The Design of Coupled Resonator Bandpass Filter With Wide Stop-Band

A compact four-pole bandpass filter with multi-order spurious response suppression is proposed. The combination of dissimilar resonator structures with the same fundamental frequency but with different spurious frequencies may improve the stop-band rejection by the mutual cancellation of spurious responses. The measured results show that better than -20 dB rejection levels in the stop-band up to 4.5 f₀ have been obtained. Moreover, an embedded-resonator topology is used, which makes the structure of filter to be more compact.