Documentation sections

Microstrip Mitered Bend Calculator — Optimum Mitre (Chamfer)

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

Slug microstrip-mitered-bend. Optimum mitre for a 90° microstrip bend from the Douville and James relation: the percentage of the corner diagonal to cut away, the cut depth along the diagonal and the chamfer length along each outer edge, ready to draw in a PCB layout.

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 microstrip-mitered-bend
Name	Unit	Range	Default	Description
widthnumber	mm	0.001 … 50	3	Width of the microstrip line going through the bend
heightnumber	mm	0.001 … 10	1.6	Dielectric thickness between the strip and its ground plane
permittivitynumber	none	at least 1	4.4	The optimum mitre does not depend on εr; it is checked against the range the relation was measured over

Outputs

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

Outputs of microstrip-mitered-bend
Field	Unit	Description
mitrePercentheadline	%	Optimum Mitre (Percentage of the Diagonal)
widthToHeight	none	Width-to-Height Ratio
diagonal	mm	Corner Diagonal (d = W√2)
mitreDepth	mm	Mitre Cut Depth along the Diagonal (x = M·d)
chamferLength	mm	Chamfer Length along Each Outer Edge (x√2)
remainingDiagonal	mm	Remaining Diagonal to the Inner Corner (d − x)

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": "microstrip-mitered-bend",
    "inputs": {
      "width": 3,
      "height": 1.6,
      "permittivity": 4.4
    }
  }'

import rftools

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

result = client.calculate("microstrip-mitered-bend", {"width": 3, "height": 1.6, "permittivity": 4.4})
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": "microstrip-mitered-bend",
    "inputs": {
      "width": 3,
      "height": 1.6,
      "permittivity": 4.4
    }
  }),
});
console.log(response.status, await response.json());

package main

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

func main() {
	body := []byte(`{
	  "slug": "microstrip-mitered-bend",
	  "inputs": {
	    "width": 3,
	    "height": 1.6,
	    "permittivity": 4.4
	  }
	}`)
	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": "microstrip-mitered-bend",
  "values": {
    "widthToHeight": 1.875,
    "mitrePercent": 57.1713680666848,
    "diagonal": 4.242640687119286,
    "mitreDepth": 2.4255757229798918,
    "chamferLength": 3.4302820840010884,
    "remainingDiagonal": 1.817064964139394
  },
  "warnings": [],
  "errors": [],
  "provenance": {
    "method": "calculator:microstrip-mitered-bend",
    "version": "api@3f2c1a9b04de",
    "formulaRef": "Douville & James, IEEE Trans. Microwave Theory Tech., MTT-26(3), pp. 175–181 (1978)",
    "assumptions": [
      {
        "code": "empirical-fit",
        "text": "The optimum mitre is Douville and James's fit to measured bends, chosen for minimum reflection; it does not depend on εr or frequency."
      },
      {
        "code": "right-angle-bend",
        "text": "The bend is 90° between two lines of the same width."
      }
    ],
    "validRange": {
      "status": "inside",
      "bounds": {
        "width": {
          "min": 0.001,
          "max": 50,
          "unit": "mm"
        },
        "height": {
          "min": 0.001,
          "max": 10,
          "unit": "mm"
        },
        "permittivity": {
          "min": 1,
          "max": null,
          "unit": ""
        }
      },
      "outside": [],
      "model": null
    },
    "computedAt": "2026-09-24T14:05:11.003Z",
    "inputs": {
      "width": 3,
      "height": 1.6,
      "permittivity": 4.4
    },
    "seed": null,
    "elapsedSeconds": 0.003
  }
}

{
  "detail": [
    {
      "type": "float_parsing",
      "loc": [
        "body",
        "inputs",
        "width"
      ],
      "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 pageMicrostrip Mitered Bend Calculator — Optimum Mitre (Chamfer), at these values