GeneralG8A12
What is QPSK modulation?
D
Answer
Signals and emissions
Type
A
Modulation using quasi-parallel to serial conversion to reduce bandwidth
B
Modulation using quadra-pole sideband keying to generate spread spectrum signals
C
Modulation using Fast Fourier Transforms to generate frequencies at the first, second, third, and fourth harmonics of the carrier frequency to improve noise immunity
D
Modulation in which digital data is transmitted using 0-, 90-, 180- and 270-degrees phase shift to represent pairs of bits
Answer Notes
QPSK stands for Quadrature Phase Shift Keying. In this digital modulation scheme, 'Quadrature' implies four distinct states. The transmitter shifts the phase of the carrier wave to one of four specific angles: 0, 90, 180, and 270 degrees.
Because there are four possible phase states, each state can uniquely represent two bits of digital data (00, 01, 10, or 11) per symbol. This allows QPSK to transmit data at twice the bit rate of basic binary phase shift keying (BPSK) while using the same bandwidth.
The distractors rely on made-up technical jargon like 'quasi-parallel', 'quadra-pole sideband', or incorrect applications of 'Fast Fourier Transforms' to trick those who are unfamiliar with what the acronym actually stands for.
Previous · G8A11
What is the modulation envelope of an AM signal?
Next · G8A13
What is a link budget?