Omid Manoochehri

Bio: Omid Manoochehri is an academic researcher from University of Illinois at Chicago. The author has contributed to research in topics: Antenna (radio) & Microstrip. The author has an hindex of 8, co-authored 26 publications receiving 244 citations. Previous affiliations of Omid Manoochehri include Tarbiat Modares University.

$\Pi$ -Model Dual-Band Impedance Transformer for Unequal Complex Impedance Loads

Abstract: This letter presents a $\pi$ -model dual-band impedance transformer which can match two unequal arbitrary complex loads at two frequencies. The required nonlinear simultaneous equations are derived to obtain the physical parameters of transmission lines and stubs. Return loss for the proposed matching circuit is measured to validate the results of the presented structure simulations. Excellent agreement between analytical and measured results confirms the proposed structure.

Ultra-Wideband Scanning Antenna Array With Rotman Lens

Abstract: An ultra-wideband (6–18 GHz) phased-array antenna with a beam scanning angle of ±28° is proposed. A step-by-step design procedure consisting of beamforming network (BFN), end-launcher feed adapter, and the radiating element is presented. Microstrip Rotman lens has been designed to act as the BFN, and optimized to achieve minimum phase-error over the whole frequency range. In order to satisfy the condition needed for avoiding grating lobes, as well as achieving a wide radiation bandwidth and a high power handling capability, an $E$ -plane double-ridged horn antenna is used as the radiating element. A novel wideband end-launcher coaxial to double-ridged waveguide transition has also been developed for connecting the BFN to the antenna array. Extensive optimization procedures have been applied to the end-launched adapter together with the antenna to achieve the best return loss over the frequency band of operation. The whole system has been simulated using CST full-wave simulator. An excellent agreement between the measurements of the fabricated system and the simulated results is observed.

A Parallel Plate Ultrawideband Multibeam Microwave Lens Antenna

Abstract: An ultrawideband multibeam microwave lens antenna operating from 8 to 18 GHz is proposed. The antenna consists of four excitation ports connected to a parallel plate waveguide filled with a cylindrical dielectric slab, which serves as a lens in order to modify the cylindrical wavefront launched by the excitation ports. The output of the lens is a plane wave guided to a radiation aperture with a linear tapered flare. Four distinct fan-beams covering 40° in the azimuth plane with an elevation beamwidth of 30° and a minimum gain of 15 dBi have been achieved. The main advantages of our design include its relative simplicity, ease of fabrication, having a low profile, not requiring an antenna feed, and high-power handling capability. The design procedure is presented together with the optimization procedures. The proposed structure has been simulated with the CST software and fabricated. There is an excellent agreement between the simulation and measurement results.

Miniaturized Microstrip Ring Hybrid with Defected Microstrip Structure

Abstract: A method for miniaturization of microstrip rat-race hybrid with the aid of “defected microstrip structure (DMS)” is proposed. Each transmission line section is loaded with cascaded DMS sections. This results in slow-wave characteristics which in turn increases the electrical length of the line. In the frequency range below the bandgap, the phase of S21 is negative and DMS behaves as a slow wave device; allowing a miniaturized structure. A reduction of 50% in the occupied area of the circuit and no bandwidth reduction is achieved using this technique. The miniaturized rat-race operates at 3.4 GHz and can be used in LTE systems. The circuits are fabricated and the measured and simulated results are in excellent agreement. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2245–2248, 2013

A dual-polarized biconical antenna for direction finding applications from 2 to 18 GHz

Abstract: An ultra-wideband dual-polarized structure based on a biconical antenna for direction finding application from 2 to 18 GHz is proposed. In addition to direction finding, the proposed structure may be used for broadband communications and radar systems. The structure consists of a biconical antenna that is surrounded by 5 layers of polarizers, which create slant polarization to receive both vertically and horizontally polarized signals. The VSWR is below 2.5 in the operational bandwidth. The whole structure has been simulated using CST software, fabricated, and measured. A good agreement between measurements and simulated results is observed.

Quasi-Optical Multi-Beam Antenna Technologies for B5G and 6G mmWave and THz Networks: A Review

Abstract: Multi-beam antennas are critical components in future terrestrial and non-terrestrial wireless communications networks. The multiple beams produced by these antennas will enable dynamic interconnection of various terrestrial, airborne and space-borne network nodes. As the operating frequency increases to the high millimeter wave (mmWave) and terahertz (THz) bands for beyond 5G (B5G) and sixth-generation (6G) systems, quasi-optical techniques are expected to become dominant in the design of high gain multi-beam antennas. This paper presents a timely overview of the mainstream quasi-optical techniques employed in current and future multi-beam antennas. Their operating principles and design techniques along with those of various quasi-optical beamformers are presented. These include both conventional and advanced lens and reflector based configurations to realize high gain multiple beams at low cost and in small form factors. New research challenges and industry trends in the field, such as planar lenses based on transformation optics and metasurface-based transmitarrays, are discussed to foster further innovations in the microwave and antenna research community.

Printed Diodes: Materials Processing, Fabrication, and Applications.

Abstract: Printing techniques for the fabrication of diodes have received increasing attention over the last decade due to their great potential as alternatives for high-throughput and cost-effective manufacturing approaches compatible with both flexible and rigid substrates. Here, the progress achieved and the challenges faced in the fabrication of printed diodes are discussed and highlighted, with a focus on the materials of significance (silicon, metal oxides, nanomaterials, and organics), the techniques utilized for ink deposition (gravure printing, screen printing, inkjet printing, aerosol jet printing, etc.), and the process through which the printed layers of diode are sintered after printing. Special attention is also given to the device applications within which the printed diodes have been successfully incorporated, particularly in the fields of rectification, light emission, energy harvesting, and displays. Considering the unmatched production scalability of printed diodes and their intrinsic suitability for flexible and wearable applications, significant improvement in performance and intensive research in development and applications of the printed diodes will continuously progress in the future.

Broadband quasi-taper helical antennas

Abstract: A unique approach is described for widening the bandwidth of a helical antenna with improved gain, pattern, and axial ratio characteristics. The antenna may be described as a nonuniform or quasi-taper helix, which consists of a combination of uniform and tapered helix sections. Measured patterns, gain, axial ratio, and VSWR for various helical antenna configurations are presented and compared. It is shown that a nonuniform quasi-taper helix can provide an operating bandwidth twice that of a conventional uniform-diameter helix.

2-D Scanning Magnetoelectric Dipole Antenna Array Fed by RGW Butler Matrix

Abstract: In this paper, a 2-D scanning magnetoelectric (ME) dipole antenna array fed by printed ridge gap waveguide (PRGW) Butler matrix is proposed. The ME dipole antenna is designed to achieve a bandwidth wider than 20% at 30 GHz and stable gain of 6.5 ± 0.8 dB over the operating frequency bandwidth. A $4\times 4$ planar PRGW Butler matrix is designed and constructed using a four PRGW hybrid couplers having a wide bandwidth performance. The overall performance of the Butler matrix exhibits about 5° phase error over the operating frequency bandwidth. The integration of ME dipole antennas with the designed Butler matrix results in four fixed beams, one in each quadrant at an elevation angle of 35° from the broadside to the array axis. The proposed passive beam switching network (BSN) has a wide bandwidth of 20% with radiation efficiency higher than 84% over the operating bandwidth. The proposed BSN shows a stable radiation pattern with a stable gain of 10.3±0.2 dB, where the sidelobe level is less than −15 dB over the whole operating frequency band. The fabricated prototype of the proposed BSN is tested, where the measured and simulated results show an excellent agreement.

Compact Air-Filled Luneburg Lens Antennas Based on Almost-Parallel Plate Waveguide Loaded With Equal-Sized Metallic Posts

Abstract: This paper presents a Luneburg lens and a Luneburg reflector lens along with the corresponding compact and cost-effective multibeam antennas in the Ka -band. The Luneburg lens is composed of an air-filled parallel plate waveguide (PPW) loaded with equal-sized metallic posts. The upper plate of the PPW is designed to a curved surface to meet the requirement of the equivalent refractive index profile, meanwhile providing a transition between the lens and the feed waveguide. Also, based on the law of reflection, a reflecting wall is introduced to the Luneburg lens to achieve a Luneburg reflector lens. By employing the WR28 rectangular waveguides as the feeders, the Luneburg lens/reflector lens antennas with single beam and multiple beams are designed and experimentally verified in the whole Ka -band. The multibeam Luneburg lens antenna show the beam scanning from −45° to +45° with 0.6 dB scan loss. The multibeam Luneburg reflector lens antenna show the beam scanning from 30° to 60° with 0.7 dB scan loss. Besides, the acceptable performances of aperture efficiency, impedance matching and multiport isolation are achieved. The results indicate that the works in this paper have application potential in the millimeter-wave (mmW) wireless communications.