Electric Tunable Radar Absorbers

Extending absorbant band is always the challenge of radar stealthy materials with definitely thickness and dielectric limit on absorbant band of radar absorbers. Focused on the dire need of electric tuned radar absorbers, we investigated the absorption and tunable properties of radar stealthy materials. What's more, models of the electric tuning radar absorbers were built and the model of wider band absorber was optimized by simulations and verified experimentally.Absorbing materials containing changeable resistance square patches were designed. The simulation on the law of reflectivity tuned with the resistance showed that reflectivity of the absorbers could be tuned by resistance in a wider frequency band. The law of resistance-current was studied by measuring voltage-current curves of PIN diode. The absorbers mounted PIN diodes were fabricated. Reflectivity test results verified that reflectivity was able to be tuned by increasing positive dc biasing current (decreasing the resistance) and help the absorption peaks tune to low frequency in the range of 2~8GHz. The influences of the period demission to the absorption were studied. The result indicated that the absorption between 10~14GHz could be stronger by the smaller period size.We designed electric tuning radar absorbers with different down-lead shape and studied on the influence of metal down-lead shape. The results indicated that when the width of the down-lead increased, the tuned band increased, but the band of the absorption peaks decreased. At the same time, the reflectivity tunable properties was able to be improved in the range of 8~15GHz. When the length down-lead increased, the absorption peak moved to the low frequency, while the band of the absorption peak increased and the tunable properties improved. The most exciting one was the down-lead shape changing into bow-tie shape. Comparing with the rectangular down-lead, their absorbent band is much wider.The influences of laying biasing line were also important to the absorbed capability of absorbents. Biasing line laying with inductive and rear through vais, the intrinsic frequency was presented. The reflectivity on the intrinsic frequency remained stable under variety positive dc biasing currents. It can be seen by the result that laying biasing line with capacitive was good for possessing tunable properties. Electric tunable radar absorbers with different distance showed us that the capacitance of the AFSS and the absorption band increased by the distance increasing.The influences of the spacer were also considered. The electric tunable radar absorbers which contained different thickness and dielectric of spacers were fabricated. The tests showed that when the thickness and dielectric real of the spacers increased, the absorption peak tuned to low frequency. Finally, the models of the electric tuning radar absorbers fabricated by PIN diode were founded. Comparing simulations and the experiment results, the model we set in this paper could show the tuned law of absorption peaks. According to the design, broadband tunable properties was simulated and optimized in 2.85z~17GHz and electric tunable radar absorbers absorbed intensity was -8dB.