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.

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Half Sine Pulse Shaping design

The standard of 802.15.4 specfies the following 'The chip sequences representing each data symbol are modulated onto the carrier using O-QPSK with halfsine pulse shaping.' For pulse shaping the ...
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17 views

BER of OQPSK Modulation

I am unable to find out a formula for the BER for the OQPSK Modulation. Currently, I am using the berawgn function from Matlab to calculate the BER for OQPSK but I am looking for an expression for ...
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21 views

A question related to “quadrature carrier multiplexing” [migrated]

While studying 'Qaudrature carrier multiplexing', I came across these statements in my text material: "Precisely varying the phase of a high-frequency carrier sine wave in a hardware circuit ...
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1answer
25 views

What is the difference between upsampling and up conversion (done during signal transmission)? Also is upconversion different from modulation?

Up sampling is when you increase the sample rate of a continuous signal. Modulation is when you, by multiplying with a carrier, shift the base frequency of a signal. But what is up conversion? How is ...
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23 views

Fractal Modulation Implementation

I would like to get help/assistance from whom could support me. I am trying to simulate the Fractal Modulation where the modulation and demodulation equations defined as: Modulation Equation ...
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1answer
52 views

WFM SDR and Audio resolution

How does SDR resolution translate to audio resolution when using FM demodulation? For example: using a 8-bit/2.048 Mhz IQ stream, what is the maximum audio sample rate and bit depth that can be ...
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45 views

DTFT of beat signal with shift due to multiplication

I am simulating a FMCW radar (Ramp signal is used for transmission)and I have created the transmit signal from matlab FMCW model ...
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2answers
37 views

Question related to Principle of Communication

Why the frequency of carrier wave is always kept at least $10$ times higher than the highest frequency of base band signal? Can you explain me this with a practical example?
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23 views

Frequency modulation of audio signals. Does increasing the pulse width of frequency tone result in larger operating distance?

I have a simple frequency modulation scheme where in I am sending simple textual data by encoding it into specific frequencies(for example 'a' is converted to ASCII value of 97 and I use 10 ...
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36 views

8x4 QAM gray coded in Matlab

I try to modulate and demodulate 8x4-QAM gray code in Matlab (see the picture). However, when I try: ...
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3answers
54 views

Can OFDM modulate analog signal?

I suppose that OFDM can't modulate analog signal. The basic mathematical description for OFDM is $$ v(t)=\sum_{k=0}^{N-1}X_{k}\exp(j2\pi k t /T),\quad 0<t<T$$ In this equation, $X_k$ is a ...
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1answer
145 views

Rectangular 8 QAM bit error rate calculation

I am simulating an 8-QAM communication system over an AWGN channel for various signal to noise ratios, in order to plot the average bit error. However I have not been able to derive an equation for ...
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1answer
28 views

Must OFDM signal be time-division in a multiple-transmitter and SFN system when the signal is free of spread-spectrum?

The OFDM baseband signal can be demodulated since each subcarrier is orthogonal to another. But In SFN system, i.e., Single Frequency Network, all OFDM signals from several transmitters are in the ...
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1answer
46 views

Processing OBPSK as OQPSK

I'm trying to create and process an OBPSK signal, which, as I understand it, transmits even bits on one axis and the odd bits on the opposite axis, resulting in a constellation with 4 unique points. ...
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1answer
33 views

How does sampling and subsequent resampling affect aliased harmonics?

If I sample a signal with a harmonic higher than half my sample frequency I can predict the aliased frequency easily as $$|F_h-kF_s|$$ But what if after sampling the signal, I re-sample at a lower ...
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0answers
33 views

Carrier power in Amplitude Shift Keying (ASK) modulation

Let's assume I am receiving the following signal, the carrier is not represented here, just the envelop: This signal has an infinite bandwidth, but let's assume for a moment that the channel also ...
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1answer
21 views

dvb-s to dvb-c direct transmodulation

Is this possible to direct trans modulate DVB-S/S2 -> QI into -> DVB-C/C2 signals without doing it the way DVB-S/S2->Demodulator.ic-Transport Stream -> Modulator.ic-Transport Stream -> DVB-C/C2 ? Qpsk ...
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7 views

Can the receiver figure out the current value of Delta?

For an Adaptive Delta Modulation sceme, can the receiver circuit know the value of the current Delta (not Delta-1)? I think that it can't because transmitter uses 1 time slot delay, can someone ...
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0answers
47 views

Modulating Gaussain Pulse

I'm trying to generate a modulated Gaussian pulse. First I'm generating the pulse in the time domain perform FFT and displaying both in time and frequency, then I'm multiplying it with cosine term ...
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37 views

Minimum Shift Keying (In-phase, Quadrature Components derivation)

In the derivation of the minimum shift keying in-phase and quadrature components in Simon-Haykin Communication Systems 4th ed (p.387-390) we start off with the definition of the signal to be $\ s(t) ...
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42 views

How to simulate two OFDM Users with low complexity FFT/IFFT?

have two User one of them sending over freq (0-B] and the other transmit over (B-2B]. Both of them are using OFDM and each one has Nc subcarriers. I wanted to simulate the received signal using ...
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106 views

Confusion in the spectrum of FSK modulated signal by using matlab fskmod module

I want to do a comparison of power spectral density of BFSK, 4FSK and 8FSK by using matlab baseband module "fskmod".Following is ...
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1answer
38 views

Calculate properties of a given Modulated Signal

I'm having a hard time trying to understand signal modulation graphics and how can I calculate/find the properties of the signal. The properties I'm talking are: Max. amplitude Carrier frequency ...
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2answers
79 views

Relationship between Carrier Frequency Offset and the Constellation Diagram

As part of a project I am doing, I have to investigate how having a carrier frequency offset would affect the constellation pattern of the received signal.This question has got me baffled because to ...
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2answers
109 views

OFDM violates sampling theorem

The "textbook" OFDM block diagram is as the below figure. But I wonder if it satisfies the sampling theorem. Here, we have N points $X[k]$ before IFFT, and $$x[n]=\frac{1}{\sqrt{N}}\sum_{k=0}^{N-1} ...
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1answer
317 views

How to recover complex values (downconvert) from FM modulation (composite signal)?

How does one recover the complex IQ data from the output of a FM modulator. I have combined my signals correctly and performed FM modulation on them, now I'm looking for a way to find the IQ values ...
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1answer
155 views

MSK signal recoverd though FM Discriminator?

I am attempting to write a FFSK (differentially encoded MSK) modulator. I have found and implemented a demodulator that works with sample data taken from a radio of a FFSK signal. The demodulator ...
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1answer
331 views

why LTE doesn't use DC subcarrier in the downlink?

I know LTE doesn't use the DC subcarrier for OFDM/OFDMA modulation for the downlink, but no author gives a detailed explanation to this stuff. Can you tell me the reason behind it? Thank you!
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1answer
52 views

phase mod x freq mod equivalence

do any of you know how to convert a FM index to a phase mod index equivalent considering they both have the same carrier and modulator frequency? Is it even possible? This is in respect for sound ...
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1answer
59 views

what are and why are sine and cosine modulated integrals used?

I have found the definition of the following formulas in a paper regarding active vibration control, where they are called sine and cosine modulated integrals. $y$ is measurement signal with a strong ...
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65 views

Gettiing a rectangular waveform from OOK in Python

I have a wave (wav) sound file with on-off keying. I can read the signal value at any point in time (granularity of the sample rate) from an array. I want to create another array, the same size as ...
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2answers
698 views

C/C++ library for digital modulation [closed]

Is there a library written in C/C++ that offers functions like QPSK modulation?
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1answer
25 views

How to model the dispersion which is introduced by an electro-absorption modulator (EML)?

I need to model the dispersion which is introduced by an EML in Matlab. The parameters are: Lambda: 1310nm PAM4 power: Pmax = 1.09 mW Pmin = 0.13 mW Bandwidth = 56Gbps
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2answers
74 views

Tuning a radio to a certain frequency

I've a fundamental problem with understanding terminology used in DSP. What does it mean to tune a radio (for example, a software defined radio) to a certain carrier frequency $f$? The received signal ...
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101 views

What is dynamic pulse-width modulation?

I'm working through exercises in a book called The Audio Programming Book and have been doing okay for nearly 300 pages, but have just got stuck. (I'm a musician, not programmer or audio specialist ...
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3answers
274 views

Reason of circular conv in OFDM

In OFDM system, after IFFT a CP is added at the beginning of the OFDM symbol by copying it from the end of the symbol.My question is that with CP why we use cyclic convolution instead of linear ...
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1answer
157 views

How to transmit the real+imaginary output of an IFFT over a transmission channel?

I'm working on a modem system using a 16-QAM scheme. The transmitter runs an IFFT to modulate the signal, and has a 12-bit DAC. The receiver runs an FFT to demodulate the signal, and has a 12-bit ADC. ...
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1answer
767 views

Modulation and it's application [closed]

Why do we need different modulation techniques? Is it because we need to convert from analogue to digital data sometimes? Also what are typical applications where modulation schemes are used apart ...
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1answer
199 views

Normalizing 32QAM constellation points [closed]

By which value can the constellation of a 32QAM be normalized? for example 16QAM is normalized by squareroot of 10.
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17 views

BER and SER of QAM [duplicate]

I want to find the SER and BER of the 4QAM,16QAM,32QAM. I know that the formulas for SER and BER are different but I cant find them in any text book. The formulas for the BER that I found: 4QAM = ...
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1answer
523 views

How is the symbol error rate for M-QAM, 4QAM,16QAM and 32QAM derived?

How do you derive the theoretical symbol error rate as a function of $E_\mathrm{b}/N_0$ for 4QAM? I know that the result should be $Q\left(\sqrt{2E_\mathrm{b}/N_0}\right)$ but I am ĺooking for the ...
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1answer
145 views

Really basic question about OFDM

I am new to signal processing and am currently doing research into the subject. I am learning about Orthogonal Frequency Division Multiplexing and have a question. Most definitions of OFDM mention its ...
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3answers
94 views

How do you perform OFDM modulation?

I'm new to OFDM modulation. During OFDM modulation in the frequency domain, are the negative frequencies modulated with a conjugate version of the data of the positive frequencies, or do the negative ...
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0answers
49 views

TDE, OFDE and FDE equalizer simplest exmple in matlab

I want to implement the equalizer in matlab. I am just learning this. I want a good kick start code that can help me to learn it further. I searched a lot on Google but do not find a good reference ...
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1answer
176 views

MSK spectral efficiency explanation

Why is MSK (minimum shift keying or FSK with a modulation index of 0.5) said to be a spectrally efficient form of FSK?
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1answer
37 views

what are the applications of fourier transform in modulation

what are the applications of Fourier transform in modulation ? What are modulation schemes that use Fourier transform? I guess, FSK & PSK are related to Fourier transform since it both have ...
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1answer
278 views

Simulink for Amplitude Modulation

I am using Matlab Simulink to analyse Amplitude Modulation in Noise. I attached my system below. My problems: 1)In the mixer I am using a bandpass filter and another one after the envelope ...
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3answers
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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). ...
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1answer
392 views

Implementing QPSK Demodulation

I conducted a research on how to implement a QPSK demodulator. I found out the Quadrature QPSK demodulation technique which seems very straight forward. Here is what i understood from the explanation ...
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54 views

TDOA using demodulated signal

Is it possible to find time delay of arrival using demodulated signals (of bandwidth ~200hz)? I have a setup in which I receive (multiple receivers, of course) modulated signal from a source. I want ...