phase shift keying
phase shift keying (PSK) A method for representing digital data with analog signals by changing the phase of the analog carrier to represent the digital information (see diagram). It is a type of modulation.
There are two ways of detecting the phase information in a signal. Fixed-reference PSK assigns a meaning to each phase position. The demodulator uses a signal source of the same frequency to compare with the incoming signal and detect its phase. Differential PSK assigns meaning to phase changes, e.g. a phase change of 180° could be taken to mean a 1, while no phase change means a 0. No comparison with another wave is needed in the demodulator.
The amount of information associated with a phase or phase change depends on the number of discrete phases that the carrier may assume. If the carrier may assume two phases then each phase or phase change represents a single bit. If four phases are used then each phase or phase change represents a different combination of two bits. The greater the number of discrete phases, the more difficult it is to generate, transmit, and detect the analog signal, thus the cost is higher; for this reason, modems that require eight or more discrete signals usually combine the phase changes with changes in amplitude in order to make the signals more distinct.
See also digital data transmission.
There are two ways of detecting the phase information in a signal. Fixed-reference PSK assigns a meaning to each phase position. The demodulator uses a signal source of the same frequency to compare with the incoming signal and detect its phase. Differential PSK assigns meaning to phase changes, e.g. a phase change of 180° could be taken to mean a 1, while no phase change means a 0. No comparison with another wave is needed in the demodulator.
The amount of information associated with a phase or phase change depends on the number of discrete phases that the carrier may assume. If the carrier may assume two phases then each phase or phase change represents a single bit. If four phases are used then each phase or phase change represents a different combination of two bits. The greater the number of discrete phases, the more difficult it is to generate, transmit, and detect the analog signal, thus the cost is higher; for this reason, modems that require eight or more discrete signals usually combine the phase changes with changes in amplitude in order to make the signals more distinct.
See also digital data transmission.
More From encyclopedia.com
Managing Change , Managing Change
Recently, one of the concepts discussed, written about, and analyzed most frequently has been organizational change and the related c… Panel Analysis , A panel study is defined as a study that collects information on the same individuals at different points in time. The various data collections are o… interchange , in·ter·change • v. / ˌintərˈchānj/ [tr.] (of two or more people) exchange (things) with each other: superior and subordinates freely interchange idea… Educational Reform , Education is generally thought to promote social, economic, and cultural transformation during times of fundamental national and global changes. Inde… Meta- , meta- (also met- before a vowel or h) • comb. form 1. denoting a change of position or condition: metamorphosis metathesis. 2. denoting position behi… Detective Jobs , Careers and Degrees for Detectives
One of the biggest differences between police officers and police detectives is that detectives focus on a specifi…
About this article
Phase modulation
All Sources -
You Might Also Like
NEARBY TERMS
Phase modulation