Issue link: https://resources.mouser.com/i/1437750
| 25 | Understanding Key Parameters for RF Data Converters Analog data converters based on vacuum-tube technology were developed during World War II for message encryption systems. Since those early days, the industry has defined and adopted key parameters such as SNR, SFDR, and ENOB to quantify data converters' performance. These historical parameters were developed for conventional architectures that use mixers and filters for channel selection and conventional Nyquist-rate (low-frequency sampling) data converters. • Spurious-free dynamic range (SFDR) is commonly used to measure the usable dynamic range of a data converter before the spurious component interferes with or distorts the fundamental signal. • Signal-to-noise ratio (SNR) is the parameter typically used to quantify the noise in data converters, which is the ratio of the input signal's power to the noise's power and is commonly expressed in dB. • The effective number of bits (ENOB) is a parameter adopted to characterize the quality of a data converter's conversion (in bits) concerning the input signal over the Nyquist bandwidth. SFDR, SNR, and ENOB are all metrics derived from the data converter's full Nyquist bandwidth for a single-tone sinusoidal wave input. The listed applications are examples of SDR implementations with usable bandwidth, narrower than the entire Nyquist bandwidth. • 4G Long Term Evolution (LTE) multi-carrier • 5G massive MIMO (sub-6GHz) • Microwave backhaul • Phased-array RADAR Direct RF Sampling Differences Recently, many new RF sampling data converters have been developed for implementation in Software-Defined Radio (SDR) applications. However, the parameters adopted for conventional data converters cannot fully characterize RF sampling converters. A new set of parameters is required to define RF sampling data converters' dynamic performance, especially for direct RF- sampling applications. • Noise Spectral Density (NSD) • Third-order Intermodulation Ratio (IM3) • Adjacent-Channel Leakage Ratio (ACLR) The Xilinx Zynq UltraScale+ Radio Frequency System- on-Chip (RFSoC) integrates UltraScale architecture programmable logic (PL), soft-decision FECs, and multichannel RF-ADCs and RF-DACs. In these RF-ADCs (12-bit) and RF-DACs (14-bit), the NSD, IM3, and ACLR metrics compare favorably with the same-resolution bit data converters offered by top-tier analog integrated circuit vendors. However, Xilinx's Zynq UltraScale+ RFSoC