i use tektronix oscilloscope perform signal acquisition. 10.000 measurement points (few signal periods) , have frequency analysis on set of data. signal 8mhz sine wave. when use either scipy or numpy same result - frequencies spreaded wide. distance between 2 values 500khz , highest frequency 2.5ghz (absurd). when want measure frequency bandwidth around 8mhz can exact values of 7.5, 8.0 , 8.5 mhz. tried change sample spacing determined (x[1]-x[0]) , got nothing better.
def calculatefft(t_val,p_val): x = t_val #two parameters: [x,y] values y = lambda x: p_val com_signal = y(x) # combined signal fft_val = abs(scipy.fft(com_signal)) freq_val = scipy.fftpack.fftfreq(len(com_signal), x[1]-x[0]) spec_val = 20*scipy.log10(fft_val) return freq_val, spec_val
it worth reading in more depth how dffts work should have following formulae in mind. time series n points , maximum time tmax, time resolution given dt = tmax / n
a dfft produce n points
fmax = 1 / dt
df = 1 / tmax
you seem suggest maximum frequency sufficient (so time resolution okay) frequency resolution isn't enough: need collect more data, @ same time resolution.
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