Radar systems are vital not only to modern warfare strategies, but also increasingly in commercial applications—collision-avoidance systems in commercial automobiles, to give but one example. Although the electronic design required for high-performance radar systems still includes some of the most elegant architectures found in RF/microwave applications of any kind (with such approaches as superheterodyne receiver circuits to detect narrow pulsed signals and high-performance frequency synthesizers to generate pulses at the transmitter), data converters are more and more replacing some of this functionality. High-speed analog-to-digital converters (ADCs) and digital-to-analog converters (DACs) are taking on more of the signal generation and analysis tasks in modern radar systems, with absolutely no tradeoffs in reliability.

On the receive side, a high-speed ADC is typically linked to each channel of a receiver’s intermediate-frequency (IF) electronics section; this provides conversion of received analog pulsed radar signals to digital signals for processing with digital signal processors (DSPs) and other digital components. With the performance levels possible from high-speed semiconductor processes—among them, the silicon-germanium (SiGe) BiCMOS process from IBM—ADCs and DACs routinely operating across 10-GSamples/s sampling rates and 5-GHz bandwidths are available for the analog/digital interface section of radar receivers and transmitters, respectively. This totally alters the design approach of these radar systems from years past.

As with modern test equipment, such as spectrum analyzers—many of which rely on high-speed ADCs and digital processing following an input signal path with frequency downconversion to an IF section—modern radar systems are as much defined by their digital circuitry as by their analog RF/microwave circuitry. The bandwidth and sampling rates of the ADCs set the limits for the radar’s IF stage, while the resolution of the ADCs (in bits) determines the resolution of the radar system receiver. Similarly, the DACs help generate complex modulated pulsed signals for a radar transmitter, relying on frequency upconversion and trusted RF/microwave components (such as amplifiers and filters) for the signal path to the radar system’s transmit antennas.

Radar technology is, of course, used in a wide array of military applications, but also in any number of non-defense-related ones. These include the aforementioned automobiles, along with weather radars, aircraft anticollision systems, ocean surveillance, and even NASA’s topographical mapping of the solar system. Military applications have always demanded systems and components with the highest performance, including ADCs and DACs with high bit resolution, as well as high sampling rates and wide bandwidths. But for radar systems to increase their reach—whether in military applications or even in potentially high-volume commercial applications—the performance/price ratio that ADC and DAC customers have enjoyed in recent years will require a continued boost.

Admittedly, the RF/microwave portions of radar receivers and transmitters have not changed a great deal in the last few decades, with perhaps some improvements in solid-state transmit output power or receive noise figure as a result of refined semiconductor processes. But the improvements being made in ADCs and DACs during the last two decades have been dramatic, when considering not only the electrical performance of these converters but the increasing density of their circuitry and their improvements in power efficiency. And it will be continued improvements in ADCs and DACs that will pave the way for future successes in radar system performance and cost/value levels.