I'm an EE from USC with mostly a software career. My hobbies of robotics and mechatronics have kept my EE skills reasonably sharp. My current role is architecting software for SDRs so I get to get DSP too!

## Re: SDR/DSP Question

I am going to echo everyone else's suggestion that you avoid using the TMS320C6713. Unless you are into retro hardware (which is cool in its own right, but the joy...

## Re: Who discovered the math of the digital polar discriminator?

Ah, that makes total sense, thanks!

## Re: Who discovered the math of the digital polar discriminator?

Does this work as an equivalent?$$R e^{j\omega t[0]}*Re^{-jwt[-1]}= R^2 * e^{jw(t[0] - t[-1])} = R^2*e^{j\omega}$$I don't see how $$t[0] - t[1]$$ becomes 1 in...

## Re: Undersampling FM radio frequencies

Typically the local oscillator will be generated by a frequency synthesizer. That and the mixer would be "in addition" to what you have on hand. That said, ...Given...

## Re: Undersampling FM radio frequencies

I suspect the part you are missing is the local oscillator. Typically in an SDR the incoming signal is "mixed" (which is a multiplication) with a sine signal that...

## Re: MathJax/Latex question

Glad it helped! Two resources I depend on heavily are the Mathjax "demo" page (that lets you type in code and see what it produces) https://www.mathjax.org/#demo...

## Re: DQPSK - New t this, and want to learn...

I completely feel your pain! When I started I was in the same spot where I didn't know if the signal was correct, the software decoding it was correct, or the circuit...

## Re: MathJax/Latex question

Hmm okay, I seem to have got it, the trick is using the begin{equation*} / end{equation*} from the ams math package, and begin{align} / end{align} to align the parts.\begin{equation*}h_j(k) ...

## MathJax/Latex question

Hi All,If this isn't the right place for this I apologize, I've tried a couple of other forums as well and I'm striking out.I'm trying to write Hoagenaur's equations...

## Re: DQPSK - New t this, and want to learn...

Welcome Kim, sounds like you are jumping right in with both feet. It is fortunate these days that there are a lot of free tools from Octave (a MATLAB equivalent)...

## Re: Curve Modelling

Hi Groger, not trying to be unkind here but did you try typing "how to estimate a polynomial curve fit" into box at www.google.com ? If so it would have shown you...

## Re: Impulse response of CIC filter

Thanks for the response @kaz, plotting the frequency response of the taps you have gives this:Not surprisingly I've got a number of different plots where I try to...

## Re: Impulse response of CIC filter

Thanks again @gretzteam for this insight, I'm trying to understand how you got it. I started by looking at the different sequences that are generated by different...

## Re: Impulse response of CIC filter

How did you choose how to do the interleaving?

## Re: Test signal names

I like that, impulse prime. I'll use that name in my code, thanks!

## Test signal names

So I've used the "unit impulse" (which is a 1.0 magnitude sample followed by zeros) to test filters, and a "unit step" (50% of the samples are 0, the remaining 50%...

## Re: Impulse response of CIC filter

Your right it does. Now nothing I've read about CIC filters talks about polyphase. That is something I need to understand, can you point me to a reference?And as...

## Re: Impulse response of CIC filter

Ok, that is pretty awesome!

## Impulse response of CIC filter

So this is a curious one. I am continuing investigating #CIC filters now that I have run @Rick Lyons tests and proven to myself that they are now correctly implemented....

## Re: #CIC filters and testing them

Rick,Thank you so much for your patience. You have helped connect a number of dots for me (that explanation of the diagram is brilliant).For other readers of this...

## Re: #CIC filters and testing them

Hi Rick, [Side note: the pictures are awesome!]Your understanding is correct. Having the two pictures is also pretty cool since its easier to see how diagrammatically...

## Re: #CIC filters and testing them

This makes a lot of sense to me, although the use of the word phase is ambiguous. I have understood differentiators to be computing the slope (i.e. the first derivative)...

## Re: #CIC filters and testing them

Hi Rick,There is certainly something different in the differentiators :-).From your first response I use M = 1, so the differentiator is looking at X(n) and Y(n...

## #CIC filters and testing them

Rick Lyons posted an informative post about testing the implementation of your #CIC decimation filters here: Two Easy Ways to Test Multistage CIC Decimation Filters...

## CIC Implementation details

I'm implementing a #CIC decimation filter. I'm doing it on an microprocessor rather than in an FPGA and that means I don't "easily" get variable bit width registers....

## Re: What is cyclic frequency α?

Consider this copy for \$104 (https://www.abebooks.com/servlet/BookDetailsPL?bi=...)Generally Abe Books is a much better source of old text books than Amazon.

## Re: phase change

Are you asking for the idiomatic way to do this in a DSP or just what does the process involve?If you're synthesizing the waveform you can just bump the value of...

## Re: New IEEE Signal Processing Society Journal

@stephanebIn my opinion the only to metrics for a "journal" are credibility and the ability to track down citations to papers in that journal.Sadly credibility has...

## Re: Increasing frequency of a sinusoids after FFT of a signal

Assuming you have the spectrum in complex form you band pass filter out the 1700 Hz, multiple the result by a .5 Hz complex sinusoid and add the result back into...

## Re: New IEEE Signal Processing Society Journal

I am always a bit annoyed by "pay to publish" journals. Especially if that journal then charges extortionately for people to get copies of the papers. Given that...

## Re: small DSP ?

Actually the Teensy 4 is pretty reasonable for this. I've got the Digilent I2S PMOD board which can do 192 kSPS in stereo.

## Re: concept of bandwidth

Hi Sharan, make your data complex with the real component being MAXVAL and your quadrature component being randomized. That will spread the signal across the entire...

Hi Chalil, It is helpful, thank you. In this particular case I am relying on the 32 bit nature of the registers to deal with overflow.The math question though is...

## Re: FFT of a sine wave signal

Per Achilles comment, the FFT is always complex, even if you feed it a purely real signal. When you combine that with the understanding that a complex signal that...