An enhanced backscatter RF-ID tag reader system and multiprotocol RF tag reader system is provided. In a multiprotocol mode, the system emits a non-stationary interrogation signal, and decodes a phase modulated backscatter signal by detecting a stronger phase component from quadrature phase representations...http://www.google.ca/patents/US7741956?utm_source=gb-gplus-sharePatent US7741956 - Dual mode transmitter-receiver and decoder for RF transponder tags
