# How do I implement the delay of the Q-Phase Input in GMSK?

I am on a project to write a function in Java to perform GMSK modulation. I have a good understanding of the GMSK modulation block diagram to an extent, but I have a challenge on what it means to delay the Q-phase input by 90°.

Do I simply multiply my Q-phase bit stream by a negative sine carrier or what? Please, what is the correct thing to do?

EDIT: The above is an answer to the question "how do I perform a $90^{\circ}$ phase shift (for non-sinusoidal signals)?". However, what I didn't notice - and what was luckily pointed out by Jim Clay in a comment - is the fact that in the given diagram there is no need for a phase shifter. The first $90^{\circ}$-block simply symbolizes the splitting of the signal in an I-component and a Q-component. It is not a phase splitter and the $90^{\circ}$-symbol is actually quite misleading.