### Greg Lapin (@GregLapin)

Research and Design Consultant in DSP and Embedded Systems

## Re: Advice for FM Demodulation Techniques

Thanks, Peter.I'm interested.Nothing was attached.Can you send it to n9gl@comcast.net?Thanks again.Greg

## Re: Advice for FM Demodulation Techniques

Kaz,I'm not sure what you mean about +/-.Are you describing the I and Q components of the original signal?Greg

## Re: Advice for FM Demodulation Techniques

Thank you for the reply, Kaz.All signals are AC coupled, evenly spaced around zero.I got that [1,0,-1] filter from Rick Lyon's FM demod paper as a method of performing...

## Re: Advice for FM Demodulation Techniques

Thanks, Neil.I read Rick's article before starting this task.  I'm following his figure 13.60.  Modeling in MATLAB with a sine wave I get a result that sort of...

## Re: Advice for FM Demodulation Techniques

Thanks for the response.I thought I had performed what you described but the results weren't as expected.In MATLAB I generated a 1000 Hz sine wave and modulated...

## Advice for FM Demodulation Techniques

I'm looking for advice on the best way to perform FM Demodulation.Most methods I've found work with baseband FM signals.I have a quadrature FM signal that is modulated...

## Re: concept of bandwidth

Hi Rick,I was referring to the amount of frequency needed to transmit the number in a fixed amount of time.Greg

Yes

## Re: concept of bandwidth

Sharan,What I meant was if you represent a number with more bits then you need more bandwidth.  The actual values don't matter but the value 1 in an 8-bit number...

## Re: concept of bandwidth

Bandwidth is a property of the data being transmitted.  The sampling rate, as long as it exceeds the minimal Nyquist rate, has no effect on the bandwidth.  Data...

## Re: Sign of the magnitude difference

Equation 1 calculates the magnitude difference ignoring the phases of z1 and z2.  I would consider that difference to be incorrect because of this.Equation 2 calculates...

## Re: Removing DC Spike from an FFT

Tom,One obvious question would be if your samples are signed or unsigned numbers.  If your ADC provides unsigned numbers you need to convert to signed values before...

## Re: Spectrum of discrete-time random process - DFT of autocorrelation, vs signal itself

It seems to me that by performing the autocorrelation you are doubling your time domain data, which is then transformed to the frequency domain.  However, you aren't...

## Re: I/Q sampling basics

Joakim,Mixing the incoming signal with a cosine in the I path and with sine in the Q path provides the 90 degree delay.Greg

## Re: Looking for tips to improve SNR

Tim,Just out of curiosity I tried modifying the phase (0, 45, 90, 135, 180) of the incoming sine wave signal and there was very little difference between the Goertzel...

## Re: Looking for tips to improve SNR

Tim,I'm not married to the Goertzel algorithm.  It just seemed like the best alternative for tone detection in my case.Would you point me to detailed descriptions...

## Re: Looking for tips to improve SNR

Rick,The end goal is to determine the modulated tones. So, you are correct that the sideband of the 1000 Hz carrier is what's important to me.Currently, I demodulate...

## Re: Looking for tips to improve SNR

Tim,I'm measuring 10 dB SNR over the air with a spectrum analyzer.  The RBW is 500 Hz.Maybe I can convince you of one of the benefits of the Goertzel algorithm. ...

## Re: Looking for tips to improve SNR

Rick,You've got it exactly.The reason I used Goertzel filtering is that I can use a custom 'N' for each frequency.  Since the tone frequencies I'm interested in...

## Re: Looking for tips to improve SNR

Rick, Fred, and Tim,Since I am somewhat graphically challenged, let me describe the receiver architecture to you in text and see if that makes it clear enough:VHF...

## Re: Looking for tips to improve SNR

Thanks for the reply, Fred.Signal is amplitude modulated with single frequency tones that range from 190 Hz to 489 Hz.  Each tone burst lasts for 60 msec.Demodulation...

## Looking for tips to improve SNR

I'm receiving an AM tone-encoded signal using heterodyne receiver hardware with I/Q output.  The second IF frequency is low but still above the modulating tones. ...

## Re: Off Topic: A geometry problem

Rick,Geometry was never my strong suit, but the solution seems correct to me.  They do make one error in wording by saying that they "minimize the combined distance,...

## Re: Off Topic: A geometry problem

If you are driving the car and your friend is the passenger then this is the correct solution.  However, what if your friend was driving?  And shouldn't the book-buyer...

## Re: Estimate battery run-time in real-time

Hi Markus,The most common way that batteries are tracked these days is with a "Battery Fuel Gauge" device.  They typically monitor the charge going in when the...

## Re: What is the most efficient way to represent or approximate a waveform?

Fourier Transforms are not the best way to exactly encode a signal.  The transform is defined over infinite time, so practical implementations window the signal,...

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