An unmodulated carrier carries no information, and therefore no communication is possible unless it is modulated in some way.
RF carrier waves are modulated with the data to be transmitted, typically using techniques like amplitude modulation, frequency modulation, or phase modulation. These modulated signals are then transmitted through the RF channel. To transmit large amounts of data, techniques like increasing the carrier frequency bandwidth, using more advanced modulation schemes, and implementing error correction coding can be employed to achieve higher data transmission rates over the RF carrier waves.
RF modulation occurs in various communication systems, including radio broadcasting, television transmission, and mobile communications. It takes place in the transmitter, where the baseband signal (audio, video, or data) is combined with a carrier wave to create a modulated signal that can be transmitted over long distances. Additionally, modulation can also occur in the receiver, where the received signal is demodulated to retrieve the original baseband information.
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
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.
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).
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).
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.
rf is must for modulation and demodulation.
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.
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
A collector modulator is a type of amplitude modulation (AM) used in RF (radio frequency) transmitters, where the modulation of the carrier signal occurs in the collector circuit of a transistor. The input audio signal varies the base current, which in turn controls the collector current and voltage, resulting in variations of the output RF signal's amplitude. This modulation technique allows for efficient transmission of audio signals over radio waves, as the carrier's amplitude reflects the changes in the input signal. The collector modulator is favored for its simplicity and effectiveness in generating modulated signals.
RF Power stage