Working as a Design Engineer in the DSP team at Analog Devices, India

Re: Estimating SNR in the Frequency Domain

Reply posted 3 years ago (03/21/2019)
I didn't say it is a must. If you choose your signal on bin, finding SNR is straightforward.

Re: Estimating SNR in the Frequency Domain

Reply posted 3 years ago (03/21/2019)
Does your signal exactly fall on bin?

Noise aliasing with CIC filter

New thread started 5 years ago
Hi,Would the amount of noise aliasing/folding back into signal band change as we change decimation ratio of the CIC filter. (Assume the input has white noise)In...

Re: SNR measurement with fixed-point FFT

Reply posted 5 years ago (09/25/2017)
I didn't get what you meant by "Regardless, if you are using the same input data for both your cases the sample length is irrelevent."Also, what is trivial data?...

Re: SNR measurement with fixed-point FFT

Reply posted 5 years ago (09/24/2017)
Hi dszabo,Thanks for your reply.Yes, input data is from ADC. I think 128-point should be sufficient to find the SNR unless you want to find some spurs, in which...

Re: SNR measurement with fixed-point FFT

Reply posted 5 years ago (09/22/2017)
What are the internal bit-formats?

Re: SNR measurement with fixed-point FFT

Reply posted 5 years ago (09/22/2017)
Hi Kaz,Yes, thats correct.Thanks,Krishna

Re: SNR measurement with fixed-point FFT

Reply posted 5 years ago (09/22/2017)
The rand() function in matlab returns only positive values from (0,1). Right? or Am I missing some other function which could generate zero mean random noise.So,...

Re: SNR measurement with fixed-point FFT

Reply posted 5 years ago (09/22/2017)
I expect the ADC ENOB to be ~12bits. To model the thermal noise, I have just used rand function with dc offset removed.I am concerned about why the fixed-point FFT...

Re: SNR measurement with fixed-point FFT

Reply posted 5 years ago (09/21/2017)
Hi Artmez,Thanks for the reply. My input data is from output of ADC including the thermal noise. Also, the tone is placed on bin. So, the SNR is not really SQNR...

SNR measurement with fixed-point FFT

New thread started 5 years ago
Hi,I measured the SNR of an input signal with full precision and 16-bit fixed-point precision FFT in matlab.The full precision resulted in 69dB SNR, but the fixed-point...

Re: Fixed-point FFT scaling

Reply posted 5 years ago (09/19/2017)
Thanks a lot. But this is true only if the signal in not on bin, right?If my input tone is placed on bin and I want to measure the SNR, then the gain should be N,...

Re: Fixed-point FFT scaling

Reply posted 5 years ago (09/19/2017)
Why is the gain dependent on my input tone?

Fixed-point FFT scaling

New thread started 5 years ago
Hi,I have seen other discussions on this topic in this forum. But I am still not too clear on this.Here is my understanding : Basically, the need for scaling FFT...

Re: Goertzel algorithm

Reply posted 5 years ago (08/23/2017)
Thanks Tavassoli.I am just wondering if DFT/FFT and Goertzel evaluates the same bin, why should Goertzel depend on additional sample?

Goertzel algorithm

New thread started 5 years ago
Hi,For Goertzel algorithm, does it require N+1 or N samples to generate the bin corresponding to N-point DFT?In Rick's book I see the following statement "For the...

Re: Magnitude of frequency components

Reply posted 5 years ago (07/11/2017)
Hi,You might want to try Goertzel algorithm and get the estimate of mag/phase of the bin you are interested in.CheersKrishna

Re: Back to back CIC filters

Reply posted 5 years ago (04/21/2017)
It works perfectly fine, if I operate the first stage integrator also with the same bit-width as the last stage differentiator.

Re: Back to back CIC filters

Reply posted 5 years ago (04/21/2017)
Hi Rick,Wouldn't that be equivalent to (1-z^-AB)/(1-z^-1) from the simplied diagram I have posted earlier?Krishna

Re: Back to back CIC filters

Reply posted 5 years ago (04/21/2017)
Tim,Absolutely. I was thinking the same, the bit-widths need to be same between integrators/differentiators. Hence, in theory what I have shown might make sense...

Re: Back to back CIC filters

Reply posted 5 years ago (04/21/2017)
Hi Chris,Could you help me with what is wrong with the math? Atleast what i was referring to is given below with simplied diagram. Let me know what is wrong in the...

Re: Back to back CIC filters

Reply posted 5 years ago (04/21/2017)
The second integrator operates at the same rate as the differentiator of the first stage. So, the 1/(1-z^-1) is infact 1/(1-z^-R1).

Re: Back to back CIC filters

Reply posted 5 years ago (04/21/2017)
Hi cfelton,I am talking about the differentiators of the 1st stage and integrators of 2nd stage. Isn;t it (1-z^-1)^3/(1-z^-1)^4 ?Krishna

Re: Back to back CIC filters

Reply posted 5 years ago (04/21/2017)
Hi Stephane,Thanks for pointing out. I have uploaded them now.Krishna

Back to back CIC filters

New thread started 5 years ago
Hi,If I have to design a decimation filter for a 4-bit sigma-delta ADC, decimation factor say 6, I plan to split the filter into 2 stages of CIC filtering (first...

Re: Can we paralleize the integrator stage of CIC?

Reply posted 5 years ago (04/07/2017)
In my case, I want the decimation ratios to be programmable. In a CIC, one need not design the filter again for different decimation ratio. But it is not the case...

Re: Can we paralleize the integrator stage of CIC?

Reply posted 5 years ago (04/07/2017)
Exactly Dave. CIC polyphase doesn't make much sense.

Re: Can we paralleize the integrator stage of CIC?

Reply posted 5 years ago (04/07/2017)
Dave,But polyphase for CIC would mean I can no longer implement a integrator/comb structure? I mean to say each of the polyphase would now look more like a regular...

Re: Can we paralleize the integrator stage of CIC?

Reply posted 5 years ago (04/07/2017)
Hi gretzteam,Thanks a lot for the comments. I am using the integrator with the delay in the forward path, so no issues there. But I further want to reduce the frequency...
Hi,Since, the integrator stage of #CIC operates at higher frequency compared to differentiator, it becomes critical for timing in a high-speed design. Is there a...

Re: How to estimate the SNR

Reply posted 6 years ago (08/12/2016)
Hi Chess,I believe SNR measurements for a system is always done with a single tone input and the procedure mentioned by you works fine for a single tone.Please correct...

Re: Polyphase CIC structure

Reply posted 6 years ago (07/22/2016)
Hi Tim,Thanks for your reply. I have implemented CIC too in my system for the sigma-delta ADC. But is any implementation available for the same where data is coming...

Re: Polyphase CIC structure

Reply posted 6 years ago (07/21/2016)
Rick,Thanks for the reply and the materials provided.Also, sorry for not being clear with my question.I am yet to go through the links you have provided, but what...

Polyphase CIC structure

New thread started 6 years ago
Hi,Any pointers to implementation of polyphase #CIC decimation filter implementation?Thanks,Krishna

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