Wilkinson power divider incorporating quasi-elliptic filters for improved out-of-band rejection

A Wilkinson power divider with improved out-of-band rejection is proposed. A fourth-order quasi-elliptic filter is used to replace each quarter-wavelength transformer in a conventional Wilkinson power divider for good passband selectivity. Additional transmission zeroes are created by using the 0° feeding structure to enhance the out-of-band rejection. A 2 GHz Wilkinson power divider incorporating quasi-elliptic filters with a fractional bandwidth of 5% has been fabricated. The measured results present 40 dB roll-off skirts at 2 ± 0.12 GHz and validate the design concept.