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Signal generation enables cost-effective testing

The characterization of modern radar system designs is the type of application that needs a variety of test signals to accurately simulate an operational environment. A suitable signal-generation solution must enable the creation of long, complex signal scenarios—a capability found in some of today’s advanced wideband arbitrary waveform generators (AWGs).

Examples include the Agilent M9330A (PXI version) and N8241A (LXI version) AWGs, which can provide wide bandwidth and 15-bit resolution simultaneously. These signal generators can replace the costly and complex custom systems that are typically capable of testing only a single radar system. AWG-based signal generation can also simplify the emulation of various operational scenarios, reducing the need for costly flight testing.

Creating complex scenarios
The M9330A and N8241A signal generators enable long scenarios with two techniques, “dynamic sequencing” and direct digital synthesis (DSS). With dynamic sequencing, signal segments can be strung together dynamically—and in any order—as the waveform is played back. DDS allows the user to separate the slowly changing attributes of a scenario—carrier frequency, phase and timing—from the rapidly changing signal modulation.

Applying dynamic sequencing
For complex simulations, dynamic sequencing is the type of clever and elegant solution any engineer can appreciate. Implementing it in an arbitrary signal generator requires three key elements: waveform memory for storage of signal samples; a waveform playback capability that contains signal segments and sequences; and a waveform play table for creating signal scenarios.

The process begins by storing or creating a variety of waveforms in the AWG’s memory. As an example, these could be a radar chirp, a continuous-wave (CW) signal, a Barker-coded waveform and an antenna-scan profile. Using only the stored waveforms—which may occupy less than 10,000 samples in memory—the arbitrary signal generator can be programmed to chain together multiple segments, loops and sequences to produce a complex signal scenario.

This is made possible with high-speed digital signal processing (DSP) technology. In an interesting coincidence, the same type of DSP used in modern radar systems also exists inside the signal generators used to test them.