To calculate IIP3, the input tones must first be translated to dBm, and then the Parameters and associated units shown in Table 3 should be present. Second, the noise spectral density (NSD) needs to be converted from a dBFS/Hzįinally, the NSD in dBm/Hz is compared against the thermal noise floor toĬalculating IIP3 for the GSPS ADC is similarly simple. The full-scale input voltage needs to be translated from V p-p to dBm. ADC Specifications Specificationįrom these three parameters the NF of the GSPS ADC can be calculated. In the ADC data sheet these specifications and their associated units are almostĪlways provided (see Table 2). Information to extract these parameters is present. Neither NF nor IIP3 are often in the specification table for GSPS ADCs, but the The small signal reception capability, while the IIP3 informs the upper limit on Two key individual performance metrics that combine to inform dynamic rangeĪre noise figure (NF) and input third-order intercept point (IIP3). Range is typically going to be limited by nonlinear RF devices, often a mixer. In a traditional heterodyne receiver, the dynamic How small a signal can be and still be received while simultaneously in the Receiver dynamic range is a commonly used performance metric that indicates This article is meant to address three critical RF aspects of the GSPS ADC: dynamic range, spurious planning, and noise performance. This transition can cause challenges for system and RF engineers, as the ADC does not behave the same as traditional RF devices such as mixers, amplifiers, and switches. This increasing frequency has allowed for GSPS ADCs to eliminate heterodyning stages, as shown in Table 1, and pull the data converter closer to the RF antenna, enabling a direct RF sampling architecture where no heterodyne stages are required. As the sample rate of the ADC has increased, so has the input frequency and instantaneous bandwidth that the data converter can digitize. The last 20 years have seen incredible advancements in analog-to-digital converter (ADC) sample rates, from less than 100 MSPS being state-of-the-art in the year 2000, to current data converters often sampling higher than 10 GSPS. This article will provide a methodology for analyzing GSPS ADCs in RF systems. This architecture can significantly reduce the size, weight, and power (SWaP) of the radio, but it introduces the new challenge of needing to simulate the data converter as an RF device, rather than a baseband device. Next-generation radio platforms are moving to a direct RF sampling architecture at an increasing pace.
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