Four-channel direct-bit detection receiver for 2-FSK/8-PSK modulated signals

A simple four channel receiver for 2-FSK/8-PSK modulated signals is proposed and its performance evaluated. Using Gray-Code mapping and direct detection of individual bits, the overall receiver performance in terms of bit error rate (BER), is evaluated as a function of E _b/N ₀ and a variable phase parameter alpha , under an assumed additive white Gaussian noise interference model. The variable phase parameter can be adjusted according to the intended application, as three out of four bits that constitute a symbol have individual error rates that depend on the value of alpha as well as E _b/N ₀. Angle settings for the minimisation of the overall BER can be obtained for different values of E _b/N ₀. This represents a slight system disadvantage, but it is partly offset by the simplicity with which the receiver is able to deliver deinterleaved data to the intended users, by performing summing and squaring operations on the correlator outputs prior to binary comparisons against zero thresholds.<>