| 摘要 |
A radio range finding system (10) includes a radio range finder (12) and a plurality of remote mobile transponders (14). The radio range finder (12) transmits a signal modulated with an address code identifying a particular mobile transponder. When a mobile transponder receives the modulated signal (Ms) transmitted by the radio range finder and the modulated signal has been modulated with an address code that corresponds to the address assigned to that mobile transponder, the mobile transponder transponds a return signal (Rs) to the radio range finder. A receiver (32) in the radio range finder conveys the received signal to a mixer (30) which also receives an internal carrier signal identical to the modulated signal output by transmitter (20). The output of the mixer is then filtered and demodulated to yield an output signal proportional to the distance between the mobile transponder (14) and the radio range finder (12).
|
