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Questions tagged [modulation]

Generic term for coding information onto another carrier signal

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27 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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34 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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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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65 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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76 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
75 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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19 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
48 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
115 views

( How-To ) Ultra Low-Profile PCB Stacking

Recently I found myself needing to stack two small circuit boards on top of each other for a modulation project. The problem is that the areas I want to connect together on the two boards have no ...
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1answer
111 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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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 ...
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76 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
88 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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58 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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41 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
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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101 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
37 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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23 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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52 views
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51 views

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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22 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
99 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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45 views

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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24 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
39 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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46 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
20 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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73 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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30 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
81 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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53 views

iPhone headphone out as a signal source for AM modulation circuit

EDIT: I wonder what is the appropriate model for an iPhone/MP3 player audio out? I imagined it as a voltage source that would support whatever current the resistance it’s connected to necessitates. Is ...
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73 views

What does the phase discriminator portion of the Costas Receiver do mathematically?

What does the phase discriminator portion of the Costas Receiver do mathematically? The output of the I-channel is \$ \frac{1}{2}A_C \cos \phi m(t) \$. Which means for small deviation of phase \$ \...
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46 views

Does DSB-SC signals retain original shape of the message signal \$ x(t) \$ when \$ x(t) <0 \$?

The conventional DSB-FC AM signal is given by: \$ s(t)=[A+x(t)]\cos \omega _C t \$ In conventional DSB-FC AM we take care of the fact that \$ |x(t) | <A\$. So that the modulated signal is not ...
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187 views

How is companding different from pre-emphasis and de-emphasis?

What I know is that interference increases linearly with frequency and thus noise power is concentrated at higher frequency. So, to reduce noise, pre-emphasis and de-emphasis filters are used which ...
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143 views

How is the power of a SSB-SC signal half that of DSB-SC signal?

Intuitively I get it that my SSB power has to be half of DSB power but mathematically I am unable to get this. Say working for tone modulation. $$m(t)=mA\cos(w_mt)$$ where m is modulation index. ...
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202 views

Amplitude modulation with diode

I was studying about amplitude modulation and I found this circuit on the internet. Does anyone know why that ground is needed? Is the first part(three resistors) an adding circuit? Does the diode ...
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2answers
217 views

Why different SFs in LoRa are said to be orthogonal?

As orthogonality is an important characteristic in LoRaWAN but most public references just make a conclusion that different SFs are orthogonal. This confused me a lot and hope to make a clear ...
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44 views

How come optical data modulation is faster than that of electrical modulation while optical modulation is done by electricity?

why optical data is of high bandwidth that that of electrical copper data bandwidth when we use electrical signal to achieve optical data modulation ?
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38 views

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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1answer
62 views

Quadrature modulation Digital to Analog

I want to use an FPGA to generate quadrature modulated signals for use with an RF transceiver (something like MAX2828 ). I am confused specifically about how the digital to analog modulation should ...
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2answers
57 views

Finding required BW with Bessel table

The FM signal (see image 1) is applied to a 50 Ohms antenna, and I am seeking the required bandwith with the Bessel table (image 2). From the FM signal, I deduced that the information frequency is ...
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254 views

FM Transmitter (Modulator) Circuit Simulation Problem [duplicate]

I've asked my question before, and I am writing this new question with some edits based on my previous problem. I am building a small FM Modulator ( Transmitting ) simulation on (Multisim). I've used ...
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1answer
473 views

FM Transmitter Circuit (range 3 km) on Multisim

I am new to the telecom simulations system specially multisim, which I am having a project that I want to simulate. My project in (Analog Communications) is consisting to have FM Transmitter (...
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1answer
51 views

Powering 4 modulated IR LEDs through transistor

I've done some research but can't seem to find an answer to my specific problem. I'm using an Arduino as a beam-break sensor. In order to do that it modulates the IR LED at 38kHz by code and listens ...
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395 views

What's the name of signal encoding used by WS2812 LEDs? [duplicate]

The WS2812b color LED uses some kind of duty cycle encoding to encode three states: one zero reset This can be seen in the following figure: (Source: https://cpldcpu.files.wordpress.com/2014/01/...
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139 views

How to understand this simple voice-over-laser circuit

The Sci-Toys project A simple laser communicator shows a surprisingly simple way to send an audio signal over a laser pointer. A transformer AC-couples an audio signal directly into the DC supply to ...
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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 ...