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Why is modulation of the carrier necessary in RF communications?
Wiki User
∙ 15y ago
An unmodulated carrier carries no information, and therefore no communication is possible unless it is modulated in some way.
Wiki User
∙ 15y ago
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What is the technical difference when it comes to the implementation of AM and FM?
In a analog transmitter the RF carrier have to be modulated with the analog signal either by AM or FM where in digital transmitter the carrier is simply switched on and off a off = a zero and on = a one
How does the intelligence signal modulates the carrier?
There are three major types of modulation:AM, Amplitude Modulation, where the modulation signal is altering the amplitude of the carrier according to its own amplitude, normally this is done in the output stage. Therefor a strong audio signal is necessary at the same or a little less than the power of the carrier, never higher, because that will over modulate the carrier that will resort in distortion of the receiver output. AM is used in the lower band of the RF spectrum.FM, Frequency Modulation, where the frequency of the carrier is altered by the audio signal. When the amplitude of the audio is going higher the frequency go lower. Modulation happen at the oscillator stage, therefor a small audio signal is used to modulate the frequency. FM is normally used in the higher frequency range of the RF spectrum, 50MHz and up.FSK, Frequency-shift keying, used for data transmission, this type of modulation is simply, switching the carrier on and of, a high bit will switch the oscillator on and a low bit will switch it off, in some designs a low will be on and a high off.
What is the Digital modulation?
There are 3 main types of digital pulse modulation:Pulse time modulation (PTM), somewhat similar to analog phase modulation.Pulse width modulation (PWM), the width of the pulse represents the signal.Pulse code modulation (PCM), serial transmission of binary bits forming numeric or character codes that represent the signal.All of these can be modulated on an RF carrier using any of the standard modulation techniques: AM, FM, Phase Modulation, etc. One advantage with AM digital pulse modulation techniques over AM analog is that the carrier can be 100% modulated, which cannot be done with analog, thereby allowing significant reductions in transmitter power without loss of coverage range. Sometimes FM digital pulse modulation techniques are referred to as Frequency Shift Keying (FSK). A very complex method of combining Phase Modulation and AM to increase the bit density of digital pulse modulation on an RF carrier is called Quadrature Amplitude Modulation (QAM).
What is the digital pulse modulation?
There are 3 main types of digital pulse modulation:Pulse time modulation (PTM), somewhat similar to analog phase modulation.Pulse width modulation (PWM), the width of the pulse represents the signal.Pulse code modulation (PCM), serial transmission of binary bits forming numeric or character codes that represent the signal.All of these can be modulated on an RF carrier using any of the standard modulation techniques: AM, FM, Phase Modulation, etc. One advantage with AM digital pulse modulation techniques over AM analog is that the carrier can be 100% modulated, which cannot be done with analog, thereby allowing significant reductions in transmitter power without loss of coverage range. Sometimes FM digital pulse modulation techniques are referred to as Frequency Shift Keying (FSK). A very complex method of combining Phase Modulation and AM to increase the bit density of digital pulse modulation on an RF carrier is called Quadrature Amplitude Modulation (QAM).
Can laser beam be used as RF signal carrier?
When modulated with a radio frequency signal, they will indeed carry information. As in fibre-optic cables. The modulation may be of the several commonly used types, amplitude, frequency, phase ... modulation.
Is rf signal much more important for capturing or not?
rf is must for modulation and demodulation.
What is difference between modulator and demodulator?
Modulation is used when information is available in analog form that varies the frequency and/or amplitude of a lower frequency wave, depending on the information it carries. The role of modulation is to place this information onto a carrier frequency that can be transmitted more readily and with least loss of information. There are three fundamental types of modulation - frequency modulation, amplitude modulation and phase modulation. In each of these, a carrier frequency is modulated by a lower frequency, to form a modulated carrier wave. A modulator modulates the carrier frequency, while a demodulator detects the modulation on the carrier wave and recovers the original lower frequency waveform at the destination. For many years the modulated carrier wave was converted to a radio signal. Now it is often an electrical signal which is sent down a teleohone line; the information is usually a set of pulses going between computers. When computers are connected to each other in a two-way conversation, the MOdulator and DEModulator are combined into a single device called a MODEM.
What is over-modulating condition in term of amplitude modulation?
When your audio modulating signal is larger than your RF carrier amplitude the peak of the modulated carrier will become flat and a distorted audio signal with flattened peaks will be send out from the detector on the receiver side
In what stage modulation is done in high power AM transmissions?
RF Power stage
How does frequency modulation work?
Frequency modulation (FM) works by taking a signal, such as an audio signal, and using it to modulate a higher frequency (Radio Frequency, RF) carrier. This modulation causes the RF to shift up and down in frequency. The RF remains relatively constant in amplitude, and its shifting frequency represents the original signal.Contrast this with Amplitude Modulation (AM) where the RF is relatively constant in frequency, but its amplitude represents the original signal.In order to recover the original signal in an FM system, the receiver must demodulate the signal by measuring the time between successive waves of the RF. In a typical broadcast band system, limitations in the the design requirements for tuning the modulated carrier and for demodulating the original signal force the tuning and demodulation to be done in different stages. Using a process known as superhetrodyning, the tuner amplifies the RF with a broad-band amplifier and mixes the RF with a local oscillator (LO) frequency, converting the RF into an intermediate frequency (IF), typically 10.7 MHz. It then passes the still modulated IF (or shifted RF) into a sharp band-pass filter, the IF stage, and removes the interference of other stations from the IF signal. It then demodulates the original signal from the IF signal.Often, the original signal contains encoded information, such as a stereo subcarrier, which is subsequently demodulated and demultiplexed in order to recover the stereo signal. The question, however, asked about frequency modulation, so the answer stops here. If further detail is required, either add it by refining the answer, or comment on the question, and I or someone will refine the answer.
What is the purpose of carrier signal in modulation?
Carrier signal is of high frequencies, it gives strength to the original signal because original signal cannot travel long distances so it needs to be strengthen a bit for transmitting. The carrier signal is a high frequency signal, called an RF. Radio Frequency signal, it is to high for the human or animal ear to detect it, so its outside the audible spectrum and can easily be transmitted over the air to receivers that is tuned to receive that frequency and detect any modulation on that signal.
What are the advantages and disadvantages of double sideband suppressed carrier modulation?
Amplitude modulation of a carrier results in a transmitted signal consisting of the carrier, plus an 'upper sideband' and a 'lower sideband', spaced above and below the carrier frequency by the frequency of the modulation.The bandwidth of the whole signal is double the modulation frequency. Also, the power in the carrier is constant, and power must be added in order to radiate the sidebands.All the receiver needs in order to extract the information from the signal is one complete sideband, and knowledge of the frequency and phase of the carrier. Economically speaking, the carrier is wasted power, and the other sideband is wasted power andwasted spectrum.If you can filter away one of the sidebands before transmission, then you save half of the occupied spectrum, and the receiver has everything it needs to decode the signal. If you can also filter away the carrier ... or at least knock it way down ... before transmission, you can save a lot of power and use it for the remaining sideband, which extends your range for a given amount of power. The receiver still has everything it needs, as long as it can pick up a sniff of carrier ... enough to derive the carrier frequency and phase.This mode is known as "Single Sideband Suppressed Carrier". It's exactly how the video portion of standard NTSC analog TV was transmitted, throughout all of human history until June 2009.
