A Planar Dual-Band Filter Based on Reduced-Length Parallel Coupled Lines

A planar dual-band filter is demonstrated that is based on reduced-length parallel coupled lines. By reactively loading a reduced-length coupled line, a dual-band performance is obtained. The dual-band filter is developed by cascading these dual-band coupled lines. A complete set of design equations is provided that can be applicable to an arbitrary number of filter stages. Experimental results for a Chebyshev-type dual-band filter with center frequencies at 2.4 and 5.2 GHz are in excellent agreement with the full-wave simulated results.