Generic term for coding information onto another carrier signal

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3answers
46 views

Difference of amplitude and frequency modulation of lasers

I found some interesting applications for modulation for lasers. They always talk about some sort of frequency modulation (ex. FMCW) AFAIK the frequency of a laser is pretty much stable (for all ...
0
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2answers
34 views

How are the Intersymbol Interference and Symbol Time (duration) related to each other?

In a lecture slide I noticed that OFDM(Orthogonal frequency-division multiplexing) mitigates the problem of Intersymbol Intereference over wireless systems because the symbol time is increased, in ...
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1answer
38 views

What happen if 0 and 1 are transmitted simultaneously with BPSK?

I'm just curious that what happen if 0 and 1 are transmitted simultaneously from different source nodes to an equidistant destination node with BPSK? Assuming perfect signal shaping, synchronization ...
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1answer
67 views

Signal drawing based on a constellation diagram

Constellation diagram of a communication system is given. S1(t) -> 0, S2(t) -> 1 Φ1 and Φ2 are basis functions and Tb is the bit period. How can I draw S1(t),S2(t) and decision boundaries?
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0answers
17 views

How to model the dispersion which introduces a modulation driver of EML?

I need to model the dispersion which introduces a modulation driver of EML, in matlab simulations. The parameters are: Lambda: 1310nm PAM4 power: Pmax = 1.09 mW Pmin = 0.13 mW Bandwidth = 56Gbps
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1answer
57 views

Understanding single sideband modulation and demodulation

I know this question has been asked a lot of times before but i cannot really understand how is the message transmitted in single sideband modulation. See the following images taken from the book ...
0
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2answers
57 views

Perform digital modulations (HW or SW)

I am considering doing a project which revolves around microcontrollers (AVR, or arduino) and digital modulation to learn about digital RF. I have simple things in mind, just for experimentation. ...
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0answers
31 views

SPICE analysis of a ring modulator

I'm designing (for fun and understanding) a simple 100 MHz BPSK modulator. I've found a simple implementation (from http://en.wikipedia.org/wiki/Ring_modulation). Haven't worried about pulse shaping ...
0
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1answer
84 views

Problem solving super heterodyne receiver question

I have two problems which i am trying to solve but i am stuck on the half way. I have the following first question, which i am trying to solve I have solved the problem as following, ...
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0answers
21 views

simulate QPSK using simulink

I have tring to simulate QPSK system using simulink , so i choose from workspace block , to enter the data into the system , but when i have simulate it , an error ...
0
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1answer
45 views

Why do more phase shifts cause the need for higher bandwidth when Frequency Shift Keying (FSK) is used?

What I don't get is why a phase shift "decreases" the data rate and thus the need for more bandwidth to get the same throughput as without the phase shift.
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1answer
38 views

Fourier transform of the components of bandpass signals

I'm referring to a book called Communication Systems by Simon Haykin, 3rd Ed. It says that a band-pass signal \$s(t)\$ with mid-band frequency \$f_c\$ and bandwidth \$2W\$ can be represented as ...
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1answer
75 views

pulse amplitude modulation

Im bit struggling with PAM question. I've been trying to solve this for few hours but I am stuck at the stage where I need to sample m(t). Could you please help me with detailed answers and workings. ...
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2answers
88 views

RFID data transfer rates?

I'm learning about RFID and am trying to figure out what the data rates are for the different types of RFID technologies. I've learned that there are three different frequencies tags and readers ...
2
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1answer
99 views

How does this direct digital synthesis accumulator work?

So, I grabbed some code online and morphed it to work with my DE2-115 board, and now I need some help understanding exactly how it works. ...
9
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3answers
958 views

What is Overmodulation?

The Wikipedia article is very short and doesn't explain the concept very well, and there aren't any other sites that I can find that give a simple explanation. What does it mean by 100% modulation? I ...
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3answers
75 views

the implementaion of communication systems [closed]

I wonder , Why when we study communications systems , we just study the theoretical part(Math) , and we never touch the electrical circuits that used to implements this systems , I have asked my DR. ...
1
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1answer
91 views

How to demodulate an overmodulated signal?

Say I have an overmodulated signal like the example above. When you demodulate this you will get distortion. Is it possible to somehow demodulate this?
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1answer
52 views

finding out the bandwidth of m(t)*m(t) if the bandwidth of m(t) is a known quantity

m(t)*m(t) in time domain is equivalent to the convolution of m(w) and m(w) in frequency domain.Thus if the bandwidth of m(t) is a known quantity then how is the bandwidth of m(t)*m(t) is determined?
1
vote
1answer
99 views

DSB-SC modulation circuit

I have the following circuit which is used for DSB-SC modulation but, I can't understand Why we use High Pass Filter(I expect to be High pass filter , I'm not sure with that ) at the carrier ? Why ...
0
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0answers
30 views

Optimizing a data link

I am running into trouble trying to optimize a VSAT running at 4096kb/s QPSK modulation. I've found that using a more advanced modulation scheme permits more bits per baud to be transmitted. But ...
0
votes
2answers
260 views

BLE113 Bluetooth 4.0 module with CR2025 3v battery power supply

A question regarding the power supply of a BLE113 Bluetooth 4.0 module: I am attempting to order several bluetooth modules, but the main concern is the power supply. Since I am new in the field of all ...
1
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1answer
96 views

What is the modulation technique used?

I own a Tx/Rx Radio Direction-Finding (RDF) set for a sport called falconry, basically, locating & recovering a pet falcon after flight. The Tx tag is at 218.025MHz from Marshall Radio Telemetry ...
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2answers
337 views

RC time constant and diode detector

For a better detection of the modulated signal with the diode detector below, one requirement is that the time constant of the RC filter conforms to: $$ \frac{1}{\omega_{c}} \leq RC \leq \frac{ ...
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0answers
75 views

Why more bandwidth means more bit rate per second? [duplicate]

According to this link ( and some other sources I have found ) more bandwidth on a wire means more bit rates per second... Can someone try to explain why this is so as simple as possible? This is ...
0
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2answers
82 views

How to increase frequency modulation index?

I'm thinking of making a low power FM transmitter. Here's a diagram. It seems an absolute pull range of a VCXO will limit the modulation index. Is there possibly a way to extend it?
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2answers
91 views

How can I toggle a astable 555?

I'm using a NE555 running at 37KHz to generate a carrier frequency for transmitting IR. Now I need to modulate it using OOK, I know that are various ways to toggle it. The most obvious way is to ...
1
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1answer
71 views

How much gain for optical open-air receiver?

I am planning to make an experimental communications system. I will use a high power LED (≈3watts) Amplitude Modulated with a sound signal and eventually Pulse modulated with digital data for the ...
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0answers
49 views

Base width modulation

Can anybody please explain what exactly happens in base width modulation for pnp devices? What happens to Base current, collector current and Emitter current(increases or decreases and why)? Please do ...
2
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1answer
166 views

The relation between light electric field and light power (optical modulation)

I have been keeping thinking this question for one week. Hope could get some help from you. Light 1: Electric field = \$\text{e}^{j\omega t}\$; Power = \$\frac{1}{2}A^2\$ light 2: \$ \alpha = ...
3
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2answers
137 views

Determining type of modulation

The circuit below is a radio transmitter circuit of a typical RC car. The circuit makes use of IC TX2 encoder. The output of IC ("SO" pin) is a series of pulses at low speed (84 Hz). This signal will ...
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2answers
1k views

RF Bandwidth vs Data Rate (modulation)

I was reading some articles about digital and analog modulating processes. One of them was this: Modulation techniques At a certain point is says: The bandwidth produced is a function of the ...
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1answer
91 views

Signal encoding on Realtek TX2 IC

I 'm trying to figure out the way IC TX2 encodes different signals (RIGHT, LEFT, FORWARD, BACKWARD, TURBO). I can understand that presence of voltage means an appropriate signal to be transmitted. ...
1
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1answer
312 views

Is there an easy way to multiplex the state of multiple switches in an AC circuit?

If I had a circuit like this... *Blurple boxes represent unknown devices/circuitry What would be the simplest way to transmit the states of the switches, using only a single wire? In essence I'm ...
0
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1answer
137 views

Amplitude modulated wave weird display in oscilloscope

In my lab experiment (http://www.ele.uri.edu/courses/ele436/labs/expA2.pdf), My amplitude modulated wave is not displaying the vertical lines-the high frequency waves of carrier (as shown in ...
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1answer
1k views

How is digital information encoded/decoded in light or radio waves?

I know exactly how DAC and ADC works; that's not my concern. What I am asking is how the constituent state of matter (and the "states" represented by them) in a circuit can be transferred to a set of ...
4
votes
2answers
176 views

Adding LFO Modulation to VCA in synthesizer

I just started sketching ideas to add LFO to VCA modulation in a device that already has a VCA circuit employed, but I’ve run into a snag… I can design a circuit to give proper modulation at full open ...
3
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2answers
289 views

Advantages of a Gray code in 16-QAM

I'm looking at a system using a gray code on 16-QAM. When a symbol changes, you move from one of the 16 symbols in the constellation to any of the 16 symbols. I'm wondering if there is in fact an ...
2
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1answer
166 views

Help design multiplication / modulation stage

I'm a self-taught amateur analog electronics enthusiast, I wonder if I can get some basic help on a simple circuit to demonstrate an interesting mathematical concept. (Not a homework assignment, but a ...
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0answers
104 views

Calculating PM side-band power with Bessel function

I am trying to predict the side-band power of my PM signal. Looking at the attached pic you can see my modulator with modulation disabled in the top left - carrier power is -61.71 dBm. You can see a ...
0
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0answers
47 views

How to calculate how many waves that can represent 1 symbol in 8-QAM?

I have an information frequency 6 khz, and my carrier frequency at 500 KHz. So, my information bit rate is 6 kbps, which is means i have 6000 bits per second and because it is 8-QAM so 1 symbol means ...
0
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0answers
23 views

OFDM with Gaussian input and output

I read in a paper that "OFDM Modulation with Gaussian output" and "OFDM Modulation with Gaussian input". What do these mean? If OFDM uses QAM, are those statements still valid?
3
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2answers
327 views

Amplitude Modulation Concepts

I am currently learning about telecommunications but I have some concept issues. Firstly, does it matter if I am using cosine or sine in the equation? I understand that they are basically the same ...
2
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2answers
365 views

The concept and circuit of 2 to 4 level converter in 8-QAM

I have a difficulty to understand the basic concept about 2 to 4 level converter in 8-QAM. I've google it but still don't understand much except this block is used to convert two voltage into 4 ...
0
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2answers
954 views

Using Bessel function graph to finde out side bands

If I am not wrong, using Bessel function we can estimate the side bands of a carrier? Is this correct? If so, what are the steps to find these values from the graph? For example if modulation index ...
-2
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1answer
56 views

Modulation that is used in WiMAX [closed]

Which modulation is used in WiMAX? And how does it work? I found QAM-64 but I'm not sure about that.
1
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1answer
715 views

Tradeoffs between QPSK and BPSK re. spectral efficiency, error rate, etc

Say I'm using binary phase-shift keying (BPSK) to transmit some data at some rate. Now say that I want to double the data rate, without increasing my transmitter power. I could either continue to use ...
1
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4answers
2k views

What is the Need for modulation

What is the need for any kind of modulation in order to transmit signals?
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2answers
78 views

Confusion with modulation/demodulation

I am following a book: Data communication and networking (Behrouz-Foruzan). It says that modulation means building a bit stream from an analog signal. However as far as I understand it's the ...
3
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2answers
213 views

UHF Phase Modulation

I would like to design a system that produces -10 degrees and +10 degrees phase shifts at 409.6MHz (Basically BPSK). The way I'm thinking about approaching this is by using a DDS to generate the BPSK ...