Questions tagged [frequency-modulation]
The frequency-modulation tag has no usage guidance.
21
questions with no upvoted or accepted answers
1
vote
0answers
139 views
Wideband FM bandwidth estimation
In the book Modern Digital and Analog Communication Systems by B. P Lathi, there is a section for the estimation of WBFM bandwidth. First, the staircase approximation of $m(t)$ is constructed by the ...
1
vote
0answers
39 views
Non-coherent FSK and Orthogonality and square-law detectors
This is a basic figure that explains how Non-Coherent FSK actually works. The incoming signal
$ r (t)=\sqrt{2 P}{Cos}(2 \pi t (\text{fc}+\text{fi})+\text{n(t)}$
where P denotes the signal power in ...
1
vote
0answers
33 views
Instantaneous frequency, PLLs, frequency mixing, cross-correlation and the cross-correlation matrix
This is as much a request for comment and critique as anything else. I am looking at tracking how a system perturbs an input that is a (real) sinoid of varying frequency.
...
1
vote
1answer
415 views
Digital FM Demodulation
I have created a Common Lisp Library to receive samples of an FM signal from BladeRF1 SDR. I want to write a subroutine to implement FM demodulation. The input should be in the format of IQ data.
...
1
vote
0answers
42 views
Help in identifying low speed image transmission protocol over RF
In the seventies I worked for Muirhead on press fax machines that used to transmit pictures over radio and landline as I recall two FM systems were used a carrier 800 Hz modulated +- 150 Hz and 1900Hz ...
1
vote
0answers
454 views
Spectrum of WBFM signal for triangular message signal spectrum
We Know:
Frequency Modulated signal is given by:
$$s_{FM} (t)=A_{c} \sin \{ w_c t + 2 \pi k_f \int m(t) \, dt \}$$
Now,
if $ \quad m(t)= A_m \cos(w_m t)$ ,
i.e, its spectrum $M(f)$:
then,
$$s_{FM} (t)...
1
vote
1answer
974 views
How to generate IQ component for transmitting 2FSK
I am trying to generate IQ components for 2FSK modulation.
I have started off from this thread FSK and IQ modulation , but I don't quite understand the IQ TX components plotted in the example there by ...
1
vote
0answers
134 views
low-frequency amplitude with phase modulation of low Hz carrier
I am writing an FM/PM synthesizer, using Java. For the most part it works pretty well. What I am curious about is an attempt to use a low frequency tone as a carrier. By low frequency, I mean in the ...
1
vote
0answers
68 views
Angle harmonic distortion in FM modulation
As you know the output form of FM modulator is something like this:
$$s(t)=A_{C}\cos(2\pi F_{c}t+\beta \sin(2\pi F_{m}t))$$
where $\beta$ is the phase deviation. I want to know why in this book the ...
1
vote
0answers
237 views
Calculating amplitudes of FM Sidebands
How are the amplitudes of FM sidebands calculated?
E.g. when negative frequencies are reflected back and their amplitudes added to any existing positive frequencies at that band, how are the ...
0
votes
0answers
32 views
Advice on generating stable FMCW waveform
I am trying to derive parameters for a triangular FMCW waveform such that the phase of the signal has consistency from one period to the next. Perhaps this is arbitrary and feel free to tell me so, ...
0
votes
0answers
37 views
Frequency modulation: which algorithm for discrete signals (Java, Swift, etc.)
I'm writing an audio app in Swift - and one task consists in frequency modulation of a given signal (microphone input or sound file) - thus I'm iterating through all frames of a buffer like
...
0
votes
0answers
45 views
FM modulation - recovering bits
I'm trying to complete one task:
Download some FM modulated signals from page http://www.w1hkj.com/modes/index.htm. Calculate their spectrograms, i.e. short-time Fourier transform. Observe different
...
0
votes
0answers
39 views
Why does sampling chirp at peak frequency yield correct frequency response?
Followup; setting Fs = bandWidth in accepted answer's code yields the "correct" frequency response of an LFM chirp: constant magnitude, parabolic phase. ...
0
votes
0answers
26 views
Wideband FM generation problem
What I found out:
The order of the multiplier would be $n=5$.
The two LO frequencies can be 90 MHz and 80 MHz.
The bandwidth is given by $BW = 2(B_f+1)W $
Where W is the modulation bandwidth given ...
0
votes
0answers
18 views
Representing the signal $ u(t)=A_c \cos (2 \pi f_c t + \beta \cos 2 \pi f_m t) $ in terms of Bessel function
I want to represent the signal $ u(t)=A_c \cos (2 \pi f_c t + \beta \cos 2 \pi f_m t) $ in terms of Bessel function. I have done the exercise. I want someone to check whether what I have done is ...
0
votes
0answers
15 views
Demodulating FM Signals. Understanding text from “Communication Systems Engineering” by Proakis
Please help me understand the following text from "Communication Systems Engineering" by Proakis.
Text:
What I was not able to understand:
1) Why is the transfer function of the FM demodulator ...
0
votes
1answer
202 views
Question about FMCW range-velocity plot
I am working on plotting range-velocity heatmap of the receiving FMCW signal. I actually have already plotted. However, I do not really understand the mapping relationship between Doppler FFT bin and ...
0
votes
0answers
116 views
Which equipment to use for testing performance of AM, FM, and DAB
I want to test the performance of AM, FM and DAB radio in RTL-SDR. I want to measure sensitivity, adjacent channel selectivity, cross-modulation/blocking, and third-order intermodulation to be some of ...
0
votes
0answers
25 views
Is there a software/application that shows the FM base stations nearby us?
I want to collect a list of FM base stations near me. I have found apps/software for finding LTE base station but found no success in finding an app for FM base station.
-1
votes
1answer
62 views
Better way for fine-tuning to FM signal
I'm looking at fine tuning the frequency to a known FM broadcast automatically. (from complex signal) My beginner's idea is to either:
lowpass filter to get ~2x the bandwidth visible
do the frequency ...
