Research and Design Consultant in DSP and Embedded Systems

Re: Advice for FM Demodulation Techniques

Reply posted 2 years ago (01/23/2020)
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

Reply posted 2 years ago (01/23/2020)
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

Reply posted 2 years ago (01/23/2020)
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

Reply posted 2 years ago (01/23/2020)
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

Reply posted 2 years ago (01/23/2020)
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

New thread started 2 years ago
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

Reply posted 2 years ago (10/22/2019)
Hi Rick,I was referring to the amount of frequency needed to transmit the number in a fixed amount of time.Greg

Re: concept of bandwidth

Reply posted 2 years ago (10/22/2019)
Yes

Re: concept of bandwidth

Reply posted 2 years ago (10/21/2019)
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

Reply posted 2 years ago (10/21/2019)
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

Reply posted 2 years ago (06/10/2019)
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

Reply posted 3 years ago (08/16/2018)
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...
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

Reply posted 3 years ago (04/23/2018)
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

Reply posted 4 years ago (02/20/2018)
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

Reply posted 4 years ago (01/25/2018)
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

Reply posted 4 years ago (01/25/2018)
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

Reply posted 4 years ago (01/24/2018)
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

Reply posted 4 years ago (01/24/2018)
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

Reply posted 4 years ago (01/23/2018)
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

Reply posted 4 years ago (01/22/2018)
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

New thread started 4 years ago
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

Reply posted 4 years ago (11/16/2017)
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

Reply posted 4 years ago (11/16/2017)
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

Reply posted 4 years ago (11/09/2017)
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...
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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