PCB Trace Impedance Calculator (Microstrip/Stripline) implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-clean

Evidence ID

t6-001

Effect

Computation or source lookup only

Input and validation requirements

The zero-height input produces an undefined normalized width and must be rejected. The signed-width probe also exposes an undocumented convention: negative physical trace width should be rejected or explicitly normalized using its magnitude.

Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "inputs": {
    "topology": "microstrip",
    "w_mm": 0.2,
    "h_mm": 0.2,
    "epsilon_r": 4,
    "t_mm": 0,
    "length_mm": 100
  },
  "expected_outputs": {
    "Z0_ohm": 74.145,
    "propagation_delay_ns": 0.569606
  },
  "working": "u = w/h = 0.2/0.2 = 1.000000. epsilon_eff = (4+1)/2 + (4-1)/(2*sqrt(1+12/1)) = 2.5 + 1.5/sqrt(13) = 2.5 + 0.416025 = 2.916025. sqrt(epsilon_eff) = 1.707637. Since u <= 1, Z0 = (60/1.707637)*ln(8/1 + 0.25*1) = (60/1.707637)*ln(8.25) = (60/1.707637)*2.110213 = 74.145 ohm. Delay = 100*1.707637/299.792458 = 0.569606 ns. This is the branch-boundary case u = 1."
}

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche6/tranche6-results.json