A generalization of the tree-cotree technique for the removal of imaginary and dc spurious modes in finite-element-based eigenanalysis of 3-D lossy unbounded structures is introduced. Five frequently encountered types of polynomial eigenvalue problems are tackled including: 1) closed structures with finite metals conductivity losses; 2) closed structures with material losses due to migrating charge carriers; 3) open-radiating structures using the absorbing boundary conditions of both first-and second-order; 4) open-radiating structures with finite conductivity metallic objects; and 5) any combination of the aforementioned cases. The resulting polynomial eigenvalue problems are linearized utilizing both the companion and the symmetric approaches. The different linearization techniques are being compared for their efficiency and robustness.
Millimeter wave (mm-Wave) technology is likely the key enabler of 5G and early 6G wireless systems. The high throughput, high capacity, and low latency that can be achieved, when mm-Waves are utilized, makes them the most promising backhaul as well as fronthaul solutions for the communication between small cells and base stations or between base stations and the gateway. Depending on the channel properties different communication systems (e.g., beamforming and MIMO) can accordingly offer the best solution. In this work, our goal is to design millimeter wave beamformers for switched beam phased arrays as hybrid beamforming stages. Specifically, three different analog beamforming techniques for the frequency range of 27–33 GHz are presented. First, a novel compact multilayer Blass matrix is proposed. Second, a modified dummy-ports free, highly efficient Rotman lens is introduced. Finally, a three-layer true-time-delay tree topology inspired by microwave photonics is presented.
This paper presents the design process of a multi-radii monofilar helical antenna that can operate in three different bands with circular polarization. The antenna is comprised of two helical antennas with different radii that are embedded and supported by an innovative structural technique. This allows reconfigurable behavior, efficient folding, packaging, and deployment. The antenna is fabricated using 2-mil-thick-FPC Kapton with a 3-mil copper trace glued appropriately on the top. An actuation mechanism of telescopic form is used for the stress-free deployment of the proposed design. The proposed origami antenna can adjust its band of operation by changing its height; therefore, it is physically reconfigurable. The main advantage of this antenna is that it can cover multiple applications, such as GPS, WiMAX, and satellite radio communications with a measured maximum right-hand circularly polarized realized gain of 6.3, 12.7, and 10.5 dB, respectively, thereby eliminating the need for multiple antennas.INDEX TERMS Circular polarization, origami, reconfigurable, multi-radii helix.
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