Reaserch On Wideband Miniaturized Wide-beam Circularly Polarized Antenna

This thesis focuses on three research directions of circularly polarized?CP?antennas:broadband,miniaturization and wide beam.Combined with scientific project,the research can be divided into three parts:The first part is the design of a concentric annular-ring patch antenna which is fed by a traveling wave feed network,achieving the characteristics of broadband,miniaturization and circular polarization.The second part focuses on the design process of a crossed dipole antenna for wideband and wide-beam circularly polarized radiation.And the last part is the research of a wideband miniaturized wide-beam terrestrial satellite receiving antenna.The main contexts of the thesis can be summarized as follows:Firstly,a compact traveling-wave-fed annular-ring patch antenna for wideband circularly polarized radiation has been proposed.The antenna is formed by an inner ring with periodic capacitive loading and an outer concentric ring.A traveling wave feed network is adopted to realize circularly polarized radiation.Periodic capacitance loading is employed to enhance the impedance bandwidth and AR bandwidth.And the feed network is wrapped on the cylindrical dielectric substrate,so the size of the antenna has been greatly reduced.Simulated and measured results show that the antenna has a wide impedance bandwidth of 96.5%and axial ratio?AR?bandwidth of 75.9%,a compact size of?37?0.11×0.075₀?³ and stable symmetrical directional radiation.Secondly,A CP crossed dipole loaded with a magnetoelectric?ME?dipole is presented to enhance the bandwidth and beamwidth.A pair of double-printed vacant-quarter rings are equipped to achieve impedance matching of the crossed dipole with the 50?coaxial line to radiate a CP wave.The parasitic ME dipole not only broadens the impedance and AR bandwidths,but also improves the 3dB AR beamwidth.Furthermore,a modified corrugated cavity is utilized to acquire unidirectional radiation with high front-to-back ratio.Simulated results show that the impedance and AR bandwidths of the antenna are 72.1%and 45.3%,respectively.And,the 3-dB AR beamwidth is greater than 162°within 1.85-2.25GHz.Finally,a compact wideband broadbeam CP antenna is designed for Satcom applications.Four sequentially rotated trapezoid planar inverted-F antennas?PIFAs?are fed by a miniaturized four-feed network to realize CP radiation.As a gradually changed structure,the PIFA element can introduce more resonance points and broaden the bandwidth of the antenna.The tight arrangement between the antenna elements and the miniaturized feed network enable the antenna to be as compact as possible.The simulated results show that the impedance bandwidth,AR bandwidth and size of the antenna are37.1%?395-575MHz?,38.3%?380-560MHz?and 0.21?0.21?0.04₀?³,respectively.Furthermore,the antenna gains are greater than-5.0dBic within the range of?60°on the vertical.All the electrical characteristics of the antenna meet the design indexes.