18,773 research outputs found
Phasemeter core for intersatellite laser heterodyne interferometry: modelling, simulations and experiments
Inter satellite laser interferometry is a central component of future
space-borne gravity instruments like LISA, eLISA, NGO and future geodesy
missions. The inherently small laser wavelength allows to measure distance
variations with extremely high precision by interfering a reference beam with a
measurement beam. The readout of such interferometers is often based on
tracking phasemeters, able to measure the phase of an incoming beatnote with
high precision over a wide range of frequencies. The implementation of such
phasemeters is based on all digital phase-locked loops, hosted in FPGAs. Here
we present a precise model of an all digital phase locked loop that allows to
design such a readout algorithm and we support our analysis by numerical
performance measurements and experiments with analog signals.Comment: 17 pages, 6 figures, accepted for publication in CQ
Multi-color Cavity Metrology
Long baseline laser interferometers used for gravitational wave detection
have proven to be very complicated to control. In order to have sufficient
sensitivity to astrophysical gravitational waves, a set of multiple coupled
optical cavities comprising the interferometer must be brought into resonance
with the laser field. A set of multi-input, multi-output servos then lock these
cavities into place via feedback control. This procedure, known as lock
acquisition, has proven to be a vexing problem and has reduced greatly the
reliability and duty factor of the past generation of laser interferometers. In
this article, we describe a technique for bringing the interferometer from an
uncontrolled state into resonance by using harmonically related external fields
to provide a deterministic hierarchical control. This technique reduces the
effect of the external seismic disturbances by four orders of magnitude and
promises to greatly enhance the stability and reliability of the current
generation of gravitational wave detector. The possibility for using
multi-color techniques to overcome current quantum and thermal noise limits is
also discussed
A Scalable, Self-Analyzing Digital Locking System for use on Quantum Optics Experiments
Digital control of optics experiments has many advantages over analog control
systems, specifically in terms of scalability, cost, flexibility, and the
integration of system information into one location. We present a digital
control system, freely available for download online, specifically designed for
quantum optics experiments that allows for automatic and sequential re-locking
of optical components. We show how the inbuilt locking analysis tools,
including a white-noise network analyzer, can be used to help optimize
individual locks, and verify the long term stability of the digital system.
Finally, we present an example of the benefits of digital locking for quantum
optics by applying the code to a specific experiment used to characterize
optical Schrodinger cat states.Comment: 7 pages, 5 figure
Theory of phaselock techniques as applied to aerospace transponders
Phaselock techniques as applied to aerospace transponder
Programmable rate modem utilizing digital signal processing techniques
The engineering development study to follow was written to address the need for a Programmable Rate Digital Satellite Modem capable of supporting both burst and continuous transmission modes with either binary phase shift keying (BPSK) or quadrature phase shift keying (QPSK) modulation. The preferred implementation technique is an all digital one which utilizes as much digital signal processing (DSP) as possible. Here design tradeoffs in each portion of the modulator and demodulator subsystem are outlined, and viable circuit approaches which are easily repeatable, have low implementation losses and have low production costs are identified. The research involved for this study was divided into nine technical papers, each addressing a significant region of concern in a variable rate modem design. Trivial portions and basic support logic designs surrounding the nine major modem blocks were omitted. In brief, the nine topic areas were: (1) Transmit Data Filtering; (2) Transmit Clock Generation; (3) Carrier Synthesizer; (4) Receive AGC; (5) Receive Data Filtering; (6) RF Oscillator Phase Noise; (7) Receive Carrier Selectivity; (8) Carrier Recovery; and (9) Timing Recovery
Fiber-optic three axis magnetometer prototype development
The goal of this research program was to develop a high sensitivity, fiber optic, interferometric, three-axis magnetometer for interplanetary spacecraft applications. Dynamics Technology, Inc. (DTI) has successfully integrated a low noise, high bandwidth interferometer with high sensitivity metallic glass transducers. Also, DTI has developed sophisticated signal processing electronics and complete data acquisition, filtering, and display software. The sensor was packaged in a compact, low power and weight unit which facilitates deployment. The magnetic field sensor had subgamma sensitivity and a dynamic range of 10(exp 5) gamma in a 10 Hz bandwidth. Furthermore, the vector instrument exhibited the lowest noise level when only one axis was in operation. A system noise level of 1 gamma rms was observed in a 1 Hz bandwidth. However, with the other two channels operating, the noise level increased by about one order of magnitude. Higher system noise was attributed to cross-channel interference among the dither fields
RAPID CLOCK RECOVERY ALGORITHMS FOR DIGITAL MAGNETIC RECORDING AND DATA COMMUNICATIONS
SIGLEAvailable from British Library Document Supply Centre-DSC:DXN024293 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
A review of modulation techniques for use in a satellite multipath environment
Modulation techniques for use in satellite multipath environmen
Parkes radio science system design and testing for Voyager Neptune encounter
The Radio Science System installed at Parkes, Australia for the Voyager Neptune encounter was specified to meet the same stringent requirements that were imposed upon the Deep Space Network Radio Science System. The system design and test methodology employed to meet these requirements at Parkes are described, and data showing the measured performance of the system are presented. The results indicate that the system operates with a comfortable margin on the requirements. There was a minor problem with frequency-dependent spurious signals which could not be fixed before the encounter. Test results characterizing these spurious signals are included
- …