Multilayer dual-path broadside coupled-line bandpass filter design in LTCC technology

A multilayer dual-path broadside coupled-lines filter is presented. The use of broadside coupling leads to more flexibility in achieving higher level of coupling, wider bandwidth, and reduction of size of the overall filter. The multilayer asymmetrical coupled-lines impedance was characterized for the low-temperature co-fired ceramic technology prior to the design to simplify the determination of the width of the filter elements. The proposed filter design was centered at 5 GHz and achieved a fractional bandwidth of 70%.