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In this study, a technique for designing a compact and low radar cross section (RCS) circularly polarized (CP) antenna is proposed. The designed CP antenna resonates at 8.7 GHz. The circular polarization is achieved by trimming opposite corners of the square patch and etching out thin slots. A new method is used to keep the radiation performance well preserved and to reduce the RCS of the CP antenna by employing polarization conversion metasurfaces. The PCM comprises double‐head arrow elements arranged around the CP antenna in four quadrants. Wideband monostatic RCS reduction is achieved for frequencies from 8.0 to 20 GHz. The experimental results verify the simulated ones, and also, the performance parameters such are realized gain, impedance bandwidth, axial ratio, and radiation pattern are well preserved after loading polarization conversion metasurface. [ABSTRACT FROM AUTHOR]

This work presents a wideband, all-side square-cut square patch multiple-input, multiple-output circularly-polarized (MIMO-CP) high-isolation antenna. The MIMO-CP antenna contains a two-port square cut on all corners of the square patch, and parasitic elements of 9 × 5 periodic square metallic plates are designed and operated. The outer dimensions of the antenna are 40 × 70 mm2, and the FR4 substrate height is 1.6 mm. The proposed antenna with the parasitic elements improves impedance matching and enhances S-parameters and axial ratio (AR). In the suggested MIMO-CP antenna, a parasitic element is designed and placed around the antenna periodically to reduce mutual coupling (MC) and improve CP. Simulated results show that the suggested antenna has a wide bandwidth (BW) from 4.89 to 6.85 GHz for S11 and was < −10 dB with AR ≤ 3 dB from 5.42 to 6.58 GHz, with a peak gain of 6.6 dB. The suggested antennas have more than 30 dB isolation and a low profile, are affordable, easily made, and are CP. To make a comparison with the measured and simulated results, a MIMO-CP antenna structure was fabricated and tested. The suggested antenna is better in terms of efficiency, envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL), and total active reflection coefficient (TARC). The proposed antenna is adequate for WLAN applications. [ABSTRACT FROM AUTHOR]

• Cube satellites are rapidly deployed in low earth orbit (LEO) to provide high data rate service to users. Cube satellites have been constellated to offer a fast and wide area coverage. • Due to the constellation of the cube satellites, a congested RF environment is created, causing signal interference between Rx and Tx systems. Along with the wide bandwidth, circular polarization, and high gain, a compact bandpass filtering system is required in the antenna to reject out-of-band noisy signals. • Artificial magnetic conductors (AMCs) are periodic elements located in the x and y direction that possess characteristics such as phase reflection between ± 90O while crossing 0O for incoming EM waves with different incidence angles. • A carefully constructed AMC can enhance wideband performance in terms of in-phase reflection and gain. To address the challenges as stated above, an angularly stable AMC-loaded antenna array and filter combined structure is modeled in this paper. This paper investigates an angularly stable artificial magnetic conductor (AMC) loaded circularly polarized (CP) antenna array and filter co-design for the K-band satellite application. The AMC array is constructed from a periodic array of square metal patch unit cells with rectangular and annular slots. The AMC unit cell has good angular stability under various incidence angles and operates in a frequency range of 18 GHz to 21 GHz. The AMC-surrounded and bandpass filter (BPF) loaded antenna array is simulated and fabricated on the single side of a 0.508 mm thick Roger/5880 substrate. The impedance matching, gain, directivity, and efficiency (%) are enhanced due to the constructive interference between AMC and antenna mutual coupling. In contrast, the axial ratio (AR) is preserved. The manufacturing of the proposed structure is comparatively less complex. Finally, based on the simulation and measured results, the suggested AMC-loaded compact, wideband, and filter-inserted array with enhanced gain and efficiency can be a good choice for the 3U satellite application working in K-band. [ABSTRACT FROM AUTHOR]

The proposed work describes a corner square-cut square-patch multiple-input multiple-output (MIMO) antenna with reduced mutual coupling for circular polarization (CP). A two-port MIMO-CP antenna was designed and operated at 5.6 GHz for wireless local area network (WLAN) applications. The dimensions of the MIMO-CP antenna were 22.5 × 50 mm 2 (0.43 λ 0 × 0.933 λ 0) and the FR4 substrate height was 1.6 mm. Between the two-elements, the edge-to-edge distance was 12.2 mm (0.227 λ 0 ), where λ 0 was the free space wavelength at 5.6 GHz. A slot was created in the middle of the ground in the proposed MIMO antenna to reduce mutual coupling and improve CP. The ground slot improves impedance matching and provides a better S-parameter and axial ratio (AR), according to the antenna results. According to the simulated results, the proposed antenna bandwidth of 5.23–6.42 GHz (21.4%) for S11 were < − 10 dB, isolation was −37 dB with a peak gain of 6 dB and AR ≤ 3 dB from 5.37 to 5.72 GHz (6.25%). The proposed antennas are simple to fabricate, have low profiles, are inexpensive, have good isolation, and are CP. The diversity gain (DG) and envelop correlation coefficient (ECC) results are better in the simulated frequency band. A MIMO-CP antenna geometry prototype is built and measured for comparison, yielding good results when compared to the simulated and measured results. The MIMO-CP antenna, as designed, is suitable for WLAN applications. [ABSTRACT FROM AUTHOR]

In this research work, a wideband metamaterial‐inspired circularly polarized antenna array is designed. The designed antenna array has a low radar cross‐section (RCS) but high gain. The basic element of the planar array is analyzed as a dual‐band electromagnetic absorber. Under normal incidence, the designed basic element has two absorbing peaks at 3.6 and 11.2 GHz. Further, four elements of the 4 × 4 elements array are connected to the feeding network through metallic vias. The feeding network is designed on the bottom layer. The circular polarization is archived by feeding the cross shape metallic resonator at two feed points, in a manner that there is a 90° time phase difference between the fields of two. It is shown that a good axial ratio is obtained over a wideband. This design method simultaneously validates high gain antenna performance and also meets the conditions of low‐RCS. [ABSTRACT FROM AUTHOR]

This paper presents a wideband metasurface, based on polarization conversion operation and its application for the radar cross-section (RCS) reduction of an isolated MIMO antenna. The wideband metasurface is capable of converting linear polarization to orthogonal and circular polarizations. Linear polarization conversion is achieved over a wideband frequency range of 7.6–9.0 GHz. Whereas, linear-to-circular polarization is achieved in two different bands, from 7.10 to 7.40 GHz and 9.20 to 9.45 GHz. The RCS reduction is accomplished by destructive interference of the scattered waves, through the two sides of the designed metasurface. RCS reduction is achieved from 7.6 GHz to 8.6 GHz, with a maximum reduction of −32 dB at 7.6 GHz. To validate the RCS reduction, the polarization conversion metasurface is integrated with the isolated MIMO antenna working from 8.0–8.6 GHz, with high isolation of −25 dB. The radiation characteristics of the MIMO antenna are well preserved. The proposed integrated metasurface MIMO antenna is experimentally validated to verify the simulated results. [ABSTRACT FROM AUTHOR]