In this paper several Defected Microstrip Structure (DMS) are used to suppress the first and second spurious responses in microstrip hairpin filters. The DMSs are integrated in filter structure, and therefore this method keeps the filter size unchanged. The DMS interconnection disturbs the current distribution only across the strip, thereby giving a modified microstrip line with certain stop band. The undesired spurious harmonics are suppressed through multiple transmission zeros which are added at these frequencies by designed DMSs. Experimental results verify that 25 dB suppression for the first harmonic and 40 dB suppression for the second harmonic, respectively, without affecting the main passband response. There is a good agreement between the simulated and measured results.
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