D
Darol Klawetter
I'm cascading two bandpass SAW RF filters. Each filter has a center frequency of 1.35 GHz and bandwidth of 20 MHz. The filters have input/output impedances of ~50 ohms in the passpand. The impedances can vary widely outside the passband. Generally, out-of-band impedance variances require using a broadband impedance network (e.g., resistive pi) between the cascaded RF filters to obtain a true cascaded response. If a broadband match is not used, out-of-band reflections can result in degraded stop band performance.
The highest frequency presented to the filters is 4.5 GHz and there is a 0.1 inch long microstrip (Zo=50 ohms) that connects the output of the firstfilter to input of the second filter.
My question: Is there any reason to add a broadband match since the length of my microstrip is much shorter than the wavelength of my highest frequency, which means that I don't really need to treat the connection as a transmission line?
Thanks,
Darol Klawetter
The highest frequency presented to the filters is 4.5 GHz and there is a 0.1 inch long microstrip (Zo=50 ohms) that connects the output of the firstfilter to input of the second filter.
My question: Is there any reason to add a broadband match since the length of my microstrip is much shorter than the wavelength of my highest frequency, which means that I don't really need to treat the connection as a transmission line?
Thanks,
Darol Klawetter