Method for determining a distance between an FMCW ranging device and a target

A method implemented in a frequency modulated continuous wave ranging device which increases an ability of the frequency modulated continuous wave ranging device to accurately determine a distance between the frequency modulated continuous wave ranging device and a target, the method comprising:

• transmitting a transmit signal toward the target;
• receiving a receive signal caused by reflections of the transmit signal from the target;
• determining a frequency difference signal of the transmit signal and the receive signal;
• calculating a frequency-domain echo profile from the frequency difference signal;
• storing a low-frequency portion of the echo profile as a temporary interference profile;
• subtracting, if already available, a valid interference profile from the frequency-domain echo profile to increase an accuracy of a subsequent determined distance between the frequency modulated continuous wave ranging device and the target;
• analyzing one of (i) the frequency-domain echo profile and (ii) an interference-free echo profile to determine the distance of the target;
• and
• returning to said transmitting the transmit signal if (i) the target is in close range to the ranging device and (ii) the valid interference profile is available;
• otherwise
• subtracting the temporary interference profile from the frequency-domain echo profile;
• analyzing the echo profile minus the temporary interference profile for another determination of the distance of the target;
• saving the temporary interference profile as the valid interference profile if a difference of a result of two determinations of the distance is within a specified tolerance;
• and
• returning to said transmitting the transmit signal if the valid interference profile is not yet available;
• otherwise updating the valid interference profile by using the temporary interference profile;
• and
• returning to said transmitting the transmit signal if (i) the target is not in close range to the ranging device and (ii) the valid interference profile is available;
• otherwise saving the temporary interference profile as the valid interference profile;
• and
• returning to said transmitting the transmit signal if the valid interference profile is not yet available.