Title :
A monofilar spiral antenna and its array above a ground plane-formation of a circularly polarized tilted fan beam
Author :
Nakano, Hisamatsu ; Shinma, Yasuhiro ; Yamauchi, Junji
Author_Institution :
Coll. of Eng., Hosei Univ., Koganei, Japan
fDate :
10/1/1997 12:00:00 AM
Abstract :
A monofilar spiral antenna is analyzed in the presence of a conducting plane reflector, using the method of moments. The circumference of the spiral antenna is chosen to be 2.3 wavelengths. A tilted beam of circular polarization is realized by superposing the fields from two active regions. The gain of the tilted beam is approximately 8 dB. The frequency bandwidths for 1-dB gain drop and 3-dB axial ratio criterions are 12% and 23%, respectively. An array consisting of the four monofilar spiral antennas is also analyzed, where the array element spacing is chosen to be 0.8 wavelength at a design frequency f0. The input impedances of the four spirals are almost the same as the impedance of the single monofilar spiral antenna at f0. The array radiates a tilted fan beam with a gain increase of approximately 6 dB from the gain of the single spiral antenna at f0. The frequency bandwidth for a 3-dB axial ratio criterion is almost the same as that of the single spiral antenna
Keywords :
antenna arrays; antenna radiation patterns; electromagnetic wave polarisation; land mobile radio; mobile antennas; spiral antennas; 1-dB gain drop; 3-dB axial ratio; active regions; antenna array; array element spacing; circularly polarized tilted fan beam; circumference; conducting plane reflector; design frequency; frequency bandwidth; frequency bandwidths; gain; ground plane; input impedance; land mobile communications; method of moments; monofilar spiral antenna; radiation fields; wavelengths; Antenna arrays; Circuits; Directive antennas; Frequency; Moment methods; Planar arrays; Polarization; Reflector antennas; Satellite antennas; Spirals;
Journal_Title :
Antennas and Propagation, IEEE Transactions on