Rectangular QAM Demodulator Baseband (Communications Blockset)

Demodulate QAM-modulated data

Library

AM, in Digital Baseband sublibrary of Modulation

Description

The Rectangular QAM Demodulator Baseband block demodulates a signal that was modulated using quadrature amplitude modulation with a constellation on a rectangular lattice.

The signal constellation has M points, where M is the M-ary number parameter. M must have the form 2^K for some positive integer K. The block scales the signal constellation based on how you set the Normalization method parameter. For details, see the reference page for the Rectangular QAM Modulator Baseband block.

The input can be either a scalar or a frame-based column vector.

Output Signal Values

The Output type parameter determines whether the block produces integers or binary representations of integers. If Output type is set to Integer, then the block produces integers. If Output type is set to Bit, then the block produces a group of K bits, called a binary word, for each symbol. The Constellation ordering parameter indicates how the block assigns binary words to points of the signal constellation. More details are on the reference page for the Rectangular QAM Modulator Baseband block.

Processing an Upsampled Modulated Signal

The input signal can be an upsampled version of the modulated signal. The Samples per symbol parameter is the upsampling factor. It must be a positive integer. For more information, see Upsampled Signals and Rate Changes in Using the Communications Blockset.

Dialog Box

M-ary number: The number of points in the signal constellation. It must have the form 2^K for some positive integer K.
Output type: Indicates whether the output consists of integers or groups of bits.
Constellation ordering: Determines how the block maps each integer to a group of output bits. This field is active only when Output type is set to Bit.
Normalization method: Determines how the block scales the signal constellation. Choices are Min. distance between symbols, Average Power, and Peak Power.
Minimum distance: The distance between two nearest constellation points. This field appears only when Normalization method is set to Min. distance between symbols.
Average power (watts): The average power of the symbols in the constellation. This field appears only when Normalization method is set to Average Power.
Peak power (watts): The maximum power among the symbols in the constellation. This field appears only when Normalization method is set to Peak Power.
Phase offset (rad): The rotation of the signal constellation, in radians.
Samples per symbol: The number of input samples that represent each modulated symbol.

Pair Block

Rectangular QAM Modulator Baseband

See Also

General QAM Demodulator Baseband

References

[1] Smith, Joel G. "Odd-Bit Quadrature Amplitude-Shift Keying." IEEE Transactions on Communications, vol. COM-23, March 1975. 385-389.

Receiver Thermal Noise Rectangular QAM Demodulator Passband