3 research outputs found
Radiation-hardened fast acquisition/weak signal tracking system and method
A global positioning system (GPS) receiver and method of acquiring and tracking GPS signals comprises an antenna adapted to receive GPS signals; an analog radio frequency device operatively connected to the antenna and adapted to convert the GPS signals from an analog format to a digital format; a plurality of GPS signal tracking correlators operatively connected to the analog RF device; a GPS signal acquisition component operatively connected to the analog RF device and the plurality of GPS signal tracking correlators, wherein the GPS signal acquisition component is adapted to calculate a maximum vector on a databit correlation grid; and a microprocessor operatively connected to the plurality of GPS signal tracking correlators and the GPS signal acquisition component, wherein the microprocessor is adapted to compare the maximum vector with a predetermined correlation threshold to allow the GPS signal to be fully acquired and tracked
Fast-Acquisition/Weak-Signal-Tracking GPS Receiver for HEO
A report discusses the technical background and design of the Navigator Global Positioning System (GPS) receiver -- . a radiation-hardened receiver intended for use aboard spacecraft. Navigator is capable of weak signal acquisition and tracking as well as much faster acquisition of strong or weak signals with no a priori knowledge or external aiding. Weak-signal acquisition and tracking enables GPS use in high Earth orbits (HEO), and fast acquisition allows for the receiver to remain without power until needed in any orbit. Signal acquisition and signal tracking are, respectively, the processes of finding and demodulating a signal. Acquisition is the more computationally difficult process. Previous GPS receivers employ the method of sequentially searching the two-dimensional signal parameter space (code phase and Doppler). Navigator exploits properties of the Fourier transform in a massively parallel search for the GPS signal. This method results in far faster acquisition times [in the lab, 12 GPS satellites have been acquired with no a priori knowledge in a Low-Earth-Orbit (LEO) scenario in less than one second]. Modeling has shown that Navigator will be capable of acquiring signals down to 25 dB-Hz, appropriate for HEO missions. Navigator is built using the radiation-hardened ColdFire microprocessor and housing the most computationally intense functions in dedicated field-programmable gate arrays. The high performance of the algorithm and of the receiver as a whole are made possible by optimizing computational efficiency and carefully weighing tradeoffs among the sampling rate, data format, and data-path bit width
A Stationless Bikeshare Proof of Concept for College Campuses
Bikeshares promote healthy lifestyles and sustainability among commuters, casual
riders, and tourists. However, the central pillar of modern systems, the bike station,
cannot be easily integrated into a compact college campus. Fixed stations lack the
flexibility to meet the needs of college students who make quick, short-distance trips.
Additionally, the necessary cost of implementing and maintaining each station prohibits
increasing the number of stations for user convenience. Therefore, the team developed a
stationless bikeshare based on a smartlock permanently attached to bicycles in the
system. The smartlock system design incorporates several innovative approaches to
provide usability, security, and reliability that overcome the limitations of a station
centered design. A focus group discussion allowed the team to receive feedback on the
early lock, system, and website designs, identify improvements and craft a pleasant user
experience. The team designed a unique, two-step lock system that is intuitive to operate
while mitigating user error. To ensure security, user access is limited through near field
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communications (NFC) technology connected to a mechatronic release system. The said
system relied on a NFC module and a servo working through an Arduino microcontroller
coded in the Arduino IDE. To track rentals and maintain the system, each bike is fitted
with an XBee module to communicate with a scalable ZigBee mesh network. The
network allows for bidirectional, real-time communication with a Meteor.js web
application, which enables user and administrator functions through an intuitive user
interface available on mobile and desktop. The development of an independent
smartlock to replace bike stations is essential to meet the needs of the modern college
student. With the goal of creating a bikeshare that better serves college students, Team
BIKES has laid the framework for a system that is affordable, easily adaptable, and
implementable on any university expressing an interest in bringing a bikeshare to its
campus