Patent ID: 6731908
Filing Date: 2004-05-04
Classification: G01S,H04B

Abstract:
A half-duplex wireless remote device for use in a distance measurement system, comprising:a receiver for receiving a first radio frequency (RF) signal during a first time slot An from a wireless communication device, the first RF signal including a sequence of carriers fn, where n is a plurality of integers, wherein the sequence of carriers fn are phase coherent with a first reference signal generated at the wireless communication device, the receiver generating a second reference signal from the received first RF signal during the first time slot An, wherein the second reference signal is phase coherent with the received first RF signal; a phase locked loop (PLL) for generating a third reference signal synchronized in frequency and phase with the second reference signal; a synthesizer for generating a second RF signal, the second RF signal being phase coherent with the third reference signal and including a sequence of carriers corresponding to the carriers in of the first RF signal; and a transmitter for transmitting the second RF signal during a second time slot Bn, alternatingly repeat as n changes, and wherein said phase lock loop comprises a switched phase comparator for comparing the phase of the second and third reference signals and generating a phase output signal indicative of phase difference between the second and third RF signal, an integrator for filtering the phase output signal and generating a voltage signal, a voltage controlled oscillator (VCO) controlled by the voltage signal and generating a system clock, and a divider for dividing the frequency of the system clock by an integer N to generate the third reference signal, and wherein the third reference signal continues after the second reference signal is removed.