Patent ID: 8203481
Filing Date: 2012-06-19
Classification: G01S

Abstract:
1. A radar system for detecting objects in a surrounding environment, said system comprising: a transmitter adapted to generate a radar signal and to emit into said surrounding environment a first portion of said radar signal as an emitted signal having a frequency that is modulated in a succession of linear frequency ramps over time, wherein said linear frequency a ramps respectively have ramp slopes that all have an identical ramp slope magnitude, and wherein said emitted signal further has, between successive ones of said linear frequency ramps, temporal gaps during which said frequency is not modulated or is modulated differently from said linear frequency ramps; a receiver adapted to receive a received signal that arises from a reflection of a portion of said emitted signal from said objects in said surrounding environment; and a signal processor comprising a mixer, a digital sampler, and a time-frequency transformation circuit; wherein said mixer has a first mixer input connected to an output of said transmitter to receive a second portion of said radar signal, a second mixer input connected to said receiver to receive said received signal, and a mixer output at which said mixer is adapted to output an intermediate signal resulting from mixing said second portion of said radar signal with said received signal; wherein said digital sampler is connected to said mixer output and is adapted to perform a sampling of said intermediate signal, N times during each respective one of K of said linear frequency ramps to produce at a sampler output of said digital sampler N samples for each one of said K linear frequency ramps; wherein said time-frequency transformation circuit comprises a series circuit comprising a first windowing element, a first fast Fourier transformation element, a time shift element for phase rotation compensation, an intermediate memory, a second windowing element, and a M second fast Fourier transformation element; wherein said time-frequency transformation circuit is connected to said sampler output of said digital sampler and is adapted to perform a two-dimensional discrete time-frequency transformation at least partially over the respective said N samples for each one of said K linear frequency ramps, whereby in said transformation relative speeds and radial distances of said objects relative to said receiver are determined from a two-dimensional frequency of said samples and are allocated to a two-dimensional frequency domain; and wherein, to suppress interference influences, said transmitter and said digital sampler are adapted to vary at least one of the following values over said succession of said linear frequency ramps: a) a respective duration respectively of said temporal gaps between said successive ones of said linear frequency ramps, b) a duration of a delay time from a respective ramp start of a respective one of said linear frequency ramps until a beginning of said sampling to produce said N samples during said respective linear frequency ramp, c) a starting frequency at a respective ramp start of a respective one of said linear frequency ramps, and d) a sign of a respective one of said ramp slopes of a respective one of said linear frequency ramps.