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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23 views

Why does DPSK constellation shrink when noise is added?

I am generating a DQPSK waveform at complex base band with constellation points on the unit circle and when I add AWG noise the constellation shrinks. The noisy constellation "blob" migrate inside ...
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1answer
24 views

What is the spectrum of modulated noise?

I use a white-noise generator in an rf bridge to measure antenna impedance. The receiver is an ordinary AM/CW/SSB communications type, nothing fancy, nothing 'coherent'. As I approach the null of the ...
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13 views

Radar Waveforms Simulation

I am looking for a simulation in any software language, preferably Matlab, that shows the steps from generating the radar signal or waveform (chirp, Barker Code) to modulation, and transmission by the ...
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11 views

What types are Radar Chirp and Barker Code Signals

I would like to know if the radar chirp signal and the Barker coded signals are analog or digital before modulating the carrier. In other words, are the radar signals getting to the antenna analog or ...
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27 views

Binary FSK optimal detection rule

Let us consider BFSK modulation with symbols $\in {{1,2}}$. For symbol m the transmitter sends $s_m(t)=\sqrt{P\over T} e^{j2\pi f_mt}$ where $m=1,2$ and $f_m$ is symbol's $m$ carrier frequency. The ...
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29 views

BFSK modulation what signal the transmitter actually sends?

I am trying to understand how modulation with carriers works(transmission part). I will express my question in terms of BFSK for simplicity. Let us condiser BFSK modulation with symbols {1,2}. Then ...
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1answer
20 views

Maximum Likelihood carrier phase estimation of $Acos(2\pi f_ct)$

This question refers to the example 5.2-1 of the book "Digital Communications, 5th Edition by John Proakis, Masoud Salehi" (example 6.2-1 in the 4th edition of the book) which asks for the estimate ...
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22 views

Reversible QIM For watermarking

I have read your paper with title "Nested Quantization IndexModulation for Reversible Watermarking and Its Application to Healthcare Information Management Systems". enter link description here ...
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41 views

Very high SNR BPSK modulation

I am using BPSK modulation to modulate a signal in continuous time (making rectangular waveform, multiplying by a carrier). The channel is band-limited and frequency-selective, and has the following ...
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14 views

Basics of Sphere Decoding for MIMO

I am working on a project that involves Spatial Modulation for MIMO channels. This uses a ML (Maximum Likelihood) detector which is computationally intensive. Sphere Decoders are developed to reduce ...
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1answer
66 views

BPSK modulation under bandlimited channel

I modulated signal using BPSK modulation and I have series of -1 and 1. Now I have to pass these signal from band limited channel that has frequency response of the form ...
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1answer
57 views

Spectral density of modulated noise process

Suppose we have a noise process $F(t)$. Suppose $F$ is stationary and we know its autocorrelation function $$\rho_F(\tau) \equiv \langle F(0)F(\tau) \rangle$$ where the average is over realizations of ...
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39 views

Effect of Pulse shaping on BER

am trying to implement OQPSK modulation with half sine pulse shaping. If I simulate the OQPSK modulation without pulse shaping, the simulated curve is similar to the theoretical value. However, when I ...
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62 views

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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0answers
73 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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1answer
45 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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30 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
79 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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60 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
64 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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30 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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45 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
70 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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199 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
31 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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2answers
83 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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40 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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55 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
29 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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8 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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54 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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41 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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45 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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154 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
44 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
89 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
122 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
493 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
182 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 ...
2
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1answer
462 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
56 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
62 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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2answers
980 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
26 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
85 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 ...
2
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0answers
108 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
367 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
221 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
871 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
251 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.