A two-arm Archimedean spiral antenna with bent ends

A two-arm Archimedean spiral antenna with bent ends is analyzed. The arms are bent at the end and connected to the neighboring arm. The outer circumference of the spiral antenna is chosen to be one-wavelength at the lower operating frequency. The analysis is performed using the method of moment. First, we analyze current distribution on the spiral antenna. It is shown that the current smoothly flows from the arm end to the neighboring arm through the bent end. Therefore, the reflected current on the end of the spiral arms reduces at lower operating frequencies. Subsequently, radiation characteristics are analyzed. Good axial ratio is obtained at lower frequency bands. The antenna gain also improves at lower frequency bands. It is concluded that simply bending and connecting the ends of the arms greatly contributes to the size reduction of the spiral antenna.