Microstrip band-pass filter with - 67 dB stop band up to 8.8 times the pass-band center frequency

摘要

Step-impedance resonators and step-impedance capacitor coupling pads are introduced to microstrip band-pass filters to suppress spurious stop-band responses up to the ninth order, thereby providing a very wide stop band. Combined with improvements in existing suppression techniques, the overall suppression in one of the filters, with 1 GHz center frequency and 42% bandwidth, is -54 dB, up to 8.9 GHz. By also using suitably placed resistors, spurious levels are now depressed to -67 dB up to 8.8 GHz, with only 0.03 dB extra pass-band loss.