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ECG COMPRESSION USING
FFT
The electrocardiogram (ECG) is a diagnostic tool that is routinely used to assess the electrical and muscular functions of the heart. Sometimes it is required to send the ECG signals from one place to another place. The ECG signals are compressed at first to reduce the amplitude and frequency and then transferred. ECG signals are compressed by using many techniques. One of the most important technique is FFT.
FFT (Fast Fourier Transform) is a technique used to convert analog signal to digital signal.
In FFT, The total process takes five steps:
1) Input signal
2) Compression (counter A)
3) Compression (counter B)
4) Recovery of the original signal by using IFFT
5) Error checking
Now the detailed explanation of the above steps is given below
At first the input signal (ECG signal) is taken.
There are two stages for compression. In first stage of compression there is a counter A. It identifies the nonzero values of the signal before compression. After compression if the length of the compressed signal is less than the length of the actual signal, then zero padding is done to make equal the lengths of compressed and actual signal.
Now the signal is passed through the counter B. It identifies the nonzero values after the compression of the signal. Now after compression if the length of the compressed signal is greater than the length of the actual signal, then TRUNCATION of the signal is done.
Now by applying IFFT (Inverse Fast Fourier Transform) the original ECG signal is recovered.
The Error is checked at the last stage.
Compression ratio is given by
CR=(BA)/B *100
CRCompression ratio
Acompression in counter A
Bcompression in counter B
Compression ratio is a major factor to determine how much compression the signal undergoes.
The compressed signal contains only positive values.
Thus ECG signal is compressed by using FFT technique.
Applications:
• It finds application in hospitals, when a patient’s report is to be send to another doctor in prenomial place.
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