A selective bandpass filter with using microstrip rectangular ring resonator is proposed for wireless LAN system such as IEEE 802.11 systems (2.45GHz or 5.25GHz). The miniaturized bandpass filter is implemented using a high permittivity dielectric substrate. The full-wave simulator IE3D is used to design the microstrip rectangular ring filter. The responses of the implemented filter using Sm(Co12 /,Ti12 /)O3 (εr = 25.5, tanγ = 0.00013) dielectric substrate are designed at dual-band frequencies of 2.45GHz and 5.25GHz. The compacted size and good agreement have been obtained between simulations and implementation results.