DADiSP Worksheet Functions > Function Categories > Fourier Transforms and Signal Processing > PHASESPEC
Calculates the phase of the N point complex amplitude spectrum.
PHASESPEC(series, N, "type")
series |
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A series, the time domain data. |
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N |
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Optional. An integer, the number of frequency domain samples to compute. |
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"type" |
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Optional. A string, the output type:
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A real series or array, the phase of the N point normalized complex spectrum of the input.
W1: gcos(1000, 1/1000, 100)
W2: phasespec(w1)
W3: phasespec(w1, "double")
W4: phasespec(w1, "shift")
W2 contains 500 real values between 0 and 500 Hz. W3 contains 1000 values with frequency values between 0 to 1000 Hz. W4 contains 1000 values between -500 and 500 Hz. In all cases, the amplitude values range from -2π to 2π.
PHASESPEC computes the phase of N equally spaced samples of the normalized complex amplitude spectrum by using the FFT. The raw FFT values are normalized by the length of the input series such that:
phasespec(s) = phase(fft(s)) / length(s)
For a sampling rate Fs, the default single sided amplitude spectrum displays N/2 frequency values from 0 to Fs/2. The double sided amplitude spectrum, "double", displays N values from 0 to Fs and the shifted spectrum, "shift", displays N values from -Fs/2 to Fs/2.
See AMPSPEC to display the complex spectrum.
See MAGSPEC to display the magnitude spectrum.
See SPECTRUM to compute a normalized frequency spectrum such that a 1 volt sinusoid at frequency F displays a peak of 1 at frequency F.
See DADiSP/FFTXL to optimize the underlying FFT computation.