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CAREER: Microfluidically Loaded Highly Reconfigurable Compact RF Devices


Fig. 1 - Mm-wave (22 – 40 GHz) SPST switch microfluidically actuated with piezoelectric disk (12.7 mm diameter under the ground plane). Characterized to operate with: 0.42 dB insertion loss, 20 dB isolation, 12 mW power consumption (only during actuation), 25 W continuous RF power handling. The concept is being extended to multi-throw switches and beam-steering arrays.

Microfluidics based reconfiguration techniques can be harnessed to design and construct RF devices with large frequency tuning ranges and low insertion losses while providing significantly higher power handling capabilities. Our research in this area continued under multiple National Science Foundation (NSF) grants one of them being the prestigious CAREER award.

Replacement of liquid metals with metallized plates repositionable within microfluidics channels enabled to perform at much higher frequencies without reliability issues. A significant milestone has recently been reached by actuating the metallized plates within the microfluidic channels with piezoelectric disks as shown in Fig. 1.

This internal actuation mechanism removes the need for external microfluidic pumps while providing very low actuation time – initially characterized as ~1 ms for mm-wave SPST switches with possibilities to reduce further as research progresses. To the best of knowledge, these are the fastest microfluidically actuated RF devices reported to date with very high reliability. Such switches can handle continuous RF power levels up to 25 W with no addition of thick ground planes or heat sinks. Realization of multi-throw switches for efficient mm-wave beam-steering has also been recently proposed as shown in Fig. 1.

Other application areas being pursued are mm-wave reconfigurable filters, phase shifters, and focal plane beam-steering arrays. Click here for accessing our publication list.

Fully Packaged Wideband Phased Arrays Using Direct Digital Manufacturing

Under multiple research awards from Air Force SBIR, Army SBIR, Raytheon (America Makes) and Draper Labs, USF our group has worked on advancing the additively manufactured antenna and phased array technology. We particularly focus on Direct Digital Manufacturing (DDM) technology that allows implementing compact, cost-effective, lightweight multilayer RF devices exhibiting alternating dielectric and conductive layers. The design flexibilities in making material choices, layer thicknesses, and material shapes allow the additively manufactured RF device performance to meet or exceed the performance level of those implemented with the well-established traditional manufacturing approaches.

In an ongoing partnership with Scipeiro Inc., we are developing fully packaged, low-cost, low-profile and conformal wideband phased arrays in X-band by strategically utilizing the unique capabilities of the Direct Digital Manufacturing (DDM) in the design and fabrication. Our team successfully demonstrated phased array unit cells fully packaged with COTS MMIC QFN phase shifters and embedded cavities as shown in Fig. 2. The unit cells are characterized to operate with 24% impedance bandwidth and > 80% radiation efficiency with > 20 dB front-to-back radiation ratio. The unit cell overall consists of nine material layers. Unit cells are being now utilized towards realization of beam-steering arrays with the inclusion of more material layers and necessary design modifications. Array details are currently not available for public release.

DDM capabilities can be harnessed to realize antennas and arrays operating from low GHz frequencies to beyond mm-wave bands. When necessary, our team utilizes picosecond laser capability within the DDM process to perform IC and antenna packaging at the die level with minimum feature sizes reaching down to 10 µm. Click here for accessing our publication list.

Fig. 2 - Fully packaged X-band antenna element with embedded cavity for platform installations and MMIC phase shifter for beam-steering capability within a phased array. It consists of nine material layers with customized dielectric constants and thicknesses. Demonstrates 24% impedance bandwidth, >80% radiation efficiency, >20 dB front-to-back radiation ratio. Phase shifting states (6 bit) are successfully verified.

Fig. 3 - A volumetric 3D printed cavity backed spiral antenna performing with better miniaturization ratio with respect to traditional miniaturization techniques.

Miniature Antennas, Arrays, and Filters

Fig. 4 - Compact 2x2 GPS antenna array loaded with metamaterial resonators for reduced mutual coupling and improved nulling capability.

Fig. 5 - Compact X-band band-stop filter realized with thin film manufacturing techniques.

Under multiple research awards from our industry partners and National Science Foundation (NSF), our group has developed novel miniature antennas, arrays, and filters. As an example, Fig. 4 shows a small footprint dual-band (L1/L2) GPS antenna array loaded with broadside-coupled split ring resonators (BC-SRR) for mutual coupling reduction and improved nulling capability. Fig. 5 depicts a compact X-band band-stop filter realized with miniaturized open loop resonators and thin film manufacturing techniques.

Our group regularly employs electromagnetics theory and full-wave electromagnetics modeling/simulation with in house manufacturing capabilities (e.g. single and multiple layer PCBs, photolithography, thin film dielectrics, advanced 3D printing and conductive deposition facilities, etc) to address the specific needs of novel/enhanced RF systems. Click here for accessing our publication list.




Dr. Gokhan Mumcu
mumcu@usf.edu
Department of Electrical Engineering
University of South Florida
4202 E Fowler Ave Stop ENG 003
P:(813) 974-8178