MATLAB: Best filter

filter curves

Hello everybody,

I am processing a large number of photovoltaic module I-V curves and due to the measuring equipment they normally present a lot of noise, although the shape is more or less visible. However, for processing the curve I need to eliminate the noise. What is in your opinion the best filter to use?

thank you all

Best Answer

It depends on what frequencies you want to get rid off.

View the FFT of the signal. Find out where you have the noise.

Easiest way: Type 'fdatool' in your command window.

You can design your own filter to your own specs. The higher the order the sharper the cut off and the better the characteristics.

You can generate the coefficients and use it in:

Y=filter(B,A,X);

Where,

X- Input Signal

Y- Filtered Output

B- Denominator coeff

A- Numerator Coeff

Related Solutions

MATLAB: FDAtool: Cutoff for “Chebyshev” and “Elliptic”

Hi Alex,

I think there is some misunderstanding regarding the design specification. In IIR filter, if you specify the filter order, the parameters for Butterworth method and the parameters for Chebyshev/Elliptic are different. For Butterworth, like you said, the parameter is the cutoff frequency, i.e. 3dB point. However, for Chebyshev/Elliptic method, you specify the passband and passband ripples. Based on your picture, I assume you are using the default passband ripple (Apass), which is 1dB. This means that between 20 and 150 Hz, the fluctuation cannot exceed 1dB. If you think you can live with a 3dB drop, you can then change your passband ripple (Apass) to 3dB, although such setting is rare in a Chebyshev/Elliptic design.

HTH

Honglei

MATLAB: LPF a random signal

You need to first determine what are the frequencies you want to keep and what are the frequencies you want to filter out. You can then use tools to help you design the filter.

Any DSP book will talk about the theory. For tools, take a look at the following documentation

doc fdatool
doc fdesign

Here is an example

x = rand(1024,1);
hd = design(fdesign.lowpass);
y = filter(hd,x);

Best Answer

Related Solutions

MATLAB: FDAtool: Cutoff for “Chebyshev” and “Elliptic”

MATLAB: LPF a random signal

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