The present invention relates to a tunable substrate integrated waveguide (SIW) filter. The SIW filter comprises a first input port for receiving an incoming radio frequency signal, a first output port for transmitting an outgoing radio frequency signal, a first input taper junction coupled to first input port and SIW section including dielectric rods, a first output taper junction coupled to first output port and SIW section including dielectric rods, and a first SIW section wherein metallic vias are placed to form resonant cavities and coupling apertures of reference filter structure. The dielectric rods are placed inside cavities or apertures or both. The position of dielectric rods is optimized corresponding to required tunability range, wherein diameter of the dielectric rods is optimized according to the requirement of tuning of center frequency, wherein dielectric permittivity of dielectric rods is varied according to tunability requirement.