Digital Signal Processing Reference
In-Depth Information
2.5% to 97.5% of the frequency span: <-80 dBfs
Lower and upper 2.5% of frequency span: <-65 dBfs
C.2.4
Input Noise
•
Input noise level
Flat top window, -51 dBVrms range, source impedance = 50
Ω
Above 1280 Hz: <-140 dBVrms/vHz
160 Hz to 1280 Hz: <-130 dBVrms/vHz
Note:
To calculate noise as dB below full scale:
Noise [dBfs] = noise [dB/vHz] + 10 LOG (NBW) - range [dBVrms];
where NBW is the noise equivalent BW of the window (see below)
C.2.5
Window Parameters
Uniform
Hann
Flat Top
-3 dB Bandwidth
0.125% of span
0.185% of span
0.450% of span
Noise Equivalent:
Bandwidth
0.125% of span
0.1875% of span
0.4775% of span
Attenuation at ±1/2 Bin:
4.0 dB
1.5 dB
0.01 dB
Shape Factor
(-60 dB BW/-3 dB BW)
800 Hz Span
716
9.1
2.6
C.2.6
Single Channel Phase
•
Phase accuracy relative to external trigger: ±4.0 deg
16 time averages center of bin, DC coupled
0 dBfs to -50 dBfs only
0 Hz < freq = 10.24 kHz only
For Hann and flat top windows, phase is relative to a cosine wave
at the center of the time record. For the uniform, force, and expo-
nential windows, phase is relative to a cosine wave at the beginning
of the time record.
C.2.7
Cross-Channel Amplitude
•
FFT cross-channel gain accuracy : ± 0.04 dB (0.46%)
Frequency response mode, same amplitude range
At full scale: tested with 10 RMS averages on the -11 to +27 dBVrms
ranges, and 100 RMS averages on the -51 dBVrms range
