How Radio Frequency Identification (RFID) Tags Were Invented

A 1970 patent describing a remote tag that powers itself using incoming radio signals to read and write data, forming the foundation of modern RFID technology.

What it covers

This patent describes a transponder that acts as a remote data storage device. It uses an incoming signal from a base station to wake up, power its internal circuits, and either read or write data to its memory. Once the data is processed, the device sends an answerback signal back to the base station. By harvesting energy directly from the interrogation signal, the device eliminates the need for an internal battery, making it entirely self-contained.

What it doesn't cover

• —Does not cover active transponders that rely on internal batteries for their primary power source.
• —Does not cover systems where the base station does not provide the energy for the transponder's operation.
• —Does not cover non-electronic storage methods that do not involve a memory means capable of being written to or read from via signal processing.

The clever bit

The innovation was using the incoming interrogation signal not just for communication, but as a power source to energize the device, solving the problem of how to power a remote, battery-less sensor.

Why it matters

This patent is widely considered the foundational document for RFID technology. It established the core architecture for passive tags used today in everything from inventory management and toll collection to secure building access and pet microchipping.

Real-world examples

• 1.Electronic toll collection systems like E-ZPass
• 2.Contactless payment cards
• 3.Retail inventory tracking tags
• 4.Animal identification microchips
• 5.Building access control badges