Standard g-value ladder synthesis, impedance-scaled to Rs.
Butterworth fc is the −3 dB point; Chebyshev fc is the
ripple-band edge. BP/BS use fc as the band centre with the stated
bandwidth mapped through the standard LP→BP/BS transform.
Even-order Chebyshev: equal terminations are impossible
(gN+1 = coth²(β/4) ≠ 1), so for even N the load is forced to
the required value — Rs·r when the last element is shunt,
Rs/r when it is series — and your RL entry is ignored
(a warning shows the value used). For Butterworth / odd Chebyshev the
prototype assumes RL = Rs; if you enter a different
RL the plot shows the true mismatched response.
The response plot always uses the snapped component values
(exact ABCD cascade of the actual ladder), so E-series effects are real,
not cosmetic.