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Modulate using GMSK method

The `comm.GMSKModulator`

System object™ modulates using the Gaussian minimum shift keying (GMSK) method. The output is a
baseband representation of the modulated signal. For more detail, see Algorithms.

To modulate a signal by using the GMSK method:

Create the

`comm.GMSKModulator`

object and set its properties.Call the object with arguments, as if it were a function.

To learn more about how System objects work, see What Are System Objects?

creates a
modulator System object that modulates the input signal using the GMSK modulation method.`gmskmodulator`

= comm.GMSKModulator

sets properties using one or more
name-value arguments. For example, `gmskmodulator`

= comm.GMSKModulator(`Name`

,`Value`

)`'PulseLength',6`

specifies the length
of the Gaussian pulse shape as 6 symbol intervals.

To use an object function, specify the
System object as the first input argument. For
example, to release system resources of a System object named `obj`

, use
this syntax:

release(obj)

The `BandwidthTimeProduct`

property represents the bandwidth multiplied by time. Use this property to reduce the
bandwidth at the expense of increased intersymbol interference. The `PulseLength`

property measures the length of the Gaussian pulse shape in symbol
intervals. These equations define the frequency pulse shape.
*B*_{b} represents the bandwidth of the pulse and
*T* is the symbol durations. *Q(t)* is the complementary
cumulative distribution function.

$$\begin{array}{l}g(t)=\frac{1}{2T}\left\{Q\left[2\pi {B}_{b}\frac{t-\frac{T}{2}}{\sqrt{\mathrm{ln}(2)}}\right]-Q\left[2\pi {B}_{b}\frac{t+\frac{T}{2}}{\sqrt{\mathrm{ln}(2)}}\right]\right\}\\ Q(t)={\displaystyle \underset{t}{\overset{\infty}{\int}}\frac{1}{\sqrt{2\pi}}}{e}^{-{\tau}^{2}/2}d\tau \end{array}$$

For this System object, an input symbol of 1 causes a phase shift of π/2 radians, which corresponds to a modulation index of 0.5.

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