Metamaterials with Active Circuits.
Xu, Wangren.
2013
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Abstract: The focus
of this dissertation is on embedding active circuits into metamaterials to mitigate some
of their intrinsic problems such as losses and to create new hybrid metamaterial
devices. The dissertation can be divided into four distinct contributions. For the first
contribution, an experimental demonstration of loss compensation in metamaterials using
embedded active transistor ... read morebased circuits is described. Each unit cell of the
metamaterial is embedded with a cross-coupled transistor pair based negative
differential resistance circuit to cancel these losses. Design, simulation and
experimental results for Split Ring Resonator (SRR) metamaterials with and without loss
compensation are presented. Results indicate that the quality factor (Q) of the SRR
improves by over 400% at 1.6GHz, showing the effectiveness of the approach. In the
second contribution, we demonstrate an example of a metamaterial absorber (MMA) detector
array that enables room-temperature, narrow-band detection of gigahertz (GHz) radiation
in the S-band (2-4 GHz). The system is implemented with a commercial printed circuit
board process and we characterize the detector sensitivity and angular dependence. A
modified MMA geometry allows for each unit cell to act as an isolated detector pixel and
to collectively form a focal plane array (FPA). Each pixel can have a dedicated
microwave receiver chain and functions together as a hybrid device tuned to maximize the
efficiency of detected power. The demonstrated sub-wavelength pixel shows detected
sensitivity of -77 dBm, corresponding to a radiation power density of 27 nW/m2, with
pixel to pixel coupling interference below -14 dB at 2.5 GHz. For the third
contribution, a diode switchable metamaterial reflector/absorber is demonstrated as
another application of metamaterials with active circuits. We embed diodes as active
circuit elements within the metamaterial array to implement a switchable metamaterial
reflector/absorber at microwave frequencies. Diodes are placed in series with the unit
cells of the metamaterial array. This results in just a pair of control lines to
actively tune all the diodes in an array. Tuning the diodes switches the function of the
metamaterial array between a perfect absorber and a reflector. The design, simulation
and experimental results of a switchable reflector/absorber in 2-6 GHz range are
presented in this dissertation. Lastly, we explore the utilization of CMOS technology
for making metamaterials. CMOS is the mainstream fabrication technology featuring low
cost, high yield and fast throughput. Continued scaling in CMOS process has resulted in
available feature sizes of tens of nanometers. It offers all the elements needed to
build new hybrid metamaterial devices including the multiple layers of metal, the vias
connecting them, diodes, resistors, capacitors, transistors, etc. Several 2D and 3D
metamaterial devices on CMOS are designed and simulation results are presented that
verify the feasibility of implementing metamaterials on CMOS. As proof of concept, a
metamaterial enhanced mid-IR detector array on CMOS is fabricated and tested. We scaled
the metamaterial enhanced detector design down to micrometer dimensions to make it
operational in the mid-IR band. Row/column decoder and readout circuits are implemented
with the metamaterial enhanced detector array monolithically on a commercial 45nm CMOS
chip. The simulation result verifies the design and the preliminary test results
validate the electronic circuits. Recommendations are made for future prospects of IR
based imager in CMOS process.
Thesis (Ph.D.)--Tufts University, 2013.
Submitted to the Dept. of Electrical Engineering.
Advisor: Sameer Sonkusale.
Committee: Willie Padilla, Chorng Hwa Chang, and Qiaobing Xu.
Keyword: Electrical engineering.read less - ID:
- vd66wb21f
- Component ID:
- tufts:22051
- To Cite:
- TARC Citation Guide EndNote
