Basic LPF: public example

A generic 5th-order Butterworth low-pass filter at fc = 1 GHz, on 50 Ω. Demonstrates the full mcp-ltspice workflow without revealing any application-specific design.

Run it

uv run python examples/basic_lpf/design.py

Takes ~25 seconds (most of it Monte Carlo).

What it shows

1. synthesize_lc_filter: closed-form Butterworth synthesis
2. substitute_real_components: Coilcraft 0402HP + Murata GJM C0G
3. evaluate_filter_spec: pass/fail per criterion with margin
4. render_response: Bode PNG with frequency markers
5. monte_carlo_analysis: 1000-trial yield analysis at 5% tolerance

Result

=== Spec compliance (PASS) ===
Criterion                    Target     Measured     Margin   Status
Passband IL                  0.5 dB      0.02 dB   +0.48 dB     pass
Passband RL                 14.0 dB     24.57 dB  +10.57 dB     pass
2 x fc                      30.0 dB     30.85 dB   +0.85 dB     pass
3 x fc                      45.0 dB     48.16 dB   +3.16 dB     pass
5 x fc                      60.0 dB     70.16 dB  +10.16 dB     pass

VERDICT: PASS  |  MC yield: 99.0%

Outputs (generated each run)

• basic_lpf.s2p: analytical Touchstone of the realized filter
• basic_lpf.asc: LTspice schematic
• response.png: S21/S11 Bode plot

These artifacts are checked into the repo as a known-good reference for CI.

Adapting it

Edit spec.json to your own targets, or duplicate the folder under a name that matches examples/private/ or examples/_local/ (gitignored) for proprietary designs.