Generic term for coding information onto another carrier signal

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43 views

Retrofit a Hi-Fi remote with a RF 433 MHz module

In the past I used a remote for a AIWA Hi-Fi to control a AVR processor and circuit I custom made. I used an infrared receiver from Vishay (tuned on the 38 kHz) to demodulate the signal, then fed to ...
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3answers
54 views

Is there a Binary Frequency Shift Keying (BFSK) with only one sine tone?

I mean a modulation technique where a binary one is represented by a sine wave with some frequency F and a binary zero is represented by an absence of any signal, or vice versa. Does it have a "right ...
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0answers
25 views

Compressed single-sideband modulation?

I've had an idea for a new form of SSB modulation, using half-angle formulas as a basis for compressing the sideband of a SSB voice transmission. However, this idea seems so simple that I feel it must ...
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1answer
34 views

Bessel Differential Equation and Angle Modulation

I'm trying to undestand the role of the Bessel differential equation in calculating the side bands of a phase modulated signal. I started out with the textbook example $$u_{PM} = cos(w_C \cdot t + ...
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1answer
39 views

QAM demodulation , hard vs soft if there is any

I am trying to find the answer to , what types of demodulation methods are exists. Each of my searches results with different names, but converging to one metric , which is finding the closest symbol ...
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1answer
48 views

Transmitting data over inductive charging coils (or boosting RFID/NFC power supply)

I know that data can be sent over power lines through various different types of modulation - that is as far as my knowledge ends. I have a small D.I.Y. project (a board game) that requires some form ...
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1answer
113 views

Definition of \$\mu\$

I have a question as follows. This is not a homework question I just need to clarify my doubt on how this modulation index is defined. Suppose a 2kHz audio tone having 2V amplitude is to be amplitude ...
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1answer
72 views

Why is the modulating shape appear in both sides of the carrier signal in AM?

It's about Amplitude Modulation. Can anyone tell me why is this signal wave or modulating waveform shape appears in both sides of the carrier sine wave? Why not in one side only? $$x_c(t) = A_c[1 + ...
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73 views

FM Transmitter, Jammer and Frequency Copying

I am trying out this FM transmitter circuit for a class project. As a test run I built this on a breadboard to see if it works. A Smartphone with FM radio was used to scan for the transmitter signal ...
3
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3answers
93 views

Radar Snr improvement

I have a simple radar module (k-band) that is capable of fm modulation and it provides both I and Q as baseband outputs. I like to extend the measurement range of this module by just signal processing ...
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1answer
82 views

How is FM modulation is achieved using a single BJT

I want to understand how this circuit achieve frequency modulation. The BJT is a 2N3904. I found that millers effect comes into play and varies the frequency of the tank circuit about a center ...
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2answers
284 views

Does a carrier wave need to be sinusoidal?

I am trying to AM modulate a song and I have an idea of how I am going to do it, but I need a carrier wave to start with and I've been having trouble creating one with a ceramic resonator because I ...
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1answer
88 views

Carrier generation at receiver in DSB-SC modulation?

As shown in fig., In this scheme input signal is square and passed through a narrow(high Q) bandpass filter tuned to \$ w_c\$.Finally the ouput comes to be a sinusoid of frequency \$ w_c\$. But to ...
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64 views

Analogue telecommunications modulations - example

Here is my task (Basics of analogue telecommunications): Block diagram of device for simultaneous transfer of two telegraphic signals \$u_1(t)\$ and \$u_2(t)\$ is shown on image 1. Both signals have ...
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1answer
41 views

Frequency Modulated Continuous Wave Radar: Basic Confusion

I was reading about Frequency modulated Continuous wave radar but still struggling to understand it. I have a few questions in the slide above. The blue line in the graph represents the transmitted ...
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1answer
58 views

How does modulation technique affect channel capacity?

Shannon's channel capacity formula does not consider modulation techniques. How then does LTE achieve high data rate using advanced modulation techniques? P.S: I am novice in RF and signal ...
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0answers
56 views

optical wireless link short range high throughput

I am student and I want to realize a wireless optical link in order to have a throughput of 100Mbps max and the distance between the emitter and the receiver is about few centimeters. I have made my ...
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2answers
84 views

24GHz Mixer - How to shift the frequency of a 24GHz(100MHz bandwidth) signal by +-4kHz

Why do I want this? When a 24GHz radar signal hits an object that has a relative velocity, the frequency of the signal will shift by a frequency on the order of kilohertz. I want to create this ...
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1answer
52 views

Matlab: Channel coding and modulation [closed]

This is a beginner level question on understanding modulation and channel coding. The confusion arises when I am trying to implement the concepts. Let's say I have the information bits as ...
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1answer
43 views

Find Power Spectral Density of given signal

I am given a question with very brief notes to study from. The question is this: Now I was wondering, are the following part of the notes relevant at all: Is this the appropriate method to solve ...
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0answers
41 views

GNU Radio - PSK Mod block - unexpected constellation diagram

I am simulating a QPSK modulation in GNU radio. Here is the flowgraph: The source is a binary stream coming from the Random Source block. There are 4 PSK Mod blocks configured identically (4 ...
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0answers
66 views

GNU Radio - QT GUI Frequency Sink block - field Bandwidth and signal frequency spectrum

I am simulating QPSK modulation in GNU Radio. The flowgraph is here: File Source is a binary file. Unpacked to packed is packing bits densely so that one incoming byte contains 4 QPSK symbols. ...
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5answers
312 views

Why can a single sine wave signal be used to send digital data but a composite signal is needed to send human talk,etc.?

I can understand the following text (Data Communications and Networking: 4th Edition, Berhouz Forouzan, Ch.5, page 179) which says that a property of a single sine wave carrier signal (phase, ...
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3answers
602 views

FM transmitter design?

I stumbled across a relatively simple FM radio transmitter online. Credit: makezine.com I wanted to understand how it works (it is called "super simple" on the website), but several hours I have ...
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0answers
44 views

Speaker designed for ultrasound operation

I've created a transmission protocol in order to transmit information bits between a PC speaker and a smartphone, or between 2 smartphones using ultrasounds. I've implemented a QFSK system which uses ...
0
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0answers
81 views

Phase reversal in over modulated AM wave and DSB-SC wave

I am new to communication systems and I only know that in an over modulated AM wave, the envelope is distorted and can't be detected properly. But is there any phase reversal in over modulated AM ...
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1answer
98 views

What's the advantage of PAM modulation over QAM?

What are the main advantages of PAM (Pulse amplitude modulation) modulation over QAM ? Ethernet is using PAM for 1000BASET and 10GBASET, but any other high speed links use QAM like DOCSIS, ADSL/VDSL ...
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55 views

internal circuitry of LM1596/1496 perform modulation

The following is the inner circuitry of LM1596 which is a modulator and a demodulator: I wanted to get an abstract idea as to how this circuit actually works and performs de/modulation... I have a ...
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2answers
79 views

How are the original signal and the AM signal related?

Use the TIMS “Variable DC” module to generate a 1V DC signal. Use the “Adder” module to add this DC signal to the message signal generated in task 1 (this will produce the ...
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4answers
3k views

If an FM signal has different frequencies, how does the radio receive the signal in a fixed frequency?

If an FM signal has different frequencies according to the modulation, how does the radio receive the signal in a fixed frequency like 103.2 MHz?
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1answer
63 views

About the combination of two signals with capacitors

Here is a link of an article I've been reading. http://www.analoguehaven.com/moog/thereminblack/hotrod.pdf In page 4 there is a circuit schematic. Notice there is a part called variable pitch ...
2
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1answer
91 views

Orthogonal Frequency Division Multiplexing (OFDM)

I am not a professional but I'm trying to figure out how OFDM works. It is clear to me that OFDM works with closely spaced subcarriers with orthogonal frequency. Each subcarrier gets modulated with a ...
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1answer
110 views

Spread spectrum

Are Frequency Hopping Spread Spectrum (FHSS) and Direct Sequence Spread Sequence (DSSS) modulations? I am confused because I have read that these are also used e.g. with Gaussian Frequency-Shift ...
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2answers
495 views

What is the required bandwidth for QAM modulation?

Why is the allocated bandwith smaller with QAM-16 or 64 compared to e.g. QAM-4? I am not a professional so I'm looking for an intuitive explanation.
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115 views

Calculating Data rate function of bandwidth and SNR

I plotted BER vs SNR for BPSK modulation in Matlab and I am given bandwidth of channel (bandlimited channel). lets say it is BW1. I would like to find the data rate based on this information. I am ...
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1answer
48 views

Channel Coding with Higher modulation

Just had a theoretical question. I'm reading a book on LTE, and I came across an introductory section that talks about using higher modulation with channel coding. I understand that usually using ...
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1answer
70 views

Estimate the bandwidth required to transmit 1Mbits/s of data using a modulation scheme which comprises 32 different frequencies and 2 amplitude levels

Estimate the bandwidth required to transmit 1Mbits/s of data using a modulation scheme which comprises 32 different frequencies and 2 amplitude levels Yes, this is a homework question that ive been ...
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2answers
77 views

Drive electo-optic modulators with FPGA

I am currently using an FPGA (Virtex II NI RIO7831R) to generate the clock for a pulse generator used to drive a Linbo3 optical phase modulator. ...
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1answer
40 views

How to identify when a pulsed rf supply is active

I have a signal that consists of a 13MHz RF signal inside a pulse envelope (around 100ms on, 300ms off). I want to convert this to a 0-5V pulse that will just tell me when the primary RF signal is ...
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5answers
808 views

Transmission of a digital signal over a medium

A digital signal is said to have a infinite bandwidth. If a transmission medium cannot have infinite bandwidth then how can a digital signal be transmitted over such mediums? Please correct me if I ...
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3answers
156 views

An alternative way to make a VCO?

from what I am able to understand, a voltage controlled oscillator is "controlled by a voltage" when this voltage is applied to vary the value of the tank circuit: eg this could happen by applying ...
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2answers
176 views

How to calculate the RMS of an AC PWM?

I am looking at a servo, which is driven by PWM. The PWM signal itself modulates NOT DC but a sine AC, so when Throttle is set to 100%, I can see a rather nicely drawn sine wave. But when Throttle is ...
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1answer
46 views

Amplitude modulation transmission distortion

I need to clarify a question. Let's say that in a wire I carry a current modulated in time so that it is an amplitude modulation of a sinusoidal carrier with a modulating sinusoidal wave. In frequency ...
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5answers
280 views

Does increasing the amplitude of a signal also increase the data rate?

I face an ambiguity when considering the carrier frequency, signal frequency, bandwidth and data rate. When I consider the Shannon formula, I wonder if increasing the transmission power also means ...
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1answer
48 views

A question related to “quadrature carrier multiplexing”

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
77 views

Working of ring modulator

I am having trouble understanding how this ring modulator works i.e. how it multiplies the input & carrier to give us appropriate output? Any help or guide will bedeeply appreciated. Reference - ...
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1answer
65 views

In Analog to Analog conversion , why we multiply instead of adding?

When we use AM i.e Amplitude Modulation , we multiply the source signal with the carrier , My Question is , why don't we add the signals ? it would be easier to modulate and demodulate I think.
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44 views

How to prove FM is superior to PM for tone modulation for a given signal?

How to verify that for tone modulation FM is superior to PM for the signal x(t) where \$ x(t)= 8cos(\omega_0 t) + cos(5\omega_0 t) \$?
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1answer
80 views

Emulating greyscale on a 1-bit LCD

I have an LCD (the DOG-M 102x64, with a uc1701 controller) that I am driving (over SPI, but that's somewhat irrelevant) from an AVR (ATMega16 @ 8 MHz) - all in all, a fairly low spec'd screen with a ...
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1answer
178 views

How to shift signal to baseband using local oscillator frequency?

If the input to a demodulator is a signal having the spectrum shown below, how would I figure out what local oscillator frequency is required to shift the signal to baseband? Is there a formula for ...