QPSK (Digital Demod)

QPSK (Quadrature Phase-Shift Keying) is a digital modulation format that modulates data onto the carrier by changing the phase of the carrier. The data is demodulated by comparing the received signal to the carrier and sampling the phase at a constant rate (symbol rate).

For QPSK, there are four possible phase values (± pi/4 and ± 3pi/4) and therefore log2(4) = 2 bits of data can be transmitted on each symbol.

A sample QPSK constellation diagram is shown below.


Reliable Carrier Lock

This table shows the minimum result length and frequency offset values for reliable carrier lock for QPSK signals:

Digital Modulation Format

Minimum Result Length (0 Hz frequency offset)

Maximum frequency offset (Result Length = 1000 symbols)


50 symbols

9.6% symbol rate

See Also

DQPSK (Digital Demod)

Available Digital Demodulation Formats

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