Method for detecting loss of sensitivity of an FMCW radar locating device by diffuse sources of loss
A method for the detection of sensitivity losses of an FMCW radar locating device due to diffuse sources of loss, in which the radar locating device emits a transmit signal whose frequency is periodically modulated in successive modulation ramps, and at least one power characteristic of at least one frequency portion of a signal received by the radar locating device is evaluated, wherein the power of the transmit signal is varied cyclically, in each case after the completion of a modulation ramp, and the sensitivity losses are determined on the basis of differences in the power characteristics of signals received during successive modulation ramps having identical modulation.
1. A method for detecting losses of sensitivity of an FMCW radar locating device due to diffuse sources of loss, in which the radar locating device emits a transmit signal whose frequency is periodically modulated in successive modulation ramps, and at least one power characteristic of at least one frequency portion of a signal received by the radar locating device is evaluated, the method comprising:
varying cyclically power of the transmit signal, in each case, after completion of a modulation ramp; and
determining the loss of sensitivity on the basis of differences in power characteristics of signals received at successive modulation ramps.
2. The method as recited in claim 1 , wherein the power characteristics that are evaluated in order to detect losses of sensitivity include overall signal power P tot1 , P tot2 .
3. The method as recited in claim 1 , wherein the power characteristics that are evaluated in order to detect losses of sensitivity include signal power and noise power.
4. The method as recited in claim 2 , wherein transmit power is switched between two power levels, and a ratio b of these power levels is selected such that it differs from a ratio a of noise powers corresponding to the two power levels.
5. The method as recited in claim 4 , wherein presence of a loss of sensitivity can be recognized in that a ratio P tot1 /P tot2 is close to the ratio a.
6. The method as recited in claim 5 , wherein the ratio P tot/ /P tot2 in successive measurement cycles is subjected to a temporal filtering.
7. The method as recited in claim 1 , wherein for a located object, a signal power difference is determined between a signal power at high transmit power and a signal power at low transmit power, and for successive cycles of the variation of the transmit power a variance of the signal power difference is determined as a measure for sensitivity losses due to precipitation.
8. The method as recited in claim 7 , wherein variances in successive measurement cycles are subjected to a temporal filtering.