DESIGN MEASUREMENT TECHNIQUES FOR LINEARLY POLARIZED HIGHLY EFFICIENT, LIGHT WEIGHT, WIDE BEAMWIDTH ULTRA WIDEBAND (UWB) CHOKE HORN ANTENNA DUAL-FED CIRCULARLY POLARIZED CHOKE HORN ANTENNA USED AS REFLECTOR FEEDS FOR SPACE APPLICATIONS

摘要

This paper discusses design & measurement techniques for two choke horn antennas used as reflector feeds for space applications. Firstly, highly efficient ultra wideband (UWB) choke horn antenna with high beamwidth & linear polarization will be discussed. This choke horn exhibits excellent VSWR characteristics as antenna shows an incredible ultra wide bandwidth (UWB) of at least 5GHz ranging from 7.5GHz -12.5GHz with an incredible VSWR< 1.2 for the entire frequency range. Wide beamwidth of approximately 45 degrees have been achieved at gain of 13.5dB. Secondly, wideband dual-fed circularly polarized choke horn antenna will be discussed. In this case, 90-degree phase shifter/power coupler is being used to feed the antenna in order to keep antenna circularly polarized making polarization independent of matching issues. Both designs meet the ruggedness, strength & reliability, durability, weight, corrosion resistance, temperature variation requirements in space environment. Design Simulation & Optimization for horn antenna has been done on Finite Element Method (FEM) based software 'Ansoft HFSS v11'. Absolute gain measurement techniques have been employed for the measurement of antenna gain.