This paper discusses how to optimize the weighting of individual subarrays to derive the low sidelobe level (SLL) based on quadratic programming (QP) and how to derive QP parameters to ensure that the objective function is composed of the quadratic function form, with the actual number identical to the standard objective function of QP. Next, in order to analyze the SLL, a 24 × 24 phased array antenna was compared with 96 transmit–receive modules (TRMs) attached only to the subarray stage and a phased array antenna with 576 TRMs attached to all radiating elements without a subarray. Optimized weighting was applied to the array antennas with a subarray, and Taylor weighting was applied to the array antennas without a subarray. The number of TRMs used in the phased array antenna with the optimized weighting was reduced by 83.3% compared to the phased array antenna in which TRMs were attached to all radiating elements. The SLL and the half-power beamwidths (HPBWs) of the two antennas were practically identical in a narrow beam-scanning environment. Finally, an array pattern (AP) in which mutual coupling between the radiating elements was considered was calculated to verify the optimized weighting. Moreover, the optimized weighting was applied to CST Microwave Studio (an EM full-wave simulation) to compare the results from the AP calculation and a simulation. It was confirmed that the two results above are largely indistinguishable. The analysis found that the HPBW is 3.6∘× 3.6∘ and the SLL is −26.18 dB from AP calculations in the boresight direction. When each 5∘ beam was scanned at the azimuth and elevation, the corresponding HPBW values were 3.7∘× 3.7∘ and 3.7∘× 3.7∘ and the SLLs were −22.70 dB and −24.44 dB according to the AP calculations.

Extraordinary transmission (ET) by a periodic conducting slot at normal incidence has potential applications in the optical and microwave frequencies. This paper presents a simple analytical model to account for the effects of oblique incidence of electromagnetic (EM) waves on a slotted periodic structure. The proposed analytical model, based on Floquet and circuit theory, provides physical insight to explain the reduction of ET frequency when the EM wave strikes the structure obliquely: ET occurs before the onset of the grating lobe. Higher evanescent Floquet modes contribute to the stored energy that represents fringing capacitance in terms of the incoming wave. Transmission bandwidth and material loading effects are also investigated. When applied on an artificial magnetic conductor (AMC), the model indicates that the thickness of the AMC can be dramatically reduced without any material loading. Results obtained by the analytical models are compared by full-wave simulations.Index Terms-Artificial magnetic conductor (AMC), equivalent circuit (EC), extraordinary transmission (ET), oblique incidence.

A composite frequency-selective surface (FSS) fabricated by using an e-beam evaporator is proposed. This manufacturing process is advantageous in that it can directly achieve an FSS function for real structural surfaces with various skin conformations. A multilayered patchgrid-patch-type FSS consisting of copper layers as capacitive or inductive surfaces and a glass/epoxy prepreg as the substrate is produced. It operates at 9-10 GHz for dual polarisation. This technique can be used to manufacture a stealth technology for communicating in a specific frequency range.

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A dual-mode annular ring antenna for both global positioning system (GPS) and satellite digital multimedia broadcasting (S-DMB) is designed. The proposed antenna consists of a coupling feed line and four slots on an annular ring patch. A gap between the feed line and the annular ring patch is used for an input impedance matching; the slots are used for adjusting the resonant frequency of the TM 21 mode at the DMB frequency. The antenna was fabricated and measured. The antenna resonates at the GPS and DMB frequencies with suitable bandwidths. It has a broadside radiation pattern in the GPS band and a conical beam radiation pattern in the DMB band.