Design of Compact Wide-band Folded Loop Feed Antenna for Parabolic Reflectors

A simple design of a dual linear polarized compact folded loop based feed antenna, operating from 1 to 15 GHz, is presented. The design of a new wide-band twin-lead line to microstrip line Balun required for broadband matching is also explained. The dimensions of the feed are 220 mm x 220 mm x 60 mm. The proposed feed antenna is developed in-house and characterized in an antenna measurement facility at an anechoic chamber. The measured gain of the feed antenna is 8.0 +/- 2 dBi from 1 to 9 GHz and 6.0 +/- 2 dBi from 10 to 15 GHz. 10 dB beam-width is +/- 55 degrees, which is nearly constant from 1 to 15 GHz frequency range and makes it suitable for reflector illumination with high aperture efficiency. Port isolation of the feed is better than 20 dB and cross-polarization is better than 15 dB over the band. Simulated and measured gain, cross-polarization, and S-parameters of dual-polarized feed are presented and compared. Based on the secondary pattern analysis from the measured feed pattern, the developed feed is suitable for parabolic reflector antennas operating in the 1-15 GHz frequency range.