Design of Compact Dual-Band LTCC Second-Order Chebyshev Bandpass Filters Using a Direct Synthesis Approach

A new lumped-element circuit model suitable for dual-band bandpass filter (D-BPF) response is proposed. Using even-/odd-mode analysis, analytical equations are developed and used for the development of a direct synthesis design procedure. The proposed procedure is applied to the design and realization of a D-BPF prototype in low-temperature cofired ceramic technology covering two industrial-scientific-medical (ISM) bands of 0.9 and 2.45 GHz. This filter has been successfully measured with an insertion loss of less than 2 dB, return loss better than 18 dB for both bands and out-of-band attenuation higher than 20 dB.