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2answers
93 views

what is this type pulses called?

I was wondering what is this type of pulses is call. Is it a sin wave? I know its the result of sinusoidal pulse modulation. is it considerd a quasi-sin wave? I would like to know the name to ...
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0answers
25 views

Foster - Seeley FM Demodulator Explanation

Consider this Foster Seeley Demodulator If I have correctly understood, its basic working principle is the fact that at the secondary coils (L2) of the Balun there will be two signals equal and ...
1
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2answers
77 views

Double Balanced Mixer

Consider this double balanced mixer: Its output contains only the frequencies generated by the product of those of LO and RF signals, where LO is supposed to be a large signal (which switches ON and ...
0
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1answer
40 views

Convering bandwidth (frequency) to bit rate without knowledge of the modulation?

How would i convert a bandwidth of say 30kHz to bps if I only know the number of bits per sample (4)? (and I was using a two chanel system). I am assuming it is simply 30KHz * 2 * 4 but this may be ...
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1answer
60 views

How phase modulation changes spectrum?

I'm studying amplitude,frequency and phase modulations for an exam. I just studied amplitude and frequency modulations, however i didn't succeed in understanding how the phase modulation changes the ...
0
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1answer
335 views

Why the OFDM symbol length is the total number of original modulated symbol, but not one symbol length?

Recently, I am learning the principle of OFDM, and the reference is http://defenseelectronicsmag.com/site-files/defenseelectronicsmag.com/files/archive/rfdesign.com/images/archive/0101Puegel30.pdf. ...
6
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4answers
2k views

What does “shift keying” mean in the context of digital modulation?

English is not my native language and I do not understand why the words "shift keying" were used to describe some types of digital modulation. What does "keying" mean in the context of signals and ...
-2
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4answers
1k views

Why amplitude modulation is not used for sending digital data?

It seems to me that the most simple way of modulating a digital signal is using amplitude modulation. When the signal has the amplitude 0 the bit is 0 and when the signal has some amplitude then the ...
2
votes
1answer
194 views

What to use as an external 100 Hz modulation source for an RF Signal Generator?

I've got an old-school HP 8656B Signal Generator, for a 433MHz RF project. Typically, I've used the internal 400Hz or 1kHz modulation but for the receiver in question I need a signal source that is ...
0
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0answers
244 views

Delta modulation (DM) signals

Trying to understand this circuit. Will this produce a representation similar to example in second image (if U_inf is the sine wave "original") ? Assuming that, I expect U_DM to look like the "...
0
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1answer
65 views

PAM nonlinear amplitude compression in lower eyes

I needed some help to understand why at Rx, we observe different effective SNRs in individual eyes for higher level PAM signalling. If you need additional info, http://literature.cdn.keysight.com/...
2
votes
2answers
2k 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 ...
1
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1answer
842 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 ...
1
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1answer
130 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 the ...
2
votes
2answers
277 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 ...
1
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1answer
91 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 ...
0
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1answer
129 views

FM signal example

Sorry if this question is too basic, but I'm a software engineer student who must study communication systems. I try to represent a FM signal in a graphing calculator, but I don't know why the result ...
0
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1answer
1k views

Maximum signal data rate

I have a frequency signal range from 25 Khz to 35 Khz. I know that the the minimum signal sampling to assure reconstruction of the signal from the samples is 70 Khz. Would it be correct to assume ...
0
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2answers
141 views

Which characteristics of a Radio signal are involved to be selected by radio receiver? [duplicate]

the radio antennas receives millions of signals. how our radio selects the appropriate signal as it's input? which characteristics of the signal are involved for this selection.
4
votes
1answer
445 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
votes
1answer
169 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 \pi ...
2
votes
2answers
2k 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 ...
1
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1answer
156 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: \$...
0
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1answer
943 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; ...
0
votes
1answer
162 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 ...
0
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1answer
1k 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. ...
1
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0answers
185 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 ...
2
votes
1answer
880 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 = \...
-1
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1answer
527 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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2answers
147 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 ...
0
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1answer
2k views

Arduino beacon for IR Seeker v2 (Mindstorms NXT Sensor) - Pulse IR at 38Khz Carrier and 1200 Frequency

I hate to ask a question like this, that is kinda just like "give me the code" but seriously. I've tried reading up on it everywhere, and I just don't seem to get a thing of having both a carrier ...
2
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2answers
193 views

BPSK bandwidth for symbols not integer wavelengths

Most of the BPSK waveform examples in text books/online are for carrier frequencies that are integer multiples of the bit rate. This means that when the symbol polarity changes there is a ...