Patent RU-2090898-C1 (RU)
Title: Method of spectral analysis of signals
Inventor: KELEKHSAEV BORIS G
IPC: G01R23/16
Filed: 1993-08-18
Granted: 1997-09-20
Abstract: FIELD: measurement technology, spectral analysis of signals for predominant use in infralow frequencies when provision for high measurement accuracy and fast response is required. SUBSTANCE: proposed method of spectral analysis of signals is based on conversion of input signal. Frequency of first harmonic of input signal is found, first reference sinusoidal signal with frequency of first harmonic of input signal is formed. First time interval where input signal does not change its sign is selected, center of first time interval is determined, second time interval where first reference sinusoidal signal does not change its sign is chosen, center of second time interval is found, momentary values of input and first reference signal at time moments t 1  and t 2  are measured correspondingly. Time moments t 1  and t 2  are chosen equidistant correspondingly from centers of first and second time intervals. Modulus of relation of momentary values of input and first reference signals is found, module of relation of momentary values of first input and first reference signal are determined many times per each pair of time moments equidistant from centers correspondingly of first and second time intervals. First averaged value of module of relation of momentary values of input and first reference signals is found which is multiplied by amplitude of first reference sinusoidal signal. Amplitude of first harmonic of input signal is obtained. Present values of differences between module of relation of momentary values of input and first reference signals and first averaged value of these module are determined, they are multiplied by present values of first reference sinusoidal signal. First additional signal is obtained, second reference sinusoidal signal with frequency equal to double frequency of first reference sinusoidal signal is formed, third and fourth time intervals where first additional and second reference signals do not change their signs are chosen. Centers of third and fourth time intervals are correspondingly found, momentary values of correspondingly first additional and second reference signals are measured at time moment t 3  and t 4  which are chosen equidistant from centers of correspondingly third and fourth time intervals. Moduli of relation of momentary values of first additional and second reference signals are determined many times per each pair of time moments equidistant from centers of correspondingly third and fourth time intervals. Second averaged value of moduli of relation of momentary values of first additional and second reference signals is determined and is multiplied by amplitude of second reference sinusoidal signal. Amplitude of second harmonic of input signal is obtained. Present values of differences between moduli of relation of momentary values of first additional and second reference signals and second averaged value of these moduli are found and multiplied by present values of second reference sinusoidal signal. Second additional signal is obtained. Third reference sinusoidal signal with frequency equal to double frequency of first reference sinusoidal signal is formed. Amplitudes of next components of harmonics of input signal are determined in similar way. In this case reference sinusoidal signal with frequency of determined harmonic is formed per each of components. EFFECT: provision for high measurement accuracy and fast response. 2 dwg