Questions tagged [modulation]

Generic term for coding information onto another carrier signal

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3answers
60 views

How to superimpose a synchronization pulse on a 12V DC power line

I have a 12V DC to DC isolated converter powering a remote display. The DCDC is connected to a 12V supply. I would like to add a 1ms or so pulse on that every second that can be detected by the ...
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1answer
164 views

Trouble with FSK VCO modulation circuit

Circuit shown is a VCO that reliably creates a 200MHz sine wave at 3V pk-pk. I would like to use this VCO to create an FSK modulated signal. My bit 1 frequency = 200Mhz and my bit 0 frequency = 205Mhz ...
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0answers
50 views

What is the modulation index of the following AM?

message signal (violet), carrier, Modulated signal (red), Click this link to see the graphs Is this formula for the modulation index correct? Which formula are you using to find the modulation ...
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1answer
70 views

Fourier transform of an integral

I am preparing for an exam. I found this problem : I am trying to use the properties then use a pre-transformed function from the table but I couldn't find one. I saw a solution on web : I think he ...
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3answers
3k views

What is the difference between frequency modulation and phase modulation?

What is the difference between frequency modulation and phase modulation?
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1answer
272 views

Build an FSK modulator using the HB100's transmitting signal

I want to use the HB100 to make an FSK modulation on a microwave signal. The reason why I use HB100 is that in this way the RF circuit is ready. I thought about doing an FSK modulator like the scheme ...
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2answers
60 views

Are there any real world examples of encoding data in EM polarization?

Data can be encoded by modulating the frequency, amplitude and phase. But I can't find any references for encoding data in the polarization of EM waves (either analog or digital). This is probably for ...
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9answers
4k views

Why doesn't higher frequency mean higher data rate?

My question is very primitive :) I've read multiple articles today and answers here, on Stack Exchange, but still don't understand one thing. Why doesn't frequency itself affect data rate in mobile ...
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2answers
96 views

Why does a higher bandwidth allow a higher data rate [duplicate]

I have not taken any signals processing classes yet but I am interning at ATnT in the RF department. I do not understand why higher bandwidth increases data rate and the other answers did not make ...
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2answers
104 views

Why is FM modulation not used in modern cellular communication?

Both bluetooth and celular links use GHz level carrier waves. Yet the modulation techniques are very different. I know why FM is more resilient to noise comparing to AM. But why is FM preferred for ...
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1answer
1k views

Design AM modulator circuit [closed]

I having an assignment that need to design AM Transmitter using Multisim with following specification: • Audio input (200-14000Hz) • Double Sideband Full Carrier • RF carrier frequency of 50 MHz ...
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1answer
42 views

Determine output filter using the bode approximation

Given that the carrier frequency Fc and modulation input frequency Fm are known, how would I use the bode approximation to determine an output filter, if the carrier frequency component must receive ...
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1answer
25 views

What does 'succeeds' and 'precedes' symbols mean in design of a peak detector circuit?

I am looking into the design of a peak detector circuit for demodulating an amplitude modulated wave. The circuit is a diode 'detector' connected to a low-pass RC filter. I have been given the ...
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2answers
163 views

Is the use of a Lock In with a signal generator appropriate and practicable?

I want to generate a 5 kHz microwave pulse to induce a sample signal. This microwave pulse has an underlying microwave frequency of 2 GHz. In order to investigate very tiny signals, which should arise ...
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1answer
34 views

Coherent and non-coherent detection

Let's say I am simulating something as simple as BFSK. It has two symbols, one entirely on the real plane, and one entirely on the complex plane for representing let's say zero. That is how the ...
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1answer
46 views

In RF433 Mhz module What is the Bandwidth and Data rate that used to transfer data?

many of document I have read it that tell me this module has 2MHz and Data rate equal to 10Kbps and using ASK modulation how did it transfer 10Kbps on 2MHz what my question is why did used a large BW ...
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1answer
514 views

Is it true that frequency deviation over 2*pi is the phase deviation of an FM/PM signal?

for ∆f frequency deviation if for FM only and PM has Phase deviation. and Kf= ∆f (Hz) of FM? Kf = ∆f (rad/s) for PM? and for th rules: ∆f=(kfmp)/(2p) for FM where mp = mp max-mp min ∆f=(kfmp)/(2p) ...
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2answers
67 views

How do we separate source signals in spread spectrum?

In a point-to-point mode, that is, one transmitter and one receiver, I understand how a spread spectrum receiver can read the transmitted signal from a spread spectrum transmitter by knowing the code. ...
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0answers
20 views

Is \$ H\left\{x_h(t)\right\} = H\left\{x\left(t-\frac{\pi}{2w_c}\right)\right\} \$ where \$H\$ is Hilbert transform

Accordind to my understanding of the following: $$H\left\{X(f)\right\} = -j\;sgn(f)\; X(f) \qquad(1)$$ my work so far: since \$ x_h(t) = x\left(t-\frac{\pi}{2w_c}\right)\$, Their Hilbert ...
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3answers
140 views

Will an RF modulator provide NTSC System M spec video from a DVD player?

I've been attempting to recreate the effect of an old NTSC television broadcast lately with the use of DVDs. The DVD-Video spec allows for up to 720 x 480 pixels at a display rate of 29.97 frames per ...
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1answer
39 views

Filtering a demodulated signal

I've created a simulation on Matlab of amplitude modulation. After demodulating the signal I need to add a low-pass filter to remove the high frequency components. I'm confused as to why this is? I ...
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1answer
67 views

FM modulation, amplitude problem

I'm trying to make an FM modulation with a Hartley oscillator that oscillates at 45MHz. The problem is that it's supposed to have an unitary gain. I can't find a good adjustment between a really low ...
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1answer
72 views

Frequency modulator won't oscillate

I'm student and I'm working on a school project. The project is a radio transmitter. My question here is only about the frequency modulator part. Here is my circuit : Here is my output signal (...
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1answer
26 views

Frequency modulation synthesis with IQ

I am trying to figure out how the I & Q signals for a frequency modulation have to look like. How do I generate a FM modulated signal with an IQ mixer?
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2answers
87 views

High Frequency Laser Modulation

I am looking at doing some phase-shift lidar experimentation. To get good accuracy, all the papers suggest that I need to be modulating the laser diode sinusoidally at ~200MHZ. I am finding ...
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1answer
35 views

Why the intersection points in SPWM define the width of the pulse?

After my previous question Why the triangle reference wave is used in PWM for sine modulation I still have some troubles on one particular point of natural sampled PWMs or more precisly SPWM. My ...
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1answer
95 views

Delta Modulation Frequency in the Integrator

Ok guys, I can't understand a thing, I have made this circuit, that is a delta modulator: As you can see with an input of 5Vpp, in the output of the integrator I found a square wave signal, that has ...
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FM Detector Using LM565

I am currently working on a power line communication project. I want to send an audio signal through the power line. In order to do that I would need to modulate my signal and in this project I am ...
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5answers
2k views

Why the triangle reference wave is used in PWM for sine modulation?

I'm implementing PWM for a three-phase inverter. The documentation on the subject, especially the technical implementations, is very good but as far as I am able to understand none of the one I read ...
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2answers
27 views

How can you handle noise in multi-level pulse amplitude modulation?

When using multi-level Pulse Amplitude Modulation to transmit a message, how should the receiver handle noise? For example, suppose there are 5 levels (0,1,2,3,or 4) and the following message is ...
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1answer
174 views

Is this figure a correct (O)QPSK waveform?

I am currently reading Pasupathy, Subbarayan. "Minimum shift keying: A spectrally efficient modulation." IEEE Communications Magazine 17.4 (1979): 14-22. The paper explains MSK as a form of OQPSK ...
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5answers
3k 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 ...
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31 views

Transmitting .mp4,.bin,.txt files with on off keying OOK (optical communication)

How do you implement OOK to transmit mp4 files etc. For instance i have LED and a video file to transmit. How do you take the video convert it to binary, send it via the LED recieve it via the ...
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3answers
51 views

Frequency demodulation with a spectrum analyzer

In my university lectures I have generated an FM signal (for instance with carrier frequency of 2GHz, frequency deviation equal to 100kHz, and modulating frequency equal to 100kHz.) In order to ...
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2answers
141 views

Data Slicer for Differential Manchester

I have a differential manchester data stream (channel1) in the form of packets. I'm showing a capture of one packet. All packets begin with a stream of 1's. This is key, as per Maxim application note ...
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Modulation index and sidebands

I have built a Mach Zehnder interferometer in which a laser beam is first split. After each splitted beam is passed through a AOM driven at a fixed RF in my case 40 MHz and 40.04 MHz they are ...
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3answers
33k 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{ \sqrt{...
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How can I remove the return paths for a series of circuits and still know when they are completed? NFC/RFID? Multiplexing? Goubau line?

Apologies for the vague title. And know that my electronics knowledge is rather limited. Also my circuit diagrams may be incorrect. I currently have something like this, which represents contacts on ...
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0answers
43 views

Zero - IF receiver main limits

I was reading these slides about receivers architectures, and I have some questions about Zero - IF receivers: Precisely: Why is the spectrum around the carrier (i.e. the 2 "side bands") mirrored ...
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3answers
169 views

How does a microwave oven modulate its output power?

My microwave has multiple power settings, ranging from 500 watts to 1500 watts. My question is how is the power reduced/modulated? I can think of a few options (but I don't know which one is correct/...
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1answer
148 views

Potentiometer volume control for a piezo buzzer in bridge (2-pin) configuration

I have a 10K potentiometer that I'd like to use to control the volume of a piezo transducer/buzzer, which is driven by one or more MCU PWM-capable pins (ranging from 0 to 3.3V). Originally, my ...
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4answers
72 views

Clarifications about up and down converting mixers

Let's look at this definition of mixers (reference): A real mixer cannot be driven by arbitrary inputs. Instead one port, the "LO" port, is driven by a Local Oscillator with a fixed amplitude ...
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4answers
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Transfering data using ultrasound

Yamaha InfoSound and ShopKick application use technologies that allow to transfer data using ultrasound. That is playing an inaudible signal (>18kHz) that can be picked up by modern mobile phones (iOS,...
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8-psk modulator design using any method

I want to build a 8-Psk modulator, I have searched the Internet but out of answers for a more simplified circuit.... I am open to any approach including arduino
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2answers
59 views

What is the price of increasing the QAM number?

In a QAM modulation scheme, you have a certain number of possible states which have different amplitudes/phases (like 4-QAM, 16-QAM). If you increase the number, for example switch from 16-QAM to 64-...
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1answer
681 views

How can i send bits using a wien bridge oscilator?

I have a string of bits that my shift register will be outputting one after another, I want to 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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3answers
1k views

Is a triangle waveform a type of pulse width modulation?

I'm confused as I have seen a triangle waveform referred to in terms of PWM but a triangle waveform does not actually modulate the pulse width. Is a triangle waveform a type of pulse width modulation?...
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0answers
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How can I know which constellation diagram has a lower symbol error just by looking?

So for the following example: How would I know which is less prone to error? $$C1=[−3−3j,−3+j,1−3j,1+j,−1−j,−1+3j,3−j,3+3j]$$ $$C2=[−3\sqrt2j,−2\sqrt2−\sqrt2j,2\sqrt2−\sqrt2j,\sqrt2j,−\sqrt2j,−2\...
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1answer
30 views

What effect does having 'measured' as a parameter in additive white gaussian noise?

I'm comparing the bit error rate of various modulation schemes with additive white gaussian noise in MATLAB. There's the option to have this noise using 'measured' which measures the power of a ...
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4answers
203 views

Why do sidebands appear after Amplitude Modulation?

In amplitude modulation, the amplitude of the carrier wave is changed according to the variations in the message signal, and that's what we draw inside the two envelops of the message signal, that's ...

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