Analysis of broadside offset coupled strips for broadband filter applications

The coupled transmission lines in nonhomogeneous medium essentially offer wide bandwidth, tight coupling (3 dB) and low attenuation. This type of structure is very useful for microwave & millimeterwave integrated circuits using planar circuit technologies as Mixers, Oscillators, Multiplier, Filters, and Couplers etc. Here a computation method based on quasi-static spectral domain technique has been developed for solving broadside-coupled suspended stripline structure. The basic parameters of the coupled transmission lines like strip capacitance per unit length, mode characteristic impedance, coupling coefficient & modal phase velocities are being calculated and tabulated. Finally the structure has been utilized to design a suspended stripline filter having broad bandwidth.