EngeeComms.RectangularQAMModulatorBaseband

Modulation using rectangular quadrature amplitude modulation.

Library	`EngeeComms`
Block	Rectangular QAM Modulator Baseband

Description

System object EngeeComms.RectangularQAMModulatorBaseband modulates the input signal using quadrature amplitude modulation with a constellation on a rectangular grid. The output is a basic representation of the modulated signal.

All power values assume a nominal impedance 1 Om.

To modulate the input signal using quadrature amplitude modulation with a constellation on a rectangular grid, follow these steps:

Create an object EngeeComms.RectangularQAMModulatorBaseband and set its properties.
Call the object with arguments as if it were a function.

To learn more about how to work with system objects, see Engee System Objects.

Syntax

Creation

rectcqammod = EngeeComms.RectangularQAMModulatorBaseband() — creates a system object for modulating the input signal using quadrature amplitude modulation with a constellation on a rectangular grid rectcqammod with the default properties.

Example:
```
rectcqammod = EngeeComms.RectangularQAMModulatorBaseband()
```
rectcqammod = EngeeComms.RectangularQAMModulatorBaseband(Name=Value) — creates a system object for modulating the input signal using quadrature amplitude modulation with a constellation on a rectangular grid rectcqammod with the specified properties as a pair Name=Value, where Name — the name of the property, and Value — the appropriate value. You can specify multiple pairs «name-value» the order of the pairs does not matter. Unspecified properties retain their default values.

Example:
```
rectcqammod = EngeeComms.RectangularQAMModulatorBaseband(InputType=Bit)
```

Using

outsignal = rectcqammod(insignal) — modulates the input signal using quadrature amplitude modulation with a constellation on a rectangular grid, as indicated on rectcqammod, to the input signal. The result is returned in outsignal.

Arguments

Input arguments

In — input signal

+ vector | scalar

Details

The input signal is in the form of a scalar or vector with the values of the elements in the range of values , where — the order of modulation.

Типы данных

Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64, Bool

Output arguments

Out — modulated signal

+ vector | scalar

Details

Rectangular modulated baseband signal.

Типы данных

Float64, ComplexF64

Features

# PhaseOffset — signal constellation rotation
Real number

Details

The rotation of the signal constellation defined as a scalar.

# NormalizationFactor — scaling condition
Real number

Details

This parameter defines the scaling condition and its value depends on the value of the * property.Normalization*.

Property value Normalization Property value NormalizationFactor

Property value Normalization	Property value NormalizationFactor
`Min. distance between symbols`	Specifies the distance between the two closest points of the constellation as a positive scalar.
`Average Power`	Specifies the average or maximum power of the symbols in the constellation in watts as a positive scalar. Power values assume a nominal impedance of 1 ohm.
`Peak Power`	Specifies the maximum power of the symbols in the constellation in watts as a positive scalar. Power values assume a nominal impedance of 1 ohm.

Min. distance between symbols

Specifies the distance between the two closest points of the constellation as a positive scalar.

Average Power

Specifies the average or maximum power of the symbols in the constellation in watts as a positive scalar. Power values assume a nominal impedance of 1 ohm.

Peak Power

Specifies the maximum power of the symbols in the constellation in watts as a positive scalar. Power values assume a nominal impedance of 1 ohm.

For example, if the property Normalization is set to Peak Power, the value NormalizationFactor will define the maximum power of the symbols in the constellation in W as a positive scalar.

# Normalization — constellation scaling method
String

Details

The constellation scaling method, specified as Min. distance between symbols, Average Power or Peak Power.

# MNumber — modulation order
Real number

Details

The modulation order given as a positive integer equal to a power of two. The modulation order determines the number of points in the signal constellation.

# InputType — input type
String

Details

Input type, specified as Integer or Bit to indicate whether the input signal consists of integers or groups of bits.

Integer - the input signal must consist of integers in the range , where is the modulation order, the value of the property MNumber.
Bit - the input signal must contain binary values and the number of lines must be an integer multiple of .

# ConstellationType — character order
String

Details

Determines how the system object maps each character to an output bit group or integer.

The options to select are Gray or Binary.

Methods

Common to all system objects

`step!`	Run the system object operation algorithm
`release!`	Allow changing the value of a system object property

Algorithms

Signals with integer values and signals with binary values

If for a property [Property:inputType] value set Integer, then the system object accepts integer values in the range , where — this is the modulation order specified by the property of the system object MNumber.

If for a property [Property:inputType] value set Bit, then the system object accepts binary values representing integers. The system object collects binary-digit signals into groups by the bit where — the number of bits per character, and — the order of modulation.

The length of the input vector must be an integer multiple of . In this configuration, the system object accepts a group of and maps it to the symbol at the output of the system object. The system object outputs one modulated symbol for each group of bits.

Property ConstellationType specifies how the system object assigns binary words to the points of the signal constellation. Such assignments are applied independently to the common-mode and quadrature components of the input signal.:

If for a property ConstellationType value set Binary, then the system object uses a binary-encoded constellation.
If for a property ConstellationType value set Gray and If the number is even, then the system object uses a constellation encoded by the Gray code.
If for a property ConstellationType value set Gray and If it is odd, then the system object encodes the constellation so that the pairs of nearest points differ by one or two bits. The constellation has a cross-shaped shape, and the diagram below shows which pairs of points differ by two bits. The scheme uses , but the general case is assumed.

rectangular qam modulator baseband 1

Since the common-mode and quadrature components are assigned independently, when the Gray code order and binary order are the same.

Constellation size and scaling

The constellation of the signal consists of points where — the value of the property MNumber. Meaning should be equal to for some positive integer . The system object scales the signal constellation depending on the value set for the Normalization property.

Property value Normalization Zoom condition

Property value Normalization	Zoom condition
`Min. distance between symbols`	The distance between the two closest points of the constellation.
`Average Power`	The average power of the symbols in the constellation.
`Peak Power`	The maximum power of the symbols in the constellation.

Min. distance between symbols

The distance between the two closest points of the constellation.

Average Power

The average power of the symbols in the constellation.

Peak Power

The maximum power of the symbols in the constellation.

Literature

Smith, J. G., "Odd-Bit Quadrature Amplitude-Shift Keying," IEEE Transactions on Communications, Vol. COM-23, March 1975, pp. 385–389.
Proakis, John G. Digital Communications. 4th ed. New York: McGraw Hill, 2001.