68,914 research outputs found
Achieving Pull-in Avoiding Cycle Slip Using Second-order PLLs
Synchronization is an essential process and one of the first tasks of the receiver in case of coherent communications as well synchronous digital data transfer. The phase lock loop (PLL), which employs the error tracking technique, has been a very popular way to implement this synchronizer since the early 1930s. A phenomenon called cycle slip occurs when the number of cycles present in the transmitted carrier (clock) differs from that of the recovered carrier (clock) at the receiver. The cycle slip can be very detrimental to some applications such as frequency modulated communications systems (FSK, multi-carrier etc.), burst digital data transfer, training pulse retrieval, and so on. This paper presents a remedy to avoid the cycle slip by using properly designed second-order Type II PLL.DOI:http://dx.doi.org/10.11591/ijece.v4i2.504
Fish tracking technology development. Phase 1 project definition desk study
The document reports on Phase 1 of a definition study to appraise the options to develop fish tracking equipment, in particular tags and data logging systems in order to improve the efficiency of the Environment Agency's tracking studies and to obtain a greater understanding of fish
biology.
Covered in this report are radio telemetry, audio telemetry, High Resolution Position Fixing, data storage and archival tags and other fish tracking systems such as biosonics
Fish tracking technology development. Phases 1 and 2, project definition desk study and equipment
The document reports on the major findings from a definition study to appraise the options to develop fish tracking equipment, in particular tags and data logging systems, in order to improve the effeciency of the Agency tracking studies and to obtain a greater understanding of fish biology. The definition study was in two parts. The first, Phase 1, collated and evaluated all the known tracking systems that may be suitable for studies of fish which are either produced commercially or have been constructed for specific in-house studies. Phase 2 was an evaluation of all the tracking equipment considered to merit further investigation in Phase 1. The deficiencies between existing and required technologies to improve the efficiency of Agency's tracking studies and to obtain a greater understanding of fish biology are also identified
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
Attitude Determination from Single-Antenna Carrier-Phase Measurements
A model of carrier phase measurement (as carried out by a satellite
navigation receiver) is formulated based on electromagnetic theory. The model
shows that the phase of the open-circuit voltage induced in the receiver
antenna with respect to a local oscillator (in the receiver) depends on the
relative orientation of the receiving and transmitting antennas. The model
shows that using a {\it single} receiving antenna, and making carrier phase
measurements to seven satellites, the 3-axis attitude of a user platform (in
addition to its position and time) can be computed relative to an initial
point. This measurement model can also be used to create high-fidelity
satellite signal simulators that take into account the effect of platform
rotation as well as translation.Comment: 12 pages, and one figure. Published in J. Appl. Phys. vol. 91, No. 7,
April 1, 200
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
Communications satellite technology
Communications satellite technology - echo, relay, and syncom project
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