RfsaFftWindowType Enumeration
- Updated2025-07-17
- 3 minute(s) read
Rfsa
Namespace: NationalInstruments.ModularInstruments.NIRfsa
Assembly: NationalInstruments.ModularInstruments.NIRfsa.Fx45 (in NationalInstruments.ModularInstruments.NIRfsa.Fx45.dll) Version: 2025
Syntax
public enum RfsaFftWindowType
Public Enumeration RfsaFftWindowType
Members
| Member name | Value | Description |
|---|---|---|
| Uniform | 500 | No window is applied. |
| Hanning | 501 |
The Hanning window is useful for analyzing transients longer than the time duration of the window, and also for general-purpose applications.
A Hanning window is applied to the waveform using the following equation:
y[i] = 0.5 * x[i] * [1 – cos(w)] wherew = (2π)i / n n is the waveform size. |
| Hamming | 502 |
A Hamming window is applied to the waveform using the following equation:
y[i] = x[i] [0.54 - 0.46 cos(w)] where w = (2π)i / n n is the waveform size |
| BlackmanHarris | 503 |
A Blackman-Harris window is applied to the waveform using the following equation:
y[i] = x[i] × [0.42323 – 0.49755 cos(w) + 0.07922 cos(2w)] where w = (2)i / n n is the waveform size |
| ExactBlackman | 504 |
An Exact Blackman window is applied to the waveform using the following equation:
y[i] = x[i] * [a0 – a1 cos(w) + a2 cos(2w)] where w = (2π) i / n n is the waveform size a0 = 0.42659 a1 = 0.49656 a2 = 0.076848667 |
| Blackman | 505 |
A Blackman window is useful for analyzing transient signals, and provides similar windowing
to Hanning and Hamming windows but adds one additional cosine term to reduce ripple. A
Blackman window is applied to the waveform using the following equation:
y[i] = x[i] × [0.42 – 0.50 cos(w) + 0.08 cos(2w)] where w = (2 π)i / n n is the waveform size |
| FlatTop | 506 |
The fifth-order Flat Top window has the best amplitude accuracy of all the window methods.
The increased amplitude accuracy (±0.02 dB for signals exactly between integral cycles) is
at the expense of frequency selectivity. The Flat Top window is most useful in accurately
measuring the amplitude of single frequency components with little nearby spectral energy
in the signal. A fifth-order Flat Top window is applied to the waveform using the
following equation:
y[i] = x[i] × [a0 – a1 cos(w) + a2 cos(2w) – a3 cos(3w) + a4 cos(4w)] where w = (2π)i/n n is the waveform size a0 = 0.215578948 a1 = 0.41663158 a2 = 0.277263158 a3 = 0.083578947 a4 = 0.006947368 |
| FourTermBlackmanHarris | 507 |
A 4 term Blackman-Harris window is a general purpose window; it has side-lobe rejection
in the upper 90 dB, with moderately wide side-lobe. A 4-term Blackman Harris window is
applied to the waveform using the following equation:
y[i] = x[i] * [0.422323 - 0.49755 cos(w) + 0.07922 cos(2w)] where w = (2 π)i / n n is the waveform size |
| SevenTermBlackmanHarris | 508 |
A 7 term Blackman-Harris window has the highest dynamic range; it is ideal for
signal-to-noise ratio applications. A 7-term Blackman Harris window is applied to the
waveform using the following equation:
y[i] = x[i] * [a0 - a1 cos(w) + a2 cos(2w) - a3 cos(3w) + a4 cos(4w) - a5 cos(5w) + a6 cos(6w)] where w = (2 pi)i/n n is the waveform size a0 = 0.27105140069342 a1 = 0.43329793923448 a2 = 0.21812299954311 a3 = 0.06592544638803 a4 = 0.01081174209837 a5 = 0.00077658482522 a6 = 0.00001388721735 |
| LowSideLobe | 509 | The Low Side Lobe window reduces the size of the main lobe. |
| Gaussian | 510 |
A Gaussian window is applied to the waveform using the following equation:
y[i] = x[i] * e((-0.5(i - (N -1 ) / 0.5)/(σ(N - 1) / 0.5)) whereN is the length of the window σ ≤ 0.5 |
| KaiserBessel | 511 |
A Kaiser-Bessel window is applied to the waveform using the following equation:
y[i] = x[i] * I0 * (n * a(1 - (2i / (N-1)-1)^2)^0.5)/(I0 * n * a) where i ≥ 0 and i ≤ N-1 N is the length of the window a determines the shape of the window I0 is the zeroth order Modified Bessel function of the first kind |