M-DPSK Modulator Passband (Communications Blockset)

Modulate using the M-ary differential phase shift keying method

Library

PM, in Digital Passband sublibrary of Modulation

Description

The M-DPSK Modulator Passband block modulates using the M-ary differential phase shift keying method. The output is a passband representation of the modulated signal. The M-ary number parameter, M, is the number of possible output symbols that can immediately follow a given output symbol.

This block uses the baseband equivalent block, M-DPSK Modulator Baseband, for internal computations and converts the resulting baseband signal to a passband representation. The following parameters in this block are the same as those of the baseband equivalent block:

M-ary number
Input type
Constellation ordering

The input must be sample-based. If the Input type parameter is Bit, then the input must be a vector of length log₂(M). If the Input type parameter is Integer, then the input must be a scalar.

Parameters Specific to Passband Simulation

Passband simulation uses a carrier signal. The Carrier frequency and Carrier initial phase parameters specify the frequency and initial phase, respectively, of the carrier signal. The Symbol period parameter must equal the sample time of the input signal, while the Output sample time parameter determines the sample time of the output signal.

This block uses a baseband representation of the modulated signal as an intermediate result during internal computations. The Baseband samples per symbol parameter indicates how many baseband samples correspond to each integer or binary word in the input, before the block converts them to a passband output.

The timing-related parameters must satisfy these relationships:

Symbol period > (Carrier frequency)^-1
Output sample time < [2*Carrier frequency + 2/(Symbol period)]^-1

Furthermore, Carrier frequency is typically much larger than the highest frequency of the unmodulated signal.

Note A model containing this block must use a variable-step solver. To configure a model so that it uses a variable-step solver, select Simulation parameters from the model window's Simulation menu and then set the Type parameter on the Solver panel to Variable-step.

Dialog Box

M-ary number: The number of possible output symbols that can immediately follow a given output symbol.
Input type: Indicates whether the input consists of integers or groups of bits. If this parameter is set to Bit, then the M-ary number parameter must be 2^K for some positive integer K.
Constellation ordering: Determines how the block maps each group of input bits to a corresponding integer. This field is active only when Input type is set to Bit.
Symbol period (s): The symbol period, which must equal the sample time of the input.
Baseband samples per symbol: The number of baseband samples that correspond to each integer or binary word in the input, before the block converts them to a passband output.
Carrier frequency (Hz): The frequency of the carrier.
Carrier initial phase (rad): The initial phase of the carrier in radians.
Output sample time: The sample time of the output signal.

Pair Block

M-DPSK Demodulator Passband

See Also

M-DPSK Modulator Baseband

References

[1] Pawula, R. F. "On M-ary DPSK Transmission Over Terrestrial and Satellite Channels." IEEE Transactions on Communications, vol. COM-32, July 1984. 752-761.

M-DPSK Modulator Baseband Memoryless Nonlinearity