3,475 research outputs found
High dynamic global positioning system receiver
A Global Positioning System (GPS) receiver having a number of channels, receives an aggregate of pseudorange code time division modulated signals. The aggregate is converted to baseband and then to digital form for separate processing in the separate channels. A fast fourier transform processor computes the signal energy as a function of Doppler frequency for each correlation lag, and a range and frequency estimator computes estimates of pseudorange, and frequency. Raw estimates from all channels are used to estimate receiver position, velocity, clock offset and clock rate offset in a conventional navigation and control unit, and based on the unit that computes smoothed estimates for the next measurement interval
GPS Carrier Tracking Loop Performance in the presence of Ionospheric Scintillations
The performance of several GPS carrier tracking loops
is evaluated using wideband GPS data recorded during
strong ionospheric scintillations. The aim of this study is
to determine the loop structures and parameters that enable
good phase tracking during the power fades and phase
dynamics induced by scintillations. Constant-bandwidth
and variable-bandwidth loops are studied using theoretical
models, simulation, and tests with actual GPS signals.
Constant-bandwidth loops with loop bandwidths near 15
Hz are shown to lose phase lock during scintillations. Use
of the decision-directed discriminator reduces the carrier
lock threshold by ∼1 dB relative to the arctangent and conventional Costas discriminators. A proposed variablebandwidth
loop based on a Kalman filter reduces the carrier
lock threshold by more than 7 dB compared to a 15-Hz
constant-bandwidth loop. The Kalman filter-based strategy
employs a soft-decision discriminator, explicitly models
the effects of receiver clock noise, and optimally adapts
the loop bandwidth to the carrier-to-noise ratio. In extensive
simulation and in tests using actual wideband GPS
data, the Kalman filter PLL demonstrates improved cycle
slip immunity relative to constant bandwidth PLLs.Aerospace Engineering and Engineering Mechanic
Design study of a low cost civil aviation GPS receiver system
A low cost Navstar receiver system for civil aviation applications was defined. User objectives and constraints were established. Alternative navigation processing design trades were evaluated. Receiver hardware was synthesized by comparing technology projections with various candidate system designs. A control display unit design was recommended as the result of field test experience with Phase I GPS sets and a review of special human factors for general aviation users. Areas requiring technology development to ensure a low cost Navstar Set in the 1985 timeframe were identified
A Multi Antenna Receiver for Galileo SoL Applications
One of the main features of the Galileo Satellite Navigation System is integrity. To ensure a reliable and robust navigation for Safety of Life applications, like CAT III aircraft landings, new receiver technologies are indispensable. Therefore, the German Aerospace Centre originated the development of a complete safety-of-life Galileo receiver to demonstrate the capabilities of new digital beam-forming and signal-processing algorithms for the detection and mitigation of interference. To take full advantage of those algorithms a carefully designed analogue signal processing is needed. The development addresses several challenging questions in the field of antenna design, frontend development and digital signal processing. The paper will give an insight in the activity and will present latest results
Characterizing Power Consumption of Dual-Frequency GNSS of a Smartphone
Location service is one of the most widely used features on a smartphone.
More and more apps are built based on location services. As such, demand for
accurate positioning is ever higher. Mobile brand Xiaomi has introduced Mi 8,
the world's first smartphone equipped with a dual-frequency GNSS chipset which
is claimed to provide up to decimeter-level positioning accuracy. Such
unprecedentedly high location accuracy brought excitement to industry and
academia for navigation research and development of emerging apps. On the other
hand, there is a significant knowledge gap on the energy efficiency of
smartphones equipped with a dual-frequency GNSS chipset. In this paper, we
bridge this knowledge gap by performing an empirical study on power consumption
of a dual-frequency GNSS phone. To the best our knowledge, this is the first
experimental study that characterizes the power consumption of a smartphone
equipped with a dual-frequency GNSS chipset and compares the energy efficiency
with a single-frequency GNSS phone. We demonstrate that a smartphone with a
dual-frequency GNSS chipset consumes 37% more power on average outdoors, and
28% more power indoors, in comparison with a singe-frequency GNSS phone.Comment: Published in IEEE Global Communications Conference (GLOBECOM
A Graphical Approach to GPS Software-Defined Receiver Implementation
Global positioning system (GPS) software-defined
receivers (SDRs) offer many advantages over their hardwarebased
counterparts, such as flexibility, modularity, and upgradability.
A typical GPS receiver is readily expressible as a block
diagram, making a graphical approach a natural choice for
implementing GPS SDRs. This paper presents a real-time, graphical
implementation of a GPS SDR, consisting of two modes:
acquisition and tracking. The acquisition mode performs a twodimensional
fast Fourier transform (FFT)-based search over code
offsets and Doppler frequencies. The carrier-aided code tracking
mode consists of the following main building blocks: correlators,
code and carrier phase detectors, code and carrier phase filters,
a code generator, and a numerically-controlled oscillator. The
presented GPS SDR provides an abstraction level that enables
future research endeavors.Aerospace Engineering and Engineering Mechanic
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Development and Demonstration of a TDOA-Based GNSS Interference Signal Localization System
Background theory, a reference design, and demonstration
results are given for a Global Navigation Satellite
System (GNSS) interference localization system comprising a
distributed radio-frequency sensor network that simultaneously
locates multiple interference sources by measuring their signals’
time difference of arrival (TDOA) between pairs of nodes in
the network. The end-to-end solution offered here draws from
previous work in single-emitter group delay estimation, very long
baseline interferometry, subspace-based estimation, radar, and
passive geolocation. Synchronization and automatic localization
of sensor nodes is achieved through a tightly-coupled receiver
architecture that enables phase-coherent and synchronous sampling
of the interference signals and so-called reference signals
which carry timing and positioning information. Signal and crosscorrelation
models are developed and implemented in a simulator.
Multiple-emitter subspace-based TDOA estimation techniques
are developed as well as emitter identification and localization
algorithms. Simulator performance is compared to the CramérRao
lower bound for single-emitter TDOA precision. Results are
given for a test exercise in which the system accurately locates
emitters broadcasting in the amateur radio band in Austin, TX.Aerospace Engineering and Engineering Mechanic
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