CPFSK Modulator Baseband

Modulate using continuous phase frequency shift keying method

Library

CPM, in Digital Baseband sublibrary of Modulation

Description

The CPFSK Modulator Baseband block modulates a signal using the continuous phase frequency shift keying method. The output is a baseband representation of the modulated signal. The M-ary number parameter, M, represents the size of the input alphabet. M must have the form 2K for some positive integer K.

This block supports multi-h Modulation index. See CPM Modulator Baseband for details.

Integer-Valued Signals and Binary-Valued Signals

When you set the Input type parameter to Integer, the block accepts odd integers between -(M-1) and M-1.

When you set the Input type parameter to Bit, the block accepts groupings of K bits. Each grouping is called a binary word. The input vector length must be an integer multiple of K.

In binary input mode, the block maps each binary word to an integer between 0 and M-1, using a mapping scheme that depends on whether you set the Symbol set ordering parameter to Binary or Gray. The block then maps the integer k to the intermediate value 2k-(M-1) and proceeds as if it operates in the integer input mode. For more information, see Integer-Valued Signals and Binary-Valued Signals in Communications System Toolbox™ User's Guide.

This block accepts a scalar-valued or column vector input signal. If you set Input type to Bit, then the input signal can also be a vector of length K.

Single-Rate Processing

In single-rate processing mode, the input and output signals have the same port sample time. The block implicitly implements the rate change by making a size change at the output when compared to the input. In this mode, the input to the block can be multiple symbols.

  • When you set Input type to Integer, the input can be a column vector, the length of which is the number of input symbols.

  • When you set Input type to Bit, the input must be a column vector with a width that is an integer multiple of K, the number of bits per symbol.

The output width equals the product of the number of input symbols and the Samples per symbol parameter value.

Multirate Processing

In multirate processing mode, the input and output signals have different port sample times. In this mode, the input to the block must be one symbol.

  • When you set Input type to Integer, the input must be a scalar.

  • When you set Input type to Bit, the input width must equal the number of bits per symbol.

The output sample time equals the symbol period divided by the Samples per symbol parameter value.

Dialog Box

M-ary number

The size of the alphabet.

Input type

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

Symbol set ordering

Determines how the block maps each group of input bits to a corresponding integer. This field is active only when Input type is set to Bit.

Modulation index

Specify the modulation index {hi}. The default is 0.5. The value of this property must be a real, nonnegative scalar or column vector.

This block supports multi-h Modulation index. See CPM Modulator Baseband for details.

Phase offset (rad)

The initial phase of the output waveform, measured in radians.

Samples per symbol

The number of output samples that the block produces for each integer or binary word in the input, which must be a positive integer. For all non-binary schemes, as defined by the pulse shapes, this value must be greater than 1.

For more information, see Upsample Signals and Rate Changes in Communications System ToolboxUser's Guide.

Rate options

Select the rate processing option for the block.

  • Enforce single-rate processing — When you select this option, the input and output signals have the same port sample time. The block implements the rate change by making a size change at the output when compared to the input. The output width equals the product of the number of symbols and the Samples per symbol parameter value.

  • Allow multirate processing — When you select this option, the input and output signals have different port sample times. The output sample time equals the symbol period divided by the Samples per symbol parameter value.

      Note:   The option Inherit from input (this choice will be removed - see release notes) will be removed in a future release. See Frame-Based Processing in the Communications System Toolbox Release Notes for more information.

Output data type

Select the data type of the output signal. The output data type can be single or double.

Supported Data Types

PortSupported Data Types

Input

  • Double-precision floating point

  • Boolean (When Input type set to Bit)

  • 8-, 16-, and 32-bit signed integers (When Input type set to Integer)

Output

  • Double-precision floating point

  • Single-precision floating point

References

[1] Anderson, John B., Tor Aulin, and Carl-Erik Sundberg. Digital Phase Modulation. New York: Plenum Press, 1986.

Was this topic helpful?