| 摘要 |
A method and apparatus for radio communication between a main unit (1) and a sub unit or tag (2) attachable to objects is disclosed. According to the invention a binary modulation of the rotation sense of circular-polarized waves, i. e. a circular polarization modulation is used for the transmission of binary data in at least one communication direction. In preferred embodiments data are encoded by symbols for outward and/or inward communication. As well, inward-communicated data may be encoded by time-selectively echoing a predefined circular polarization pattern received from the main unit (1). Both active and passive tag (2) designs are disclosed that are very simple, power-saving and lightweight. Compared to conventional ASK, PSK or FSK modulation schemes the new circular polarization modulation distinguishes itself by reduced complexity and reduced power requirements at low demodulation error rates and better performance with interfering signals. In particular the system is largely tolerant against linear-polarized jammers, against cross-talk between outward-bound and inward-bound signals at the main unit (1) and against polarization inversion due to metallic reflections. <IMAGE> |
