A Compact Outer-Fed Leaky-Wave Antenna Using Exponentially Tapered Slots for Broadside Circularly Polarized Radiation

A novel leaky-wave slot antenna for broadside circularly polarized (CP) radiation is presented. The antenna simply consists of a slotline for the feed, an exponentially tapered slot for the radiator, and a shaped end for the terminator. Separating the feed from the curved radiating slot makes the presented antenna unique in design and compact in size. The resulting antenna yields inherent broadband characteristics of leaky-wave antennas on the input impedance, axial ratio (AR), and radiation gain. Particularly, to solve the tilt-beam problem commonly seen in leak-wave antennas, we proposed an extended dual-slot design that successfully achieved the pattern stability over a wide bandwidth. An antenna module with a reflector for unidirectional pattern applications was also developed. The measured performances of the final prototype were found to exhibit 10-dB return loss bandwidth of 40%, 3-dB AR bandwidth of 53%, and half-power gain bandwidth of 59% with CP gain level about 8 dBic. The measured and simulated results were well consistent with each other.