SPREAD SPECTRUM DISTANCE MEASUREMENT SYSTEM

摘要

PURPOSE:To measure a long-distance range effectively by changing the modulation code between a received and a resent radio signal by a local station. CONSTITUTION:The spread spectrum transmitter 58 of a base station 52 imposes carrier code modulation by using the codes of two kinds of pseudo noise generators which differ in code cyclic period and sends a signal. The spread spectrum receiver 74 of the local station 56 receives the code-modulated signal from the transmitter 58 through an antenna 54 and demodulates the received signal by code synchronization. A spread spectrum transmitter 76 uses synchronous timing used at the time of the demodulation as the synchronous timing of code conversion for local transmission and resends a signal from the antenna 54. This signal is received by an antenna 50 and a spread spectrum receiver 78 demodulates the signal by code synchronization. A distance measurement system 80 measures a deviation in code synchronous timing used by a base station receiver from pseudo noise contrarily to code synchronous timing used at the time of transmission from the base station, calculates the distance of the local station from the base station from the measured value, and outputs the distance as distance data.