Communications Blockset

OQPSK Modulator Baseband

Modulate using the offset quadrature phase shift keying method

Library

PM, in Digital Baseband sublibrary of Modulation

Description

The OQPSK Modulator Baseband block modulates using the offset quadrature phase shift keying method. The output is a baseband 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 can be either a scalar or a frame-based column vector.

If the Input type parameter is set to Bit, then the input must be a binary-valued vector. In this case, the input can be either a vector of length two or a frame-based column vector whose length is an even integer.

The symbol period is half the input period. The first output symbol is an initial condition of zero that is unrelated to the input values.

The constellation used to map bit pairs to symbols is in the figure below. If the block's Phase offset parameter is nonzero, then this constellation is rotated by that parameter value.

Frame-Based Inputs

If the input is a frame-based column vector, then the block processes several integers or several pairs of bits in each time step. In this case, the output sample time equals the input sample time, even though the period of each output symbol is half the period of each integer or bit pair in the input.

Upsampling the Modulated Signal

This block can output an upsampled version of the modulated signal. The Samples per symbol parameter, S, is the upsampling factor. It must be a positive integer.

• If the input is a frame-based column vector, then the output vector length is 2S times the number of integers or pairs of bits in the input vector, while the output sample time equals the input sample time. The one-symbol initial condition inherent in this block corresponds to the first S elements of the first output vector.
• If the input is a sample-based scalar, then the output vector is a scalar, while the output sample time is 1/(2S) times the input sample time. The one-symbol initial condition inherent in this block corresponds to the first S samples.

Dialog Box

Input type

Indicates whether the input consists of integers or pairs of bits.

Phase offset (rad)

The amount by which the phase of the zeroth point of the signal constellation is shifted from /4.

Samples per symbol

The number of output samples that the block produces for each integer or pair of bits in the input.

Pair Block

OQPSK Demodulator Baseband

See Also

QPSK Modulator Baseband

OQPSK Demodulator Passband

OQPSK Modulator Passband