Electronic-warfare (EW) threat simulators provide the means of reproducing the complex electromagnetic (EM) environments common to the battlefield, typically combining voice and data communications streams, radar signals, and jamming signals. For any kind of new application, such as testing radar warning receivers (RWRs) or EW countermeasures systems, to operate successfully in such a hostile environment, it must be able to withstand this barrage of other signals.
First, though, the application must pass a series of performance tests, and to do so, those test signal environments must be recreated. Fortunately, a two-part EW threat simulator from Keysight Technologies provides the solution, combining hardware adapters for wideband vector signal generators and powerful simulation software to duplicate the complex pulsed and modulated signals found in EW signal threat environments.
Starting with the sources, the N5194A UXG agile vector adapter is designed for use with the N5193A UXG agile signal generator. The combo delivers extended frequency coverage of 10 MHz to 44 GHz. with fast frequency, amplitude, phase hopping capabilities (Fig. 1).
1. The combination of the model N5194A UXG agile vector adapter works with the model N5193A UXG agile signal generator and additional software to emulate multi-emitter threat signal environments from 10 MHz to 40 GHz. (Courtesy of Keysight Technologies)
For the N5194A with the N5193A configured as the local oscillator (LO), switching transition times are in the 190- to 250-ns range in narrowband mode with 3-µs latency. In wideband mode, the transition times are typically 170 to 220 ns with 2.5-µs latency. Transition times slow a bit in internal LO mode, typically 470 to 740 ns with 3.5-µs latency.
For cases that do not require fast switching speeds, the model N5192A vector adapter is designed for use with the model N5191A UXG agile signal generator and provides frequency coverage of 10 MHz to 20 GHz with 101-µs switching transition times in external LO mode. Both vector adapters derive frequency accuracy and stability from an external 6-GHz, 50-Ω reference oscillator provided by the N5193A/N5191A sources. The signal sources are based on direct digital synthesis (DDS).
No matter the operating mode or configuration, the agile vector signal generators and adapters deliver outstanding frequency and phase stability. The CW frequency can be tuned with 0.001-Hz resolution while phase offsets are adjustable in 0.1-deg. increments. Maximum signal amplitude is +1 dBm or better across the full frequency range in external LO mode and −2 dBm or better across the full frequency range in internal LO mode. The specified power is +3 dBm from 50 MHz to 18 GHz in either LO mode, with available power of +4 dBm or more. Power can be set with 0.01-dB resolution.
As expected for sources equipped for EW and ECM duties, both adapters/generators provide fast switching speeds from pulse to pulse or frequency to frequency. When generating multiple signals, such as the wave fronts produced by phased-array antennas or multiport angle-of-arrival (AoA) simulations, multiple UXG agile vector adapters can be synchronized together with one UXG agile signal generator. In such a setup, one of the UXG vector adapter units is configured as the LO controller.
The sources can operate in standard vector mode (sampling at 250 Msamples/s) and, as an option, in wideband vector mode (sampling at 2 Gsamples/s), with slightly faster transition times in wideband mode. CW power can be set as low as −120 dBm with the aid of a step attenuator that ranges from 0 to 65 dB in 5-dB steps. The CW output power of both sources is linear for most power levels. At all frequencies, amplitude accuracy is no worse than ±2.5 dB and typically ±0.5 dB when using an external LO. It’s no worse than ±3.0 dB and typically ±0.6 dB when using an internal LO.
Surveying Spectral Purity
Signals from the agile vector sources are as clean as they are quick, with low harmonics and spurious contributions and low phase noise. For units working with an internal LO, sampling at 250 Msamples/s (narrowband mode), harmonics are −30 dBc or better for fundamental-frequency signals from 50 MHz to 4 GHz at an amplitude of −10 dBm and −63 dBc or better with fundamentals from 4 to 20 GHz at −10 dBm. For signal sources in external LO mode and 2 Gsamples/s, the harmonic levels are −24 dBc or better for fundamental signals from 50 MHz to 4 GHz at −10 dBm and −63 dBc or better for fundamental signals from 4 to 20 GHz at −10 dBm.
Non-harmonic spurious content depends on internal or external LO operating modes. For example, for operation in standard vector mode (250 Msamples/s) with an internal LO, the line-related spurious levels are −69 dBc offset 300 Hz or less from carriers 50 MHz to just under 2.5 GHz, −45 dBc offset 300 Hz or less from carriers 2.5 GHz to just below 18 GHz, and −49 dBc at offsets of 10 kHz or more from carriers of 18 to 20 GHz.
With an external LO in standard vector mode, spurious levels are −53 dBc or better at offsets of 300 Hz or less from carriers of 50 MHz to just less than 12.5 GHz. And they are −50 dBc or better at offsets of 300 Hz or less from carriers of 12.5 through 20 GHz, with spurious levels dropping further for offsets further from the carrier.
Whether with internal or external LO, the sources maintain excellent frequency stability and low phase noise throughout the wide frequency ranges. With an internal LO, at a 1-GHz carrier, the phase noise is −132 dBc/Hz or better offset 10 kHz from the carrier and drops to −145 dBc/Hz or better offset 1 MHz from the carrier. Even at a 20-GHz carrier, the phase noise remains low, −113 dBc/Hz or less at a 10-kHz offset and −125 dBc/Hz or better at a 1-MHz offset. In external LO mode, the phase noise is −132 dBc/Hz offset 10 kHz from a 1-GHz carrier and −145 dBc/Hz offset 1 MHz from the same carrier. For a 20-GHz carrier in external LO mode, the phase noise is −106 dBc/Hz offset 10 kHz from the carrier and −117 dBc/Hz offset 1 MHz from the carrier.
The Simulation Side
By operating these vector signal sources and adapters with the control possible using commercial-off-the-shelf (COTS) modeling software packages like Keysight’s Z9500A Simulation View software and N7660C Signal Studio for Multi-Emitter Scenario Generation (MSEG) software, the hardware/software combination enables full-spectrum modeling with dynamic scenario control to adapt to changing signal environments. The company also provides UXG system integration with automated multi-source and system-level calibration software.
The N7660C MESG and Z9500A Simulation View software are capable of multi-emitter threat simulations (Fig. 2). They can simulate an electronic battlefield with thousands of emitters including advanced pulse-modulated or chirped signal waveforms and even perform AoA analysis on signals used in direction-finding (DF) applications.
2. Powerful software tools are used with the vector signal generators and adapters to simulate electronic battlefields. (Courtesy of Keysight Technologies)
The Z9500A Simulation View software uses real-time pulse-descriptor-word (PDW) streaming for creating radar signals. The Z9500A’s open architecture also makes it possible to work with other software tools to create realistic threat signal simulations based on a user’s database of models and threat scenarios. In addition to Keysight’s simulation software tools, customers have the flexibility to use their own software tools to create PDW-based scenarios with the UXG agile signal generators.
Keysight Technologies Inc., 1400 Fountaingrove Pkwy., Santa Rosa, CA 95403-1738.