Modulation is a fundamental concept in RF communications, where it refers to the process of varying an electromagnetic wave's properties to transmit information. Called a carrier (or subcarrier), each individual frequency is modulated to encode data, allowing the signal to carry information over a distance. This modulation process involves altering the carrier signal's amplitude, frequency, and/or phase, to encode the desired data within the carrier.
Ship-to-ship communications made up some of the earliest forms of modulation - known as On-Off Keying (OOK), lamps were turned on and off in sequence to communicate messages between vessels. Today's RF modulation schemes are considerably more advanced, but the underlying principle remains unchanged.
Modulation is crucial because it allows the transmission of signals over radio waves that can travel through space, penetrate obstacles, and be received by antennas tuned to the carrier frequency. Without modulation, the transmission of complex information, such as voice, video, or digital data, is not possible. Modulation not only enables the efficient use of the electromagnetic spectrum but also helps to minimise interference and optimise the signal's robustness against noise and distortion. Each modulation technique has its advantages and is chosen based on factors like bandwidth efficiency, power consumption, and the specific requirements of the communication system.
| Name | Full Name | Description |
|---|---|---|
| FM | Frequency Modulation | Frequency Modulation (FM) is a method of encoding information in a carrier wave by varying its frequency. Unlike Amplitude Modulation (AM), which varies the amplitude of the carrier wave, FM changes the frequency to transmit data. This modulation technique is particularly effective in reducing noise... |
| CCK | Complementary Code Keying | The Complementary Code Keying (CCK) modulation scheme is a sophisticated digital modulation technique employed in wireless communication, particularly in 802.11b Wi-Fi standards. This technique enhances data rates and improves the efficiency of wireless communication. CCK modulation utilises a set... |
| CSS | Chirp Spread Spectrum | The Chirp Spread Spectrum (CSS) modulation scheme is a digital communication method that utilises wideband linear frequency modulated chirp pulses to encode information. A chirp is a signal in which the frequency increases ('up-chirp') or decreases ('down-chirp') over time. In CSS, the data bits are... |
| DSSS | Direct Sequence Spread Spectrum | The Direct Sequence Spread Spectrum (DSSS) modulation scheme is a method used in wireless communication to reduce interference and noise. It works by spreading the signal across a wider frequency band than the original signal bandwidth. This is achieved by multiplying the data bits with a faster... |
| FSK | Frequency Shift Keying | The Frequency Shift Keying (FSK) modulation scheme is a frequency modulation system used primarily for digital signals. In FSK, the digital information is transmitted through discrete frequency changes of a carrier signal. This method is typically used in radio and wired communication systems due to... |
| GFSK | Gaussian Frequency Shift Keying | The Gaussian Frequency Shift Keying (GFSK) modulation scheme is a digital modulation technique used in various wireless communication systems, including Bluetooth. GFSK is a variation of Frequency Shift Keying (FSK), where the key difference lies in the application of a Gaussian filter to the... |
| GMSK | Gaussian Minimum Shift Keying | The Gaussian Minimum Shift Keying (GMSK) modulation scheme is a digital modulation technique used in many mobile communication systems, including GSM. It is a type of Frequency Shift Keying (FSK) where the digital information is carried through changes in the frequency of the carrier wave. GMSK is... |
| BPSK | Binary Phase Shift Keying | The Binary Phase Shift Keying (BPSK) modulation scheme is a type of phase modulation technique where the phase of the carrier signal is altered based on the input data bits. In BPSK, there are two phases, 0 and 180 degrees, representing binary values 0 and 1 respectively. This modulation scheme is... |
| QPSK | Quadrature Phase Shift Keying | The Quadrature Phase Shift Keying (QPSK) modulation scheme is a digital modulation technique used for data communication. In QPSK, the data is transferred by modulating the phase of the carrier signal. It divides the data into groups of two bits, known as symbols, and each symbol is represented by a... |
| 8PSK | 8 Phase Shift Keying | The 8PSK (8 Phase Shift Keying) modulation scheme is a digital modulation technique that alters the phase of the carrier signal to represent data. In this scheme, the carrier signal is divided into eight different phases, each representing a unique set of bits. This allows for the transmission of... |
| 16QAM | 16-Quadrature Amplitude Modulation | The 16QAM (Quadrature Amplitude Modulation) scheme is a modulation technique utilised in digital communication systems. It is a combination of both amplitude and phase modulation, allowing for the transmission of data over radio or cable. The '16' in 16QAM signifies that there are 16 different... |
| 64QAM | 64-Quadrature Amplitude Modulation | The 64QAM (Quadrature Amplitude Modulation) scheme is a modulation technique utilised in digital communication systems. It is a type of amplitude modulation where the carrier signal is varied in accordance with the input signal. In 64QAM, two carrier waves are used, each out of phase by 90 degrees... |
| 256QAM | 256-Quadrature Amplitude Modulation | The 256QAM (Quadrature Amplitude Modulation) scheme is a high-level modulation technique used in digital communication systems. It is a combination of both amplitude and phase modulation, where 256 different signals or symbols are represented, each corresponding to a unique 8-bit pattern. This... |
| 512QAM | 512-Quadrature Amplitude Modulation | The 512QAM (Quadrature Amplitude Modulation) scheme is a high-level modulation technique used in digital communication systems. It is a combination of both amplitude and phase modulation, allowing for the transmission of large amounts of data. In 512QAM, the digital information is represented by 512... |
| 1024QAM | 1024-Quadrature Amplitude Modulation | The 1024QAM (Quadrature Amplitude Modulation) scheme is a high-level modulation technique that allows for the transmission of large amounts of data over a communication channel. It works by varying both the amplitude and phase of a carrier signal to create 1024 unique combinations, each representing... |
| 2048QAM | 2048-Quadrature Amplitude Modulation | The 2048QAM (Quadrature Amplitude Modulation) is a highly advanced digital modulation scheme utilised to transmit data through a communication channel. It combines both amplitude and phase modulation to achieve high data rates. In 2048QAM, the transmitted signal is divided into 2048 different states... |
| 4096QAM | 4096-Quadrature Amplitude Modulation | The 4096QAM (Quadrature Amplitude Modulation) is a highly advanced digital modulation scheme utilised predominantly in broadband communication systems, such as advanced microwave transmission. This scheme allows for the transmission of large amounts of data by modulating both the amplitude and phase... |