V. N. Seleznev – Post-graduate Student, Department of Radio Devices and Antenna Systems, NRU “MPEI”
I. V. Belkovich – Post-graduate Student, Department of Radio Devices and Antenna Systems, NRU “MPEI”
B. L. Kogan – Dr.Sc. (Eng.), Professor, Department of Radio Devices and Antenna Systems, NRU “MPEI”
In this paper the design and structure of the dual-band feed for “COSPAS-SARSAT” terrestrial systems antennas has been given. The developed feed is intended for 3,5-meters reflector antennas. The main requirements for such antenna feeds have been specified. Particularly, the feed should provide simultaneous reception of circularly polarized waves in three frequency bands. Also the require-ments to the radiation pattern beamwidth and VSWR have been set.
Initially the log-periodic feed antenna covering the entire operation frequency range from 1,5 GHz to 2,3 GHz was chosen. This feed was designed and manufactured. The radiation characteristics of the log-periodic feed are not optimal due to the phase center variation. Thus the second feed has been designed as an annular slot antenna.
The annular slot antenna allows to combine radiators of different ranges. In the presented implementation the feed consists of two radiators: the resonator with a larger diameter is adjusted to two low-frequency ranges (1544,5 ± 5 MHz and 1570 – 1615 MHz), the smaller diameter resonator is adjusted to the high frequency range (2226,5 ± 5 MHz). By optimizing the geometry and introduction of the outer rings the desired characteristics were achieved. The experimental layout was manufactured and the characteristics were meas-ured. The results of the measurements and comparison with the calculated results have been given.