Low Latency Decimator Filter

Hello everyone,

Can anyone let me know what is the best decimator filter structure to achieve low latency compare to the tradisional CIC filter with cascade Comb and integrator section?

Thanks.

To my opinion, the CIC filter has low latency (group delay) compared to other filters, of course depending on the order. For minimum delay, try an IIR or a low order FIR filter at the input sampling rate and resample without additional averaging.

But I don't know your application requirements, so I can't make specific suggestions. In the general downsampling case, you need a low pass filter, that cuts off frequency components above the Nyquist rate of the downsampled signal, to prevent from aliasing. Additionally, you're possibly trying to achieve a particular frequency or time domain characteristics. Typically, increasing the filter order and/or stop band attenuation also increases the group delay. Thus a minimum delay decimation filter always requires a trade-off.

Hello FVM,

I am currently using 3 stage CIC with 128 decimator factor. And the group delay is 190.5 sample.

I need a decimator filter which decimator factor of 128 but i need lower group delay for this filter.

That why i am looking for other decimator structure. Thanks.

In other words, you're requiring a group delay lower than 1.5 sample periods of the downsampled signal. Most filters with a good stop band attenuation according to Nyquist criterion have probably a higher group delay.