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  1. Transponder data processing methods and systems [electronic resource]

    Washington, D.C. : United States. Dept. of Energy. ; Oak Ridge, Tenn. : distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2003

    This invention is a radar/tag system where pulses from a radar cause a tag (or transponder) to respond to the radar. The radar, along with its conventional pulse transmissions, sends a reference signal to the tag. The tag recovers the reference signal and uses it to shift the center frequency of the received radar pulse to a different frequency. This shift causes the frequencies of the tag response pulses to be disjoint from those of the transmit pulse. In this way, radar clutter can be eliminated from the tag responses. The radar predicts, to within a small Doppler offset, the center frequency of tag response pulses. The radar can create synthetic-aperture-radar-like images and moving-target-indicator-radar-like maps containing the signature of the tag against a background of thermal noise and greatly attenuated radar clutter. The radar can geolocate the tag precisely and accurately (to within better than one meter of error). The tag can encode status and environmental data onto its response pulses, and the radar can receive and decode this information.

    Online OSTI

  2. Importance of transponder operation and altitude reporting

    [Washington, D.C.] : Dept. of Transportation, Federal Aviation Administration, [1977]

    Online purl.fdlp.gov

  3. Radar transponder apparatus and signal processing technique [electronic resource].

    Washington, D.C. : United States. Dept. of Energy. ; Oak Ridge, Tenn. : distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 1994

    An active, phase-coded, time-grating transponder and a synthetic-aperture radar (SAR) and signal processor means, in combination, allow the recognition and location of the transponder (tag) in the SAR image and allow communication of information messages from the transponder to the SAR. The SAR is an illuminating radar having special processing modifications in an image-formation processor to receive an echo from a remote transponder, after the transponder receives and retransmits the SAR illuminations, and to enhance tile transponder`s echo relative to surrounding ground clutter by recognizing special transponder modulations from phase-shifted from the transponder retransmissions. The remote radio-frequency tag also transmits information to the SAR through a single antenna that also serves to receive the SAR illuminations. Unique tag-modulation and SAR signal processing techniques, in combination, allow the detection and precise geographical location of the tag, through the reduction of interfering signals from ground clutter, and allow communication of environmental and status information from said tag to be communicated to said SAR.

    Online OSTI

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Geospatial content, including GIS datasets, digitized maps, and census data.
  1. North Atlantic Passenger AIS Vessel Density 2012

    United States. National Oceanic and Atmospheric Administration
    2012

    This raster dataset represents density of passenger vessel traffic in 2012 from vessels with Automatic Identification System (AIS) transponders in ...

  2. North Atlantic Tanker AIS Vessel Density 2011

    United States. National Oceanic and Atmospheric Administration
    2011

    This raster dataset represents density of tanker vessel traffic in 2011 from vessels with Automatic Identification System (AIS) transponders in 100...

  3. North Atlantic Tanker AIS Vessel Density 2012

    United States. National Oceanic and Atmospheric Administration
    2012

    This raster dataset represents density of tanker vessel traffic in 2012 from vessels with Automatic Identification System (AIS) transponders in 100...

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