Source: https://guthlabs.ai/docs/instruments/transmission-line-swr-calculator/mechanism/

instrument mechanism / verified-clean

# Transmission Line / SWR Calculator mechanism

The inspectable method record for Transmission Line / SWR Calculator, kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Model scope

The reflection-coefficient, VSWR, and return-loss formulas are standard under the stated real-positive-Z0 assumptions. The instrument cannot pass as specified because mismatch loss is claimed but not defined, and the power-input mode overclaims a complex reflection coefficient without phase information.

- The listed formulas omit mismatch loss, although mismatch loss is claimed as an output. The standard passive-load formula is ML=-10log10(1-|Γ|^2) dB, equivalently -10log10(P_transmitted/P_incident).

- The forward/reflected-power input path determines only |Γ|=sqrt(Pr/Pf); it cannot determine the complex reflection coefficient Γ without a reflection phase input.

- VSWR=(1+|Γ|)/(1-|Γ|) is valid for |Γ|<1. At |Γ|=1 it is infinite, and for |Γ|>1 it is not a physically valid passive-load VSWR result.

- The reflection-coefficient formula assumes a real, positive characteristic impedance Z0. If a complex reference impedance is intended, the reference-conjugation convention must be specified.

- Return loss is undefined/infinite at Γ=0 and requires an explicit UI/output convention for that case.

## Units and conventions

- Z0 and ZL are impedances in the same units, conventionally ohms; their ratio is dimensionless.

- Z0 is assumed real and positive, and ZL may be complex in rectangular or polar form.

- Forward and reflected powers must use the same power units, such as both watts or both milliwatts; only their ratio is used.

- For power inputs, Pf must be positive and 0<=Pr<=Pf for a passive one-port.

- Angles in the complex-number UI must explicitly declare degrees or radians; the specification does not currently state which is used.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "Z0": "50 ohm",
    "ZL": "100 + j0 ohm"
  },
  "expected_outputs": {
    "reflection_coefficient": "1/3 + j0",
    "reflection_magnitude": 0.3333333333333333,
    "VSWR": 2,
    "return_loss_dB": 9.542425094393248,
    "mismatch_loss_dB": 0.511525224473813
  },
  "reference_data": {
    "formulas": [
      "Gamma=(ZL-Z0)/(ZL+Z0)",
      "VSWR=(1+abs(Gamma))/(1-abs(Gamma))",
      "RL=-20log10(abs(Gamma))",
      "ML=-10log10(1-abs(Gamma)^2)"
    ]
  },
  "working": "Gamma=(100-50)/(100+50)=50/150=1/3. |Gamma|=1/3. VSWR=(1+1/3)/(1-1/3)=(4/3)/(2/3)=2. RL=-20log10(1/3)=20log10(3)=9.542425094393248 dB. ML=-10log10(1-1/9)=-10log10(8/9)=10log10(9/8)=0.511525224473813 dB."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

The specified formulas have singular or out-of-domain cases that require explicit validation: ZL=-Z0 causes division by zero, |Gamma|=1 makes VSWR and mismatch loss infinite, and |Gamma|>1 produces a negative raw VSWR and a non-real mismatch-loss logarithm. The complex-impedance convention can also reverse the sign of the imaginary part of Gamma.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/transmission-line-swr-calculator/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/transmission-line-swr-calculator/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/transmission-line-swr-calculator/qualification/>)

## Sources and evidence

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

- `VERIFIED_LEDGER.json`

- `evidence-tranche8/tranche8-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`