Questions tagged [frequency-modulation]

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FSK and IQ modulation

I am having trouble understanding the FSK modulation process. There are many ways of demodulating the FSK signal. What is the advantage of performing the FSK using IQ modulation? How to demodulate ...
106 views

How to estimate the frequency characteristics of a nonlinear chirp?

Given a partial time-domain recording of a noise-corrupted chirp that asymptotically approaches a frequency, and the function that determines the non-linearity, how can I accurately estimate the final ...
51 views

Fourier transform of frequency division

I need a mathematical description of what happens to the spectrum of a signal when that signal is processed to divide its frequency. As an example, construct an input signal as the sum of two sine ...
579 views

How does the RaspberryPi radio hack convert digital GPIO signals to an FM signal?

After having looked at various explanation of how the RaspberryPi FM transmitter hack works, I realize there are some fundamental pieces missing. Most explanations talk about how to construct a ...
202 views

Recommendation for good ressources on digital processing and D-QPSK

I've been a C++ developer for 10 years. Quite high level. And I am completely new to Digital Signal Processing. I am trying to implement a Software Defined Radio. Specifically I am trying to receive ...
154 views

Simulation of a Frequency ramp

This might be an easy one! Please preface your answer with spoiler notation by typing the following two characters first ">!" Given the following equation that describes a cosine wave as a function ...
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FM modulation audio 50 Hz – 16 kHz MATLAB

I'm trying to modulate in FM an audio signal $x(t)$ coming from a microphone which works from 50 Hz to 16 kHz in MATLAB. But the problem is that I want a FM Bandwidth of 25 kHz at the output of ...
755 views

Hilbert Transform of an FM Signal

The Hilbert Transform of an Amplitude Modulated signal returns the envelope of the signal. What does the Hilbert transform of a Frequency Modulated signal return? How can I use the Hilbert Transform ...
552 views

Formula of frequency modulated sine wave from data points

I'm trying to determine the formula of a variable frequency sine wave based on the values of max1, max2, min1 and min2. y(0) isn't necessarily 0 and I can assume the frequency increases or decreases ...
284 views

Biquad cookbook formula for broadcast FM de-emphasis?

Can a simple IIR biquad filter be used as an audio de-emphasis filter for broadcast FM radio? If so, how does one translate the filter requirements (50 uS time constant in the U.S.?) into parameters ...
679 views

How to express FM and PM the most simple way?

I'm trying to understand how to tell phase modulation from frequency modulation by looking at their respective expressions, simplified, particularly frequency modulation. Also, it would be nice for ...
82 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. ...
33 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 ...
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FM synthesis algorithm is not very efficient

I have very little knowledge of DSP, I'm trying to implement an FM synthesis algorithm in code / software. So far I've successfully implemented a FM algorithm using the following: ...
372 views

Software to extract frequency spectrum data from an audio file

I've been trying to learn how computers recognize musical notes, and I found apps like spectrogram which shows the frequency spectrum of a sound, but what I need is the data which is plotted or the ...
297 views

Carrier Recovery, Frequency and Phase offset in (CP)FSK

I wanted to ask what exactly is meant for phase recovery of signal (at least intuitively). I have a working example of an acoustic fsk modulation and demodulation software but i don't know how to ...
142 views

How is multiplexing on FM signals performed? [closed]

How does multiplexing differ from FM signals to AM signals. If both FM and AM shift the message signal in frequency, then is there a difference between multiplexing for FM or AM signal?
47 views

The link of the statement is evidenced in this book: I don't understand how equation 85 come? I try to use Carson rule to see this inequality but turns out I have $2 \Delta f$ instead of $3 \Delta f$....
310 views

FM demodulation

I have a frequency modulated signal. My problem is the following: The sidebands are asymmetric. Meaning that the amplitudes of the sidebands left and right are not equal. Does anyone know what this ...
55 views

MATLAB produces too short output for frequency modulation

I have a voice data contained in a vector. Vector length is 118796 and sampling frequency is 8000 Hz. So it's around 15 seconds of voice data. When I doing frequency modulation with fmmod (Carrier ...
1k views

IQ FM Demodulation of Wow and Flutter Signal in Software

Background: I have a recording device that exhibits Wow and Flutter, or periodic frequency deviation. I use this device to record a calibrated 3.15kHz test tone from a tape film to generate a .wav ...
762 views

Combining 2 sinusoids of equal amplitude with different frequencies into 1 new “wave”

This question is about combining 2 sinusoids with frequencies $\omega_1$ and $\omega_2$ into 1 "wave shape", where the frequency linearly changes from $\omega_1$ to $\omega_2$, and where the wave ...
Solving for frequency deviation, $\Delta f$ (FM modulation)
I'm sorry if I posted this in the wrong section. I solved the question and got $50\textrm{kHz}$, but the solution says it is $100\textrm{kHz}$ without any proof. Im asking for someone to tell me ...
How do we compute maximum frequency deviation of a NBFM wave, given by following equation$:$ $cos(2\pi f_c t) - \beta sin(2\pi f_c t )sin(2\pi f_m t)$ Where $f_c$ is carrier frequency and $f_m$ is ...