Signal Processing Stack Exchange
Signal Processing Stack Exchange

Questions tagged [modulation]

Modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with the amplitude of low-frequence modulating signal which typically contains information to be transmitted.

The three key parameters of a periodic waveform are its amplitude ("volume"), its phase ("timing") and its frequency ("pitch"). Any of these properties can be modified in accordance with a low frequency signal to obtain the modulated signal. Typically a high-frequency sinusoid waveform is used as carrier signal, but a square wave pulse train may also be used.

Source: Wikipedia.

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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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How to mimic/copy/fake someone's voice?

Is there any existing application to sample someone's voice and use it to modulate any other voice or synthesize a text to resemble the original one? For example, this Text-to-Speech Demo by AT&T lets you choose a voice and a language from presets…
clapas
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What mathematical tools exist for understanding modulated noise?

Suppose we have a signal $n$ that consists of Gaussian white noise. If we modulate this signal by multiplying it by $\sin 2\omega t$, the resulting signal still has a white power spectrum, but clearly the noise is now "bunched" in time. This is an…
nibot
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Can we break the Shannon capacity?

I have a friend working in wireless communications research. He told me that we can transmit more than one symbol in a given slot using one frequency (of course we can decode them at the receiver). The technique as he said uses a new modulation…
Learning
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Transmit data through sound between 2 computers (very close distance)

I'm writing an example on transmitting data through sound betwwen 2 computers. Some requirements: The distance is very close , i.e the 2 computers are basically adjacent to each other Very little noise (I do not think my teacher would turn on a…
Dang Manh Truong
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Why do SDR receivers emit I/Q samples?

To my understanding hardware receivers for software-defined radio applications basically take the input signal, mix it with the tuning frequency to remove the carrier frequency and then sample the resulting voltage with a sampling rate that is just…
AndreKR
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FSK Demodulation, Bit Timing Recovery

I am currently implementing acoustic FSK modulation and demodulation. I am not a signal processing guy so any help about the bit timing recovery would be very appreciated. Currently I implemented the demodulator using two matched filters for each…
peter
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What are the basic categories of operations performed on audio signals to create interesting sounds?

I don't know if this question will make sense as I'm very new to dsp. In my limited foray into audio dsp I've come across: Frequency Modulation Amplitude Modulation Additive Synthesis Subtractive Synthesis My question is: are these the main…
kiman
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the relationship between bandwidth and the datarate

One Question of my note is like this. Consider a communication channel with a bandwidth of 2400Hz. If QPSK technique is used, what is the possible transmission rate? (Assume that rectangular pulses are used in the baseband signals, and that 90%…
Samuel
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What are thoughts on best modulation to use for underwater acoustic communications at low frequencies?

I wanted to ping the DSP hivemind for general thoughts on what would be the best modulation type to use for low frequency underwater communications. I have chosen this project since I can learn a lot from it. Some context: Low frequency as in <…
Spacey
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How to soft decode DQPSK?

I'm successfully soft-decoding D-BPSK by taking the dot-product of the constellation-position of the symbol and of the previous symbol. If the result is >= 1, then the symbol phase hasn't changed and the bit is a zero. If the result is <= -1 then…
Dan Sandberg
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Deep space communications BER and FEC?

What kind of bit error rate do they get from deep space communications (Pioneer, Voyager, et.al.), and what kind of modulation and FEC allows them to recover messages with that microscopic level of received signal power? Are there more modern…
hotpaw2
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What is a $BT$ (Bandwidth-Time) product with reference to modulation?

I would like to know what does Bandwidth-Time product mean. I understand that Bandwidth ($B$) = 1/Symbol Time ($T$), hence $BT = 1$. But how can it vary? What is its significance? e.g. When we say GFSK is GMSK when $BT = 0.5$, what does that mean…
eecs
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Spectrum of FSK signal

I have implemented a simple V.23-like FSK modem in C here. The peculiarity of the chosen modulation is such that 0's and 1's are sent as tones of two different frequencies (2100 Hz and 1300 Hz respectively) and the duration of each symbol is…
Alexey Frunze
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Why are sidebands generated in AM and FM?

When the signal is modulated onto the carrier in the electromagnetic spectrum, that signal occupies the small portion of the spectrum surrounding the carrier frequency. It also cause sidebands to be generated at frequencies above and below the…
Sufiyan Ghori
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