Filters & transmission
After checking the two-port setup, investigate low-pass, high-pass, band-pass and band-stop filters. Find cutoff frequencies, resonance peaks and notches and learn to interpret their dB values.
You then see that coax at RF is a transmission line, not just a connection. Electrical length, velocity factor and termination determine the impedance seen at its input. At a quarter wavelength, an open end can appear as a low impedance and a shorted end as a high impedance.
View it along the transmission line In the interactive explanation of reflection, phase and S11 you can see how the measurement plane, electrical cable length and forward and reflected waves are related.
S21AttenuationFiltersTransmission lines
After this module you can
- set up a two-port S21 measurement
- interpret transmission and attenuation in dB
- recognise low-pass, high-pass, band-pass and band-stop filters
- identify a -3 dB point, resonance peak and notch
- explain why the same LC circuit can pass or reject a signal
- recognise quarter-wave behaviour and the velocity factor of coax