Multioctave Bandwidth of Parallel-Feeding Network Based on Impedance Transformer Concept

A generalized scheme to design a parallel-feeding network with a bandwidth of several octaves for uniform distribution arrays is proposed. Considering the entire network as a continuous impedance-transition device between the feed and all element ports, and therefore applying the design methods of the impedance transformer on the device, a broad matching bandwidth can be achieved without the traditional quarter-wavelength T-junctions concept. Three feeding networks based on the binomial and Chebyshev polynomial and exponential taper transformers for a 4 × 4 patch array are designed for demonstration, verification, and comparison of the proposed concept. An experimental sample of the taper network is fabricated and tested, and a fractional bandwidth better than 3:1 can be achieved. This method is not limited to the specific form of transmission lines and can perform even better for grander scale arrays.