The airborne radomes have to cater superior electromagnetic (EM) performance with bandpass characteristics of stealth application. In this regard, a hybrid A-sandwich radome is proposed in this paper. The proposed radome consists of a novel strongly coupled frequency selective surface (FSS) core sandwiched between two dielectric layers (acts as skin) to form an A-sandwich structure. The dielectric layers are cascaded in such a way that the middle layer has less dielectric parameters than the skin dielectric. The core layer comprises a modified FSS array using strongly coupled FSS layers through a series of metallic vias. This strongly-coupled FSS element will have the advantage of eliminating inter-element interference and improves the EM performance characteristics of the structure. The structure exhibits very good band-pass characteristics (>90%) at a normal impinging angle with sharp roll-off characteristics. To show the efficacy of the proposed structure, the transmission loss has been compared with that of conventional A-sandwich radomes at 0°, 50° incidence angle for both TE and TM polarization. Conformal analysis of the unit cell has been carried out, and sector-wise thickness optimization was performed to analyze the structure for the conformal shaped radome application. Finally, a physical prototype has been fabricated and measured its scattering parameters, radiation characteristics in a fully shielded anechoic chamber. The results are encouraging and prove its suitability for radome application.

In this work, a novel method for the mode content extrapolation in multimode waveguides with focus on the characterization of mode converters is presented. The proposed method is based on the direct determination of the correlation coefficients between the structural functions of all possible propagating modes and the complex measured near-field pattern. To implement the method, standard near-field equipment is simply required. Test simulations and measurements from 4 to 8 GHz on a 6-in. circular pipe for radar level monitoring are reported in the last section and demonstrate that the proposed technique provides accurate information about the mode content of the structure under test.