High-precision distance estimation method for oil tank liquid level meter

The invention discloses a high-precision distance measurement method for a millimeter wave radar of an oil tank liquid level meter. The method comprises the following steps of 1, selecting system parameters under the conditions of ensuring that a frequency spectrum is not fuzzy, parameter selection meeting a precision requirement and ensuring the real-time performance of a system; 2, establishing an emission and echo signal model, obtaining a difference frequency signal, and sampling; 3, performing frequency estimation by using a two-step method, firstly performing coarse frequency estimation by using FFT, and then performing fine frequency estimation by using a least square method; 4, obtaining the fuzzy high-precision phase estimation by using maximum likelihood, and performing ambiguity resolution by using the coarse phase estimation to finally obtain a high-precision estimated value of the distance. Compared with an FFT algorithm, the method has the advantages that the frequency can be estimated with high