Characteristic of narrowband hairpin BPF as influence of number of its elements

The investigation of characteristics of narrowband hairpin bandpass filter (BPF) which is influenced by the number of its elements is presented. The proposed hairpin BPF which is designed to work at around frequency center of 3GHz is deployed on Rogers R4350 dielectric substrates with the thickness of 1.52mm. The number of filter elements for characterization is 3, 5 and 7 elements. Whilst the filter characteristics which will be investigated include the physical dimension, working bandwidth, return loss and insertion loss. From the characterization results, it shows that the dimension of hairpin BPF increases up to 120% for the filter with 3 elements to 7 elements. While the working bandwidth for hairpin BPF with 5 elements is 35% wider than of 3 elements. The most significant effect influenced by the number of filter elements is the shape of frequency responses in which the result demonstrates that the higher number of filter element sharpens the selectivity of frequency response.