Learn more about Communications Blockset

M-FSK Modulator Baseband - Modulate using M-ary frequency shift keying method

Library

FM, in Digital Baseband sublibrary of Modulation

Description

The M-FSK Modulator Baseband block modulates using the M-ary frequency shift keying method. The output is a baseband representation of the modulated signal.

The M-ary number parameter, M, is the number of frequencies in the modulated signal. The Frequency separation parameter is the distance, in Hz, between successive frequencies of the modulated signal.

The sampling frequency must be greater than M multiplied by the Frequency separation or the output signal will be aliased. Sampling frequency is Samples per symbol divided by the input symbol period (in seconds).

If the Phase continuity parameter is set to Continuous, then the modulated signal maintains its phase even when it changes its frequency. If the Phase continuity parameter is set to Discontinuous, then the modulated signal comprises portions of M sinusoids of different frequencies; thus, a change in the input value might cause a change in the phase of the modulated signal.

Note that a model with the M-FSK Modulator block will not run if it is used for sample-based signals unless Tasking mode for periodic sample times (in Simulation > Configuration Parameters > Solver) is set to SingleTasking.

Input Signal Values

The input and output for this block are discrete-time signals. The Input type parameter determines whether the block accepts integers between 0 and M-1, or binary representations of integers:

If Input type is set to Integer, then the block accepts integers. The input can be either a scalar or a frame-based column vector of type int8, uint8, int16, uint16, int32, uint32, or a double with an integer value. They can also be boolean if the size of the alphabet is 2 (i.e. M = 2).
If Input type is set to Bit, then the block accepts groups of K bits, called binary words. The input can be either a vector of length K or a frame-based column vector (whose length is an integer multiple of K), and must be boolean or double typed, valued from the set {0, 1}. The Symbol set ordering parameter indicates how the block assigns binary words to corresponding integers.
- If Symbol set ordering is set to Binary, then the block uses a natural binary-coded ordering.
- If Symbol set ordering is set to Gray, then the block uses a Gray-coded ordering. For details about the Gray coding, see the reference page for theM-PSK Modulator Baseband block.

Whether the input is an integer or a binary representation of an integer, the block maps the integer 0 to the highest frequency and maps the integer M-1 to the lowest frequency. In baseband simulation, the lowest frequency is the negative frequency with the largest absolute value.

Dialog Box

M-ary number: The number of frequencies in the modulated signal.
Input type: Indicates whether the input consists of integers or groups of bits. If this parameter is set to Bit, then the M-ary number parameter must be 2^K for some positive integer K.
Symbol set ordering: Determines how the block maps each group of input bits to a corresponding integer.
Frequency separation (Hz): The distance between successive frequencies in the modulated signal.
Phase continuity: Determines whether the modulated signal changes phases in a continuous or discontinuous way.
Samples per symbol: The number of output samples that the block produces for each integer or binary word in the input.
Output data type: The output type of the block can be specified as either a double or a single. By default, the block sets this to double.

Pair Block

M-FSK Demodulator Baseband