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Ladder Filters, Butterworth Chebyshev Filters, Filter Tables Freq/Imp Scaling Ladder Filter: A network composed of alternating series and shunt reactive elements Low Pass: R a2 a4 Vs a1 a3 R The network is “doubly terminated” with the same source and load resistance. Some observations: • The inductors and capacitors are chosen such that the filter has a cutoff frequency at ω and it is matched to the load R . c • Using a higher-order ladder network, the roll-off of the filter’s response in the pass band is steeper than a traditional R-L or R-C type filter. • Doubly terminated ladder filters have a lower sensitivity to component variations. • The reactive elements can be chosen in a manner to “synthesize” a desired response in the pass band, and stop band EE521 pg. 1 Ladder Filters, Butterworth Chebyshev Filters, Filter Tables Freq/Imp Scaling Types of Ladder Filters: Four Basic Types: • Maximally Flat, or Butterworth Filters • Equal Ripple, or Chebyshev Filters • Linear Phase Filters • Elliptic Filters Note that the topology of the filters are the same (except Elliptic filters require mutually coupled elements). However, the filter’s “response” will differ depending on the design. Filter Response Loss Factor: P average input power L i P average output power Note that: