Patent ID: 7778317

Claim:
A method for detecting inductive elements in a communication line, comprising: inputting a detecting signal to an end of the communication line; sampling a time domain voltage vector of one end of the communication line; generating an amplitude-frequency characteristic curve of a differential input impedance of one end of the communication line according to the time domain voltage vector, including converting the time domain voltage vector into a frequency domain voltage vector, V a1k , V 12k (k=0, 1 . . . N−2, N−1), extracting a frequency subsequence vector, V′ a1k , V′ 12k , corresponding to the detecting signal from the frequency domain voltage vector, wherein the relation between the frequency subsequence vector and the frequency domain voltage vector of the detecting signal satisfies a formula as follow: { V a ⁢ ⁢ 1 ⁢ k ′ = V a ⁢ ⁢ 1 ⁢ j ( k = 0 , 1 ⁢ ⁢ … ⁢ ⁢ M - 1 ; j = f k f s ⁢ N ) V 12 ⁢ k ′ = V 12 ⁢ j ( k = 0 , 1 ⁢ ⁢ … ⁢ ⁢ M - 1 ; j = f k f s ⁢ N ) wherein, V′ a1k , V′ 12k are the frequency subsequence vectors, V a1k , V 12k are the frequency domain voltage vectors, f s is the sampling frequency for sampling the time domain voltage vector, N is the number of sampling points of the time domain voltage vector, M is the number of subsequences in the detecting signal, f k is the frequency value of each frequency component in the detecting signal, computing a differential input impedance sequence of one end of the communication line according to the frequency domain voltage vector and the frequency subsequence vector, and generating the amplitude-frequency characteristic curve of the differential input impedance corresponding to the differential input impedance sequence; and determining the number of the inductive elements in the communication line according to the number of the apexes or zeros on the curve.