Leaky waves on periodically-modulated Yagi-Uda arrays

A Yagi-Uda array characterized by surface wave lines permits generation of leaky waves provided its element length or location is periodically varied. The paper analyzes a periodically modulated Yagi-Uda array consisting of unevenly spaced rods of various lengths. The generation of leaky waves from the array is theoretically confirmed. An experimental Yagi-Uda array is tested at 10 GHz. The attenuation constant of leaky waves, the interference pattern of near fields, and the radiation pattern are measured. Test results at 10 GHz are found to be in good agreement with theory. This type of array is well suited for frequency scanning in the direction of the main beam.