OQPSK Modulator Passband (Communications Blockset)

Modulate using the offset quadrature phase shift keying method

Library

PM, in Digital Passband sublibrary of Modulation

Description

The OQPSK Modulator Passband block modulates using the offset quadrature phase shift keying method. The output is a passband representation of the modulated signal.

If the Input type parameter is set to Integer, then valid input values are 0, 1, 2, and 3. In this case, the input must be a sample-based scalar. If the Input type parameter is set to Bit, then the input must be a binary-valued sample-based vector of length two.

The constellation used to map bit pairs to symbols is in the figure below.

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

Input type: Indicates whether the input consists of integers or pairs of bits. If this parameter is set to Bit, then the M-ary number parameter must be 2^K for some positive integer K.
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 pair of bits 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

OQPSK Demodulator Passband

See Also

OQPSK Modulator Baseband

OQPSK Modulator Baseband OVSF Code Generator