An effective design of parallel coupled microstrip band pass filter without the spurious bands

Parallel coupled microstrip filters are extensively used as band pass filter in microwave communication because they are compact in size, easy to fabricate due to its planar structure. The responses of these filters are satisfactory for narrow bandwidth due to their relatively weak coupling. A severe limitation of the conventionally designed parallel coupled filters is parasitic response at harmonics. In this paper some techniques are discussed to minimize the spurious bands, and also an effective design to suppress these spurious pass bands has been proposed.