In microwave systems, RF front end devices are subjected to interference signal, this interference signal can damage the receiver end or disrupt wanted signals. This thesis proposes a method of sensing the interference signal by weak coupling a resonator to the filter. The proposed method employs a combline bandpass filter at 2 GHz center frequency at 5% bandwidth, which was designed on Advanced Design System (ADS) software and space mapping was performed to optimize the parameters. By weakly coupling the resonator to the filter, the interference signal of certain threshold power can be sensed. The resonator sensor designed are of two bandwidths, the narrower bandwidth resonator and the wider bandwidth resonator which are discussed in this thesis. During the design process of the wide bandwidth sensor the simulation results shows that a tunable attenuator can be realized. The filters is designed, fabricated and tested. The 3-pole filter with no sensor is fabricated and tested first while evaluating different ways to realize the vias from the top to bottom layers of the microstrip structure. It is determined that all methods show promise, though the best results are found using the soldered wire method. The narrow and wideband sensors are also fabricated and tested showing reasonable results when compared to the electromagnetic simulations. The wideband sensor design is tested with a circulator to demonstrate the proposed tunable attenuator design.