Matlab functions / m files for sample by sample filtering using a digital IIR filter

Hi All,

I want to implement an butterworth low pass filter to filter a DC component of a signal inside a phase locked loop. The process is done in sample-by-sample basis. Therefore I have to filter the signal sample by sample (Not the whole signal or block by block). I have implemented a filter to filter the whole signal. I couldn't make it to work sample by sample basis.

I highly appreciate if someone can advice me regarding this issue. I have included the code Im using to filter.

[b,a] = butter(2, 4*fc/Fs); % 2nd Order butterworth filter coefficient generation (Cutoff frequency is 2*fc)

x=filter(b,a,y); % y is the input signal.

% Here these two lines do the perfect filtering operation for the entire signal, But I want to process sample by sample (In-side a phase locked loop)

Can someone please advice how to do that using available matlab function or different approach?

Thanks.