US RE35,607 EGranted

Distance measuring method and apparatus therefor

AssigneeNKK Corporation

InventorsAkio Nagamune, Koichi Tezuka, Yoshiyuki Kanao

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Abstract

A distance measuring method and apparatus in which first and second pseudo random signals which are the same in pattern but slightly different in period are generated to obtain a correlation output of the first and second pseudo random signals before transmission thereof as a reference correlation output, and the first pseudo random signal is directly transmitted toward a target or alternatively a carrier wave is modulated by the first pseudo random signal and transmitted toward the target. A correlation output of the signal reflected and received from the target and the second pseudo random signal is detected and the distance to the target is measured from the time interval between the reference correlation output and the received correlation output. Alternatively, the modulated carrier wave reflected and received from the target and the second pseudo random signal are subjected to correlation processing to detect a correlative modulated carrier wave and the correlative modulated carrier is subjected to orthogonal detection by a reference carrier wave thereby obtaining a target detection output. Then, the distance to the target is measured from the time interval between the reference correlation output and the target detection output.

Claims12

Dependent claims

A distance measuring method comprising the steps of:

generating a first pseudo random signal having a clock frequency f.sub.1 ;
transmitting said first pseudo random signal toward a target as an electromagnetic wave signal;
receiving a signal reflected from said target and obtaining a received signal;
generating a second pseudo random signal which is the same in pattern as said first pseudo random signal but having a clock frequency f.sub.2 which is slightly different from said clock frequency f.sub.1 ;
multiplying said first pseudo random signal by said second pseudo random signal to make a first product;
multiplying said received signal by said second pseudo random signal to make a second product;
obtaining a first smoothed signal by passing said first product through a first low-pass filter;
obtaining a second smoothed signal by passing said second product through a second low-pass filter;
generating a first pulse when the value of said first smoothed signal reaches a maximum;
generating a second pulse when the value of said second smoothed signal reaches a maximum;
measuring the time interval between the point when said first pulse is generated and the point when said second pulse is generated, multiplying one half of said time interval by the propagation velocity of said electromagnetic wave to form a first operation value as the product of said multiplication, dividing the frequency difference between said clock frequencies f.sub.1 and f.sub.2 by said clock frequency f.sub.1 to form a second operation value as the quotient of said division and multiplying said first operation value by said second operation value to calculate the distance to said target as the product of said multiplication.

8 more elements

A distance measuring apparatus comprising:

means for generating a first pseudo random signal having a clock frequency f.sub.1 ;
means for transmitting an output of said first pseudo random signal generating means as an electromagnetic wave signal toward a target;
receiving means for receiving a reflected signal from said target to obtain a received signal;
means for generating a second pseudo random signal which is the same in pattern as said first pseudo random signal but having a clock frequency f.sub.2 which is slightly different from said clock frequency f.sub.1 ;
a first multiplier for multiplying the output of said first pseudo random signal generating means by an output of said second pseudo random signal generating means;
a second multiplier for multiplying an output of said receiving means by the output of said second pseudo random signal generating means;
a first low pass filter for smoothing the output of said first multiplier and outputting a first smoothed signal;
a second low pass filter for smoothing the output of said second multiplier and outputting a second smoothed signal;
first pulse generating means for generating a pulse when the first smoothed signal from said first low pass filter reaches a maximum;
second pulse generating means for generating a pulse when the second smoothed signal obtained from said second low pass filter reaches a maximum;
measuring and calculating means for measuring the time interval between the point when said first pulse is generated and the point when said second pulse is generated, multiplying one half of said time interval by the propagation velocity of said electromagnetic wave to form a first operation value as the product of said multiplication, dividing the frequency difference between said clock frequencies f.sub.1 and f.sub.2 by said clock frequency f.sub.1 to form a second operation value as the quotient of said division and multiplying said first operation value by said second operation value to calculate the distance to said target as the product of said multiplication.

8 more elements

A distance measuring method comprising the steps of:

generating a first pseudo random signal having a clock frequency f.sub.1 ;
generating a second pseudo random signal which is the same in pattern as said first pseudo random signal but having a clock frequency f.sub.2 which is slightly different from said clock frequency f.sub.1 ;
multiplying said first pseudo random signal by said second pseudo random signal and outputting the correlated code signal as the product of said multiplication;
generating a reference carrier wave;
modulating said reference carrier wave in coded phase by each code of said first pseudo random signal;
transmitting said modulated carrier wave in coded phase toward the target as an electromagnetic wave signal;
receiving a signal reflected from said target to obtain a received signal;
multiplying said received signal by said second pseudo random signal and outputting the phase correlated carrier wave as the product of said multiplication;
respectively multiplying said phase correlated carrier wave by an inphase component (I signal) and by a quadrature component (Q signal) which are extracted from said reference carrier wave, their phases being mutually orthogonal, and respectively outputting both products, the real part and the imaginary part of the orthogonal detected signal;
respectively smoothing said real part and imaginary part of said orthogonal detected signal and calculating the signal absolute value of a composed detection signal from said smoothed two component signals;
passing said correlated coded signal through a low pass filter and outputting the smoothed correlated coded signal;
measuring the time interval between point when said smoothed correlated code signal value reaches a maximum and the point when said signal absolute value of a composed detection signal reaches a maximum, multiplying one half of said time interval by the propagation velocity of said electromagnetic wave to form a first operation value as the product of said multiplication, dividing the frequency difference between said clock frequencies f.sub.1 and f.sub.2 by said clock frequency f.sub.1 to form a second operation value as the quotient of said division and multiplying said first operation value by said second operation value to calculate the distance to said target as the product of said multiplication.

9 more elements

A distance measuring apparatus comprising:

means for generating a first pseudo random signal having a clock frequency f.sub.1 ;
means for generating a second pseudo random signal which is the same in pattern as said first pseudo random signal but having a clock frequency f.sub.2 which is slightly different from said clock frequency f.sub.1 ;
a first multiplier for multiplying the output of said first pseudo random signal generating means by the output of said second pseudo random signal generating means and outputting the correlated code signal as the product of said multiplication;
carrier wave generating means for generating a reference carrier wave:
modulating means for modulating the output of said carrier wave generating means in coded phase by each code signal of said first pseudo random signal generating means;
transmitting means for transmitting the output of said modulating means toward the target as an electromagnetic wave signal;
receiving means for receiving a reflected signal from said target to obtain a received signal;
a second multiplier for multiplying an output of said receiving means by the output of said second pseudo random signal generating means and outputting the phase correlated carrier wave as the product of said multiplication[.] ;
orthogonal signal detecting means for respectively multiplying said phase correlated carrier wave outputted from said second multiplier by an inphase component (I signal) and by a quadrature component (Q signal) which are extracted from said carrier wave generating means, their phases being mutually orthogonal, and outputting respective both products, the real part and the imaginary part of the orthogonal detected signal;
signal absolute value calculating means for respectively smoothing said real part and imaginary part of said orthogonal detected signal and calculating the signal absolute vale of a composed detection signal from said smoothed two component signals;
a first low pass filter for smoothing the correlated code signal outputted from said first multiplier and outputting smoothed the same signal;
and
measuring and calculating means for measuring the time interval between the point when the output of said first low pass filter reaches to a maximum and the point when the output of said signal absolute value calculating means reaches to a maximum, multiplying one half of said time interval by the propagation velocity of said electromagnetic wave to make a first operation value as the product of said multiplication, dividing the frequency difference between said clock frequencies f.sub.1 and f.sub.2 to make a second operation value as the quotient of said division and.Iaddend .
multiplying said first operation value by said second operation value to calculate the distance to said target as the product of said multiplication.

11 more elements

Dependencies are inferred from the claim text.