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Questions tagged [frequency-modulation]

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How do we compute maximum frequency deviation of a NBFM wave?

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 ...
87 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. ...
344 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 ...
821 views

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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 ...
35 views

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 ...
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 ...
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.
14 views

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 ...
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 ...
51 views

Frequency modulation audio synthesis: clicks/pops when changing modulator frequency dynamically

I'm very new to DSP and working on a FM VST. It's mostly up and running, or at least it generates FM-like sounds. I want to be able to change various parameters dynamically while audio is generated, ...
195 views

137 views

How to isolate overlapping FM signals?

Analogue radio stations often have a range of frequencies that they can use. Different transmission towers will transmit on different carrier frequencies in this range, because the signal takes time ...
159 views

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 ...
97 views

Increase Radar Detection range using Modulation

I have been reading about pulse compression which helps with the range resolution. In my application I do not need to measure the range of the object however I am more interested in boosting the SNR ...
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 ...
779 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 ...
106 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 ...
64 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 ...
311 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 ...
471 views

FM signal detection

I'm just playing around with cheap RTL based SDR dongle and I wanted to implement a simplistic FM radio receiver. I managed to get mono sound with no problem, however I decided to implement automatic ...
904 views

How to Design a Pre-emphasis filter knowing the gain, a zero and a pole?

I am simulating an FM radio signal in order to use it as a waveform in passive radar; for this purpose I'm following an article: Analysis and Emulation of FM Radio Signals for Passive Radar In a ...
179 views

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 ...
2k views

How does complex data of an FFT and IQ modulation differ?

If I have an arbitrary time domain signal (e.g. a simple cosine) i can sample it with an ADC and get a time discrete representation. I can perform an FFT on the samples and get a complex output. The ...
74 views

How does the earphone cable in a mobile phone pick up the FM reception?

As I understand, the RF frequency-modulated signal centered in the range of $88-108\textrm{ MHz}$, is picked by the earphone antenna and is directly sampled by the sound card adc at $48\textrm{ kHz}$ ...
556 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 ...
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 ...