Publications

This report begins with a review of reduced size ultra-wideband (UWB) antennas and the peculiar problems that arise when building a UWB antenna. It then gives a description of a new type of UWB antenna that resolves these problems. This antenna, dubbed the hemispheric conical antenna, is similar to a conventional conical antenna in that it uses the same inverted conical conductor over a ground plane, but it also uses a hemispheric dielectric fill in between the conductive cone and the ground plane. The dielectric material creates a fundamentally new antenna which is reduced in size and much more rugged than a standard UWB conical antenna. The creation of finite-difference time domain (FDTD) software tools in spherical coordinates, as described in SAND2004-6577, enabled this technological advance.

This report gives a description of several types of wireless, unpowered remote sensors. Surface acoustic wave (SAW) devices were coupled with conventional sensors to create entirely new types of sensors. These sensors report physically measurable data in the same manner as the conventional sensors, but they do it remotely and without any local power source. The sensors are measured remotely using a radar-like interrogation device, and the sensors and their related communication electronics draw all of the power needed for communicating from the radar pulse. The report covers only a description of prototype sensors and not of the manufacturing requirements of these devices.

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This paper describes the development of a set of software tools useful for analyzing ultra-wideband (UWB) antennas and structures. These tools are used to perform finite difference time domain (FDTD) simulation of a conical antenna with continuous wave (CW) and UWB pulsed excitations. The antenna is analyzed using spherical coordinate-based FDTD equations that are derived from first principles. The simulation results for CW excitation are compared to simulation and measured results from published sources; the results for UWB excitation are new.

An electrically programmable surface acoustic wave (SAW) correlator was recently completed from design through small scale production in support of low power space-based communications for NASA. Three different versions of this RF microsystem were built to satisfy design requirements and overcome packaging and system reliability related issues. Flip-chip packaging and conventional thick film hybrid assembly techniques are compared in the fabrication of this microsystem.

This paper describes the development of a set of software tools useful for analyzing ultra-wideband (UWB) antennas and structures. These tools are used to perform finite difference time domain (FDTD) simulation of a conical antenna with continuous wave (CW) and UWB pulsed excitations. The antenna is analyzed using spherical coordinate-based FDTD equations that are derived from first principles. The simulation results for CW excitation are compared to simulation and measured results from published sources; the results for UWB excitation are new.

We report the surface acoustic wave (SAW) correlator devices fabricated using nanoimprint lithography. Using step-and-flash imprint lithography (S-FIL), we produced SAW correlator devices on 100 mm diameter z-cut LiNbO 3 devices and an aluminum metal etch process. On the same chip layout, we fabricated SAW filters and compared both the filters and correlators to similar devices fabricated using electron-beam lithography (EBL). Both S-FIL- and EBL-patterned correlators and SAW filters were analyzed using a bit-error rate tester to generate the signal and a parametric signal analyzer to evaluate the output. The NIL niters had an average center frequency of 2.38 GHz with a standard deviation of 10 MHz. The measured insertion loss averaged -31 dB. In comparison, SAW filters fabricated using EBL exhibited a center frequency of 2.39 GHz and a standard deviation of 100 kHz. Based on our preliminary results, we believe that S-FIL is an efficient and entirely viable fabrication method to produce quality SAW filters and correlators. © 2004 American Vacuum Society.

This report describes both a general methodology and specific examples of completely passive microwave tags. Surface acoustic wave (SAW) devices were used to make tags for both identification and sensing applications at different frequencies. SAW correlators were optimized for wireless identification, and SAW filters were developed to enable wireless remote sensing of physical properties. Identification tag applications and wireless remote measurement applications are discussed. Significant effort went into optimizing the SAW devices used for this work, and the lessons learned from that effort are reviewed.

This report describes a project to develop both fixed and programmable surface acoustic wave (SAW) correlators for use in a low power space communication network. This work was funded by NASA at Sandia National Laboratories for fiscal years 2004, 2003, and the final part of 2002. The role of Sandia was to develop the SAW correlator component, although additional work pertaining to use of the component in a system and system optimization was also done at Sandia. The potential of SAW correlator-based communication systems, the design and fabrication of SAW correlators, and general system utilization of those correlators are discussed here.

This report describes both a general methodology and some specific examples of passive radio receivers. A passive radio receiver uses no direct electrical power but makes sole use of the power available in the radio spectrum. These radio receivers are suitable as low data-rate receivers or passive alerting devices for standard, high power radio receivers. Some zero-power radio architectures exhibit significant improvements in range with the addition of very low power amplifiers or signal processing electronics. These ultra-low power radios are also discussed and compared to the purely zero-power approaches.

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This report describes the development of an ultra-low power spread spectrum receiver based on a programmable surface acoustic wave (SAW) correlator. This work was funded under LDRD 02-26573, Ultra-Low Power Spread Spectrum Receiver. The approach taken in this project uses direct demodulation of a radio frequency (RF) signal from carrier frequency to data frequency. This approach was taken to reduce power consumption and size. The design is based on the technique of correlating the received RF signal with the preprogrammed spreading code. The system requirements, applications, design methodology, and testing results are all documented in the following pages.

High-speed multiplication is frequently used in general-purpose and application-specific computer systems. These systems often support integer multiplication, where two n-bit integers are multiplied to produce a 2n-bit product. To prevent growth in word length, processors typically return the n least significant bits of the product and a flag that indicates whether or not overflow has occurred. Alternatively, some processors saturate results that overflow to the most positive or most negative representable number. This paper presents efficient methods for performing unsigned or two's complement integer multiplication with overflow detection or saturation. These methods have significantly less area and delay than conventional methods for integer multiplication with overflow detection and saturation.