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An Introduction To High Efficiency And Multi-rate Digital Filters

John Edwards - Watch Now - Duration: 01:07:59

There are many ways to implement digital filters and many architectures that can be chosen to achieve the optimum performance, which is typically measured in terms of MIPS and memory. This presentation will describe several optimized filtering techniques and architectures and show how they are used.

Examples will include Comb, Polyphase, Cascaded Integrator Comb (CIC) and more.

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Score: 0 | 2 years ago | 1 reply

Hi John, very nice presentation thank you.
I would like to ask on the latency of filtering signals in lower rates. Will it have an impact compared to filtering the signal in the original higher rates?
Is my understanding correct that with the technique that you presented, the latency should remain unaffected?

Score: 0 | 2 years ago | no reply

Hi FK,
That can depend on the overall specification of the filter you are trying to implement but you are correct, that in general, the group delay is the same because ultimately the group delay for the filter at the higher sample rate will be very long.

Score: 0 | 2 years ago | 1 reply

fred h here.
can always go back to 1-D filter and deliver 4-inputs tp single stage and of course with first in first out the sample go to addres -3, -2 -1 ,0

Score: 0 | 2 years ago | no reply

yes, indeed, fred

Score: 0 | 2 years ago | 1 reply

embedd the resampler between the input integrator and the output comb.... filter becomes a hogenauer filter instead of CIC.. I always recommend to avoid using the cic.... the polyphase will outperfomr the cic in number of registers and width of adders ..


Score: 0 | 2 years ago | no reply

Thank fred and welcome to the conference.
Yes, agreed, I referenced hogenauer in the presentation.
I also referenced your excellent presentation from last year, regarding PP filters.
I'm looking forward to your talks later :-)

Score: 0 | 2 years ago | 1 reply

Hi john,
ignore my question of 7bit Accumulator overflowing, it was very stupid of me.
keeping the 8th, 16th, 24th and 32nd bit zero solves any issue of overflows from lower 7bit group to any upper group.

Score: 0 | 2 years ago | no reply

Thanks RK,
There are no stupid questions in DSP.
I'm glad you understand.
Best regards, John

Score: 0 | 2 years ago | 1 reply

Hi John! Thank you, it was very nice talk. As far as I understood, polyphase filtering provides both sample rate conversion and lowpass filtering (correct me if I am wrong). CIC filters provides only lowpass filtering (without sample rate conversion). The advantage of CIC is that is computationally efficient but is it the real constraint nowadays? Does CICs are being used in real systems? Cheers!

Score: 1 | 2 years ago | no reply

Thank you for your kind words.
Both techniques use filtering and sample rate conversion to achieve the goal.
Yes, computational efficiency is very important to reduce power consumption and cost. Especially in battery applications such as mobile phones.
CIC filters are used in almost all digital radios - laptops (wifi, bluetooth), base stations, phones etc. and are very common. Having said this, PP filters can also be used in these applications and fred harris' 2020 talk, which you can still access this year, gives great insight into how PP filters can be used in place of CIC for wireless applications.