Calculating noise figure and third-order intercept in ADCs

Introduction Noise figure (NF) and the third-order intercept point (IP3) are used in radio receiver link budget analysis as a means to quantify the effects of device noise and nonlinearity on the sensitivity of the radio. Analog-to-digital converters (ADCs) are used in radio receivers to convert the signal from the analog domain to the digital domain. NF and IP3 typically are not specified for the device, but equivalent parameters are given whereby they can be calculated. ADCs specify signal-to-noise ratio (SNR) and two-tone, third-order intermodulation distortion (IMD3) under certain input signal and clocking conditions. With this information, NF and IP3 can be calculated. In general, a low NF and high IP3 are desired. The actual values required to meet the design goals depend on the architecture of the system.