a Variation of frequency with different L1
b Variation of frequency with different Ls1
As shown in Fig. 4 (b), with the increase of parameterL s1, the position of center frequencyf 2 of the second passband is basically unchanged, while the center frequencies f 1 andf 3 of the first and third pass bands move to the lower frequency, and f 3 moves faster thanf 2, so center frequency of the passband can be controlled by parameters L 1 andL s1.
Experimental results: The structure of the proposed sext-band BPF is shown in Fig.5.