Miniature filter with double-coupled horse-shoe microstrip resonators capacitively loaded by using high-permittivity material

A novel miniature band-pass filter with double coupled horse-shoe microstrip resonators capacitively loaded by using high-permittivity dielectric material is proposed. The transmission line theory and the finite difference time domain (FDTD) method based simulations are used to analyze the performance of filters with normally fed stepped impedance microstrip resonators (SIMR) and to develop the new design. It is demonstrated that the plugs of higher permittivity dielectric used for capacitive loading of stepped impedance sections provide for shrinkage the filter size down several times. The prototypes of the novel filter were fabricated by using the low temperature cofired ceramics (LTCC) technology.