Low-Sidelobe Design of Microstrip Comb-Line Antennas Using Stub-Integrated Radiating Elements in the Millimeter-Wave Band

A novel radiating element with a matching circuit was developed for comb-line antennas of traveling-wave operation. In the design of low-sidelobe traveling-wave array antennas, large coupling is required for array elements of the comb-line antenna around the input port. Furthermore, the traveling-wave arrays, whose number of elements is small, also require large coupling because the radiation power for each array element is assigned to be much larger. However, wide radiating elements for large coupling perform poor impedance matching characteristics and radiate large cross polarization. Thus, we proposed a novel radiating element with matching stub in parallel to the radiating element to realize strong radiating power, low reflection, and low cross-polarization, simultaneously. The simulated and measured performances of low-sidelobe 14-element and 6-element antennas were demonstrated in this paper.