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# comm.OQPSKDemodulator System object

Package: comm

Demodulate using OQPSK method

## Description

The OQPSKDemodulator object demodulates a signal that was modulated using the offset quadrature phase shift keying method. The input is a baseband representation of the modulated signal.

To demodulate a signal that was modulated using offset quadrature phase shift keying:

1. Define and set up your OQPSK demodulator object. See Construction.

2. Call step to demodulate the signal according to the properties of comm.OQPSKDemodulator. The behavior of step is specific to each object in the toolbox.

## Construction

H = comm.OQPSKDemodulator creates a demodulator System object™, H. This object demodulates the input signal using the offset quadrature phase shift keying (OQPSK) method.

H = comm.OQPSKDemodulator(Name,Value) creates an OQPSK demodulator object, H, with each specified property set to the specified value. You can specify additional name-value pair arguments in any order as (Name1,Value1,...,NameN,ValueN).

H = comm.OQPSKDemodulator(PHASE,Name,Value) creates an OQPSK demodulator object, H. This object has the PhaseOffset property set to PHASE and the other specified properties set to the specified values.

## Properties

 PhaseOffset Phase of zeroth point of constellation from $\pi }{4}$ Specify the phase offset of the zeroth point of the constellation shifted from $\pi }{4}$, in radians, as a finite, real-valued scalar. The default is 0. BitOutput Output data as bits Specify whether the output consists of groups of bits or integer values. The default is false. When you set this property to true the step method outputs a column vector of bit values. The vector length must equal to twice the number of demodulated symbols. When you set this property to false, the step method outputs a column vector. The length of this vector equals to the number of demodulated symbols that contain integer values between 0 and 3. The object produces one output demodulated symbol for each pair of input samples. OutputDataType Data type of output Specify output data type as Full precision | Smallest unsigned integer | double | single | int8 | uint8 | int16 | uint16 | int32 | uint32. The default is Full precision. When you set this property to Full precision, the step method output inherits the data type from the input. When the input is of single or double data, the step method outputs the same data type as the input. When the input data is of a fixed-point type, then the step method outputs the same data type as if you set the OutputDataType property to Smallest unsigned integer. When you set the BitOutput property to true, the logical data type becomes a valid option. When the input signal is an integer data type, you must have a Fixed-Point Designer™ user license to use this property in Smallest unsigned integer or Full precision mode.

## Methods

 clone Create OQPSK demodulator object with same property values constellation Calculate or plot ideal signal constellation getNumInputs Number of expected inputs to step method getNumOutputs Number of outputs from step method isLocked Locked status for input attributes and nontunable properties release Allow property value and input characteristics changes reset Reset demodulator state step Demodulate using OQPSK method

## Examples

Modulate and demodulate a signal using OQPSK modulation with a constellation with pi/8 radians of phase offset.

```    hMod = comm.OQPSKModulator(pi/8);
hAWGN = comm.AWGNChannel('NoiseMethod', ...
'Signal to noise ratio (SNR)','SNR',6);
hDemod = comm.OQPSKDemodulator(pi/8);
% Create an error rate calculator, account for the one symbol delay
for counter = 1:100
% Transmit a 50-symbol frame
data = randi([0 3],50,1);
modSignal = step(hMod, data);
noisySignal = step(hAWGN, modSignal);