QPSK modulated backscatter system
US6456668B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 31, 1996 |
| Grant date | Sep 24, 2002 |
| Priority date | — |
| Expiry date | Dec 31, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/2331
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
In accordance with the present invention, a duplex radio communication system comprises an Interrogator which generates a radio signal to at least one remote Tag. The remote Tag receives the radio signal. The Tag then generates a subcarrier signal, and using Quadrature Phase Shift Keying (QPSK), modulates an information signal onto the subcarrier. A Backscatter Modulator, using this modulated subcarrier, modulates the reflection of the radio signal, the reflected signal being a reflected modulated signal. The Interrogator receives and demodulates the reflected modulated signal to obtain the information signal. In one embodiment, demodulation utilizes a homodyne detector. In another embodiment, the Interrogator modulates an information signal onto the radio signal, transmits that modulated radio signal to the Tag, and the Tag demodulates that modulated radio signal to recover the information signal. In another embodiment, higher order phase modulations are used to modulate an information signal onto the subcarrier.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.