Fundamental Study on Novel Loop-Line Antennas Radiating a Circularly Polarized Wave

We propose two types of microstrip-line antennas, designated as connected and penetrated loop-line antennas. Each antenna is composed of loops and straight lines and analyzed using the method of moments. It is found that a circularly polarized beam with an axial ratio of 0.1 dB can be formed by shifting the straight lines with respect to the loop centers. Further analysis reveals that local radiation from the straight lines of the penetrated loop-line antenna is remarkably small (-17 dB) in comparison to that (-7 dB) of the connected loop-line antenna.