# [TECH] Radar

**Radar** (Radio Detection And Ranging) uses reflected radio waves to detect and locate objects, developed in the 1930s and decisive in WWII, with descendants in aviation safety, weather forecasting, autonomous vehicles, and medicine.

## Overview

Robert Watson-Watt demonstrated practical radar to the British Air Ministry (1935), leading to the Chain Home network that was decisive in the Battle of Britain (1940). The cavity magnetron (Boot & Randall, 1940) produced compact, high-power microwave sources enabling airborne and ship radar. Post-WWII, radar became essential for air traffic control, weather forecasting (Doppler radar), automobile collision avoidance, and medical imaging (ultrasound shares principles).

## Key Actors

- **Companies**: Marconi (UK), Raytheon (US, 1922), Telefunken (DE), Bell Labs
- **Inventors**: Robert Watson-Watt (1892–1973), Henry Boot & John Randall (cavity magnetron, 1940)

## Key Patents

- Watson-Watt, R. UK Patent 593,017 (1935) — radio direction finding
- Boot, H. & Randall, J. UK Patent (1940) — cavity magnetron (classified initially)

## Economic Value

Global radar market: **\$45 billion/year** (2023, Grand View Research). Aviation radar infrastructure: \$8B/year. Weather radar networks: \$1B+/year. Autonomous vehicle radar: growing to \$25B+ by 2030.

## Notes

Grand View Research *Radar Market* 2023. Aviation safety enabled by radar represents trillions in airline/freight value. The cavity magnetron technology was transferred to the US in the Tizard Mission (1940), directly accelerating US radar and ultimately microwave oven technology.

## What This Enables
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- **[TECH] Digital Computing** — Wartime radar required fast computation of trajectories and signal processing, motivating early computer development (e.g., Colossus).
- **[TECH] GPS (Global Positioning System)** — The radar ranging concept — measure time-of-flight of reflected pulses — is the direct precursor to GPS satellite ranging.
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# Parents

* [TECH] Radio & Wireless Communication
* [TECH] Radio & Wireless Communication