#### Question 6.4

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## Orthogonal Signalling

#### Two symbol states ai(t) and aj(t) are said to be orthogonal over the symbol period Ts if: #### If the frequencies of M-ary FSK symbols are chosen to be of the form: #### #### where m = 1, 2, ..., M, then these frequencies are orthogonal over a symbol period. |

#### An orthogonal 8-ary FSK set with a symbol rate of 1200 symbols/second could thus use frequencies of, say, 1000 Hz, 1600 Hz, 2200 Hz, 2800 Hz, 3400 Hz, 4000 Hz, 4600 Hz, and 5200 Hz respectively with the same starting phase.