Questions tagged [frequency-modulation]
111 questions
27
votes
6 answers
Why can so little digital information be stored on a cassette tape?
I had heard that tape is still the best medium for storing large amounts of data. So I figured I can store a relatively large amount of data on a cassette tape. I was thinking of a little project to read/write digital data on a cassette tape from my…
Pouria P
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7
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3 answers
Why do we integrate the modulating function in FM?
I've been reading about FM and I keep coming to an expression, where the instantaneous phase
$$\Theta=2\pi f_it+\phi\text, \tag1$$ where
$$f_i=f_c+k_fm(t)\text,\tag2$$
($f_c$ being the base carrier frequency and $k_f$ being some proportionality…
Ivan
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4
votes
1 answer
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 of time:
$$m(t) = \cos(2\pi f t) $$
We know that…
Dan Boschen
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3
votes
1 answer
Positive slope of BER with a greater frequency deviation?
I am trying to implement a frequency-modulated communication channel on MatLab. However, there is something I don't understand about the sensitivity of the frequency modulator (or the frequency deviation as my signal has an amplitude equal to 1). My…
Théo
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3
votes
1 answer
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 waves of different frequencies (as commonly used in…
Brian K1LI
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3
votes
1 answer
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 frequency it approaches?
Here's an example of…
rsaxvc
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3
votes
2 answers
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 the FSK signal?
Does the FSK signal look…
Fedaa
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2
votes
2 answers
I'm missing something when it comes to understanding FM
I understand why FM is preferred for music: noise is mostly amplitude modulated, FM yields much higher fidelity. I also understand why commercial FM signals have a much larger bandwidth than commercial AM signals: the signal spectra of the former…
Nick Elias
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2
votes
1 answer
How to Modulate down a hidden message after filtering base signal from audio file
I have an audio file that is 6 seconds long. The file has a message hidden into it in the ultra high frequency range. I plot the Mel Spectrogram with a sample rate of 44100 and use a high-pass filter to filter the base signal, here is the mel…
Alan Judi
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2
votes
1 answer
What is the advantage of using a Stepped Frequency waveform over FMCW?
What is the advantage of using a Stepped Frequency Waveform instead of a traditional linear FMCW ?
Hp179
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2
votes
2 answers
Spectrum of FM signal?
If a carrier ($f_c$) is FM modulated by a single sine wave ($f_m$), its spectrum is composed of frequencies at $f_c + kf_m$ ($k \in \mathbb{Z}$) whose amplitudes are weighted by $J_n(\beta)$, the $k$-order Bessel function of modulation index…
Elaws
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2
votes
2 answers
Power of an angle-modulated wave
Let $$\phi(t) = A\cos(\omega_c t + km(t)) \tag{1}$$ be an angle-modulated wave(FM or PM). What's the power of $\phi(t)$? Intuitively, it seems that the answer is $$P = \frac{A^2}{2} \tag{2}$$ since the amplitude $A$ remains constant but I couldn't…
S.H.W
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2
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1 answer
How to convert sampled real audio signal to it's IQ components for IQ modulation?
So my question is this:
How to convert sampled real audio signal to it's IQ components for IQ modulation?
For instance: WHen I have my DSP or FPGA receive a audio signal through a ADC, which is just the RAW A/D value. Now I want to run this…
SpinlockData
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2
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1 answer
About phase unwrapping
I am not too familiar with phase-related problems so I need some suggestions or corrections in a problem that might be an old but easy one. Here is my problem: given a complex signal:
$$y(t) = e^{j\phi(t)}$$
where $\phi(t)$ is the instantaneous…
ZHUANG
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2
votes
1 answer
What's the relationship between the parameters of this noise generator and the gaussian curve it produces in the frequency domain?
This algorithm produces a sequence $y$ having a magnitude spectrum that resembles a normal distribution, peaking at frequency $\omega$:
$$b[n]=(1-\sigma)b[n-1]+\frac{\sigma}{\omega} C$$
$$p[n]=p[n-1]+\omega(1+b[n])$$
$$y[n]=cos(p)$$
where $b[n]$ is…
JavariG
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