Generic term for coding information onto another carrier signal

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36 views

Power efficiency of SSB-Large carrier

i was studying SSB demodulation and learned that a local carrier is added to the SSB signal to make sure that envelope detection is possible. I came across a problem to find the percentage of power ...
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35 views

frequency modulation and incoming signal selection

I have some understanding of what frequency modulation entails - it entails "adding" a new frequency to the frequency spectrum of a signal. But how, exactly, is a modulated signal selected in the ...
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2answers
63 views

How does this AM Modulator work?

I have been given a question and tasked with identifying the various components. However, this circuit doesn't really seem to make sense to me. Error: RC RE inverted simulate this circuit ...
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0answers
32 views

QAM-modulation-how-data-in-different-frequencies-are-laid-out

Monday 27th October 2014 Q.A.M Animation (URL QAM modulation - how data in different frequencies are laid out?) Can you please explain the two instrument icons at the left hand side of the ...
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1answer
133 views

Why it has used BPSK modulation after OFDM?

I am quite new to OFDM modulation. I am reading this from a tutorial. In one of its parts, for showing amplitude variation of the OFDM signals, there is a graph that has used 8 sub-carriers and BPSK ...
2
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1answer
47 views

How is CPM Modulation Different from PSK?

Continuous phase modulation has been described to me very similar to wikipedia's definition, which basically indicated that the CPM is different from QPSK, for example, because QPSK abruptly shifts ...
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20 views

How to modulate RF signal using LabView? [duplicate]

I am using Acousto-Optic Modulator (AOM) in my experiment to modulate laser light using controlled modulations in phase and intensity of RF signal being fed into the AOM. I want to know what program ...
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2answers
86 views

How does an AM-modulated signal sound like in a speaker?

Let us compare two signals: one is a normal sinusoidal signal with single frequency 5khz with 1V amplitude (2V peak-to-peak). The other signal has a carrier frequency of 5khz and 2V peak-to-peak, but ...
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1answer
63 views

Finding the Power developed by the Nominal Frequency in FM

Question The sinusoidal signal \$f(t) = \cos(2 \pi f_m t)\$ is applied to the input of an FM system. The corresponding modulation signal output for \$f_m = 1kHz\$, is $$Q(t)=100 \cos(2 ...
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76 views

Finding the bandwith of FM by using Bessel functions with 1% rule

Question A 100-MHz carrier is frequency modulated by a 10-kHz sinusoid so that the peak frequency deviation is 30 Hz. Using Bessel functions with 1% rule, i.e. 40 dB down from the unmodulated ...
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1answer
47 views

How to get BPSK data from I/Q signal

I am using AD8347(0.8 GHz to 2.7 GHz Direct Conversion Quadrature Demodulator) to demodulate a BPSK modulated carrier wave. There is no intermediate frequency used. By feeding the signal into this ...
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54 views

Difference between “user” and “layer”

I am new to multiple access communication theory. I read some articles on LDS, and I thought that "layers" is a term used for "users" (In another language I thought that for example when we say "we ...
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2answers
98 views

What happens to a DSB signal if I use an envelope detector instead of Low Pass Filter

What happens to a DSB signal Modulated signal if I use an envelope detector instead of Low Pass Filter ? I am interested in knowing how the output signals vary in case of a envelope detector. I know ...
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1answer
37 views

Why is the RC value of a demodulator near the geometric mean of the period of carrier and message signal?

The figure below is a AM demodulator. My instructor told me to chose RC so as to satisfy the following inequality Tc << RC << Tm. Where Tc is the period of the carrier wave and Tm is the ...
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33 views

Ideal Sampling Rate for LFM Signal

I'm confused on how to set the ideal sampling rate for an LFM pulse. As an example, if I create a pulse with a PRF of \$10^3\$, a sweep bandwidth of \$10^5\$ with a pulsewidth of \$10^{-5}\$. The ...
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0answers
33 views

Confusion about PCM and quanization

Suppose that we are going to encode a signal with rate R = 24 kbps. Find the proper values of sampling rate, quantization level and bits. I certainly know how to find the number of bits needed, if I ...
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1answer
43 views

Nyquist Sampling rate

We have \$z(t)=\cos(100πt)\cos^2(500πt)\$ . Find Nyquist sampling rate. Well, I know that \$f_s=2f_{max}\$. My main problem is that I am not entirely sure if I could re-write the above signal as: ...
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2answers
53 views

Spreading vector

I am reading an article that is about CDMA. In that article I encountered a term "spreading vetor". I searched some books such as Proakis and Gallager to see what it means. I even surfed internet for ...
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65 views

Carrier Wave in Wired Data Networks

I know this must be trivial for many... Which are the main reasons why line data is not modulated/demodulated in normal enterprise wired networks (in the sense that discrete voltage levels are used)? ...
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1answer
54 views

FM and phase/frequency deviation

I have a small understanding issue here, so I would be very glad if someone could help me a bit! We are given this FM modulated signal to volts; ...
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0answers
66 views

Would my project be affected by lack of a filter?

I have chosen to do a final project, I will be transmitting bits using a wien bridge oscilator, I want a 160 MHZ sine wave and I have chosen values for it. I have chosen the AD8041 op amp because it ...
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1answer
151 views

How can i send bits using a wien bridge oscilator?

so i have a string of bits that my shift register will be outputting one after another, i wanna use a wien bridge to send them into air. if a bit is a "1", i want the wien bridge to send a wave, and ...
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1answer
133 views

I want to make an oscillator with 160 MHz

I want this for my project. So I have decided to make a basic Wien bridge oscillator. $$f = \frac{1}{2\pi R C}$$ So if I choose a capacitor of 0.1 nano farads and a resistor of 10 ohms, I should ...
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2answers
52 views

Why frequency and coordinatino make sense in FM? [closed]

In FM modulation, the signal changes frequency depending on the amplitude of the original signal. So when you input the coordination frequency how does that makes any sense? For example, you input ...
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64 views

Varying the Frequency of PWM Inverter Modulation Function

I'm modelling a PWM inverter with a triangular carrier signal, and a sinusoidal modulation function. In order to get certain frequency of sine wave out of the inverter, I need to vary the frequency of ...
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1answer
50 views

How to modulate Transceiver module for use with ATmega164PA

I am using a transceiver TFDU4101-TR3 to communicate with another device which has exactly the same transceiver. I bought this thinking I can communicate with the transceiver using my microcontroller ...
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1answer
63 views

Check me on this modulation question?

I need to check my answers for parts (a) and (c); a) I got q(t) = p(t)cos(5pit) c) i got y(t) as a rectangle with amplitude 1 from -pi to pi. So, y(t) = 1/8 f(t) Am I correct for both parts;
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75 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 ...
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2answers
46 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
50 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
121 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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136 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 ...
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69 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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56 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 ...
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1answer
246 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
35 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 ...
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1answer
73 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
41 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
139 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
139 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 ...
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1answer
195 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. ...
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2k 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
82 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. ...
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1answer
125 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
54 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?
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1answer
227 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 ...
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31 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 ...
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2answers
469 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 ...
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1answer
111 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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888 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{ ...