Electronic Military & Defense Annual Resource

6th 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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Page 8 of 43

Techniques Electronic Military & Defense Annual Resource, 6th Edition 9 the FEM is strong when a full scattering matrix is required for a situation with more than a dozen antennas, while the FDTD method can perform wide frequency sweeps efficiently. We will continue to focus on the MoM, though, because of its ability to handle rotor-blade modulation. Rotor-Blade Modulation The problem depicted in Figure 2 becomes worse when trying to account for the movement of the rotor blades. The antenna pattern shown, with its many maxima and minima, is valid for only one snapshot of the rotor position. Rotor movement will make the pattern undulate. Analysis of the effect of rotor-blade position on the installed antenna performance involves a nonchanging rotorcraft body (static part) and a rotating set of rotor blades (dynamic part). One can reduce the computational time significantly if the solution of the static part can be reused when analyzing a new rotor blade position. The Numerical Green's Function (NGF) utility 5 in the MoM can serve this purpose. Although the solution (the electrical currents and fields) of the static part changes all the time when the blades rotate, the main part of the "number crunching" is done only once and then is reused. Thus, new full-model solutions for every blade position are generated at a low cost (Figure 3). Note that the movement of the blades changes the pattern by several dB. In some directions, the difference easily exceeds 5 dB. Figure 2: Turnstile antenna placed on a rotorcraft and the corresponding radiation pattern SINCE 1968 508-695-0203 mini-systemsinc.com info@mini-systemsinc.com 20 David Road, North Attleboro MA 02761-0069 Thick & Thin Film Resistor Products • Faithful scheduled deliveries under 2 weeks • Values from 0.1 Ohm to 100G Ohm • Abs. tolerance to ±0.005%, matching to ±0.0025% • TC R 's t o ±2ppm/°C, t racking to ±1ppm/°C • O perating frequencies to 40GHz • H igh performance at cryogenic temperatures • C ase sizes to 0101 • Space level QPL's, F.R.-"S", per MIL-PRF-55342 • Zero failures wi t h over 200 million life test hours • I S O 9001:2000 certified • Full line of RoHS compliant products • 24-hour quote turnaround 47 YEARS OF EXCELLENCE PROVEN RELIABILITY. TRUSTED PERFORMANCE. PRECISION PASSIVE COMPONENTS & ELECTRONIC PACKAGES Electronic Package Products • Hi Reliability Hermetic Packages: • Lightweight glass sidewall flatpacks • Metal flatpacks, leadless chip carriers (LCC) and ceramic quad flat pa cks ( C Q FP) • S urface mount and plug-in packages • H ermet icit y per MIL-STD-883, Met hod 1014, C ondit ion A4 (greater than 10 -9 at m cc/sec) • P lating per MIL-DTL-45204 and QQ-N-290 for st andard packages (unless otherwise specified) • Custom design available • R oH S and DFA R S compliant

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