An ultra-thin switched state active frequency selective surface absorber with wide bandwidth using semi-analytical method

Using low-voltage forward biased PIN diodes, an ultrathin switched states active frequency selective surface based microwave absorber is designed. Using a semi-analytical method, the NXP#BAP70-03 PIN diode-based single polarised unit-cell of the active FSS absorber is rigorously analysed and its equivalent circuit model is developed. The unit-cell of the structure is selected as such to increase the envelope of the operating bandwidth and thus a total measured operating bandwidth extending from 1.70 to 11.36 GHz with reflectivity ≤−10 dB and the fractional bandwidth of 148.4% is achieved. This envelope also contains a 21.05% minimum, and 94.76% maximum fractional bandwidths corresponding to their resonance frequencies. It has been achieved by the absorber with the unit-cell size of 0.113λ_L × 0.113λ_L × 0.048λ_L where λ_L is the wavelength corresponding to the lowest operating frequency. The structure has been fabricated and experimentally verified for the normal and the angular incidences of the electromagnetic wave up to 30°. An exhaustive state-of-art comparison has also been made to demonstrate the novelty of the proposed work. Due to its low thickness of 0.048λ_L, and wide envelope of the operating bandwidth; it is a potential candidate for a smart stealth system, electromagnetic camouflage, and adaptive radar absorbing materials.