Graduation Year

2019

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Electrical Engineering

Major Professor

Thomas M. Weller, Ph.D.

Committee Member

Stephen Saddow, Ph.D.

Committee Member

Thomas Ketterl, Ph.D.

Committee Member

Gokhan Mumcu, Ph.D.

Committee Member

Yu Sun, Ph.D.

Keywords

3-D Printing, MMIC Packaging, Multipath environments, Package integrated antennas, Picosecond laser machining

Abstract

Four main aspects are studied and explored throughout this dissertation: (1) On-Package Multipolar antenna system design for integration with commercial wireless sensor nodes for machine-to-machine communication applications; (2) Development of a novel MMIC packaging process and subsequent antenna integration for chip-to-chip communication applications, (3) Design and characterization of additively manufactured lumped passive elements for integration with MMIC and hybrid circuits, (4) Design and characterization of antennas for on- and off-metal radio frequency identification (RFID) applications.

This work presents the design of different 3-D printed tripolar antenna systems operating at 2.4 GHz. The antennas are designed for integration with commercial wireless nodes with the purpose of mitigating multipath and depolarization channel effects that might be present in many machine-to-machine (M2M) deployments. The antennas are fabricated utilizing an additive manufacturing (AM) approach that combines fused deposition modeling (FDM) of ABS plastic for dielectric parts and micro-dispensing of silver paste Du-Pont CB028 for conductive layers as the majority of the devices presented in this work. Over the air testing demonstrates a 1% channel improvement of up to 14 dB, achieved in a highly-reflective, Rayleigh-like fading environment by implementing selection diversity between three mutually orthogonal monopoles. This improvement leads to better bit error rate (BER) performance (as is also shown). Additionally, RSSI measurements show significant improvement when the prototype antenna system is integrated with commercial wireless sensor hardware. Implications of tripolar antenna integration on M2M systems include reduction in energy use, longer communication link distances, and/or greater link reliability.

In order to incorporate the proposed multipolar selection diversity technique into short range wireless chip-to-chip communications, a novel and versatile 3D printed on-chip integration approach using laser machining is subsequently demonstrated for microwave and mm-wave systems in a process herein referred to as Laser Enhanced or Laser Assisted Direct Print Additive Manufacturing (LE-DPAM). The integration process extends interconnects laterally from a MMIC to a chip carrier. Picosecond laser machining is applied and characterized to enhance the 3D printing quality. Specifically, the width of micro-dispensed printed traces is accurately controlled within micrometer range (e.g. laser cuts ~12 μm wide), additionally, 150 μm probe pads are cut in order to facilitate RF measurement. The S-parameters of a distributed amplifier integrated into the package are simulated and measured from 2 to 30 GHz. It is seen how the overall performance is significantly better than a traditional wirebonded QFN package and previously reported AM MMIC interconnections. The attenuation of the microstrip line including interconnects is only 0.2 dB/mm at 20 GHz and return loss with the package is less than 10 dB throughout the operating frequency band

A 17 GHz package integrated linearly polarized patch antenna, fabricated with a multi-layer and multi-material LE-DPAM process is then introduced for vertical interconnection with a MMIC die. Performance is successfully measured and characterized achieving a return loss greater than 19 dB at the desired design frequency. Good agreement between simulated and measured radiation patterns is also obtained with a peak gain of 4.2 dBi.

Another section of this work utilizes LE-DPAM to fabricate lumped capacitors and inductors for coplanar waveguide (CPW) circuits, especially useful for filtering and matching network implementation. Laser machining is used to achieve ~12 µm slots on printed conductors, producing aspect ratios greater than 2:1, as well as to fabricate vertical interconnects or vias that allow for the fabrication of the multilayer inductors. Inductances in the range of 0.4-3 nH are achieved, with a maximum quality factor of 21, self-resonance frequencies up to 88 GHz, and an inductance per unit of area of 5.3 nH/mm2. Interdigital capacitors in the range of 0.05-0.5 pF are fabricated, having a maximum quality factor of 750 and self-resonances up to 120 GHz. All the components are made on the center line of a CPW that is 836 µm wide. The results show that LE-DPAM enables the fabrication of compact passive circuits that can be easily interconnected with MMIC dies, which at the same time, can be manufactured as part of a larger component. This enables the fabrication of structural electronics that are functional into the mm-wave frequency range.

A final aspect of this work goes through antenna designs for specific RFID (radio frequency identification) applications. RFID tag design is generally focused specifically on either off-metal or on-metal configurations. In this work passive 2D and 3D RFID tags are presented which perform similarly in both configurations. The presented tags operate in the ISM RFID UHF bands that cover 864-868 MHz and 902-928 MHz. A matching loop consisting of two parallel stubs to ground is used for impedance matching to a passive integrated circuit, which has -18 dBm sensitivity. A planar 2D tag with a footprint of 13126.5 mm2 is first introduced, showing a simulated gain of approximately 3 dBi and a measured read range of 10 m (for 31 dBm transmit power from the reader) in both on-metal and off-metal conditions. The tag is miniaturized into a 3D geometry with a footprint of 2524.25 mm2 (520% reduction) and achieves the same broadside simulated on-metal gain. The antennas are fabricated using a DPAM process, and a meshed ground configuration is explored in order to accomplish a 50% conductive paste reduction without disrupting the performance. The proposed tags are compared with commercially available tags as well as previously published tags in terms of read range and size. The tags in this work present an improvement in terms of read range, gain, and area with respect to previous designs covering the ISM RFID UHF bands. Moreover, the performance of these tags is maintained in on- and off-metal conditions, achieving comparable performance and a reduction in volume of 11482% with respect to the best tag reported.

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