A CDE Definition
An unencrypted digital channel from the cable company. Most digital TV sets have a built-in clear QAM tuner, which can decode a limited number of TV stations, such as local broadcasts, PBS and shopping channels. Premium channels are always encrypted, and non-premium channels may be as well. See QAM.
(1) (Quality Assessment Measurement) A system used to measure and analyze voice transmission.
(2) (Quadrature Amplitude Modulation) A modulation technique that employs both phase modulation (PM) and amplitude modulation (AM). Widely used to transmit digital signals such as digital cable TV and cable Internet service, QAM is also used as the modulation technique in orthogonal frequency division multiplexing (see OFDM). The "quadrature" comes from the fact that the phase modulation states are 90 degrees apart from each other.
Analog QAM uses two carriers 90 degrees out of phase with each other. Each carrier is modulated by an analog signal, and the resulting modulated waves are combined (see example below).
In digital QAM, the number of modulation states determines how the digital signal is split up. For example, in 8QAM, each three bits of input alters the phase and amplitude of the carrier to derive eight unique modulation states (see example below).
In 16QAM, 32QAM, 64QAM, 128QAM, 256QAM, 512QAM and 1024QAM, from four to 10 bits generate from 16 to 1,024 modulation states respectively. See modulation and binary values.
Digital QAM (8QAM)
Quadrature PSK (QPSK)
Before/After Your Search Term
|clean room technique||clear text|
|clean startup||clear to send|
|clear box testing||CLEF|
Terms By Topic
Click any of the following categories for a list of fundamental terms.