в совокупности со слабонаправленной антенной для оценки ее характеристик направленности. Для исследования с двумя типами экранов использована квадрупольная антенна, так как ее ДН является достаточно широкой как на нижних, так и на верхних частотах ГНСС. Далее постобработкой данных для скользящих углов 80 100 получены вторичные результаты: отношение ДН и ДОИ в нижней полусфере 90 180 90 DU, в направлениях, зеркальных относительно скользящего угла 90 : DU θ
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