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Sorting Test Gear for Military Measurements
By Jeffrey Paulownia M
ilitary electronic systems are governed by their own sets of standards and demanding requirements in order to meet performance
levels under a wide range of highly difficult envi- ronmental conditions. Testing these electronic sys- tems and their components usually calls for meas- urement instruments that can reconstruct the sig- nal and operating conditions faced by the electron- ic systems in the field. The list of test equipment includes signal generators, signal and spectrum analyzers, and oscilloscopes, all designed to meet the operating limits commonly found in military electronic systems. Establishing a test laboratory for characteriz-
ing military-grade electronic products depends on the type of system being serviced, since the operat- ing parameters for military electronic systems can vary widely, from the short, high-frequency pulses used in radar systems to the much longer, broad- band signals used in electronic warfare (EW) and electronic countermeasures (ECM) systems. In sort- ing through available test signal sources or genera- tors, many are designed for continuous-wave (CW) signal use with a much smaller number aimed at pulsed applications such as testing radar systems.
Frequency Range Needed A practical starting point in selecting a mili-
tary test signal generator is frequency range, since the instrument must have the bandwidth and fre- quency coverage to duplicate the real-life signals that will be handled by the system under test and its components. While a frequency range of 2 to 18GHz has traditionally been used for testing elec- tronic-warfare (EW) components and systems, newer requirements may extend the lower fre- quency span from 500 or 300MHz to 18GHz, with a tuning resolution as fine as 1Hz as needed. A
related performance specification is frequency switching speed, which will also be determined by the system under test. Frequency agility may be required of a signal
generator intended for characterizing the perform- ance of tactical radios and other military commu- nications systems that rely on fast frequency tun- ing speeds to prevent signals from being intercept- ed. Some commercial analog test signal sources are capable of microsecond or better switching speeds to change frequencies. And some digital sources, such as those based on arbitrary waveform gener-
power with frequency. Test signal generators for military applica-
tions are available from a large number of quality suppliers, including the former electronic instru- ments group of Agilent Technologies, now operat- ing as Keysight Technologies, Anritsu Co. , Berkeley Nucleonics, Hittite Microwave Corp., National Instruments, Rohde & Schwarz, and Tektronix, many of which also offer analyzers and other test equipment suitable for military meas- urement applications.
Modular Formats Helpful Some of these signal generators are supplied
Cutting-edge signal generators such as this model N5193A agile signal generator can
reproduce many military signal waveforms, including radar signals, from 10MHz to 40GHz. (Photo courtesy of Keysight Technologies)
ators (AWGs) and direct-digital-synthesizer (DDS) technologies, are capable of frequency-switching speeds in the nanosecond range in addition to advanced modulation capabilities. Additional sig- nal-generator performance specifications that must be considered for military test applications include modulation capabilities, spectral purity (such as phase noise and harmonics), and output
in modular form, such as the model M8195A arbi- trary waveform generator from Keysight which is built into a five-slot modular AXIe chassis. The digital source operates at sampling rates to 65 GSamples/s, and generates instantaneous analog bandwidths from DC to 20GHz for radar and EW testing as well as for commercial communications testing. Similarly, the model AWG70000A Series of arbitrary waveform generators from Tektronix operates at sample rates to 50GSamples/s, enabling them to generate signals to 20GHz, including many of the complex waveforms used in radar and EW systems. One of the important requirements in a digital signal generator such as an arbitrary waveform generator is to outfit it with enough waveform memory to store the variety of different waveforms needed for a series of tests. In a more traditional, rack-mount housing,
the model MG37020A signal generator from Anritsu Co. has gained acceptance in many mili- tary test applications for its wide bandwidth, from 10MHz to 20GHz, and fast frequency switching speed, of 10µs or better to shift to as new frequen-
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December, 2014
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