Shoaib Muhammad

60-GHz Textile Antenna Array for Body-Centric Communications

To demonstrate that commercial textiles can be used as antenna substrates at millimeter waves, a microstrip patch antenna array printed on textile is proposed for off-body communications in the 60-GHz band. The textile substrate is characterized in V-band using the open stub technique. A new fabrication process is introduced for the reliable and accurate manufacturing of millimeter-wave microstrip antennas on textiles. The antenna reflection coefficient, radiation patterns and efficiency are studied in free space, with and without bending, and on a homogeneous skin-equivalent phantom. The numerical and experimental results are in a good agreement. To the best of our knowledge, this is the first textile millimeter-wave antenna optimized for off-body communications presented in the literature at millimeter waves.

Small-Size Shielded Metallic Stacked Fabry–Perot Cavity Antennas With Large Bandwidth for Space Applications

New configurations of small-size shielded metallic Fabry-Perot (FP) antennas with improved performance over a large frequency band are presented in S-band for space missions. The bandwidth enlargement is obtained by stacking two FP cavities of different size, each of them presenting a low quality factor. Their radiating apertures measure around λ0 and 2 × λ0, respectively. Concentric corrugations are also introduced between both cavities to control the higher-order modes that are excited systematically in shielded small-size FP antennas due to lateral resonances. The obtained results are compared to those of a single-stage FP cavity antenna with the same aperture size. Several prototypes have been fabricated and measured. An aperture efficiency higher than 70%, a reflection coefficient smaller than -15 dB, and sidelobe levels lower than -20 dB have been obtained experimentally, over a wide frequency band (2.4-2.66 GHz). These characteristics make stacked FP cavity antennas very attractive to replace global coverage horn antennas, or to be used in feed clusters of multiple-beam antennas, especially in C- and S-bands, where they lead to more compact and less bulky solutions compared to classical feed horns.

Self-Generation of Circular Polarization Using Compact Fabry–Perot Cavity Antennas

A new configuration of a compact self-polarizing Fabry-Perot (FP) cavity antenna is presented. It is excited in single-linear polarization at 45° and radiates in circular polarization. It consists of a polarizing FSS (used to ensure the polarization conversion) and a corrugated ground plane (designed to guarantee the resonance conditions for both incident orthogonal linear polarizations). A compact shielded FP antenna with an aperture of 1.62 λ0 is optimized and fabricated in S -band to validate the concept at 2.5 GHz. A 3-dB axial-ratio bandwidth of about 1.9% is achieved with an antenna height of only 0.8 λ0. The experimental results are in good agreement with the simulations. This antenna configuration is attractive for narrowband applications, like the space ones in C- or S-bands.

Self-Polarizing Fabry–Perot Antennas Based on Polarization Twisting Element

A new configuration of a self-polarizing Fabry-Perot (FP) antenna is presented to generate circular polarization with high gain levels using a simple linearly polarized feed. It consists of an FP resonator combined with a polarization-twisting ground plane. An analytical model is proposed to facilitate the antenna design, and the corresponding results are shown to be in very close agreement with full-wave simulations. The experimental prototype built in -band exhibits a combined bandwidth (3 dB axial ratio, 3 dB gain drop, and 10 dB impedance matching) of 3% with a maximum realized gain of 18.0 dB. The antenna is completely shielded with an aperture size of and a height of only . Such antennas are attractive candidates for high-power space applications at low frequencies ( -to -bands) where standard horns are very bulky.

Hexagonal-Shaped Broadband Compact Scrimp Horn Antenna for Operation in

The performance of compact linearly polarized Short Circular Ring-loaded horn with Minimized cross-Polarization (Scrimp) horns with different aperture sizes is first evaluated using an in-house finite-difference time-domain (FDTD) computer-aided design (CAD) tool. Then, a very short hexagonal Scrimp horn with an aperture size of 1.5λ0 is designed in C -band; its height is only 1.26λ0 . The experimental results demonstrate that the aperture efficiency is higher than 80% with a reflection coefficient lower than -17 dB over a 12.6% frequency bandwidth. Radiation patterns of excellent quality are measured with a cross-polarization level lower than - 28 dB over the entire bandwidth. These antennas are very attractive candidates for high-power focal array configurations in multifeed systems.