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College of Engineering and Computing

Microwave Engineering Lab

Description: The Microwave Engineering Lab is focused on conformal antennas, broadband metamaterials, conformal broadband pixelated reconfigurable antennas, conformal reconfigurable antennas, low cost phased arrays for portables/wearables, wireless power transfer and wireless sensing.
Area: Smart antennas; Broadband metamaterials; Wireless power transfer; Wireless sensing
Email: alimo@cec.sc.edu
Phone: 803-777-1488
Location: Department of Electrical Engineering, University of South Carolina
Columbia, SC 29208
Director: Ali, Mohammod

About:

The Microwave Engineering Lab researches in the areas of conformal antennas, broadband metamaterials, conformal broadband pixelated reconfigurable antennas, conformal reconfigurable antennas, low-cost phased arrays for portables/wearables, wireless power transfer and wireless sensing. Learn more about these areas and our capabilities below.

Conformal antennas are both antennas and structures at the same time. Having the ability of using the surface of a structure allows the design of conformal high-performance antennas. Examples include conformal Log-Periodic Dipole Arrays, Log-Periodic slot Arrays, cavity backed spirals, waveguide slot arrays, microstrip patch phased arrays, and distributed array of dipole radiators to name a few. Applications include cognitive radio, geological survey and wireless internet to remote areas.

Electromagnetic Bandgap (EBG) materials are engineered structures. Many applications need directional dipole, spiral antennas that can be flush mounted on the surface of a structure. But the presence of the ground plane below the antenna poses a challenging environment to develop very thin conformal antennas. Typically, the antenna height can very well exceed 3-5 inches at UHF (Ultra High Frequency) frequencies. Recently we demonstrated that by designing and using a Non-Uniform Aperiodic (NUA) metasurface a dipole can be placed less than one inch from the ground for operation from 570-1100 MHz.

Pixelated antennas present a unique opportunity to ideally reconfigure infinite number of antenna shapes and sizes. However, the feeding constraints, materials, and device availability, integration, and biasing present the challenges to attain the highly desired properties e.g. high gain, broad bandwidth, and large Forward to Backward Ratio (F/B). In our research, broad bandwidth is achieved using by reconfiguring a pixelated antenna in an aperture coupled patch concept.

Antennas that can be reconfigured with respect to frequency, pattern, polarization, etc. have gained notice from engineers and researchers for the advantages they provide. Of particular interest are pixelated antennas which make use of individual conducting pixels to form changeable aperture geometry. This makes broadband or multiband operation feasible using a single antenna.

These arrays are designed using the parasitic antenna arrays concept where the parasitic elements are controlled using RF switches. Unlike traditional phased arrays where elements are placed half wavelength apart and are controlled using expensive phase shifters our proposed array consists of parasitic elements that are placed 1/30th of the wavelength from each other. By controlling the distances between the driven and the parasitic elements and the feed-point impedances of the parasitic elements the array beam can be steered in space. For the first time, beam steering (Ali) approaches at the mobile are being combined with time-frequency utilization considering enhanced partially overlapped domains (Arslan).

Historically, wireless power transfer has adopted one of two principles, near-field and far-field power transfers. The former applies to very short distance power transfer where power is transferred through magnetic fields that are coupled between the transmit and receive sides. Examples include RFID systems, wireless cell phone battery charging, vehicle battery charging using below the pavement magnetic coils. In most cases these are achieved at frequencies below 100 MHz and at distances of at most several feet. Cases where wireless power needs to be transmitted over large distances the method of transmission is called far-field where the transmit and receive antennas are no longer coupled to each other. Power transfer is governed by the Frii’s transmission formula. UofSC researchers in Dr. Ali’s lab have done considerable amount of work on wireless power transfer and rectifying antennas. A rectifying antenna or rectenna is an antenna and a rectifier integrated together that receives RF power and converts that to DC.

 


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