Impact of RF impairments on a DS-CDMA receiver

This letter provides an analysis of the impact of classical radio frequency (RF) front-end impairments (RF mismatch and direct current (dc) offset) on the performance of direct-sequence code-division multiple-access (DS-CDMA) receivers; such issues are of particular importance in the case of zero intermediate-frequency (Zero-IF) receivers. Using a standard expression of the baseband signals as well as basic properties of spreading codes used in DS-CDMA communications, we show that the consequence of such RF mismatch and dc offset is essentially a degradation of the wanted signal´s level and an increase of the noise power. We give closed-form expressions (in E_b/N₀ form) for both. The results are then shown to be in accordance with numerical simulations utilizing the codes of the universal terrestrial radio access in the frequency-division duplex mode downlink standard.