A frequency reconfigurable microstrip patch antenna with two asymmetric L-slots is proposed in this article. Two RF pin diodes inserted on the asymmetric L-slots are used to switch the operating frequency over the C band. Design and optimization of different physical parameters of the antenna viz. slot dimensions, feed location, notch size, and pin diode positions are carried out using High Frequency Structure Simulator Version 13.0. The design is implemented on an FR4 substrate (ε r = 4.4) of dimension (35 × 40 × 1.6) mm 3 . DC bias circuitry for RF PIN diode activation is also integrated with the antenna. Switching combinations of two PIN diodes offer four reconfiguration modes of operation at 4. 75, 5.05, 5.11, and 5.18 GHz. In all the states, the −10 dB bandwidth shows minimal changes with average variations of 15.8% with respect to the state when both PIN diodes are OFF. The gains of the antenna for different modes of operation are found almost stable with an average of 6.64 dBi.
Bismaleimide (BMI) resins are a new breed of thermosetting resins used mainly for high temperature applications and have major usage in aerospace. FTIR studies have shown the signatures of imide, CNC stretching, malemide and N-H stretching. These BMI polymer coatings were deposited on aluminum and mild steel substrates by sprinkling powers followed by baking.Thermo gravimetric analysis and Differential scanning calorimetric studies showed the degradation temperature of these polymers around 370 o C. Aluminum coatings were deposited on BMI previously deposited on Al and mild steel to make a metal-BMI-metal trilayer. These trilayers can solve the problem charging of the aircraft bodies at high altitudes. Atomic force microscopy was done to determine the morphology of the surface. Roughness and thickness measurements of the BMI coatings were carried out by surface profilometer. Vickers microhardness tests showed an increase in hardness of the metal-BMI-metal trilayer. FTIR spectrum showed signature of imides, CNC stretching, maleimide and N-H stretching in BMI.We observed that peak broadens at which shows the release of the stress during thermal treatment of the coating. The coating is subject to variable APPJ conditions which improve the properties at high temperature.
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