3rd Order Filter Design
Simulated response and found cutoff low
4:19
Started: Simulating AC response around 120 MHz.
Ran simulation.
Ran simulation.
Ran simulation.
Evaluated results for 18 sec
Ran simulation.
Evaluated results for 58 sec
Simulation complete.
Running calculation.
Running calculation.
Completed your request.
12:25
Started: Tuning L and C to hit 120 MHz.
Ran simulation.
Evaluated results for 8 sec
Ran simulation.
Ran simulation.
Evaluated results for 42 sec
Ran simulation.
Evaluated results for 5 sec
Ran simulation.
Evaluated results for 14 sec
Simulation complete.
Running calculation.
Running calculation.
Running calculation.
Ran simulation.
Evaluated results for 9 sec
Ran simulation.
Evaluated results for 4 sec
Ran simulation.
Evaluated results for 12 sec
Ran simulation.
Evaluated results for 1 min 2 sec
Ran simulation.
Evaluated results for 43 sec
Simulation complete.
Thought for 1 sec
- Set L1's Inductance to "103nH"
- Set L2's Inductance to "103nH"
- Set C1's Capacitance to "48.2pF"
Thought for 1 sec
- Set L1's Inductance to "85.1nH"
- Set L2's Inductance to "85.1nH"
- Set C1's Capacitance to "58.3pF"
Thought
Work done
- Added and wired a 3rd order LC ladder low-pass filter: L1 (series), C1 (shunt to GND), L2 (series) with named nets IN, OUT, GND.
- Documented the architecture in the existing
project-specification(includes Mermaid block diagram). - Ran AC simulations with 50 ohm source/load.
Success criteria review
- ✅ Filter schematic shows correct 3rd order ladder topology with labeled L/C values.
- ❌ Simulation cutoff did not reach 120 MHz: multiple tuned attempts still yielded ~109.6 MHz (-3 dB).
- ✅ Topology is layout-ready (0402 footprints, single shunt-to-ground element).
Next steps
To hit 120 MHz, I need either (1) to redefine how cutoff is measured (e.g., match -3 dB of insertion loss vs ideal transfer definition), or (2) to change the network (e.g., Pi topology with 2 shunt caps) and re-optimize values. Tell me which definition/topology you want and I can re-tune accordingly.
To hit 120 MHz, I need either (1) to redefine how cutoff is measured (e.g., match -3 dB of insertion loss vs ideal transfer definition), or (2) to change the network (e.g., Pi topology with 2 shunt caps) and re-optimize values. Tell me which definition/topology you want and I can re-tune accordingly.
