Taking advantage of FPGA-based hardware in your RF measurement systems can provide a number of benefits ranging from low-latency DUT control to CPU load reduction. The following sections describe various usage scenarios in more detail.
Improve Test System Orchestration With Interactive DUT Control
In many RF test systems, the device or chip under control must be controlled via digital signals and custom protocols. Traditional automated test systems have the ability to sequence through DUT modes, taking the needed measurements in each stage. In some cases, automated test equipment (ATE) systems incorporate intelligence to progress between DUT settings according to the measurement values received.
In either scenario, software-designed instruments that incorporate an FPGA can result in cost and time savings. Consolidating both measurement processing and digital control into a single instrument reduces the need for additional digital I/O in the system, and avoids the necessity to configure triggering between instruments. In cases where the DUT must be controlled in response to measurement data received, software-designed instrumentation can close the loop in hardware, reducing the need for decisions to be made in software at a significantly higher latency.
Decrease Test Time and Increase Confidence With In-Hardware Measurements
Although today’s software-based test systems can perform a limited number of measurements in parallel, software-designed instrumentation is limited only by the available FPGA logic. Dozens of measurements or data channels can be processed with true hardware parallelism, removing the need to choose between measurements of interest. Computations such as fast Fourier transforms (FFTs), filtering, and modulation/demodulation can be implemented in hardware, reducing the amount of data that must be passed to and processed by the CPU. With software-designed instruments, functionality such as real-time spectral masking can be achieved at a significantly higher rate than with traditional boxed instruments.
In addition, the low latency associated with performing measurements in hardware means that in the same time a standard test system may have required to perform a single measurement, tens or hundreds of live measurements can be taken and averaged together, as shown in Figure 2. This translates to improved quality of test results and increased confidence in your RF measurements. Furthermore, since measurements can be taken continuously in hardware and sampled periodically from a host test application, you can be confident that you will never miss important data.
Figure 2. With software-designed instruments, you can continually acquire data and perform measurements (sampling results periodically) rather than stopping the acquisition process to transfer information.
Reach Optimal Test Conditions Quickly With Closed-Loop Feedback
Certain classes of RF test require that DUT settings or environmental and manufacturing process quantities are varied according to the measurements received; this requires a closed-loop system that is often limited by the latency of the software stack. In many cases, the loop can be closed directly in hardware, eliminating the need for subsequent setpoints to be computed using the CPU. This can reduce closed-loop test times from ten of seconds to fractions of a second.
Focus on Data of Interest With Custom-Defined Triggers
Options for low-latency trigger behavior are traditionally fixed according to the instrumentation hardware being used. However, with software-designed instrumentation, you can incorporate custom triggering functionality into your device to quickly zero in on situations of interest. Flexible hardware-based triggering means that you can implement custom spectral masks or other complex conditions as criteria for either capturing important measurement data or activating additional instrumentation equipment. And, by selecting data of interest in hardware you can free up the CPU for other important tasks.