DQPSK Modulator Baseband

Integer-Valued Signals and Binary-Valued Signals

When you set the Input type parameter to Integer, the valid input values are 0, 1, 2, and 3. In this case, the block accepts a scalar or column vector input signal. If the first input is m, then the modulated symbol is

where θ represents the Phase rotation parameter. If a successive input is m, then the modulated symbol is the previous modulated symbol multiplied by exp(jθ + jπm/2).

When you set the Input type parameter to Bit, the input contains pairs of binary values. In this case, the block accepts a column vector whose length is an even integer. The following figure shows the complex numbers by which the block multiples the previous symbol to compute the current symbol, depending on whether you set the Constellation ordering parameter to Binary or Gray. The following figure assumes that you set the Phase rotation parameter to $$\frac{\Pi }{4}$$; in other cases, the two schematics would be rotated accordingly.

The following figure shows the signal constellation for the DQPSK modulation method when you set the Phase rotation parameter to $$\frac{\Pi }{4}$$. The arrows indicate the four possible transitions from each symbol to the next symbol. The Binary and Gray options determine which transition is associated with each pair of input values.

More generally, if the Phase rotation parameter has the form $$\frac{\Pi }{k}$$for some integer k, then the signal constellation has 2k points.