| T O P I C R E V I E W |
| cosy |
Posted - 05/30/2006 : 05:11:03 AM
Origin Version (Select Help-->About Origin): Pro7
Operating System:xp
Hi,
Please verify if my assumptions about the relationship between the Normalised FFT amplitude and the signal amplitude is right:
Signal Amplitude = Normalised FFT Amplitude/2.
FFT Power = (Normalised FFT Amplitude)^2/Number of points
Regards,
COSY. |
| 3 L A T E S T R E P L I E S (Newest First) |
| Mike Buess |
Posted - 01/24/2007 : 9:49:10 PM
2. The peak area will be the same. For a perfect sinusoid the peak is a delta function with area under one point. Apodization (windowing) broadens the peak so peak height must decrease to maintain same area.
Mike Buess
Origin WebRing Member
Edited by - Mike Buess on 01/24/2007 9:50:07 PM |
| 6jal2 |
Posted - 01/24/2007 : 8:29:31 PM
1. When doing Analyze-->FFT--->Normalized, is output amplitude from the FFT analysis the actual amplitude or the amplitude/2?
2. Why might I get such a significant difference in peak amplitude for my fundamental when using the rectangular (2.59) and Hanning (1.37) windows?
The actual peak of my data is 2.8 and the curve is a nearly perfect sinusoid. |
| Mike Buess |
Posted - 05/30/2006 : 07:04:43 AM
Hi COSY,
There are more tha one FFT normalization methods but I assume you are talking about Analysis > FFT. According to the Origin Reference...quote:
Normalization in a Forward FFT divides the Real results by N/2 (both AC and DC components). Normalization in a Backward FFT divides the Real results by 2, except for the DC component which is left unchanged.
andquote:
The Power is derived from the Real^2/N, where N is the number of points
The first normalization occurs only when the Normalize Amplitude FFT setting is checked. The power normalization is independent of that setting.
Mike Buess
Origin WebRing Member
Edited by - Mike Buess on 05/30/2006 07:43:41 AM |
