The duplexer and antenna are vital components in the communication infrastructures such as satellites, base stations, synthetic aperture radars, etc. Traditionally, the duplexers and the antennas are separately designed before being cascaded into a system by impedance matching circuit. This technique leads to a larger size system and reduced performance as one or more of the components deteriorate. To avoid low performance in the system, an integrated duplexer and antenna can be used. This is a situation where the duplexer and the antenna are co-designed. The integration results in a less complex system as the feeding/matching circuits are no longer required and are replaced by a filter/duplexer. At this stage, the antenna acts as a resonator with radiating characteristics to the filter/duplexer resulting in response with low insertion loss and sharp skirts leading to good guard bands.