Design Of The Broadband Planar Spiral Antenna

The principle and realization method of the ultra-wideband and miniaturized circularly polarized planar spiral antenna are studied in this paper. The main content of this paper includes two parts. The design of an ultra–wideband double-armed planar spiral antenna at 2~18GHz in the first part. A four-arm sinuous antenna with miniature balun at 2~12GHz is developed in the second part. The simulation and the measurement results of the two antennas showa good radiation and matching characteristics in the working frequency band and can meet the practical needs.For detail:Firstly, a planar spiral antenna with a working frequency band as 2~18GHz is made. The anntenna with a diameter of 59 mm is designed to make sure it is miniaturization. The impedance matching and current balance conversion are realized by using the coaxial taper balun. A back cavity and multilayer absorbing material are used to realize the unidirectional radiation. The broadband design is realized by using the method of the end load and the mixed helix. Simulation and experimental results show that the proposed antenna can achieve good working performance at 2~18GHz, whitch satify the miniaturization and lightweight requirements.Next, a planar four-arm sinuous antenna working at 2~12GHz is designed and the diameter of the antenna is also 59 mm.The antenna is feeding by the "miniaturization" double microstrip balun. A back cavity and multilayer absorbing material are also used to realize the unidirectional radiation. Two pairs of spiral arms are located on both sides of the dielectric material for feeding. Combined with the work of the network, the antenna can work in horizontal / vertical line polarization, left / right circular polarization and other four kinds of state. The simulation and test results show that the electrical characteristics of the antenna operating frequency band are better in line with the expected results and meet the needs of practical engineering.Finally, the paper studies the two-arm planar Archimedean spiral antenna fed by coaxial line and a three-arm planar Archimedean spiral antenna with gradient strip line measurement. The structure of this kind of antenna has the advantages of low profile, and can realize the miniaturization of antenna.