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  1. Book ; Online: Characterization and Mitigation of Sinusoidal Carrier Modulation Signals by Short-Term Sinusoidal Analysis

    Ellingson, S. W.

    2020  

    Abstract: Most radio signals can be described as a form of sinusoidal carrier modulation. These signals have the property that when observed over a sufficiently short period of time, the waveform is approximately sinusoidal, exhibiting constant magnitude, ... ...

    Abstract Most radio signals can be described as a form of sinusoidal carrier modulation. These signals have the property that when observed over a sufficiently short period of time, the waveform is approximately sinusoidal, exhibiting constant magnitude, frequency, and phase. When coherently digitized with sufficiently high sample rate, it is possible to discern this sinusoid. The associated signal can be represented as a sinusoid with time-varying frequency, magnitude, and phase. These parameters can subsequently be used for detection and characterization, including identification. The parameters can also be used to synthesize a noise-free estimate of the signal. The synthesized signal can be coherently subtracted from the original data in order to cancel the signal, nominally without distortion of the associated noise or nearby signals. In this report, the conditions required for the short-time sinusoidal approximation are described. Performance of the canceling technique is examined in the case of a VHF-band narrowband FM-modulated signal.

    Comment: 9 pages, 5 figures
    Keywords Electrical Engineering and Systems Science - Signal Processing
    Subject code 621
    Publishing date 2020-04-07
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Book ; Online: Coherent Time-Domain Canceling of Interference for Radio Astronomy

    Ellingson, S. W. / Buehrer, R. M.

    2022  

    Abstract: Radio astronomy is vulnerable to interference from a variety of anthropogenic sources. Among the many strategies for mitigation of this interference is coherent time-domain canceling (CTC), which ideally allows one to "look through" interference, as ... ...

    Abstract Radio astronomy is vulnerable to interference from a variety of anthropogenic sources. Among the many strategies for mitigation of this interference is coherent time-domain canceling (CTC), which ideally allows one to "look through" interference, as opposed to avoiding the interference or deleting the afflicted data. However, CTC is difficult to implement, not well understood, and at present this strategy is not in regular use at any major radio telescope. This paper presents a review of CTC including a new comprehensive study of the capabilities and limitations of CTC using metrics relevant to radio astronomy, including fraction of interference power removed and increase in noise. This work is motivated by the emergence of a new generation of communications systems which pose a significantly increased threat to radio astronomy and which may overwhelm mitigation methods now in place.

    Comment: Accepted Publ. Astron. Soc. Pac. Added appendices addressing a real-world example and impact of non-stationarity. Various other minor changes
    Keywords Astrophysics - Instrumentation and Methods for Astrophysics ; Electrical Engineering and Systems Science - Signal Processing
    Publishing date 2022-08-08
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Book ; Online: Sidelobe Modification for Reflector Antennas by Electronically-Reconfigurable Rim Scattering

    Ellingson, S. W. / Sengupta, R.

    2021  

    Abstract: Dynamic modification of the pattern of a reflector antenna system traditionally requires an array of feeds. This paper presents an alternative approach in which the scattering from a fraction of the reflector around the rim is passively modified using, ... ...

    Abstract Dynamic modification of the pattern of a reflector antenna system traditionally requires an array of feeds. This paper presents an alternative approach in which the scattering from a fraction of the reflector around the rim is passively modified using, for example, an electronically-reconfigurable reflectarray. This facilitates flexible sidelobe modification, including sidelobe canceling, for systems employing a single feed. Applications for such a system include radio astronomy, where deleterious levels of interference from satellites enter through sidelobes. We show that an efficient reconfigurable surface occupying about 11% of the area of an axisymmetric circular paraboloidal reflector antenna fed from the prime focus is sufficient to null interference arriving from any direction outside the main lobe with little change in the main lobe characteristics. We further show that the required surface area is independent of frequency and that the same performance can be obtained using 1-bit phase control of the constituent unit cells for a reconfigurable surface occupying an additional 6% of the reflector surface.

    Comment: Accepted for publication in IEEE Antennas & Wireless Propagation Letters. Minor revisions from previous version. 5 pages, 5 figures
    Keywords Astrophysics - Instrumentation and Methods for Astrophysics ; Electrical Engineering and Systems Science - Signal Processing
    Subject code 600
    Publishing date 2021-02-16
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Conference proceedings: A radio frequency interference survey of central Ohio

    Dixon, R. S / Ellingson, S. W / Koch, R. J

    Crawford DL, ed. Light pollution, radio interference, and space debris

    (Astronomical Society of the Pacific conference series, ; vol. 17)

    1991  

    Abstract: A long-term radio frequency interference monitoring program is now in progress at the Ohio State University Radio Observatory. Current observations encompass the 1-2 GHz band, measuring the signal strength in each 150 KHz subband. Preliminary results ... ...

    Event/congress International Astronomical Union Colloquium (112th, 1989, :WashingtonDC)
    Author's details R.S. Dixon, S.W. Ellingson, R.J. Koch
    Series title Astronomical Society of the Pacific conference series, ; vol. 17
    Abstract A long-term radio frequency interference monitoring program is now in progress at the Ohio State University Radio Observatory. Current observations encompass the 1-2 GHz band, measuring the signal strength in each 150 KHz subband. Preliminary results show many strong and persistent signals, and wide bands in which no signals are detected. Daily and weekly variations appear to be correlated with periods of maximum human activity such as "rush hours". It may be that aircraft reflections are causing many of the signals to be received, and that airline schedules correlate with "rush hours". The program is being upgraded to automatically measure the direction of arrival of each signal, as an aid to further identify it. This directional information will also be used in designing rolled edges and side shields for the co-located OSU Radio Telescope, to further reduce its vulnerability to RFI.
    MeSH term(s) Astronomy ; Exobiology ; Extraterrestrial Environment ; Radio Waves ; Aircraft ; Time Factors
    Keywords Ohio ; Exobiology
    Language English
    Size p. 181-187.
    Publisher Astronomical Society of the Pacific
    Publishing place San Francisco
    Document type Article ; Conference proceedings
    Note Conference held 1989 Aug 13-16.
    ISBN 0937797368 ; 9780937797365
    Database Catalogue of the US National Library of Medicine (NLM)

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