Modulation

For the musical use of "modulation", see modulation (music).

Modulation is the process of varying a carrier signal, typically a sinusoidal signal, in order to use that signal to convey modulation scheme information. One of the three key characteristics of a signal linear modulation is usually modulated: its phase, frequency or amplitude. A device that performs modulation is known pulse code modulation as a modulator and a device that performs demodulation is known as a demodulator. A device that can do both operations is a uhf modulation am modulation modem advantage of pulse width modulation (a contraction of the two terms).

In frequency modulation circuit amplitude pulse position modulation receiver modulation questions ssb modulation free schematics for modulation cb digital modulation, the changes in the frequency modulation theory signal measuring amplitude modulation are chosen from pulse width modulation theory a fixed list (the modulation alphabet) each entry of which conveys a different possible piece of information modulation amplitude modulation systems transfer function modulation (a symbol). The alphabet is often conveniently represented on a constellation diagram.

In analog modulation, the change is applied continuously in response to the data signal. The modulation definition of frequency modulation may be applied to various aspects of the signal as the lists below indicate.

Modulation is generally performed to overcome signal transmission issues such as to allow

• Easy gsm modulation (low loss, low dispersion) propagation as electromagnetic waves
  
• Multiplexing — the transmission of multiple data signals in one frequency band, on different carrier frequencies.
  
• Smaller, more directional antennas

Carrier advantage and disadvantage of amplitude modulation signals are usually high frequency electromagnetic pulse position modulation pulse width modulation for motor control waves.

Analog Modulation Techniques

• Phase modulation (PM)
  
• Frequency modulation (FM)
  
• Amplitude modulation (AM)
  
  
  
  • Single-sideband modulation (SSB, or SSB-AM), very similar to single-sideband suppressed carrier modulation (SSB-SC)
    
  • Vestigial-sideband modulation (VSB, or VSB-AM)
  
  
• Sigma-delta modulation (∑Δ)

Digital Modulation Techniques

Any digital modulation form of digital modulation amplitude modulation circuit necessarily uses a finite number of distinct signals to represent digital data.

• In the case of PSK, a finite number of phases are used.
  
• In the case of FSK, a finite number of frequencies are used.
  
• In the case of ASK, a finite number of amplitudes are used. This is very similar to pulse code modulation

Each of these phases, frequencies fm modulation or amplitudes are assigned a unique pattern of binary bits. Usually, each phase, frequency or amplitude encodes an equal number of bits. This number frequency modulation of bits comprises pulse width modulation pwm overview modulation analyzer the symbol that is represented by the particular phase.

These are the general steps used by the modulator to transmit gmsk modulation in gsm data:

1. Accept incoming digital data;
   
2. Group the data into symbols;
   
3. Use these symbols to set or change the phase, frequency modulation technique frequency modulation work frequency or amplitude of the reference examples of frequency modulation signal appropriately;
   
4. Pass the modulated signal on for further processing, such as filtering and channel-coding, before transmission.

At the receiver, the demodulator

1. Is passed the de-filtered and de-channel-coded signal;
   
2. Determines its phase, frequency or amplitude;
   
3. Maps the phase, frequency or ampltude to its corresponding symbol;
   
4. Translates the symbol into its individual bits;
   
5. Passes the resultant bit stream on for further processing such as removal of any error-correcting codes.

As is common to all digital communication systems, the design of both explain frequency modulation the modulator and advantages of amplitude modulation demodulator must be done simultaneously. Digital modulation schemes are possible because the transmitter-receiver pair have prior knowledge of how data is encoded and represented modulation modulation scheme in the communications system. In all digital communication systems, both the modulator amplitude modulation at the transmitter and the demodulator at the amplitude modulation report receiver are structured so that they perform frequency modulation synthesis inverse operations.

The modulation schemes used by cellphones modulation index principal classes pulse amplitude modulation of modulation are:

• Phase-shift keying (PSK)
  
• Frequency-shift keying (FSK) and audio frequency-shift keying (AFSK)
  
  
  
  • Minimum-shift keying (MSK)
    
  • Gaussian minimum-shift keying (GMSK)
    
  • Very minimum-shift keying (VMSK)
  
  
• Amplitude-shift keying (ASK) and its most common form, on-off keying (OOK)
  
• Quadrature amplitude modulation (QAM), a combination of PSK and ASK.
  
• Trellis coded modulation (TCM) also known as trellis modulation

MSK and GMSK are particular cases of continuous fsk modulation index phase modulation (CPM). modulation transformer Indeed, MSK is a particular pulse width modulation circuits case pulse width modulation qpsk modulation of the sub-family of CPM known as continuous phase-frequency-shift keying (CPFSK) which is defined by a rectangular frequency pulse (i.e. a linearly increasing phase pulse) of one symbol-time pulse width modulation tutorial duration definition amplitude modulation pdf notes on am modulation (total response signalling).

Often incorrectly referred history of frequency modulation to as a modulation scheme, orthogonal frequency division multiplexing (OFDM) usually takes advantage of one of the digital techniques. It is also known as discrete multitone (DMT). When OFDM is used in conjunction with channel coding techniques, it is described as Coded orthogonal frequency division multiplexing (COFDM). OFDM is strictly a channel access method and not a modulation scheme.

Pulse modulation

These are hybrid digital and analogue techniques.

• Pulse-code modulation (PCM)
  
• Pulse-width modulation (PWM)
  
• Pulse-amplitude modulation (PAM)
  
• Pulse-position modulation (PPM)
  
• Pulse-density modulation (PDM)

Miscellaneous Techniques

• The use of on-off keying to transmit Morse code at radio frequencies is known as continuous wave (CW) operation.
  
• Adaptive modulation
  
• Wavelet modulation

See also

• Types of radio emissions
  
• Communications channel
  
• Channel access methods
  
• Channel coding
  
• Line code
  
• Telecommunication
  
• Modem
  
• RF modulator
  
• Codec

External links

• "Data Encoding Techniques" and "Specifications for Data Encoding" discuss the various encoding techniques that have been used with various types of Ethernet.

Electronics Topics

The field of electronics is the study and use of systems that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves and semiconductors. The design and construction of electronic circuits to solve practical problems is part of the fields of electronic engineering, and the hardware design side of computer engineering. The study of new semiconductor devices and their technology is sometimes considered as a branch of physics.

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