Spelling suggestions: "subject:"radio interference"" "subject:"radio nterference""
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Frequency characteristics of artificial staticMangum, Otto Kempe January 1932 (has links)
No description available.
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Susceptibility of binary DPSK to periodic FM interferenceLowery, Cecil Adair 08 1900 (has links)
No description available.
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Investigation of a carrier cancellation technique for extending the dynamic range of spectrum analyzersHoley, John Gerald 05 1900 (has links)
No description available.
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A new detector for channels with state variable modelsRoach, John Kenna 12 1900 (has links)
No description available.
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An interference monitor for a radio observatoryRomalo, David N. January 1988 (has links)
This thesis describes the design, construction, and testing of a radio-frequency interference monitoring system for use with the synthesis array telescope at the Dominion Radio Astrophysical Observatory near Penticton, B.C. The system is designed to provide continuous, automated surveillance of the radiospectrum around 408 MHz. Interfering signals are characterized and catalogued according to strength, duration, frequency, and direction. Although the monitor is presently a very useful tool for detecting and finding sources of interference, it is ultimately intended to communicate directly with the telescope's control computer, so that sporadic bursts of interference can be removed automatically.
The system can detect a weak interfering signal that is within 5 dB of the smallest signal that can contaminate the astronomical observations. The smallest signal was calculated based on the following conditions, considered to be the case for which a synthesis telescope is most sensitive to interference, i.e., the worst case:
a) observing at high declination (towards the North Pole), so that the fringes of the synthesis telescope are too slow to reduce the effects of the interference, and
b) with the interference present continuously during the observation.
These weak signals can be detected in the presence of other signals, nearby in frequency, which are up to 40 dB stronger, i.e., the dynamic range of the monitor is 40 dB. The monitor consists of an antenna system, a computer-tunable radio receiver, a fast Fourier transform (FFT) spectrum analyzer, and a microcomputer for control and data analysis. Everything except the microcomputer hardware was built as part of the project.
A thorough survey of the literature on the design of dedicated FFT machines was required. It was discovered that there had been no investigation of the design details for fixed-point FFT machines which are required to do long integrations. In such situations, fixed-point errors limit the performance of the machine. A computer simulation of the Welch process was developed to analyze the effects of these errors and to optimize the design. Some new results concerning the detectability of small signals are presented.
The FFT spectrum analyzer is used to estimate the power spectrum of 500 kHz-wide sub-bands using Welch's method of modified periodograms. It computes 256-point transforms in real-time with a resolution of 3.91 kHz (corresponding to one FFT every 512 μsec). This is comparable to the speed of a large array processor but at a fraction of the cost. Since the FFT is equivalent to a bank of contiguous filters, it can analyze the spectrum in much less time than the single swept filter found in most commercial spectrum analyzers, i.e., it is much more sensitive.
The analyzer was specially designed and built using recently-available digital integrated circuits. The design draws upon several high-speed architectural concepts including pipelining, parallel arithmetic, and hard-wired control. Except for expensive array processors, the analyzer is much faster than any commercial FFT processors or FFT-based spectrum analyzers.
As part of the antenna system, an array of helical antennas was designed and constructed, its characteristics were investigated and found to be suitable for the present application, and a method of remotely switching them on and off was devised.
One more note - the radio spectrum is becoming more and more cluttered with man-made signals. Unprotected radio astronomy bands are being adversely affected and radio astronomers are turning to FFT spectrometers to cope with the relatively large interfering signals. The work herein on FFT-based design is applicable in such cases. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate
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Intermodulation interference probabilities in cellular mobile radio systemsHu, Y. F. January 1987 (has links)
No description available.
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Interference cancellation in impulse radioWang, Xufang., 王徐芳. January 2005 (has links)
published_or_final_version / abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy
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Interference cancellation for shot-code DS-CDMA in the presence of channel fadingDutta, Amit K. 21 August 1997 (has links)
Interference from other adjacent users in wireless applications is a major problem
in direct-sequence code-division multiple-access (DS-CDMA). This is also known as the
near-far problem where a strong signal from one user interferes with other users. The
current approach to deal with the near-far problem in DS-CDMA systems is to use strict
transmitter power control. An alternative approach is to use near-far resistant receivers.
The practical near-far resistance receiver structure is the adaptive decorrelating detectors
since it avoids complex matrix inversion.
The existing CDMA standard known as IS-95 uses a long signature code
sequence. However for simplicity, the adaptive multi-user receiver uses short signature
code sequence. The problem is that adaptive receivers lose near-far resistance as the
number of users increases in the system. This thesis describes a novel method of multistage
decision feedback cancellation (DFC) scheme immune from the near-far problem.
The performance of the new DFC structure is constructed using three different adaptive
algorithms: the least mean squared (LMS), the recursive least squared (RLS) and the
linearly constraint constant modulus (LCCM) adaptive algorithms. It is found that LMS
adaptive algorithm provides the best result considering its simple hardware complexity.
It is also found that the LMS adaptive receiver along with the DFC structure provides a
better bit synchronization capability to the over all system. Since the receiver is near-far
resistant, the LMS adaptive receiver along with the decision feedback cancellation
structure also performs better in the presence of Rayleigh fading. / Graduation date: 1998
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Effects of high voltage transmission lines on NDB performanceIsmail, Ibrahim January 1981 (has links)
No description available.
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FM weaker-signal suppression with narrow-band limitersJanuary 1960 (has links)
Robert J. McLaughlin. / "This report is based on a thesis submitted to the Department of Electrical Engineering, M.I.T., June 1958, in partial fulfillment of the requirements for the degree of Master of Science." / Bibliography: p. 33. / Army Signal Corps Contract DA36-039-sc-78108. Dept. of the Army Task 3-99-20-001 and Project 3-99-00-000.
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