Questions tagged [modulation]

Generic term for coding information onto another carrier signal

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60 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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23 views

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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38 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
88 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
37 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
63 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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21 views

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
48 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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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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38 views

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
29 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
196 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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1answer
26 views

What does division order mean in Rayleigh Fading?

So I'm just beginning to understand how Rayleigh Fading works and I'm trying to model some different modulation schemes with Rayleigh fading channels. I'm doing this on MATLAB where one of the ...
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0answers
20 views

What is the difference between using a baseband representation of a QPSK modulation scheme and a theoretically simulated QPSK modulation scheme?

I'm looking to compare the BER vs SNR performance of a QPSK modulation scheme, one which is a theoretical simulation on MATLAB and the other is a baseband simulation on MATLAB but I'm struggling to ...
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1answer
44 views

can not get required gain with gilbert cell on ltspice

I designed a very basic Gilbert cell using BJT's. The function is a DSB modulator where one input is a 2.5mvpp sine wave, and the other a 5vpp square wave. The current at the bottom is a simple ...
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27 views

Phase and constellation diagram

I have noticed that when, for example, \$cos(t)\$ is in-phase (I) component of the modulated signal, we can determine the phase from the constellation diagram measured counterclockwise from the ...
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2answers
349 views

Why is BER higher for binary modulation compared to quaternary?

I came across this image in my notes and I fail to understand why BER seems to decrease as the modulation order increases and I was hoping for an answer
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15 views

LA72910V Demodulator and Modulator Noise Problem

The project includes a DC power supply that supplies two cards and provides a network. The video signal is modulated through LA72910V whether a card is demodulated in the other card. There is no ...
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31 views

Setting up parameters for generating QAM signals

I am trying to simulate multiple baseband QAM signals for random data at varying power levels, data-rate, carrier frequency, and modulation order using MATLAB. Here is how I set up the parameters: <...
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1answer
37 views

How high should I make an FSK modulation index value?

After consulting with the radio manufacturer about a setup for my FSK radio module (HM-TRP), they have suggested I program it with the following values when setting up the module for 115kbps: ...
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2answers
97 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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1answer
106 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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1answer
486 views

Design AM modulator circuit

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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39 views

How to get a band-limited digital modulation of X type?

I am developing a program which should create modulated signals and combine them to get an RF signal with different modulations on different frequencies with non-interfering bandwidths. The problem ...
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1answer
111 views

How to determine time needed to stay in a voltage vector state in Space Vector PWM for 3 phase inverter?

I need some clarifications on how and when to switch between voltage vector states (for the sake of discussion lets take V1 and V2 in the image below). Below is the image of 6 possible voltage vector ...
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20 views

How to perform multiplication at the time series level for chirp signals

As the title said: How to perform multiplication at the time series level for chirp signals? In LoRa modulation, when received a chirp modulated signal, to demodulate it, LoRa will first multiple the ...
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1answer
83 views

Correlation b/w output voltage frequency and angle theta for Conventional Space Vector PWM 3-Phase inverter drive

Im writing code for SP-PWM for a 3 phase voltage source inverter but since im a bit naive to the topic I need some clarifications regarding some questions I have. Lets cut to the point. For 3-phase ...
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1answer
129 views

Toy “pull tab”-style feature on PCB

I have recently designed a passive-based modular PCB. When I click the secondary board into the base board, I would like it to break the current circuit at a fixed point, and insert itself in series ...
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0answers
46 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 ...
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2answers
209 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 ...
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1answer
98 views

2n7000 used for inductively coupled load modulation apparently latched

So I've got a fairly basic circuit set up for load modulation of an inductively coupled circuit: A few notes on the above: LC's were designed for 1 MHz but work better at 950 kHz, thus the chosen ...
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75 views

Bandwidth for a Butterworth filter

How to choose the bandwidth of a 2 pole Butterworth filter for QPSK modulation? What bandwidth should be chosen, if symbol duration is 10 ms? How to limit ISI for QPSK modulation?
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44 views

How to choose an antenna for an FM transmitter? [duplicate]

Ok guys I can't understand something. Say that I have this circuit: Assuming that I apply at the antenna 5V, how can I calculate how much power I will trasmit? I found on internet that the current ...
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1answer
44 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
164 views

FSK generation with Timer 555

On the Internet I found FSK generator connection diagram. And I'm trying to connect up it in Qucs. I' sure, 555 timer is working properly. But at the output of the whole schema I get unclear result. ...
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1answer
40 views

Is there a difference between rise and fall time and modulation frequency

I was wondering if there was a difference between modulation frequency and rise and fall times of a laser diode or LED? If a laser had a modulation frequency of 100MHz would that be the same as a rise ...
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27 views

Bessel function normalization graph

This graph is drawn bessel function table but ı stick around reading table.Does table gives directly frequency spectrum amplitude values or only jn(ß) values?
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21 views

Data rate with modulation and conventional encoding

I had a rather simple question. Say I had a SISO communications system with an information data rate of 50 Mbps that uses QPSK modulation and a rate 1/2 conventional coding. What would be my symbol ...
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vestigial sideband modulation [closed]

If we are given the following equation of Vestigial Side-band Modulation, what values will I put in the equation? $$ H_0(f)=\frac{1}{H_i(f+f_c)+H_i(f-f_c)} $$
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1answer
24 views

prevent receiver components from interfering with output of modulator

I am working on an ASK modulator and de-modulator. The modulator works fine (thanks to great folks at SE). However when I try to pass the modulator output to the input terminal of the receiver, the ...
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2answers
149 views

ASK modulator using transistor not working properly at high frequencies

I am trying to make a simple ASK modulator circuit using an npn transistor. It works acceptably at lower frequencies. However at higher frequencies, it doesn't work properly. The amplitude of output ...
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What effect do R5,R6,R7,R8 have on the following DSBSC Modulator?

I know that the first 741 essentially adds m(t) and c(t).The gain should be 1 so why do we have 3.9kohms resistance ? What use is it ? The second 741 circuit is a band pass filter . I think there is a ...
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28 views

Single Ended DAC to Differential Input Modulator

I'm trying to drive a differential input IQ modulator (LT5571) with a single ended DAC (MCP4912) for modulation of a narrow band signal (~10kHz max). Because of the nature of the low frequency ...
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1answer
44 views

Source generator for Satellite Tuner input

I need to design a source generator for a TV factory. They want to automatize the functional tests by applying a test module to the TV's at the end of the production line. All the peripherals of the ...
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49 views

Three level PWM modulator circuit feedback simulation

I'm trying to design a three level PWM circuit with feedback and i'm struggling to understand the feedback aspect. The design is based on this design by Texas instruments and modified to suit three ...
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1answer
21 views

Conversion Gain Definition for DSB-SC Upconversion

If I multiply a baseband signal \$A cos(C\omega t)\$ and a carrier signal \$B cos(D\omega t)\$, the result is \$\frac{AB}{2} [cos(C-D)\omega t+cos(C+D)\omega t]\$, which is a double sideband, ...
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1answer
113 views

understanding AFSK and FSK

I’d like to understand 1200Hz/2200Hz AFSK in commonly used APRS/Packet/AX.25 applications. When I look at the datasheets for some of the chips existing projects use (e.g the Si446x transceiver-on-a-...
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32 views

Labview - Active amplifier

I need to create a pulsed current variable from 0 to 20A to run solenoid with a very low resistance. Which is the best solution for you? Right now I am trying to generate a pulsed current with ...
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2answers
82 views

Why don't we use analog remote mics?

All remote microphones sends digital samples over the ether. Why no analog remote microphones? I know that digital signals are less sensitive to noises, but there are several advantages of analog ...

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