this invention uses the structures of the finite - sized conductor - backed coplanar waveguides for designing broadband switchable and tunable signal filters . the design methods construct a plurality of configurations , which including waveguides , via holes , metallic posts , and conductor planes in the structures , for selecting , coupling , converting , and dissipating of the signals with specific electromagnetic modes and frequencies propagating through the structures . the dominant electromagnetic modes of the signals include coplanar waveguide modes and microstrip - like modes . the design methods thereby produce a plurality of filter types , such as bandstop filters , bandpass filters , multiband filters , etc . the design methods can apply to the structures with single and multi - layer dielectric and metallic materials , such as integrated circuits , thin - film transistor circuits , low temperature / high temperature co - fired ceramics , pcb , and others . in addition , the design methods add switches to perform electrically controllable functions including frequency band selection and filter type selection . the design methods can also perform impedance matching of broadband signals by electrically tuning the values of inductance and capacitance in conjunction with the structures .