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.
Original patent title: “Method of receiving high-frequency oscillations”
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. Granted to Individual in 1920 with 31 forward citations, and it is now in the public domain.
Coverage
What does this patent actually cover?
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.
The gap
What does this patent 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.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
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.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
AM/FM radio receivers
Television tuners
Radar systems
Early satellite communication equipment
Why it matters
The bigger picture
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.
Filed
February 8, 1919
Granted
June 8, 1920
Market context
Who's building on this
Companies in this space
While the original patent has long expired, the superheterodyne principle remains a core concept taught in electrical engineering and utilized by major semiconductor companies like Texas Instruments and Analog Devices in modern RF front-end designs.
Market impact
This patent enabled the mass-market radio industry by making receivers affordable and easy to use for the general public. It effectively ended the era of 'fiddly' experimental radio sets and established the technical foundation for the global broadcasting industry.
Claim 1 — Plain English
What this patent covers
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.
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.
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.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
This patent is in the public domain
See the Freedom to Build guide — what is free to use, what is not, and how to cite this patent.
PatentBrief Score
Impact Score
Early stage
Citation count
30/40
Moderately cited
Claim breadth
0/20
Narrow claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$13K – $40K
Midpoint $25K · expired or expiring · industry ×1.4
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Claim text not yet imported for this patent
Concepts involved
Citations
Patent lineage
Cite this patent
Armstrong, E. H. (1920). How Edwin Armstrong Invented the Superheterodyne Radio Receiver (U.S. Patent No. 1,342,885). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/1342885/superheterodyne-radio-armstrong
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
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.
Same assignee
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