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Questions tagged [modulation]

Generic term for coding information onto a carrier signal.

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Cannot decode IR signals using IRRemote Library

I'm using RC5 encoding for my project. I'm sending signals using RC5 Protocol. The transmitter is sending the signals correctly. But on the receiver node, when I decode the signals, Library is unable ...
Tauseef_Ahmed's user avatar
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0 answers
36 views

Modifying modulation parameters in RC5 [closed]

I am a computer science student working on a research project that uses IRRemote library for IR communication. I'm using RC5 modulation and the system is working. However, for the next part of this ...
Tauseef_Ahmed's user avatar
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Why is my oscilloscope math mode showing an RMS voltage in gigavolts (unexpectedly high value)

I'm experiencing an issue with my Rigol DS1202 oscilloscope. When using the math function to measure the RMS voltage of the difference between two channels (A - B), the RMS value is displayed in ...
raymysterioso's user avatar
1 vote
0 answers
62 views

Is the probability transition matrix of M-PSK signaling in AWGN channel invertible?

Consider an AWGN channel with MPSK modulation, and let \$P=[p_{i,j}]\$ denote the corresponding transition probability matrix, where \$p_{i,j}\$ denotes the probability that symbol \$j\$ is detected ...
Ben's user avatar
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-2 votes
4 answers
117 views

How can an audio signal with varying frequency be modulated using FM? [closed]

An audio signal can have varying frequency and amplitude and both are the part of the information. As I understand it, frequency modulation is a technique where the frequency of the carrier wave is ...
Ritam Sarkar's user avatar
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2 answers
82 views

How to properly trigger and measure a modulated square wave signal with an oscilloscope

I'm having trouble getting a stable trigger on my Rigol DS-1202 oscilloscope for a complex waveform. The waveform is composed of a 25.5kHz carrier square wave modulated by a 200Hz square wave, both ...
raymysterioso's user avatar
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1 answer
72 views

How to inject and extract a high frequency modulated signal onto and from the AC powerline?

I'm generating a square wave carrier signal of 125 kHz using 555 timer, I modulate it with a data signal generated from ATmega32 Tx pin (UART 9600 Baudrate) using OOK-Modulation, and now I'm trying to ...
Joe's user avatar
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2 answers
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How do we calculate the amplitude levels in QAM modulation technique

so I came across M-ary Modulation technique in my ADC subject. While I understood the basic principle behind it, I still cant get my head around the amplitude levels taken . Like lets say i am using ...
blitzzz's user avatar
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3 answers
100 views

Amplitude modulation problems

I am trying to do amplitude modulation using a diode, but my circuit will not work. This is the circuit I am using: simulate this circuit – Schematic created using CircuitLab I don't know why ...
Marcus Marchese's user avatar
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1 answer
55 views

Why 8051 is not detecting logic from circuit's voltage?

I am working on a ASK modulator and demodulator circuit which I wish to interface with a 8051 microcontroller to read serial data from demodulator circuit. The mod/demod circuit is developed and ...
Akshat Panda's user avatar
3 votes
3 answers
228 views

Must LC resonant frequency be identical to oscillating frequency in RF circuit?

I am developing an RF circuit for 503.3 MHz. It will be an AM RF transmitter. The LC circuit I built into this circuit consists of L = 0.1 μH and C = 1 pF. The carrier frequency which carries the ...
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2 answers
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Switching circuit with logic 3.3V control on p-channel JFET

The task is to derive sinewave (of higher frequency) chopped by step-function (also periodic but of lower frequency, i.e. several periods of sine wave are placed in that pulse). So I have a sinewave ...
Sombercy's user avatar
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3 answers
79 views

Modulate a digital message using FSK/PSK combination

I am beginner and I want to modulate the digital signal: 101101 based on the combination: frequency/phase (2 frequencies/2 phases). For that, I set the 4 possible combinations: ...
Mus's user avatar
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1 answer
50 views

Error probability of BPSK with intersymbol interference

Consider an AWGN channel with BPSK modulation. Assume that the information bits are i.i.d. Bernoulli with parameter 0<p<1, we have ISI due to a timing offset at the transmitter, and the decoder ...
Ben's user avatar
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2 votes
3 answers
180 views

Why do we need to transmit in a cable with a digital modulation? Can't we just put high voltage for 1 and no voltage for 0? [closed]

We know that we can't transmit a square wave pulse via EM and we need to convert it to an analog signal via some modulation. But why can't we just put high voltage in the cable to represent bit 1 and ...
allexj's user avatar
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2 votes
2 answers
393 views

Phase modulation for binary data - higher frequency harmonics?

I've recently learned about PSK and QAM. I first came across it in this youtube video (timestamped), and my understanding for how it works has remained the same as what is shown in that video. (I also ...
TrisT's user avatar
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Delta Sigma Modulator for 2/3 Multi modulus divider used in FracN PLL

I have been trying to implement a Delta Sigma modulator for a 2/3 Multi Modulus divider. I am referring to Riley's paper: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=229400 I have designed ...
Pranjal Mahajan's user avatar
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17 views

Equidistant PAM-n symbols

Why do we choose PAM-n symbols to be equidistant ? What will happen if it's not so? Any references are welcomed !
Isha's user avatar
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1 answer
166 views

Difference between MC1496 / LM1496 balanced modulator

I am working on a project that uses an MC1496, but unfortunately it’s not available here. Luckily I have found an LM1496 which seems to be an alternative, but I have no clue how to bias it correctly ...
Mohamed Abuain's user avatar
0 votes
1 answer
42 views

Bit sharing in IQ channel

In 16 QAM, each channel \$I\$ and \$Q\$ carries bits of the information it wants to encode. For example: if the symbol is (0011) then \$I\$ and \$Q\$ channel carries two bits (00 and 11 respectively). ...
Ananth Tenappan's user avatar
1 vote
1 answer
61 views

QAM Modulation - destructive addition?

Doesn't symbols in QAM modulation add destructively as they are symmetric about the origin (equal amplitude and opposite phase) about the I axis?
Ananth Tenappan's user avatar
-1 votes
1 answer
119 views

Frequency demodulation circuit

This is how I designed the frequency modulation circuit, but I cannot perform the demodulation process. It can be done with a PLL but I couldn't install it. How can I demodulate?
Orhunemre's user avatar
2 votes
4 answers
812 views

Are these low frequency FFT components due to insufficient op-amp slew rates?

In my circuit I have three op-amps in (direct) series connection: AD8422 acting as an input buffer (a large input impedance is needed) with a fixed gain (slew rate: 0.8 V/us) LTC6910 being used as a ...
Maxim's user avatar
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Why do we get increase in BER with increase in Eb/N0 of the signal?

I'm working on a problem of MSK modulation scheme. I have passed my modulated signal through SUI channel Models and AWGN. But As I want to do analysis on the performance of SUI channels I'm getting ...
Fatima Ismail's user avatar
7 votes
2 answers
2k views

How is power line communication (PLC) possible without screwing up the line as a viable power source?

[I am not an EE so bear with me with this] I've been learning about power line communication and see that it is mainly achieved by modulating the carrier signal (for this discussion let's say that's ...
Leftover Salad's user avatar
0 votes
1 answer
125 views

SRIX4K Emulator - ASK transceiver

I'm trying to build a simple SRIX4K emulator using an ATMEGA328p, I found this circuit on the internet, and it should work as a simple ASK transceiver, using the MCU to transfer data using the SRIX4K ...
Giovanni Visentin's user avatar
0 votes
1 answer
125 views

AM radio spectations - how does it work

I have captured a RF-AM transmitter circuit on internet. It is clear that the input signal will be pre-amplified and then it will begin to modulate the signal. The question is about how the circuit ...
user avatar
0 votes
1 answer
125 views

How to increase the carrier signal voltage of RF AM modulation?

The circuit below is an example for RF modulation: Question is about carrier signal voltage of RF AM modulation. What happens when the message signal is amplified and it would have more voltage and ...
user avatar
0 votes
0 answers
21 views

Effect of 2ASK Sampling Points on Bit Rate

“I reduced the only one sampling points while using 2ASK modulation, and the bit error rate increased by 20%. Can you help me with this?” Question happens in this line: ...
Aliang's user avatar
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0 votes
1 answer
42 views

How can I design a beta modulator block

I am simulating a block beta modulator, but the problem is to switch uses in that block. What component do I have to use in place of U3? I did not find this type of any component in LTspice library ...
Usha Kumari's user avatar
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2 answers
417 views

Understanding an op-amp modulator circuit

I'm trying to understand an op-amp modulator circuit I came across in a book. The circuit uses switches. According to the book, switches S1 and S4 are on during the positive half cycle of the carrier ...
Urthona26's user avatar
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0 answers
37 views

Delta Sigma modulation proof of average

It can easily be proven that an ideal analogue delta sigma modulator shapes the quantisation noise, as explained for example in this AD note under EQ 3: https://www.analog.com/media/en/training-...
PalimPalim's user avatar
2 votes
2 answers
141 views

QPSK Modulation towards DAC

Modern DACs are able to accept 2 digital values (representing I and Q), multiply them internally by a Sine and Cosine waveforms and combining the result to form the output signal. When dealing with ...
shaiko's user avatar
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1 vote
1 answer
87 views

How to convert low voltage digital signal (0-3.3V) to high power current signal 15-40W ranging from 1kHz to 1MHz?

I need to convert a digital signal generated from a microcontroller GPIO (0-3.3V) to a high-power (15-40W) current signal to drive an LED chip for illuminance, where the signal frequency can range ...
hailstone's user avatar
8 votes
3 answers
486 views

Can Bandwidth be Traded Off with SNR in Analog Modulation?

With typical linear digital modulation schemes, we can, for a given bit rate, make a trade-off between modulation bandwidth and modulation order (effectively, how close the constellation points are). ...
LetterSized's user avatar
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0 votes
1 answer
132 views

Designing loop filter for frequency-modulated PLL

I'm designing a PLL circuit to stabilize a ~200MHz VCO against temperature-induced frequency drift. However, I need to be able to occasionally (~few times/sec) send a short pulse (~few μs) to modulate ...
Ryan White's user avatar
1 vote
0 answers
46 views

Testing an IC : IO PAD experiences 2nd-order ramping effect

The IO is a regular PMOS-PULL-up and NMOS-PULL-dn IO with series resistors on pull-up and pull-dn branches. The IO is input an clock signal around 50MHz and it experiences an approximately 2nd-order ...
JohnLai's user avatar
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0 votes
0 answers
157 views

How to determine Phase Angle of 16-QAM

I am trying to figure out how the angles for the following input are obtained. For example, why is 0100 -105 degrees and not 45 degrees? Is there a specific method or do we estimate what the angle ...
miu.spiro's user avatar
0 votes
0 answers
48 views

How phase is modulated according to our message signal?

My question: let message signal m(t) be sin(w1t).For frequency modulation (instantaneous phase deviation=phi(t)) d[phi(t)]/dt=kf m(t) so i get that at 90° or π/2 frequency will be max because the ...
user305532's user avatar
0 votes
1 answer
77 views

What is the transfer function of electroabsorption modulators?

Can anyone give me a reference that I may find a closed-form formula for the output electric field (not power) in terms of the input small-signal electrical waveform (not input power) of an ...
CLAUDE's user avatar
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0 votes
0 answers
219 views

IQ data for analog FM modulation

I am trying to understand how I can produce analog FM modulation using IQ data. So far, I know to generate the FM modulation with an IQ modulator (like the LTC5599.) I have to apply IQ data in ...
Grag's user avatar
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2 votes
1 answer
584 views

Why does the frequency deviation of a FM wave have different definitions?

Source 1 defines the modulation index in the expression for FM as follows: As per the expression for frequency modulated wave, isn't the frequency deviation same as Modulation index 'M'? "The ...
Dynamic_equilibrium's user avatar
0 votes
0 answers
56 views

CC1125 tramsmit data from the nanosatellite to ground station

does the chip cc1125 can transmit data between nanosatellites to ground stations the distance between them is up to 400km with band frequency UHF from uplink and vhf of the downlink. If yes can use ...
PCB-ABBS's user avatar
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0 votes
3 answers
874 views

How to improve the sine wave coming in to reduce the power bill?

Can the sine wave from the electricity that comes from the electric company be modified to make your appliances run more efficiently in turn saving electricity cost? How? Related: How to make pure ...
Justintimeforfun's user avatar
1 vote
2 answers
360 views

LoRa - Frequency Shift Chirp Modulation - chips in a symbol

I am trying to create a form of FSCM (frequency shift chirp modulation) based on LoRa principle just to learn from it and to obtain a deeper understanding. What I do not get: why is (or must be?) the ...
Mart's user avatar
  • 376
0 votes
1 answer
130 views

VHDL: Testbench for ASK modulator

I've been trying to learn VHDL recently and came across the following tutorial for an ASK modulator: https://surf-vhdl.com/implement-digital-ask-modulator-vhdl/ I tried writing a testbench for this ...
user1397215's user avatar
4 votes
1 answer
190 views

Where and how are the carrier and message signal multiplied in this circuit?

I have this circuit diagram of an AM modulator and I am trying to understand what is going on. I know that the c(t) is taken from the collector of transistor Q1 and the multiplication of signals : m(t)...
Ashwin Singh's user avatar
0 votes
0 answers
59 views

Signal modulation with VNA

I want to apply a 1 V, 1 MHz signal to my DUT (coaxial waveguide) while sweeping the frequency from 300 kHz to 6 GHz by the VNA. Right now, I applied the signal by the signal generator to the bias tee ...
Ferrofluid's user avatar
4 votes
1 answer
440 views

FSK Modulation in Python

I am currently writing a script that uses I/Q data to do FSK modulation. My question is about the FFT plot. I expected to have a peak at 1Hz and 2Hz which are the frequencies that represent binary 0 ...
PrematureCorn's user avatar
1 vote
1 answer
138 views

How to amplify signal enough to make a Langevin transducer vibrate?

I'm a little out of my zone of mechanical engineering here, so I'll need your help. Up to date, I got the right frequency (40 kHz modulated for a 200 Hz low frequency) coming out of my function ...
qc_engineering's user avatar

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