---
title: "Calculate the cascaded noise figure of a multi-stage receiver chain using the Friis formula. Each stage has a noise figure and gain in dB. The first stage dominates overall system noise, which is why low-noise amplifiers (LNAs) are placed at the front of the chain. Returns total cascaded noise figure, total gain, and equivalent noise temperature. Feeds into link_budget for complete receive-chain sensitivity analysis."
method: POST
path: "/api/noise_figure_cascade"
tags: ["rf"]
---

# Calculate the cascaded noise figure of a multi-stage receiver chain using the Friis formula. Each stage has a noise figure and gain in dB. The first stage dominates overall system noise, which is why low-noise amplifiers (LNAs) are placed at the front of the chain. Returns total cascaded noise figure, total gain, and equivalent noise temperature. Feeds into link_budget for complete receive-chain sensitivity analysis.

`POST /api/noise_figure_cascade`

## Request

- Base URL: `https://calc.engineer`
- URL: `https://calc.engineer/api/noise_figure_cascade`
- Auth: none declared

## Request body

- object
  - `stages` object[], required: Ordered array of receiver chain stages, each with nf_db and gain_db
    - `nf_db` number, required: Noise figure of the stage in dB
    - `gain_db` number, required: Gain of the stage in dB

## Response `200`

Computed result for noise_figure_cascade

- object
  - `result` object, required
    - `total_nf_db` number, required: Total cascaded noise figure in dB
    - `total_gain_db` number, required: Total gain of the chain in dB
    - `noise_temp_k` number, required: Equivalent noise temperature in kelvin (T0 = 290 K)
  - `tool` string, required
  - `version` string, required
  - `computed_at` string, date-time, required
  - `chain` object, required
    - `feeds` unknown[]
      - unknown
    - `accepts_from` unknown[]
      - unknown

## Other responses

- `400`: Validation error or invalid JSON
- `404`: Tool not found

---

[API](https://skmtc.dev/calc/apis/calc-engineer-api.md) · [All operations](https://skmtc.dev/calc/apis/calc-engineer-api/llms.txt) · [OpenAPI document](https://skmtc.dev/calc/apis/calc-engineer-api/revisions/8830480ec488?raw)