Verification of receive performance requirements for direct-conversion digital receivers

The authors explain a nonstandard test procedure that verifies the noise figure and BER (bit error rate) requirements of a direct-conversion digital receiver. They discuss the performance specifications and verification methods for a conventional superheterodyne receiver and show why the verification methods could not be applied to a direct-conversion receiver. They derive a relationship between the minimum receive signal level, noise figure, and E _b/N₀ for a specified BER for a direct-conversion receiver. They also propose a nonstandard specification requirement for digital-processing receivers, based on this work. The critical performance requirement for a digital receiver is the BER at the minimum receive signal level. They show how the specification of (E_b/N₀)_RF , as used in an equation given here, allows a receiver designer to make tradeoffs between noise figure and implementation loss of the demodulator for a specified BER performance of the receiver. They recommend that BER at a particular (E_b/N ₀)_RF be used to specify the performance of a digital receiver, rather than noise figure and BER at a specified E _b/N₀ into the demodulator