Documentation sections

PCB Trace Crosstalk (EMC)

POSThttps://rftools.io/api/py/v1/calculate

Slug pcb-crosstalk-emc. Analyze PCB trace crosstalk from capacitive and inductive coupling. Calculate coupling voltage and dB isolation for EMC pre-compliance.

Inputs

Send every one of these in inputs, in the units shown. Most are required: a call without one is refused (400) and costs nothing; one the calculator can do without takes the default shown. An input outside its range is still computed and flagged in the provenance.

Inputs of pcb-crosstalk-emc
Name	Unit	Range	Default	Description
aggressorVoltagenumber	V	at least 0.001	3.3	Aggressor Voltage
mutualCapacitancenumber	pF	0.001 … 10000	1	Total mutual capacitance between traces (pF)
mutualInductancenumber	nH	0.001 … 10000	3	Total mutual inductance between traces (nH)
frequencynumber	MHz	at least 0.001	25	Frequency
lineImpedancenumber	Ω	at least 1	50	The victim is terminated in this impedance at both ends, and the aggressor carries V_A/Z.

Outputs

Returned in values, by key. A value that is unbounded or undefined is null.

Outputs of pcb-crosstalk-emc
Field	Unit	Description
capacitiveCoupling	mV	Capacitive Contribution (each end)
inductiveCoupling	mV	Inductive Contribution (each end)
totalCrosstalkheadline	mV	Near-End Crosstalk
crosstalkDb	dB	Near-End Coupling
farEndCrosstalk	mV	Far-End Crosstalk

Calling it

Calculate: one call, the request and response in full, and its errors.
Batch: this calculator with others, or a sweep, in one request.
Solve for a target: the value of one input that brings an output to a target.

curl -X POST https://rftools.io/api/py/v1/calculate \
  -H "X-API-Key: $RFTOOLS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "slug": "pcb-crosstalk-emc",
    "inputs": {
      "aggressorVoltage": 3.3,
      "mutualCapacitance": 1,
      "mutualInductance": 3,
      "frequency": 25,
      "lineImpedance": 50
    }
  }'

import rftools

client = rftools.Client()  # reads RFTOOLS_API_KEY, or the key `rftools login` saved

result = client.calculate("pcb-crosstalk-emc", {
    "aggressorVoltage": 3.3,
    "mutualCapacitance": 1,
    "mutualInductance": 3,
    "frequency": 25,
    "lineImpedance": 50,
})
print(result.values)
print(result.warnings, result.provenance.formula_ref)

const response = await fetch("https://rftools.io/api/py/v1/calculate", {
  method: "POST",
  headers: {
    "X-API-Key": process.env.RFTOOLS_API_KEY,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "slug": "pcb-crosstalk-emc",
    "inputs": {
      "aggressorVoltage": 3.3,
      "mutualCapacitance": 1,
      "mutualInductance": 3,
      "frequency": 25,
      "lineImpedance": 50
    }
  }),
});
console.log(response.status, await response.json());

package main

import (
	"bytes"
	"fmt"
	"io"
	"net/http"
	"os"
)

func main() {
	body := []byte(`{
	  "slug": "pcb-crosstalk-emc",
	  "inputs": {
	    "aggressorVoltage": 3.3,
	    "mutualCapacitance": 1,
	    "mutualInductance": 3,
	    "frequency": 25,
	    "lineImpedance": 50
	  }
	}`)
	req, err := http.NewRequest("POST", "https://rftools.io/api/py/v1/calculate", bytes.NewReader(body))
	if err != nil {
		panic(err)
	}
	req.Header.Set("X-API-Key", os.Getenv("RFTOOLS_API_KEY"))
	req.Header.Set("Content-Type", "application/json")
	res, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer res.Body.Close()
	out, _ := io.ReadAll(res.Body)
	fmt.Println(res.Status, string(out))
}

application/json

{
  "slug": "pcb-crosstalk-emc",
  "values": {
    "capacitiveCoupling": 12.959069696057897,
    "inductiveCoupling": 15.550883635269477,
    "totalCrosstalk": 28.509953331327374,
    "crosstalkDb": -41.27034866951207,
    "farEndCrosstalk": 2.59181393921158
  },
  "warnings": [],
  "errors": [],
  "provenance": {
    "method": "calculator:pcb-crosstalk-emc",
    "version": "api@3f2c1a9b04de",
    "formulaRef": "C. R. Paul, Introduction to Electromagnetic Compatibility, 2nd ed., Wiley, 2006, §9.4, the inductive–capacitive coupling approximate model",
    "assumptions": [
      {
        "code": "lumped-weak-coupling",
        "text": "The coupled length is electrically short and the coupling weak, (ωC_m·Z + ωL_m/Z)/2 ≤ 0.1; above that no value is reported."
      },
      {
        "code": "both-ends-terminated",
        "text": "The victim is terminated in the line impedance Z at both ends, and the aggressor drives a current V_A/Z."
      }
    ],
    "validRange": {
      "status": "inside",
      "bounds": {
        "aggressorVoltage": {
          "min": 0.001,
          "max": null,
          "unit": "V"
        },
        "mutualCapacitance": {
          "min": 0.001,
          "max": 10000,
          "unit": "pF"
        },
        "mutualInductance": {
          "min": 0.001,
          "max": 10000,
          "unit": "nH"
        },
        "frequency": {
          "min": 0.001,
          "max": null,
          "unit": "MHz"
        },
        "lineImpedance": {
          "min": 1,
          "max": null,
          "unit": "Ω"
        }
      },
      "outside": [],
      "model": null
    },
    "computedAt": "2026-09-24T14:05:11.003Z",
    "inputs": {
      "aggressorVoltage": 3.3,
      "mutualCapacitance": 1,
      "mutualInductance": 3,
      "frequency": 25,
      "lineImpedance": 50
    },
    "seed": null,
    "elapsedSeconds": 0.003
  }
}

{
  "detail": [
    {
      "type": "float_parsing",
      "loc": [
        "body",
        "inputs",
        "aggressorVoltage"
      ],
      "msg": "Input should be a valid number, unable to parse string as a number",
      "input": "abc"
    }
  ]
}

An input sent as text. Nothing was counted.

{
  "detail": "More than 120 requests in 60 seconds from this address.",
  "errorKind": "rate_limited",
  "limit": 120,
  "windowSeconds": 60,
  "upgradeUrl": "https://rftools.io/pricing/"
}

Too many requests in a minute, with Retry-After.

Same inputs on the calculator pagePCB Trace Crosstalk (EMC), at these values