Patent ID: 8665139
Filing Date: 2014-03-04
Classification: G01S

Abstract:
1. A distance measuring apparatus comprising: a first pseudo random signal generator for generating a first pseudo random signal of clock frequency of f a second pseudo random signal generator for generating a second pseudo random signal which has the same pattern as that of the first pseudo random signal and clock frequency of f a first multiplier for multiplying the first pseudo random signal by the second pseudo random signal; a first carrier wave generator for generating a carrier wave of a first frequency; a first modulator for modulating the carrier wave of the first frequency by the first pseudo random signal; a first transmitter for transmitting the modulated carrier wave of the first frequency to a target as a modulated signal for transmission of the first frequency; a first receiver for receiving the modulated signal for transmission of the first frequency reflected by the target as a received signal of the first frequency; a second multiplier for multiplying the received signal of the first frequency by the second pseudo random signal to obtain a modulated received signal of the first frequency; a first hybrid coupler for receiving a part of the carrier wave of the first frequency and delivering a first I signal and a first Q signal which are two components phases of which are orthogonal to each other; a third multiplier for multiplying an output signal of the second multiplier by the first I signal; a fourth multiplier for multiplying the output signal of the second multiplier by the first Q signal; a first low-pass filter for low-pass filtering of an output of the first multiplier; a second low-pass filter for low-pass filtering of an output of the third multiplier; a third low-pass filter for low-pass filtering of an output of the fourth multiplier; first and second units for obtaining a square of the output signal of the second low-pass filter and a square of the output signal of the third low-pass filter, respectively; an adder for adding outputs of the first and second units; a first pulse generator for generating a first pulse when a maximum amplitude value of an output signal of the first low-pass filter is detected; a second pulse generator for generating a second pulse when a maximum amplitude value of an output signal of the adder is detected; a time measuring section for measuring a time period between generation of the first pulse and generation of the second pulse; a first phase detector for detecting a phase of the modulated received signal of the first frequency based on outputs of the second and third low-pass filters; a second carrier wave generator for generating a second carrier wave of a second frequency which is lower than the first frequency; a second modulator for modulating the second carrier wave by the first pseudo random signal; a second transmitter for transmitting the modulated second carrier wave to the target as a modulated signal for transmission of the second frequency; a second receiver for receiving the modulated signal for transmission of the second frequency reflected by the target as a received signal of the second frequency; a fifth multiplier for multiplying the received signal of the second frequency by the second pseudo random signal to obtain a modulated received signal of the second frequency; a second hybrid coupler for receiving a part of the carrier wave of the second frequency and delivering a second I signal and a second Q signal which are two components phases of which are orthogonal to each other; a sixth multiplier for multiplying an output signal of the fifth multiplier by the second I signal; a seventh multiplier for multiplying the output signal of the fifth multiplier by the second Q signal; a fourth low-pass filter for low-pass filtering of an output of the sixth multiplier; a fifth low-pass filter for low-pass filtering of an output of the seventh multiplier; a second phase detector for detecting a phase of the modulated received signal of the second frequency based on outputs of the fourth and fifth low-pass filters; and a distance computing unit for computing a distance to the target based on outputs of the time measuring section, the first phase detector and the second phase detector.