Modulation Definition and 135 Threads

Hi, I have here an elenco s-1325 analog oscilloscope. I am hacking it into a display unit for one of my projects and have designed two raster scans for the x and y-axis (the oscilloscope is running in x-y mode). I now need to be able to modulate the intensity of the electron beam so as to form...

Homework Statement A given DSB-LC AM transmitter develops an unmodulated power output of 1kW across a 50 ohm resistive load. When a sinusoidal test tone of 5V is applied to the input of the modulator, it is found that the spectral line for each sideband carrier in the magnitude spectrum is...

In the amplitude modulation equation, V=(Ec+Ei*coswt)coswt I don't understand why the instantaneous value of information signal is used. Shouldnt it be peak value as that would give the maximum value (amplitude)?

hi gang, just a quick clarification please :) was looking at the Wiki articke on Frequency modulation http://en.wikipedia.org/wiki/Frequency_modulation This comment is in the Modulation Index section... The signal frequency is referring to the applied audio signal doing the...

hello all. If one uses polarization modulation of radio waves does this imply a broad frequency spectrum knowing the carrier frequency and amplitude remain the same only the direction of the electric field is being changed ?

I have read a lot of articles on pulse width modulation and I am none the wiser as to how it generates different voltages by simply varying the pulse width of the waveform. What I read was that if you have a rectangular wave train of some amplitude and change the 'ON' period the "NET" voltage...

Homework Statement See figure attached. Homework Equations The Attempt at a Solution See pdf attached for my attempt at the solution. I'm a little confused as to how to draw the phase spectrum for y(t). Would it simply be a line equation of, -\frac{\pi}{6000}f \pm...

Does anyone have any idea about modulation ratio of voltage and modulation frequency in power systems?What is the relation between between two?

the 2 signals shown are used for modulating ( DSB-SC) a carrier with frequency fc. Now i need to find the similarities and differences between their time domain representation. Clearly the both will have same envelope. Now i tried for the difference part but could not find it. One possibility...

In our lab we are to measure speed of light by making a light signal travel through optical fiber. At one end there is the transmitter, which will output the light signal into the fiber, and it will also "modulate" the signal. According to my lab manual, "The reason that the signal is made to...

I am looking for average values of the signal-to-noise ratio for pulse width modulation and for a direct signal?

Hello Everyone! About Amplitude Modulation, Usually it is seen in the book or web that (e.g. http://www.ni.com/white-paper/3002/en ) '''' The message signal can be represented by m(t) = Mb cos(2πfb + φ) and the carrier signal can be represented by c(t) = Ac cos(2πfc + φ), Now...

I have an image taken with a camera. I know the f/#, focal length, CCD characteristics, and an approximate distance to my scene. I computed the modulation transfer function but I am trying to map the pixel space to cy/m and having trouble. I essentially want to determine the cutoff spatial...

Q1. A device with input x(t) and output y(t) is characterized by y(t) = x(t). If a FM signal with frequency deviation 90 Khz and modulating frequency 5 Khz is applied to the input terminals of the device then what will be the bandwidth of the output signal received ? What i did was...

I read on a website that in amplitude modulation the actual carrier wave does not change its amplitude but rather the sidebands. Is this true

Why isn't it possible to invent a custom digital modulation scheme that would use much less RF bandwidth than all the schemes available? What are the limiting factors that do not allow for high data rates to be coded so that the occupied bandwidth is much less than all the others like ASK, PSK...

I thought that the frequency was constant for AM modulation, and just the amplitude was modulated. So why are there a range of frequency's (side bands around the baseband) when the signal is plotted on a frequency domain graph?

Hey Everyone, Can someone explain to me the natural of amplitude modulation in regards to sound. As in one modulator frequencies' amplitude modulating the amplitude of a carrier frequency. Because at low frequencies the modulator only affects the carrier in a way that makes its volume go up...

Hey everyone, I am trying to understand the phenomena behind the technique of using amplitude modulation in sound synthesis. When you have two frequencies, for example, w1=200hz and w2=300hz, and you use the amplitude of one (w1) to modulate the amplitude of the other (w2), it creates 3...

Hi I have read a paper, where they distinguish between wavelength and frequency modulation. More specifically: "FMS (frequency modulation spectroscopy) can be broken down into two regimes: wavelength modulation (WM) and frequency modulation (FM). In the case of WM, the modulation depth is...

In the context of optometry. I can't seem to find a formal definition anywhere.

Hello, I have attached a diagram of QPSK modulation angles. I was wondering how would the red and yellow dots be interpreted. Those dots are not exactly on either of the 4 different phase angles. But I understand QPSK has a discrimination of 90 degrees so would the red equate to 45 degrees and...

A signal, x(t)=4sin(0.5\pi t), is transmitted by a DSB modulator. What is the frequency range of the carrier wave corresponding to the given message (data) signal? My basic misunderstanding here is if the given signal is the message signal that I should demodulate from a DSB modulated...

Hi On page 11 of this book, http://books.google.dk/books?id=Wv2OIC_SaDUC&printsec=frontcover&hl=da#v=onepage&q&f=false, it is stated that: "The phase modulation has an additional advantage: The first two sidebands at frequencies ω+Ω and ω-Ω have equal amplitudes, but opposite phases. A lock-in...

http://pokit.org/get/c2d0bb4355d353d0ff5bc47c7158ce45.jpg Suppose we have an op-amp configured as a comparator. At -ive lead, we are sending the carrier wave, specifically in my example, triangle wave. At +ive lead, we are sending the input signal, the one that we want to modulate...

Hello, I am trying to understand how the most basic form of AM works. Can someone please confirm if my brief description below is essentially correct ? I know that upper and lower sidebands are created when a signal is modulated onto a carrier frequency. These sidebands result in a signal that...

ive been trying to proof the modulation index for Am transmission, it goes like this Vmax = a(1+u) Vmin = a(1-u) it basicilly describes the amount of infromation in the total power transmitted and should allways be between 0 & 1 eventually the answer should come out to be u =...

What is the purpose of using a chopper to modulate an optical source? The Wikipedia article is not that informative.

Hi All, I wonder if the modulation of RF waves (Amplitude Modulation, Frequency Modulation, and Phase Modulation) can be explained in terms of photons. Thanks, Srini

For Amplitude Modulation, it is understood that the bandwidth of a passband signal is always twice as much as that of a baseband signal, for example if the bandwidth/max frequency of a message/baseband signal is 1 kHz and a carrier of 1 MHz is modulated with this baseband, then a "sum"...

Hi guys, I need some help. I have the following modulation equations: \Re:-\zeta a+\lambda a\cos 2\delta-\eta \cos (\delta+\phi)=0 and \Im:\omega a+\lambda a\sin 2\delta-\eta \sin (\delta+\phi)=0 which, with proper manipulation (i.e. by squaring and adding and/or diving them with each...

Homework Statement I'm going to do the experiment that generates a square wave using the 555 timer this weekend, but I'm wondering why sometimes we have to modulate the square waves to sin waves, and decode them in the terminal receiver? Could square wave(or any other non-sin wave) itself...

Hi, This is a general question rather than an explicit question, so apologies for not using the template. I'm a bit confused by the relationship between frequency and data rate in a communications system and wondered if someone could help clarify please. Say I want to achieve a data...

If I modulate a pulse X(t) with a.) a sine wave or b.) a cosine wave, I have the frequency spectrum expressions a.) \frac{1}{2j}[X(f-f_0)-X(f+f_0)] b.) \frac{1}{2}[X(f-f_0)+X(f+f_0)] When I plot these for a pulse, I see a difference in the magnitude spectrum, but I should not expect...

In the context of electromagnetic wave propagation in ferromagnetic medium, what is meant by magnetostatic spin wave? This terminology one came across in the wave modulation in ferromagnetic medium. Thanks in well advance..

Hi guys, my first post on these forums. I am learning electronics and am still very new to this all. My current tinker project is to learn how regular tv remote controls work. So far I have understood that the remote sends blinking IR pulses through an 940 nm LED. The remote uses...

Hi guys, I'm currently generating OFDM signal and send it to DAC and then upconvert them to 1 GHz carrier signal. I want to multiplex several of them, like say I upconvert them to 1 GHz, 800 MHz, 1.2 GHz, which represents 3 different signals, then multiplex them together using FDM, is it...

While reading about frequency modulation, I found that it was clearly written that the amplitude of the carrier wave remains unchanged. However, i didn't find a statement stating that the frequency of the carrier wave remains unchanged for amplitude modulation. So, is the frequency of the...

Hi everyone, plx help me on this! I've worked out frequency modulation but can't understand amplitude modulation ... A sinusoidal carrier wave has a frequency of 750kHz and an unmodulated amplitude of 4.0V. The carrier wave is to be amplitude-modulated by a sinusoidal signal of frequency...

fastest modulation: laser diode vs LED... Hello Forum, in the telecomm industry, the most common and economical form of modulation is direct modulation, acting on the current operating LEDs or diode lasers. Using an external intensity modulator (OOK), like a super fast chopper, the...

Actually i m new to electrical sciences, can anyone please explain me the working principle of a PWM?? and its applications , please provide any relevant links concerning it. Thanks in advance

Hi there, I'm a bit beffudled by some of the workings of a MOSFET transistor. First of all, in the saturation region of operation, I understand that the inversion channel is "pinched off" as it approaches the drain. In other words the inversion channel thickness tapers off as it approaches the...

We know to make antenna dimension reasonably small, we modulate baseband signal with a high frequency carrier. Antenna size as far as I know is in the order of one tenth of carrier signal wavelength. For example, for a 3 GHz carrier signal, receiver antanna size is 1 cm. But, in frequency...

Hello, So I was studying for my exam and came across this exercice we did in class and which I really don't know how we got the answer. It says that if we have a FM with a carrier frequency of 4MHz, and the bandwidth is 400KHz, what is then the maximum deviation.. The answer is 200KHz...

We have recently developed a motion sensor that introduces charge into an electric field. From the 200V (containment field) we derive a modulation of 100mV. Although the sensor has passed pre-production tests we are struggling to come up with a simple formula to describe the operation. Can...

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...

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...