Welcome to the exciting new frontiers in high-performance data conversion: GHz bandwidths, giga-samples-per-second, and direct RF conversion. As CMOS process technology has advanced, speeds have increased and the addition of signal processing to data converters has become commonplace. The lines continue to blur between analog and digital as the trend toward software-defined systems and broad-band signal conversion grows. Our two feature articles this month both deal with design details of ADI’s latest RF data converters. These blazingly fast embodiments of devices that used to be considered mostly analog now incorporate just as much digital functionality. In fact, these devices, with output data that is processor-ready, are more like integrated data conversion systems than components.
Jonathan Harris provides an in-depth look at the digital down conversion function in a couple of ADI’s high-speed ADC devices. This digital signal processing function obviates the need to implement multiple analog down conversion stages in a GHz RF signal chain, and it has the added advantage of improving dynamic range within selected bands. This article explains the signal-tone flow through a DDC block and introduces an online Frequency Folding Tool that aids in the analysis of the sampled spectrum.
The second article addresses the transmit side of the radio signal chain. Dan Fague describes how a new breed of RF DAC can directly synthesize GHz signals, eliminating the need for entire stages of analog frequency upconversion, thus simplifying frequency planning, and reducing power consumption and the size of the radio. Advancements in CMOS process, innovations in DAC architectures, and implementation of JESD204B serial interface, have come together to enable a practical high-performance GHz DAC. Dan explores the functionality and performance of this remarkable product.
With more and more digital processing and frequency translation being done inside the direct RF data converter solution itself, and the output data seamlessly interfacing to an FPGA, the radio system designer’s IP can largely reside in the digital domain. This unprecedented flexibility in system architecture is helping designers reach the next level in truly software-defined radio platforms. All of which enables many innovative applications that couldn’t have been considered even a few years ago. Or as we like to say around here, “Ahead of what’s possible.”