3,048 research outputs found
Instrumentation of a high-sensitivity microwave vector detection system for low-temperature applications
We present the design and the circuit details of a high-sensitivity microwave
vector detection system, which is aiming for studying the low-dimensional
electron system embedded in the slots of a coplanar waveguide at low
temperatures. The coplanar waveguide sample is placed inside a phase-locked
loop; the phase change of the sample may cause a corresponding change in the
operation frequency, which can be measured precisely. We also employ a
double-pulse modulation on the microwave signals, which comprises a fast pulse
modulation for gated averaging and a slow pulse modulation for lock-in
detection. In measurements on real samples at low temperatures, this system
provides much better resolutions in both amplitude and phase than most of the
conventional vector analyzers at power levels below -65 dBm.Comment: 7 pages, 11 figures, 1 table, lette
A space communication study Final report, 15 Sep. 1967 - 15 Sep. 1968
Transmitting and receiving analog and digital signals through noisy media - space communications stud
Theory of phaselock techniques as applied to aerospace transponders
Phaselock techniques as applied to aerospace transponder
Threshhold analysis of phase locked loops
Computer technique for predicting threshold in phased locked loops with and without frequency modulatio
Multipath signal model development
The development and use of mathematical models of signals received through the multipath environmental of a TDRS-to-user spacecraft link and vice versa are discussed. The TDRS (tracking and data relay satellite) will be in synchronous orbit. The user spacecraft will be in a low altitude orbit between 200 and 4000 km
Phase-locked loop FM demodulator
A conventional phase-locked loop is improved by replacing its phase detector with one comprising a linear ramp generator and a sample-and-hold circuit, thus eliminating the need for a lowpass loop filter, although the output of the sample-and-hold circuit may be filtered in the case of a very low level modulating signal on the incoming FM signal, but then filtering is not a difficult problem as in a conventional phase-locked loop. The result is FM demodulation by zero-order estimation. For FM demodulation by first-order estimation, the arithmetic difference between adjacent samples is formed, and using a second sample-and-hold circuit an arithmetic difference signal is produced as an input to a second ramp generator that is reset after each sampling cycle to generate a ramp the slope of which is a function of the arithmetic difference signal stored in the second sample-and-hold circuit. The ramp thus generated by the second ramp generator is arithmetically summed with the zero-estimation signal from the first sample-and-hold circuit to form a first-order estimation signal. Filtering such a first-order estimation signal is less of a problem than filtering a zero-order estimation signal
Numerical investigation of a feed-forward linewidth reduction scheme using a mode-locked laser model of reduced complexity
We provide numerical verification of a feed-forward, heterodyne-based phase noise reduction scheme using
single-sideband modulation that obviates the need for optical filtering at the output. The main benefit of a
feed-forward heterodyne linewidth reduction scheme is the simultaneous reduction of the linewidth of all modes
of a mode-locked laser (MLL) to that of a narrow-linewidth single-wavelength laser. At the heart of our simulator
is an MLL model of reduced complexity. Importantly, the main issue being treated is the jitter of MLLs and we
show how to create numerical waveforms that mimic the random-walk nature of timing jitter of pulses from
MLLs. Thus, the model does not need to solve stochastic differential equations that describe the MLL dynamics,
and the model calculates self-consistently the line-broadening of the modes of the MLL and shows good agreement with both the optical linewidth and jitter. The linewidth broadening of the MLL modes are calculated after
the phase noise reduction scheme and we confirm that the phase noise contribution from the timing jitter still
remains. Finally, we use the MLL model and phase noise reduction simulator within an optical communications
system simulator and show that the phase noise reduction technique could enable MLLs as optical carriers for
higher-order modulation formats, such as 16-state and 64-state quadrature amplitude modulation
Basics of RF electronics
RF electronics deals with the generation, acquisition and manipulation of
high-frequency signals. In particle accelerators signals of this kind are
abundant, especially in the RF and beam diagnostics systems. In modern machines
the complexity of the electronics assemblies dedicated to RF manipulation, beam
diagnostics, and feedbacks is continuously increasing, following the demands
for improvement of accelerator performance. However, these systems, and in
particular their front-ends and back-ends, still rely on well-established basic
hardware components and techniques, while down-converted and acquired signals
are digitally processed exploiting the rapidly growing computational capability
offered by the available technology. This lecture reviews the operational
principles of the basic building blocks used for the treatment of
high-frequency signals. Devices such as mixers, phase and amplitude detectors,
modulators, filters, switches, directional couplers, oscillators, amplifiers,
attenuators, and others are described in terms of equivalent circuits,
scattering matrices, transfer functions; typical performance of commercially
available models is presented. Owing to the breadth of the subject, this review
is necessarily synthetic and non-exhaustive. Readers interested in the
architecture of complete systems making use of the described components and
devoted to generation and manipulation of the signals driving RF power plants
and cavities may refer to the CAS lectures on Low-Level RF.Comment: 36 pages, contribution to the CAS - CERN Accelerator School:
Specialised Course on RF for Accelerators; 8 - 17 Jun 2010, Ebeltoft, Denmar
Computer programs: Electronic circuit design criteria: A compilation
A Technology Utilization Program for the dissemination of information on technological developments which have potential utility outside the aerospace community is presented. The 21 items reported herein describe programs that are applicable to electronic circuit design procedures
A space communications study Final report, 15 Sep. 1966 - 15 Sep. 1967
Investigation of signal to noise ratios and signal transmission efficiency for space communication system
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