Researches On Multi-band And Broadband Circularly Polarized Antennas

Along with the GPS bands of L1 (1.57542 GHz), L2 (1.2276 GHz) and L5 (1.17645 GHz) were opened gradually, and Chinese Compass Navigation Satellite System (CNSS), or"BeiDou"in its Chinese name, is continuously mature, it is very important to carry out the research on multi-band and broadband circularly polarized antennas.Firstly, this paper tallied up several usual methods of designing circularly polarized (CP) antennas. There are: (1) introducing multi-resonant to achieve multi-band and broadband CP radiation, the stacked planar antennas and the dielectric-loading quadrifilar helix antennas are discussed and analyzed in detail; (2) according multi-modes to achieve multi-band CP antennas, slot-loaded microstrip antennas are discussed and analyzed in detail; and (3) selecting wide slot to achieve CP antennas, the perturbation structures are discussed and analyzed in detail.Secondly, the concept of circular polarization and theories about quadrifilar helix antenna and microstrip antenna are introduced as basic theories.Then, based on the methods of achieve multi-band and broadband CP radiations, kinds of multi-band and broadband CP antennas are proposed and studied:1. Dual-band CP stacked square microstrip antenna with small frequency ratio;2. Broadband CP square wide slot antenna;3. Allow for conventional self shifting method is difficult to achieve excellent impedance matching and CP radiation simultaneously over a wide band in quadrifilar helix antenna (QHA) designs, a novel compact QHA attached a novel low-profile feed network on its bottom end is proposed to achieve broadband CP radiations, delivers balanced power division and quadrature phasing for mobile handset applications. Its principle of the wideband characteristics and details of the design are discussed.