PSK comes in many forms but here
are some of the major ones.
BPSK or Binary Phase Shifting Keying
uses two phases which are separated by 180° and so can also be termed 2-PSK. It does not particularly matter exactly where the constellation points are positioned, and in this figure they are shown on the real axis, at 0° and 180°. This modulation is the most robust of all the PSKs since it takes the highest level of noise or distortion to make the demodulator reach an incorrect decision. It is, however, only able to modulate at 1 bit/symbol (as seen in the figure) and so is unsuitable for high data-rate applications when bandwidth is limited.
which can be from a very low baud to way up in the thousand or more.
Depiction of BPSK in two phases
QPSK or Quadture Phase Shifting
Sometimes known as quaternary or quadriphase PSK, 4-PSK, or 4-QAM, QPSK uses four points on the constellation diagram, equispaced around a circle. With four phases, QPSK can encode two bits per symbol, shown in the diagram with Gray coding to minimize the BER - twice the rate of BPSK. Analysis shows that this may be used either to double the data rate compared to a BPSK system while maintaining the bandwidth of the signal or to maintain the data-rate of BPSK but halve the bandwidth needed.
As with BPSK, there are phase ambiguity problems at the receiver and differentially encoded QPSK is used more often in practice.
also it can be a very low baud to a very high baud.
Some of the more common baud is 31 and 63
And BPSK31 being the most popular of the PSK modes.
Depiction of QPSK signal
