Dual-band filter design with new frequency-transformation method having both band-pass and high-pass responses

A new frequency-transformation concept is proposed to design a dual-band filter having both band-pass and high-pass responses. The new frequency-transformation incorporates an extra frequency parameter to achieve the additional high-pass response. To realize the concept, the conventional band-pass filter´s resonators are modified based on their frequency responses and formulae for the new resonators are derived. A new dual-band filter is also designed with the modified resonators and design equations, fabricated and measured, demonstrating the desired dual-band band-pass and high-pass characteristics.