Patent ID: 9134406
Filing Date: 2015-09-15
Classification: G01S

Abstract:
1. A method for measuring a change in distance between a stationary initial point and a largely stationary object with a FMCW radar apparatus, which emits frequency-modulated, continuous electromagnetic microwaves as an output or emitting signal as well as receives and evaluates them as an echo signal, comprising the steps of: sending from said radar device an emitting signal from said initial point in the direction of said object such that said emitting signal is reflected by said object, receiving at said radar device an echo signal, which is generated by the reflection of said emitting signal at said object, mixing said emitting signal with said echo signal in a mixer for generating a mixed signal, evaluating said mixed signal via evaluating means by determining a temporal change in the mixed signal phase, i.e. the frequency of said mixed signal, in order to determine the distance between said initial point and said largely stationary object based on said temporal change in the phase, including evaluating a time-independent part of said mixed signal phase taking into consideration a propagation time of said emitting and/or echo signal between initial point and object, and determining the change in the distance between said initial point and said object is determined based on a change in said time-independent part of said phase, determining via determining means a frequency modulation-superimposed frequency drift of at least one of said emitting and said echo signal, device-specific for said FMCW radar, as well as a calculative propagation time error resulting therefrom, and considering said calculative propagation time error caused by said frequency drift is considered in the evaluation of said time-independent part of said mixed signal phase, wherein a high-frequency portion of said mixed signal is filtered out of said mixed signal prior to evaluation using a low-pass filter, and wherein for determining said device-specific frequency drift, an intermediate frequency is formed in said mixer by mixing a reference signal frequency with a nominal center frequency of at least one of said emitting and said echo signal of said radar and subsequent low-pass filtering.