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.

Filter by
Sorted by
Tagged with
1
vote
1answer
353 views

Modeling Load Modulation

I'm trying to create a simple NFC/RFID software simulator and am having a hard time understanding the math fully. I know that NFC tags respond by load modulating the 13.56 MHz wave that the reader is ...
1
vote
0answers
125 views

Calculate a Kind of Equivalent Baseband Signal by Examining the Zero Crossing

I have a device (whose behaviour I can't change) which does the following signal processing: The incomming signal contains two frequencies $f_1$ and $f_2$. One has a huge amplitude, the other a ...
0
votes
2answers
804 views

16 psk demodulation

I have to implement a complete receiver in digital communications. The transmitter gives me an output vector which has real and imaginary values. It uses 16psk for modulation. How would I ...
2
votes
3answers
1k views

How would sigma-delta modulation work in software?

I've recently come across this YouTube video that shows a PCM stream being played back via the 1-bit internal "PC Speaker", and after hours of googling I've come to think this is done via Sigma-Delta ...
1
vote
0answers
205 views

PPM Variant - Analytic symbol error probability

I'm trying to calculate symbol error probability of variant of pulse position modulation considering only AWGN channel. The decoder is maximum likelihood so the implementation of the detector is by ...
0
votes
1answer
59 views

Algorithm to change an already sampled guitarstring to sound like it was a bit damped by the hand [closed]

I'm trying to simulate the damping of the hand on a guitarstring on an already recorded/sampled open guitarstring sound. I've been trying to use low pass filter and had a moving frequency range but ...
0
votes
1answer
639 views

I can't figure out why spectral features are “displaced” on a spectrogram

I'm trying to create a spectrogram of a complex signal 'y', but I'm running into a problem where the spectrogram that I create appears to have its spectral features "displaced" in frequency space, and ...
2
votes
1answer
995 views

QPSK, from Square Root Raised Cosine to Rectangular Impulse Shaping

I have implemented a QPSK modulator and demodulator using classic text-book examples: Square Root Raised Cosine Impulse shaping and Matched Filtering. The problem is that I've been told that I could ...
0
votes
1answer
9k views

Power Relation in DSB-FC AM [closed]

So, in my class I have to learn how to derive the power relation in a Double Side Band, Full Carrier Amplitude Modulated Wave However, I have hit a wall somewhere. ...
0
votes
1answer
152 views

Complex Exponential Narrow Band Channel

We can describe a BPSK signal, x, as: $$x=cos(2\pi f_c t+n\pi),\;n\in \{ 0,1 \}$$ The BPSK signal is then transmitted through a narrow band frequency flat Rayleigh channel, described by a single ...
0
votes
1answer
3k views

SINR calculation

I would like to calculate the total SINR of a IQ modulation system in time domain. $$ SINR = \frac{P}{N+I}$$ The blocks of the system are. Bit generation QAM modulation pulse shaper (sq root raised ...
3
votes
1answer
288 views

Improving the communication speed on a 10km cable (with high capacitance)

I'm working on improving the modem communication speed that can be achieved over a 10km cable. The current modem achieves a speed of 9600 bps via hardware (phase locked loop) and I'm looking for ways ...
0
votes
1answer
693 views

Barker Sequence for QPSK

I'm trying to implement a QPSK burst modulation and demodulation through a channel and I'm now considering the synchronization part. I've read that Barker sequence were excellent option for this as ...
2
votes
2answers
5k views

Is there a way to calculate modulation depth after the modulation process?

Suppose I have some amplitude modulated carrier wave $x$. If I have no access to the original message wave nor the unmodulated carrier, is it some how possible to calculate what is the modulation ...
0
votes
1answer
99 views

FM synthesis fuzzy sound

I'm trying to reproduce this !!!WARNING LOUDNESS!!! sound in C. In the website, it says to use Carrier: 500 Hz, modulator frequency: 1 Hz, modulator index: 500, however I'm getting lots of clicks and ...
0
votes
2answers
2k views

Why the carrier frequency does not appear after AM modulation?

Okay, this might be a very basic question, but I'm completely new to the field. I have a $40$ Hz sine wave ($1000$ samples, $fs = 1$ kHz), which I have amplitude modulated to a $4$ Hz sine wave ($...
2
votes
1answer
966 views

Frequency detection

What I have: A digital signal sampled at Fs composed of a QPSK modulation at Fmod plus some additive white gaussian noise. ...
0
votes
1answer
72 views

Double sideband AM

In A3E transmission, I wonder how a single antenna is used to transmit a carrier wave, upper sideband and lower sideband altogether at the same time?
0
votes
1answer
778 views

FM Modulation Index and Frequency trippler

Suppose I have an FM signal with modulation index mf which is passed through a frequency tripler, then what will be the modulation index of output waveform ?. Thanks in advance....
3
votes
3answers
597 views

What is the most computationally efficient way to generate 100 sine waves layered on top of each other?

Right now I simply do this (pseudocode) for freq in freqs: for i in len(samples): samples[i] += sin(...) Is there a better way? This is for ...
2
votes
1answer
874 views

How to implement IDFT using the positive frequencies of DFT, modulation and resampling on MATLAB?

This question is a continuation of the discussion at How can a linear operator on DFT vector produce the same vector using only half of the DFT vector?, where the higher level motivation is better ...
2
votes
2answers
1k views

Bandpass filter BPSK

I have a question concerning BPSK and the bandpass filter that seems to be sometimes placed before the receiver circuit (the receiver is a mixer and lowpass filter). Basically, from what I've noticed,...
3
votes
1answer
211 views

What are the options for turning a bit stream into a byte stream?

I am creating a system (modulator and demodulator) for broadcasting binary data through an analog signal. I'm using BPSK with great success – at least, I'm generating great graphs. Green is input ...
5
votes
1answer
2k views

OFDM training symbol format

For OFDM synchronisation, we are using two training symbols according to the Schmidl and Cox method of frequency synchronization and timing synchronization. The paper says: The first OFDM training ...
3
votes
1answer
871 views

obtaining “4 Hz modulation energy”

Could anybody tell me a method to calculate the "4 Hz modulation energy" for a speech signal? Thanks. EDIT I get some details : 4 Hz modulation energy: Speech has a characteristic energy modulation ...
0
votes
1answer
213 views

How should I modulate a $16$ bit input using FSK?

I need to graph a $16$ bits binary sequence, assuming that it'll be a FM analog signal I need to apply FSK to it. So, I think I should use the formula $A \cos(2\pi f_1 t)$ for binary $1$'s $A \cos(...
1
vote
2answers
830 views

Why is a precoder necessary for DQPSK and what does it accomplish?

I've implemented a soft-decoder for DQPSK using the wonderful answers I received here: How to soft decode DQPSK? To get the soft-decoder working properly I needed to precode the data I was sending ...
9
votes
2answers
4k views

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 ...
2
votes
1answer
738 views

Non-coherent receiver for DBPSK: Implementation details

I am implementing a non-coherent receiver for DBPSK. I have a computer science background with little knowledge of DSP so my questions here may seem obvious. The design of the receiver I am trying to ...
2
votes
0answers
9k views

Maximum Frequency deviation in Frequency Modulation

I am writing a script to frequency modulate the stereo audio signal, and later calculating the modulation index wrt time. As we have to modulate the stereo audio signal, I have to first synthesize ...
20
votes
4answers
88k views

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&...
2
votes
1answer
2k views

NRZ vs. Manchester pulse shaping filter (Modulator)

I'm trying to visualize the differences on the output waveform of a modulator when using NRZ or a Manchester pulse shaping filter. To keep it simple, let's think of a binary PAM signal with an input ...
2
votes
1answer
539 views

Finding the Amplitude spectrum of a FM signal

My textbook have a question p.360 problem 6.26 is like this Consider the signal $v(t) = 8 cos (2\pi [10^5 + 4 sin(5 \times 10^3 t)]t)$. And Please Draw the amplitude spectrum of $v(t)$ So, The ...
2
votes
1answer
4k views

What is the meaning of BPSK(n)

I am doing some research into GNSS (Global Navigation Satellite Systems) and have come across various signals listed as having the in-phase or quadrature channels modulated with BPSK(2) or BPSK(10), ...
0
votes
1answer
41 views

How can I graph a simulation of a FM 16 bits codification?

I have to develop a software where the user inputs a 16 bits binary sequence, which is supposed to be the codification of a FM (or even AM) signal, then I should graph it according to Frequence / Time ...
3
votes
1answer
153 views

About FM signal's proving

My text book (Communication Systems analysis and design P.334, 335) have a FM signal is $s_{FM}(t) = A cos[2\pi[f_c+ks(t)]t+\phi]$ where k is a constant and $\phi$ is the arbitrary phase angles ...
4
votes
1answer
2k views

Finding out modulation index and DC offset

I have a question form my teachers, and I cannot understand why I can find out the modulation index form the figure. The question provide a Figure like this: And the information signal is a ...
8
votes
2answers
6k views

PC-to-PC data communication over Sound FSK / PSK / DSSS

For fun and work I've to implement a java based application that can Encode text or data to sound and transmit using PC's speaker and on the receiving side is a microphone with decoder software. I ...
1
vote
1answer
2k views

OFDM transmitter data rate

i am simulating OFDM transmitter in matlab....As u all know OFDM consists of different sub systems such as FEC coding, Bit interlever , Modulator , IFFT block and Adding cyclic prefix.... i have ...
8
votes
2answers
60k views

the relationship between bandwidth and the datarate

One Question of my note is like this. ...
1
vote
0answers
115 views

The transmitted signal of DPSK

I am very confused about how to get the transmit sequence of the DPSK signal. In my lecture notes, teacher give as the following example. ...
1
vote
2answers
2k views

Need help understanding 16QAM constellation diagram

Is the identification of each point on the constellation diagram arbitrary as long as the sender and receiver know the mapping? I have seen some diagrams which order in an outward spiral, while ...
3
votes
1answer
395 views

Envelope following using FFT bin power -> Low pass effect on the modulation transfer function

I am deriving the temporal envelope of a signal (in a particular frequency band) by summing some FFT bin powers and taking the average, I do the FFT frame by frame, windowing and some overlap. ...
3
votes
2answers
3k views

Half Subcarrier spacing in LTE Uplink

First post here, trying to make it as good as possible. Do not know how to make the Python code look nice - any tips? :) Anywho - to the main problem: I am currently working on simulating the uplink ...
9
votes
2answers
1k views

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 ...
5
votes
2answers
1k views

Hexagonal Modulator Comparison with Square Modulator

Hexagonal shaped Modulator is designed to get better BER than Square Modulator. The constellation diagram is like the figure: It is supposed to give better BER measurement than Square as it has wider ...
4
votes
2answers
1k views

Is it possible to transmit and/or receive multiple types of signals at the same time?

Using an inexpensive SDR (such as the USRP or Per Vices Phi), I want to process two or more communication protocols at the same time (e.g. WiFi and GSM). Is it possible to Tx (or Rx) both at the same ...
5
votes
3answers
2k views

What exactly happens with Spread Spectrum Modulation

With regard to DSSS and CDMA(DS), what does it mean to spread a signal over a spectrum of frequencies in terms of individual frequencies? Is it about sending the same signal redundantly on multiple ...
7
votes
1answer
257 views

Why would I want to define a modulation index for each tone (DSB-FC)?

So the exercise is basically a signal $f(t)$ that is going to modulate the carrier $A\cos(\omega_ct)$ using a modulation index of $m=1$. I have to find $A$ and the power of the modulated signal: $$ f(...
9
votes
2answers
4k views

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 ...

1
5 6 7
8
9