Measurement of the fabricated filter is performed using Agilent E8363B
network analyzer. Fig. 6 shows the simulated and measured S-parameters
of the sext-band BPF, and the photograph of the fabricated BPF is also
demonstrated in the inset of Fig. 5. The measured six passbands are
centered at 1.88/2.59/3.48/5.26/5.82/6.75 GHz with 3 dB fractional
bandwidth of 4.26%/11.97%/6.32%/5.19%/5.17%/2.96%. The minimum
insertion losses of each band are 0.85/1.36/0.74/0.98/
1.14/0.82 dB. The band-to-band isolations are above 23.34, 16.59, 28.43,
15.31, 41.93 dB, which generate sharp and deep rejections between the
adjacent passbands.
The mismatch between the measured and simulated results may be leaded by
the nonuniformity of the relative permittivity of the substrate, the
fabrication tolerance and SMA connectors.
In order to evaluate the achieved performance, Table I presents a
performance comparison of the proposed sext-band BPF with some
previously reported works. The proposed sext -band BPF in this letter
exhibits compact size, low insertion and switchable bands.
Conclusion: This letter has presented a miniaturised sext-band
BPF by using two split-type multiple-mode resonators. The proposed
sext-band BPF features very high design freedom of every single band.
The simulated and measured results have a good agreement, which shows
that the proposed filter features compact size, low insertion loss,
sharp skirt. Owing to these merits, the proposed structure is a good
candidate for sext-band BPF design.