---
title: "Design a Pi-topology resistive attenuator pad. Given a desired attenuation in dB and characteristic impedance (default 50 ohm), computes the three resistor values for a symmetrical Pi-pad network. The Pi attenuator uses two shunt resistors (R1, R3) and one series resistor (R2). Commonly used in RF signal chains to reduce signal level while maintaining impedance match. Compare with attenuator_tee for T-pad topology."
method: POST
path: "/api/attenuator_pi"
tags: ["rf"]
---

# Design a Pi-topology resistive attenuator pad. Given a desired attenuation in dB and characteristic impedance (default 50 ohm), computes the three resistor values for a symmetrical Pi-pad network. The Pi attenuator uses two shunt resistors (R1, R3) and one series resistor (R2). Commonly used in RF signal chains to reduce signal level while maintaining impedance match. Compare with attenuator_tee for T-pad topology.

`POST /api/attenuator_pi`

## Request

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

## Request body

- object
  - `attenuation_db` number, required: Desired attenuation in decibels (positive value)
  - `z0_ohm` number: Characteristic impedance in ohms (default 50)

## Response `200`

Computed result for attenuator_pi

- object
  - `result` object, required
    - `r1_ohm` number, required: Shunt resistor R1 (input side) in ohms
    - `r2_ohm` number, required: Series resistor R2 (middle) in ohms
    - `r3_ohm` number, required: Shunt resistor R3 (output side) in ohms
    - `topology` string, required: Attenuator topology identifier
  - `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)