Generic term for coding information onto another carrier signal
0
votes
0answers
33 views
complex signals and modulated signals [duplicate]
I'm taking an intro electrical engineering class in an online university and have come across something that is confusing, at least to me, since the text we are using does not go into detail about ...
0
votes
1answer
17 views
Controlling initial phase of carrier during modulation?
During the process of modulation, any of the three parameters, viz \$\ A_c\$ , \$ω_c\$ and φ, of the carrier wave can be controlled by the message signal where φ is the initial phase.
How is it ...
0
votes
3answers
103 views
Operation of LC circuit in Frequency Modulation with simulation and linking it to the basic principle of frequency modulation [duplicate]
Can somebody help how message signal (words spoken near microphone) is modulated using LC circuit and how lc circuit oscillates at particular frequency by applying dc voltage. In the below circuit ...
14
votes
1answer
411 views
Why FM stereo uses DSB-SC instead of VSB?
Using vestigial sideband instead of double sideband supressed carrier could make the baseband stereo signal more compact.
Would there be any other benefits or downsides of employing VSB?
1
vote
2answers
70 views
Why doesn't Class C modulator operate in saturation?
The following circuit is a class C (actually class B) amplifier used in AM modulator in my previous question.
According to the textbooks, the transistor is driven into saturation in this class. A ...
1
vote
1answer
89 views
Analysis of Class C AM modulator
The following schematic is a class C AM modulator without use of any transformers I've just changed the parameters in spice to get a correct modulation. however I want to find the theoretical value ...
3
votes
1answer
67 views
Help identifying modulation scheme
I'm trying to identify the following modulation scheme being used to transmit a infrared code. It looks like manchester, but there's some gaps where there's no transitions.
The code being ...
0
votes
1answer
60 views
Gray coding for 8-triangular signal constellation
I'm trying to find the gray coding for the 8-triangular signal constellation below, but no matter what I try, one of the neighbors always has 2 bits differing.
For example, two of the neighbors for ...
0
votes
2answers
94 views
How to modulate a LED to send data and recieve with a photodiode
What is the concept of modulating a light source (white led, IR led, etc) to send data and then demodulating it with a photodiode back into data?
I am wanting to experiment with trying to use ...
0
votes
0answers
34 views
Find demodulation path of a CRT TV from Composite to before amplification to CRT
I have a small, portable 5" CRT TV (Brand is "ITS", Model name is "TV2016" which makes it horrible to search for on the Internet).
The tiny TV set has a Composite input, which makes it interesting to ...
1
vote
1answer
54 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 ...
-1
votes
3answers
70 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 ...
1
vote
0answers
28 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 ...
1
vote
1answer
45 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 $$u_{PM} = cos(w_C \cdot t + ...
0
votes
1answer
48 views
QAM demodulation , hard vs soft if there is any
I am trying to find the answer to , what types of demodulation methods are exists. Each of my searches results with different names, but converging to one metric , which is finding the closest symbol ...
0
votes
1answer
63 views
Transmitting data over inductive charging coils (or boosting RFID/NFC power supply)
I know that data can be sent over power lines through various different types of modulation - that is as far as my knowledge ends.
I have a small D.I.Y. project (a board game) that requires some form ...
2
votes
1answer
116 views
Definition of \$\mu\$
I have a question as follows. This is not a homework question I just need to clarify my doubt on how this modulation index is defined.
Suppose a 2kHz audio tone having 2V amplitude is to be amplitude ...
3
votes
1answer
83 views
Why is the modulating shape appear in both sides of the carrier signal in AM?
It's about Amplitude Modulation. Can anyone tell me why is this signal wave or modulating waveform shape appears in both sides of the carrier sine wave? Why not in one side only?
$$x_c(t) = A_c[1 + ...
3
votes
3answers
110 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 ...
0
votes
1answer
112 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 ...
3
votes
2answers
316 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
vote
1answer
123 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 ...
0
votes
1answer
46 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 ...
1
vote
1answer
81 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 ...
0
votes
0answers
61 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 ...
0
votes
2answers
98 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 ...
0
votes
1answer
64 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 ...
1
vote
1answer
46 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 ...
0
votes
0answers
99 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. ...
2
votes
5answers
431 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, ...
3
votes
3answers
660 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 ...
1
vote
0answers
57 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
votes
0answers
105 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 ...
0
votes
1answer
127 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 ...
0
votes
0answers
62 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 ...
2
votes
2answers
81 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 ...
12
votes
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?
1
vote
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
votes
1answer
96 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 ...
1
vote
1answer
119 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 ...
1
vote
2answers
922 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.
0
votes
1answer
176 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 ...
1
vote
1answer
51 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 ...
0
votes
1answer
71 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 ...
0
votes
2answers
79 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.
...
0
votes
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 ...
3
votes
5answers
921 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 ...
1
vote
3answers
199 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 ...
0
votes
2answers
285 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 ...
0
votes
1answer
51 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 ...
