Electronic Military & Defense Annual Resource

2nd Edition

Electronic Military & Defense magazine was developed for engineers, program managers, project managers, and those involved in the design and development of electronic and electro-optic systems for military, defense, and aerospace applications.

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Techniques Figure 3: A spectrogram displays frequency (left to right) and amplitude (color) information versus time (bottom to top). technique itself to develop: covering the victim radar pulse; capturing its AGC; and walking it off range, Doppler, or both. This is also called the time required to establish a jam-to-signal (J/S) ratio capable of deceiving the victim radar. Determining these values requires measurements of a signal's frequency and amplitude as well as its time- domain characteristics. A spectrogram display provides an informative overview of all three aspects (see Figure 3). Working in concert, these capabilities enable measurements of PRI and Doppler. Also, on-screen marker capabilities such as occupied bandwidth (OBW) and band power provide additional information about the jamming signal. Emulating Radar Signals Achieving an accurate emulation of a radar or jammer signal can be quite challenging. Fortunately, COTS-based equipment and software is making it easier to create such signals in the lab, whether the need is to generate realistic radar signals to stimulate a jammer design or playback recorded jammer signals to test a radar system. As noted earlier, a proposed solution includes signal-creation software, an AWG, and a vector signal analyzer. To emulate current-generation radar techniques, the software should support the creation of pulse-based signals. Example capabilities include built-in PRI patterns and pulse-width timing patterns, automated playback of user-defined pulse patterns, and precise control of time- and frequency-domain attributes. In addition, compatible math software can be used to add customized clutter and jamming impairments. Other useful capabilities include built-in antenna radiation patterns and antenna scanning, as well as import and export of scenario databases. 36 Electronic Military & Defense ■ www.vertmarkets.com/electronics A suitable AWG is capable of providing high resolution and wide bandwidth simultaneously. This ensures highly realistic testing whether working with low observables or high-density scenarios. Of course, the AWG should also be compatible with the chosen signal-creation software and vector signal generator. The vector signal generator should be versatile enough to generate a wide range of signals, from simple to complex and from clean to impaired. It should also provide the purity and precision needed to test radar, EW, electronic countermeasures (ECM), and electronic counter-countermeasures (ECCM) systems within and beyond the limits of their specified performance. Finally, two modulation inputs are needed to accept I and Q data from the AWG. Referring back to the characterization solution, acquired jamming signals can be passed along to the emulation system. For example, a jammer signal acquired with a signal analyzer could be transferred to the signal-creation software, manipulated as needed, and then transferred to the AWG for playback as I/Q signals that modulate the vector signal generator. Keeping Pace With Evolving Threats In all, the capabilities presented here provide the flexibility needed to keep pace with evolving threats in radar and EW applications. In addition, automation capabilities in the signal analyzer and VSA software can reduce the time required to fully characterize captured signals in the time, frequency, and modulation domains. John Hansen is a senior application engineer for Agilent Technologies' Electronic Measurements Group. He has more than 20 years of expe- rience in system engineering and new product development within the wireless, microelectronics, and defense industries.

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