Questions tagged [frequency-modulation]

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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. ...
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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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159 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)...
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305 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 ...
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104 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 ...
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61 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 ...
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136 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 ...
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41 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 ...
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77 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 ...
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39 views

Losing lowest Frequencies in frequency modulated signal, rest of spectrum is fine

For several reasons I am attempting to re-modulate a de-modulated FM (as in WFM Radio) signal using python. Demodulating the initial signal goes well, it produces the PSD chart below which looks just ...
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30 views

Find the SNR of an FM broadcast signal in GNU Radio?

Any ideas on how to find the SNR of an FM broadcast signal in GNU Radio? I have seen an SNR estimator block for MPSK modulation? Do I need to create an OOT block for calculating SNR of FM signals or ...
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23 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.
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magnitude spectrum of a signal xc(t), where xc(t) = square function * cosine function

im currently learning about signal processing in school. The objective i want to achieve is to modulate the square wave to a certain frequency for transmission and apply a LPF and demodulate at the ...
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50 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 ...