# How Edwin Armstrong Invented the Superheterodyne Radio Receiver

> A foundational 1920 patent by Edwin Armstrong that describes the superheterodyne circuit, the technology that allowed radios to tune into specific stations clearly and reliably.

- **Patent:** US 1342885
- **Original title:** Method of receiving high-frequency oscillations
- **Owner:** Individual
- **Granted:** 1920
- **Status:** Public domain (expired)
- **Times cited:** 31
- **Field:** telecommunications, consumer_electronics

## What it does

The patent describes a method for receiving high-frequency radio signals by converting them into a lower, intermediate frequency before processing. By mixing the incoming signal with a locally generated oscillation, the device creates a beat frequency that is easier to amplify and filter. This process allows a radio to isolate a single broadcast station from the crowded airwaves without losing signal quality. It essentially acts as a high-precision filter for invisible radio waves.

## What it does NOT cover

- Does not cover the basic concept of radio transmission itself.
- Does not cover digital signal processing or software-defined radio techniques.
- Does not cover the vacuum tube hardware components themselves, only the circuit arrangement.

## The clever bit

By shifting the signal to a fixed intermediate frequency, Armstrong allowed engineers to build a single, highly optimized amplifier stage that worked for all stations, rather than needing to retune the entire circuit for every frequency.

## Real-world examples

1. AM/FM radio receivers
2. Television tuners
3. Radar systems
4. Early satellite communication equipment

## Why it matters

This invention solved the problem of radio interference and poor sensitivity that plagued early wireless communication. It became the standard architecture for almost every radio, television, and radar receiver built throughout the 20th century.

## Frequently asked questions

### What does How Edwin Armstrong Invented the Superheterodyne Radio Receiver cover?

A foundational 1920 patent by Edwin Armstrong that describes the superheterodyne circuit, the technology that allowed radios to tune into specific stations clearly and reliably.

### Who owns patent US 1342885?

Individual owns this patent, granted in 1920.

### When does this patent expire?

This patent has expired and is now in the public domain — anyone can use the invention freely.

### What is patent US 1342885 cited by?

This patent has been cited by 31 later patents that build on its ideas.

### What problem does this patent solve?

This invention solved the problem of radio interference and poor sensitivity that plagued early wireless communication. It became the standard architecture for almost every radio, television, and radar receiver built throughout the 20th century.

### What does this patent NOT cover?

Does not cover the basic concept of radio transmission itself.

**Full plain-English explainer:** https://patentbrief.org/patent/us/1342885/superheterodyne-radio-armstrong

**Original patent:** https://patents.google.com/patent/US1342885

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_Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._


## Related patents

Semantically similar inventions in the PatentBrief corpus:

- [How Marconi Patented Early Wireless Telegraphy Signals](https://patentbrief.org/patent/us/586193/radio-wireless-marconi) — Guglielmo Marconi's 1897 patent for sending electrical signals through the air to enable early wireless communication.
- [Lee De Forest's Early Radio Telegraphy System](https://patentbrief.org/patent/us/879532/de-forest-audion-vacuum-tube) — A 1908 patent by radio pioneer Lee De Forest describing methods for transmitting and receiving wireless telegraphy signals using early vacuum tube technology.
- [How Robert Moog Used Transistors to Shape Synthesizer Sounds](https://patentbrief.org/patent/us/3475623/moog-synthesizer-ladder-filter) — A 1969 invention by Robert Moog that uses the internal resistance of transistors to create the iconic filters that define the sound of analog synthesizers.
- [The Invention of the Junction Transistor](https://patentbrief.org/patent/us/2569347/junction-transistor) — William Shockley's 1951 patent for the junction transistor, the fundamental building block of all modern digital electronics.
- [How Early Cell Phones Handled Calls Across Different Towers](https://patentbrief.org/patent/us/3906166/cellular-mobile-phone-radio-telephone) — This patent describes a system for early portable phones to automatically find the strongest signal from a base station and switch channels as the user moves, reducing battery drain and interference.