what is the difference between the coherent and non coherent detection of orthogonal FSK signals. i.e.: the minimum required frequency separation in coherent detection is 1/2T, where T is the symbol duration, to achieve the orthoganality. at the same time the minimum required separation in frequency to achieve orthogonality in non coheret detection is 1/T!! how is that?? isn't it the same signal, I mean the generation process in both coherent and non coherent is the same, but the detection process is different. so how is the minimum separation in frequency is 1/T and 1/2T at the smae time to achieve orthogonality. anyone can explain that supported with references or papers.
Thanx in advance.