Electronic – LTSpice – simulation doesn’t match predicted (Chebyshev filter)

high pass filterltspicepassive-filter

I'm a newbie who's trying to simulate a Chebyshev filter for which I used the calculator at https://www-users.cs.york.ac.uk/~fisher/lcfilter in LTSpice. The behavior I'm seeing in LTSpice (XVII if that makes a difference) doesn't match what's predicted by the calculator.

Here's the circuit:
Chebyshev highpass filter generated by website

Here's what's predicted:
Graph with low values up to around 150 MHz, and high values beyond that

Here's what I built in LTSpice – definitely not a 171 MHz highpass filter based on the graph.
Graph that looks more like a 1 kHz filter with no ripple

What am I doing wrong?

Arsenal pointed out in the comments that my range was obscuring things. I adjusted the range to show more reasonable values:
Graph from -100dB to 100dB and phase angles

Best Answer

The are two problems. Firstly the graph you are trying to reproduce is linear, but you are plotting logarithmic amplitude. Secondly you are only computing one point per decade, so the 'curve' is made from just a few straight lines.

Change the sweep to linear with 100 points and left vertical scale to linear, then you should get something like this:-

enter image description here

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