The effect of ADC resolution on concurrent, multiband, direct RF sampling receivers

Connectivity using interband frequencies in 4G and 5G radio access networks, for example, carrier aggregation or dual-connectivity, incurs high receiver complexity and power consumption, in particular, when implemented using multiple radio units. Employing concurrent, multiband, direct RF sampling in a single radio chain architecture reduces the RF component count, leading to lower receiver complexity and power consumption. For this architecture, as the composite signal from multiple concurrent bands is digitized by a common analog-to-digital converter (ADC), the bit resolution critically affects system performance. In this paper, the effect of ADC resolution on the error vector magnitude (EVM) and Block Error Rate (BLER) performance of a concurrent, multiband, direct RF sampling receiver is investigated. Simulation and hardware measurement of a tri-band Long Term Evolution (LTE) system supporting three simultaneously active channels at 888 MHz, 1.92 GHz and 2.52 GHz is evaluated when reducing the ADC resolution from 8 to 3 bits. Interband interference measurements demonstrate that the multiband, direct RF sampling, wideband LTE receiver remains 3GPP compliant at 4-bit ADC resolution with the signal-to-noise-ratio (SNR) desensitization over a single-band receiver limited to 9 dB in the 888 MHz band.