This paper introduces novel derived transformation equations to design dual-band filters. The design utilizes the approach adopted for dual-band bandpass filter design based on asymmetric half-wavelength resonator. The obtained optimized filter by this approach is used as a reference and the proposed transformation is applied to calculate the new filter design hardware parameters that satisfy its given specifications. Two dual-band filters are demonstrated by using this ransformation. The reference dual-band filter is designed to have: bandwidths of 96 MHz and 185 MHz at the central frequencies 2.1 GHz and 5.6 GHz for UMTS/ Wi-MAX applications, respectively. Another two dual-band filters for GPS/WiLAN and GPS/Wi-MAX applications are illustrated to verify the transformation technique. The momentum simulations for these filters show that the specifications are: bandwidths of 85 MHz and 100 MHz at the central frequencies 1.575 GHz and 5.8 GHz for the first one while bandwidths of 95 MHz and 100MHz at the central frequencies 1.5 GHz and 3.8 GHz for the second filter, respectively. All the results are obtained using circuit and momentum simulation of the Agilent Design Simulator (ADS) package.