Method for the linearization of FMCW radar devices

1. A method for the linearization of frequency-modulated continuous wave (FMCW) radar devices having a non-linear, ramp shaped, modulated transmitter frequency progression x(t) comprising the steps of:

correcting a phase term on a receiver side of a FMCW radar device said correction for compensating a phase error in a reception signal q(t) which further comprises the following steps:

selecting a number (L) of consecutive ramp-shaped reception sequences q k (n) of the reception signal, wherein said number is predetermined with k=1, . . . , L;

representing a set of phases arg{q k (n)} which are represented as a polynomial of an N th order for a time index n, with a polynomial coefficient m l , with l=1, . . . , N , ;

transforming a spectrum range Q(e jΩ ) of the selected reception sequences q(n) into a predetermined base band, wherein a set of base band reception sequences {circumflex over (q)} k (n) with k=0, . . . , L−1 are generated in each instance;

iteratively calculating a correction phase term for partial compensation of non-linear frequency components in said base band of reception sequences {circumflex over (q)} k (n) by calculating a set of polynomial coefficients {tilde over (m)} i,k (i) of the individual base band reception sequences {circumflex over (q)} k (n) via estimation methods, wherein {circumflex over (q)} k (n) are the sequences that have already been iteratively phase corrected, wherein said iteration is stopped once a parameter change between two consecutive iterations, which are predetermined, remains below a threshold ε which is predetermined.

2. The method as in claim 1 , wherein said step of calculating polynomial coefficients, includes using said coefficients {tilde over (m)} l,k (i) which includes estimating a distance {tilde over (R)} k (i) between a radar device emitting a transmission signal x(t) and an object reflecting a transmission signal x(t).

3. The method as in claim 1 , wherein said step of iteratively calculating a correlation phase term comprises the steps of:

calculating an individual discrete Fourier transformation {circumflex over (Q)} k (i) (μ) of the base band reception sequences {circumflex over (q)} k (i) (n) whereby {circumflex over (Q)} k (i) (u)=FFT{{circumflex over (q)} k (i) (n)} for k=1, . . . , L

calculating filtered base band reception sequences {overscore (q)} k i (μ) by means of a band pass filter according to {overscore (Q)} k (i) (μ)=w(μ){circumflex over (Q)} k (i) (μ) wherein w (μ) is a spectrum window that is predetermined and indicates a range of a spectrum window having a μ max that is predetermined wherein μ∈[μ μ , μ l ] with a low limit μ u that is predetermined and an upper limit μ l that is predetermined;

calculating an individual inverse Fourier transformation {overscore (q)} k (i) (n) of a filtered base band reception sequence {overscore (Q)} k (i) (μ) wherein {overscore (q)} k (i) n=IFFT{{overscore (Q)} k (i) (μ)} for k=1, . . . , L;

estimating at least one distance {tilde over (R)} k (i) by means of a maximum likelihood estimation method;

calculating a polynomial coefficient {tilde over (m)} l,k (i) from the estimated distances {tilde over (R)} k (i) ;

averaging of said polynomial coefficient {tilde over (m)} l,k (i) with l=1, . . . , N over L reception sequences {circumflex over (q)} k with k=1, . . . , L;

averaging a set of distances {overscore (R)} k (i) over L reception sequences {circumflex over (q)} k (n);

calculating the reception sequences {circumflex over (q)} k (i=1) (n)with the averaged, estimated polynomial coefficients as the starting point for the next iteration.

4. The method as in claim 1 , wherein said iteration step is stopped upon reaching a predetermined number of iteration steps.

5. The method as in claim 3 , wherein said iteration step is stopped if a condition |R (i−1) −R (i) |<ε is reached with ε being a threshold that is predetermined.

6. The method as in claim 5 , further comprising the step of calculating a set of final estimate values {tilde over (R)},{tilde over (m)} t via the following formula

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7. The method as in claim 3 , wherein said spectrum window is a rectangular window or a Hamming window.

8. The method as in claim 4 , wherein a position of a center point μ max of a spectrum window corresponds to a maximum amount of FFT |{circumflex over (Q)} k (i) (μ)| generated by averaging of an amount FFT of a base band reception sequence |{circumflex over (Q)} (i) (μ max )| over a number L.

9. The method as in claim 1 , wherein said reception signal is mixed with said transmission frequency into a lower frequency position that is predetermined.

10. The method as in claim 3 , wherein after said step of base band transformation, the method further comprises the step of reducing a scanning cycle T A of a ramp signal q k (n), wherein the ramp signals q k (n) are filtered by means of an Antialias low-pass.

11. The method as in claim 10 , wherein scanning cycle T A , is reduced by a factor K which lies between K=30 and K=60.

12. The method as in claim 4 , wherein said number of predetermined iterations, is between 10 and 20 iterations.