Achieser–Zolotarev filter

[2] Zolotarev polynomials were first applied to the design of filters by Ralph Levy in 1970.

The inverse Zolotarev filter has equiripple in the stopband except for the last peak with increasing frequency.

[5] The region of high attenuation of the Achieser–Zolotarev filter can be made to occur below the guide cutoff frequency, in which case the response is indistinguishable from a low-pass response because the low-frequency attenuation is masked by the guide cutoff effect.

Waveguide filters will usually require stepped impedance matching at their input and output.

A better match results in fewer impedance steps being required and a significant reduction in bulk and weight.

[9] Waveguide designs are very bulky compared to other technologies but are preferred for microwave high-power applications and where low loss is needed.