| 摘要 |
<p>PURPOSE:To measure a long-distance range effectively by varying the frequency of the modulation code between a received and a resent radio signal by a local station. CONSTITUTION:The spread spectrum transmitter 58 of a mobile station 52 imposes code modulation on a carrier by using the codes of two kinds of pseudo noise generators and sends out a signal of center frequency F1. A fixed station 56 receives the signal by an antenna 54 and performs amplification 74, a frequency converter 76 converts the center frequency from F1 to F2, and a modulator 78 modulates it with an input tone signal, etc., and resends the modulated signal through a transmitter 80, etc. The spread spectrum receiver 82 of the mobile station 52 receives the resent radio wave by an antenna 50 and outputs a regenerated tone, etc., to an office local identification system 84. The system 84 feeds a channel selection control signal back to the receiver 82, which demodulates the code-synchronized received signal. A distance measurement system 86 measures the deviation between the code synchronous timing used for the transmission of the transmitter 58 and the code synchronous timing used for the demodulation for respective pseudo noises, calculates the distance to a fixed station 56 from the measured distance, and supplies it to a normal position system 88.</p> |
