# Minimal Shift Keying clarification

1. ## Minimal Shift Keying clarification

Hi, I have come across a simple problem that has me stumped in MSK. It states that for MSK, the modulation index used (h) = 0.5, in other words, the minimum frequency difference of the two frequencies used f1-f2=1/2T (I hope this T refers to bit duration, I am confused here too).

My problem is that I have not met a single proper reasoning as to why this is the case(h=0.5). With quite some searches I have found only that it is a requirement for frequencies to be orthogonal over one bit interval. Most documents state this as an obvious statement.

Can someone please provide an explanation of this to me, or better yet direct me to some source material that explains why h=0.5 is the minimum frequency spacing required for two signals to be orthogonal. It seems like I have overlooked some per-requisite knowledge before studying MSK.

Thank You

•

2. ## Re: Minimal Shift Keying clarification

Read Digital Communications by John Proakis. He has a good section on this.

--[[ ]]--