| 摘要 |
<p>Apparatus for measuring distance has an interrogator which transmits an interrogation pulse (S2) to a transponder where it is received (pulse S5) after a time delay (td). The interrogator measures the time of occurrence of a pulse (S4) which is delayed by the signal processing time delays (t1) in the interrogator. The transponder responds to pulse (S5) after internal processing response time delays (t2) and (tx) by transmitting consecutively a reply pulse (S11) and echo pulse (S17) back to the interrogator where they are received as pulses (S9) and (S15) and produce pulses (S10) and (S16) after respective time delays (t1). Echo pulse (S17) is produced in response to reception in the transponder via an internal signal path of the first reply pulse (S11) delayed by the internal processing delay time of the transponder. The interrogator measures the times of occurrence of pulses (S10) and (S16) and determines (tA) and (tB). It is shown how subtraction of (tB) from (tA) produces a time duration dependant on (td) but independant of (t1, t2) and (tx).</p> |
