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# General QAM Modulator Baseband

## Library

AM, in Digital Baseband sublibrary of Modulation

## Description

The General QAM Modulator Baseband block modulates using quadrature amplitude modulation. The output is a baseband representation of the modulated signal.

The Signal constellation parameter defines the constellation by listing its points in a length-M vector of complex numbers. The input signal values must be integers between 0 and M-1. The block maps an input integer m to the (m+1)st value in the Signal constellation vector.

This block accepts a scalar or column vector input signal. For information about the data types each block port supports, see the Supported Data Types table on this page.

### Constellation Visualization

The General QAM Modulator Baseband block provides the capability to visualize a signal constellation from the block mask. This Constellation Visualization feature allows you to visualize a signal constellation for specific block parameters. For more information, see the Constellation Visualization section of the Communications System Toolbox™ User's Guide.

## Dialog Box

Signal constellation

A real or complex vector that lists the constellation points.

Output data type

The output data type can be set to double, single, Fixed-point, User-defined, or Inherit via back propagation.

Setting this to Fixed-point or User-defined will enable fields in which you can further specify details. Setting this to Inherit via back propagation, sets the output data type and scaling to match the following block..

Output word length

Specify the word length, in bits, of the fixed-point output data type. This parameter is only visible when you select Fixed-point for the Output data type parameter.

User-defined data type

Specify any signed built-in or signed fixed-point data type. You can specify fixed-point data types using the sfix, sint, sfrac, and fixdt functions from Fixed-Point Designer™ software. This parameter is only visible when you select User-defined for the Output data type parameter.

Set output fraction length to

Specify the scaling of the fixed-point output by either of the following two methods:

• Choose Best precision to have the output scaling automatically set such that the output signal has the best possible precision.

• Choose User-defined to specify the output scaling in the Output fraction length parameter.

This parameter is only visible when you select Fixed-point for the Output data type parameter, or when you select User-defined and the specified output data type is a fixed-point data type.

Output fraction length

For fixed-point output data types, specify the number of fractional bits, or bits to the right of the binary point. This parameter is only visible when you select Fixed-point or User-defined for the Output data type parameter and User-defined for the Set output fraction length to parameter.

## Supported Data Types

PortSupported Data Types

Input

• Double-precision floating point

• Single-precision floating point

• 8-, 16-, 32-bit signed integers

• 8-, 16-, 32-bit unsigned integers

• $ufix\left(⌈{\mathrm{log}}_{2}M⌉\right)$

Output

• Double-precision floating point

• Single-precision floating point

• Signed fixed-point

## Pair Block

General QAM Demodulator Baseband