Kevin Geary

Single-Feed Dual-Band Stacked Patch Antenna for Orthogonal Circularly Polarized GPS and SDARS Applications

We describe a single-feed stacked patch antenna design that is capable of simultaneously receiving both right hand circularly polarized (RHCP) satellite signals within the GPS LI frequency band and left hand circularly polarized (LHCP) satellite signals within the SDARS frequency band. In addition, the design provides improved SDARS vertical linear polarization (VLP) gain for terrestrial repeater signal reception at low elevation angles as compared to a current state of the art SDARS patch antenna.

Millimeter- and submillimeter-wave characterization of various fabrics

Transmission measurements of 14 fabrics are presented in the millimeter-wave and submillimeter-wave electromagnetic regions from 130 GHz to 1.2 THz. Three independent sources and experimental set-ups were used to obtain accurate results over a wide spectral range. Reflectivity, a useful parameter for imaging applications, was also measured for a subset of samples in the submillimeter-wave regime along with polarization sensitivity of the transmitted beam and transmission through doubled layers. All of the measurements were performed in free space. Details of these experimental set-ups along with their respective challenges are presented.

Requirements for next generation automotive radars

Active safety is one of the most dynamic emerging topics in the automotive industry. Radars currently play a major role in providing sensing capabilities required to meet active safety requirements. Requirements, parameters, and characteristics of automotive radars change as a function of the operation range. The main goal of this work is to summarize sensing requirements of both short- and long-range automotive radars and to highlight present challenges to both systems. This work discusses various aspects of automotive radars, states their main challenges, and suggests possible solutions.

Next generation short range radar (SRR) for automotive applications

We discuss the unique requirements of automotive active safety systems which drive the challenging specifications of next-generation automotive short range radar sensors. Sensor level performance, vehicle integration, worldwide regulation, cost, and reliability are highlighted, along with possible paths towards achieving future performance metrics.

Automotive radar target characterization from 22 to 29 GHz and 76 to 81 GHz

The radar signatures of automotive targets were measured from 22 to 29 GHz and 76 to 81 GHz inside an anechoic chamber using a vector network analyzer. Radar cross section maps of a sedan, truck, van, pedestrian, motorcycle, and bicycle as a function of effective radar sensor bandwidth, center frequency, and polarization are presented.

Polymer Optical Waveguide Switch Using Thermo-Optic Total-Internal-Reflection and Strain-Effect

A new optical waveguide switch using thermo-optic total-internal-reflection and strain-induced effects in polymer materials has been experimentally demonstrated. The switch consists of three-layered slab waveguides and two metal strip lines that are located close to one another on top of the upper cladding. The deposition of metal strips introduces strain in the underlying polymer materials, creating two strain-induced optical waveguides for the cross state. Current applied along these metal strips results in a thermo-optic based total-internal-reflection waveguide between the two metal strips for the bar state. The fabrication and the device characteristics of the new optical switch are reported.

Characterization of automotive radar targets from 22 to 29 GHz

The radar signatures of various automotive targets were measured from 22 to 29 GHz inside an anechoic chamber using a vector network analyzer. Radar cross section maps of a sedan, truck, and van as a function of effective radar sensor bandwidth, height, and polarization are presented.

Compact electro-optic modulator for direct integration into an X-band antenna array front-end

A compact electro-optic modulator comprising a waveguide grating formed on a small piece of lithium niobate can be integrated directly into an X-band antenna array element. A prototype link with this modulator was demonstrated.

Active plasmonic and metamaterials and devices

This communication focuses on the integration of organic nonlinear optical and gain materials into plasmonic and metamaterial device architectures and most specifically focuses on the integration of organic electro-optic (OEO) materials into such structures. The central focus is on structures that lead to sub-optical wavelength concentration of light (mode confinement) and the interaction of photonic and plasmonic modes. Optical loss and bandwidth limitations are serious issues with such structures and optical loss is evaluated for prototype device architectures associated with the use of silver and gold nanoparticles and membranes supporting plasmonic resonances. Electro-optic activity in organic materials requires that chromophores exhibit finite noncentrosymmetric organization. Because of material conductivity and integration issues, plasmonic and metamaterial device architectures are more challenging than conventional triple stack all-organic device architectures and electro-optic of a given OEO material may be an order of magnitude less in such structures. Because of this, we have turned to a variety of materials processing options for such integration including crystal growth, sequential synthesis/self assembly, and electric field poling of materials deposited from solution or by vapor deposition. Recent demonstration of integration of silicon photonic modulator and lithium niobate modulator structures with metallic plasmonic structures represent a severe challenge for organic electro-optic material plasmonic devices as these devices afford high bandwidth operation and attractive VμL performance. Optical loss remains a challenge for all structures.

Au and Ag nano-particle embedded plasmonic metal-slotted polymer electro-optic waveguide modulator

A new electro-optic (EO) plasmonic metal-slotted optical waveguide (PMOW) modulator based on gold and silver metal islandized thin films is proposed and experimentally demonstrated that can be operated at both 1310 nm and 1550 nm wavelengths. The fabricated PMOWs are also able to support both TM and TE polarizations, and their characteristics of the EO PMOW modulators are discussed.