Modulation Definition and 145 Threads

Hello everybody! I have a question on amplitude modulation. Homework Statement I'm given an input signal m(t)=0.2sin(1000*Pi*t)+0.5cos(\sqrt{2}*1000*Pi*t) and I'm asked to sketch the AM waveform and to find the modulation percentage.Homework Equations The Attempt at a Solution I'm asking for...

For frequency modulation, will the modulated signal always be periodic? or does the periodicity depend on the modulation index? or does it depend on whether the message signal is periodic? Thanks for any help on this

Hello Everyone, I am working on a system for an undergraduate project that uses pulse width modulation to power two electromagnetic clutches. I have a pic microcontroller that is supplying a PWM signal to a MOSFET that is in turn switching the ground side of my clutches. Everything seems...

The Problem Hi, I am trying to modulate two sinusoids in Matlab. I have some and some , where fx and fc are different frequencies. I then modulate them together, using dot multiplication, . I then plot each in the time domain using and I obtained the correct solution. The problem comes with...

Hello, Not sure if this is the appropriate forum for this, but I'll give it a shot. I am recording a laser signal through my experiment which is running an FM scan at 20 kHz. The time scale of the experiment I'm running is much larger than the 20 kHz signal, so each scan is about the same. In...

Hi guys, I'm new to the forums and hope someone can help with this. Homework Statement Compare the modulation techniques used by 2 different applications, giving reasons for their use. Use data tables, diagrams and any other sources to help Homework Equations None The Attempt...

Homework Statement I used MATLAB to perform simulation on 8psk modulation, and this is the result i obtained. I would need your help to help me to verify whether the result I obtained is valid. Thanks. [PLAIN]http://img132.imageshack.us/img132/8124/8pskverification.jpg Homework...

Hello, I know that you send digital signals using ASK, FSK, PSK modulation. I was wondering though if it was possible to send that same digital signal using FM or AM modulation? If not, I was wondering if anybody knew of any popular ASK or FSK modulation IC's? Thanks!

why it is disaster if asignal exists in am at frequency of 455 khz , i mean asignal is at the IF frequency. also why IF not greater or smaller than 455khz i need to know thanks

any one tell me briefly why in the superheterodyning we take the IF as 455 khz? also why not to take aparallel resonance circuit instead of band pass filter? thanks

Ok I am trying to solve this problem, I will lay it out, then say what I've done so far, and I would appreciate if someone could help me figure out where I am going wrong. I am very new to MATLAB (using it for the first time) so I've only got the basics down so far. Problem: Message signal...

what is the meaning of modulation and what is types can anyone explain that to me and give me any book.

This is not a HW question but an activity i am working on. The attachment is a symbolic AM transmitter. The carrier is 15MHz and message frequency is 2Mhz. I want to sketch the waveforms labelling them in as much detail as possible. Also sketch the output waveform in both time and...

I'm learning about radios at the moment but there's a few things I'm not clear about concerning modulation. I'll use audio amplitude modulation as an example. Let's say I have a device which I speak into and this device converts the variations of the sounds waves coming outta my mouth into an...

Given m(t) = 25cos(2*pi*1000t) and sc(t) = 75cos(2*pi*150000t), hence the AM signal equation is 75[1+0.333cos(2*pi*1000t)]cos(2*pi*150000t). Expanding it will yield 75cos(2*pi*150000t) + 12.5cos(2*pi*149000t) + 12.5cos(2*pi*151000t) and proceeding with Fourier Transform, i got delta functions...

Homework Statement analyze the MC1496 circuit and explain how it produces an AM signal. Homework Equations The Attempt at a Solution this is my understanding to modulation: Amplitude Modulation AM is mostly used when we need to transmit information over a radio signal; to do so...

Homework Statement In my electronics practical class, i assemble a ckt of amplitude modulation using BC107 transistor ,but the modulated wave always has the same phase up and above , there is no phase difference b/w the upper and lower part of the wave . My teacher also couldn't...

Homework Statement Consider a tone modulated PM signal of the form s(t) = A_{c}\cos\left(2\pi f_{c}t + \beta_{p}cos(2\pi f_{m}t))\right) where \beta_{p} = k_{p}A_{m}. This modulated signal is applied to an ideal BPF with unity gain, midband frequency f_{c} and passband extending from...

I'm working with a couple different diode lasers, attempting to automate control of them (on and off mainly) by modulating the source currents externally. One of them is a green laser that draws ~1.4A, 3.3V but has no modulating chip in the power line. I've got another smaller red laser module...

Hey guys, was just wondering if you could explain what modulation and demodulation is and more importantly, why it needs to occur in things such as radio stations. Also, can you also explain how modulation and demodulation occur when fibre optics are involved?

A sinusodial carrier wave has amplitude 12 volts and frequency 600 kHz. The frequency of the carrier wave changes by 25 kHz per volt. The carrier wave is to be used for the transmission of a signal of frequency 3 kHz and amplitude 2 volts. For the frequency modulated carrier wave, state...

I used to think that the frequencies obtained by a Fourier Series or Transform from a signal in the 'time domain' were simply a consequence of our mathematical system. In other words, it is a consequence of the fact that sinusoids are used to recreate or synthesize the signal. It's just an...

i hav got some doudts regarding AM (amplitude modulation) 1) the amplitude of carrier wave is changed according to the signal --- defn of modulation wats the amplitude of modulated wave is it A+B or other ... if "A" is the amplitude of carrier & "B" is the amplitude of signal ...

Homework Statement The problem is about the http://en.wikipedia.org/wiki/Quadrature_amplitude_modulation" . This is a work from my course Analog signal processing. Here is the scheme http://img99.imageshack.us/img99/9449/zrgwj2.jpg Two things to do : 1. Find the expression of x_qam(t) 2...

Hello, I need help with modulation techniques. If I have a sequence I want to transmit, and need to be modulated, how do I know its length? : I know the time duration of the sequence=t => t/T(carrier period)=number of cycles per sequence...

Hi everyone:smile:, This is my question: " Describe the concepts of PCM (Pulse Code Modulation) in a computer keyboard which its data are in digital format." This is my justification: How to describe the concepts of PCM ? Isn't PCM a technique used to transmit analog signals in digital...

Homework Statement Illustrate in wave forms for data “101001000111010011110100” by using the following modulation techniques: (a) 8-QAM (2 bit ASK + 1 bit PSK) (b) 8-QAM (2 bit PSK + 1 bit ASK) (c) 2 bit PSK + 1 bit FSK 2. The attempt at a solution *attached* apparently I got it all wrong. I...

Hi Guys, I was hoping someone could explain why commercial satellite uplinks (like those used in TV broadcast) are able to achieve such high bandwidth rates vs. radio uplinks like HAM OSCAR uplinks. I don’t completely understand how digital modulation is done onto radio wave, but at 1st...

hey everyone I really don't know whether this is the right stream for posting these kind of questions, but anyways here it goes.. Can anyone please explain to me the amplitude modulation and frequency modulation, or at least any website that xplains it, bcoz i am totally confused with...

Hi to everyone. I have heard that we usually prefer to modulate signals at high frequencies so the wave length is small compared to the length of the antenna. Is there any rule or equation that implies this requirement?

Hi, a quick and easy one I hope someone can help me with. What would be the general expression for a DSB-AM modulated signal in terms of the Carrier Signal C(t), Baseband Signal S(t) and the modulation index m? Many Thanks

Hello to everyone i am looking for a book dedicated to the modulation schemes. I want to read about the basics but also more advanced modulation schemes such as OFDM,QAM,DPSK etc Do u know any book or url that i can find the information i need?

I have searched and read some sites concerning this topic but I did not find one that has explicit how each type of modulation is affected by distortion, interference and noise. So, could someone mention some? For example, I read this site which has good information but not what I was looking...

Hi do u have any good articles about signals and modulation... I want to know why we use modulation and how the world would be if no modulation was used at all... Waht arre the types of modulation? What are the differences between them? What are the adgvantages and disadvantages for each...

I have the following problem: I measure a sinusoidally varying signal at a number of phase points. I then fit a sine curve to the data points using least squares. The fitting function looks like: f = a1 + a2 cos(phi) + a3 sin(phi) I want to evaluate the modulation depth from the measurements...

Hello everybody, I am trying to use a pair of Tektronix FG 503 Function Generators to modulate a carrier wave and produce an AM modulated signal. I tried running the output of one generator into the VCF input of the other, but it seems to give me FM modulation. I did this because I am...

Hello, I want to know why phase modulation (PM) transmitters are not used for practical broadcasting, though its almost similar partner frequency modulation (FM) is used widely for broadcasting.

Quardrature Amplitude Modulation. I know the basic techniques, like when you have 1 point and only two signals are to be multiplexed. But the constellations got me a bit confused. My text-book doesn't explain it thoroughly, and there isn't much deep information about it on the internet...

What is modulation in radio communication?

Ok A question here about how AM & FM modulation works. I know that AM trasmits the sound by varying the voltage of the radio signal, and FM varies the frequency itself of the signal, however, viable sound needs two things, varying frequency AND VARYING AMPLITUTE. So the modulation, whether FM...

How come a signal modulated using Amplitud Shift Keying and/or Phase Shift Keying (such as QAM) require a bandwidth? I mean, since the frequence is constant; only the amplitude and phase is changed. Thanks in advance!

Hi guys, Need some help and guidance here, I'm having some difficulty(and confused) trying to understand Modulation in telecommunication systems. From what I understand (pls correct me if I am wrong); AM - the amplitude changes, but not the frequency. FM - the frequency changes, but not...

CAn someone explain how sound waves is modulated into Am and FM carrier waves? I only have a poor illustrarion i don't understand.

If anyone is an expert on Velocity Modulation of Electrons within Electric Field, please try to help me. The dilemma is, I'm reading through waveguide theory on TPUB and hit a page that deals with VELOCITY MODULATION. http://www.tpub.com/content/neets/14183/css/14183_85.htm It clearly...

What role do Bessel functions play in frequency modulation theory?