90E36 Datasheet, PDF (19/79 Pages) Integrated Device Technology – Poly-Phase High-Performance Wide-Span Energy Metering IC

90E36
POLY-PHASE HIGH-PERFORMANCE WIDE-SPAN ENERGY METERING IC
3.6 FOURIER ANALYSIS FUNCTION
The 90E36 offers a hardware DFT Engine for 2^nd to 32^nd order har-
monic component, both V and I of each phase with the same time
period.
Line Frequency
Sample
Frequency
The registers can be divided as follows:
- voltage and current for each phase
- phase A / phase B / phase C
- 32 frequency components (fundamental value, and harmonic
ratios)
- Total Harmonic Distortion (THD)
The harmonic analysis is implemented with a DFT engine. The DFT
period is 0.5 second, which gives a resolution frequency bin of 2Hz. The
input samples are multiplied with a Hanning window before feeding to
the DFT processor. The DFT processor computes the fundamental and
harmonic components based on the measured line frequency and sam-
pling rate, which is 8KHz.
Input
sample
from DSP
processor
Hanning
Window
Harmonic Analyzer
Scaler
X
X
Sample
Capture
DFT
Computation
Engine
Frequency
Components
for
Fundamental
and Harmonic
Post-
Processing
Ratios for
Fundamental
and Harmonic
To DMA Module
Figure-6 Analysis Function
Function Description
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December 9, 2011