Abstract: A radiometer (100) uses the fringe pattern of an interferometer (110) to scan a scene to produce a time record from which a high-resolution radio frequency, or other radiation, distribution of the scene can be reconstructed. A matched filter (120), or other means, transforms the time record according to a function of a signature of the determinable scanning motion relative to the fringe pattern.For many applications, the modulation transfer function (123) of an included matched filter is the complex conjugate of the Fourier transform of the signature that would be produced by a constant point emitter scanned by the lobes of the interferometer fringe pattern.Two-dimensional reconstructions may be provided for by multiple scans at different orientations. Alternatively, frequency scanning or another scanning technique can provide resolution orthogonal to the fringe pattern scanning motion.

Abstract: A microwave radiometer is formed of a set of frequency scanning antennas disposed parallel to each other and connected by a common microwave feeder. Signals of individual ones of the antennas are translated to different intermediate frequencies such that differences between the intermediate frequencies are proportional to baseline spacings between pairs of antennas of nested interferometers. A correlator containing parallel delay lines and a set of multiplier channels coupled to paired taps of the delay lines receives signals at the intermediate frequencies to produce a set of correlation signals. A two-dimensional Fourier transformation is applied to the correlation output signals to provide the power spectral density of microwave radiation incident upon the array of antennas.

Abstract: A radiometric imager for providing a series of registered images of a scene, each image corresponding to the radiation pattern for a unique, narrow frequency band. One embodiment includes a single frequency-dispersive linear antenna providing an output signal based on a series of conical fanbeams, with the antenna being controllably rocked about one axis and rotated about a perpendicular axis such that each fanbeam intersects each segment of the scene a plurality of times. In alternative embodiments, the imager includes a second frequency-dispersive linear antenna arranged in parallel with the first antenna to produce a fanbeam interferometer. Rocking movement of the two antennas coupled with either translation of the two antennas, rotation of the two antennas about an axis parallel with the antenna axes, or movement of the two antennas toward and away from each other, provides sufficient data to permit creation of the registered images.

Abstract: A method and apparatus for precisely determining the relative velocity of an interferometer and a scene being scanned. The apparatus uses a matched filter technique in which reference signals based on high and low relative velocity estimates are correlated with an incoming interferometer signal and controllably adjusted until the correlation is maximized. The controllably adjusted reference signals are then used to produce an extremely accurate and precise measurement of relative velocity.

Abstract: A fanbeam inversion radar system (100) includes a frequency synthesizer (102) or other transmission means, a fanbeam antenna (104), an orientation sensor/controller (106) and a computer (110). The antenna is adapted for frequency scanning so that fanbeam position data is determined by the computer which controls the variable frequency synthesizer. By scanning a scene with fanbeams for each of a series of fanbeam orientations spanning 180.degree., a two-dimensional image reconstruction can be performed by algorithms well known in image processing fields.By presorting radar returns by delay time (at 112), multiple reconstructed images can be obtained corresponding to different ranges. By mixing (at 122) the synthesizer output with a reference from a local oscillator (120) and "beating" the return against the same reference by means of synchronous demodulators (132), Doppler sorting can provide multiple images with respective relative velocities.The radar system (100) uses serial frequency scanning.

Abstract: A microwave radiometer reconstructs images by fanbeam inversion. True time delay (100), frequency (600, 700) and mechanical scanning systems (200) are disclosed. The mechanically scanning radiometer includes a fanbeam antenna (210) to scan a scene so that the antenna output is a projection of the scene taken along the direction of scan. The mechanical scanning motion is provided by a rocking motor (254) controlled by a computer (214). Projections are obtained for successive orientations as the antenna is rotated by another motor (212). By application of an inverse Radon transform, the scene scanned is reconstructed by the computer.In one frequency scanning system (600), a filter bank spectrometer is implemented to obtain the projections, and in the other frequency scanning system (700), a transform spectrometer implemented. In the delay scanning system (100), a beam forming computer is used in the reconstruction process.

Abstract: A passive imaging system (400) includes a frequency scanning array (412) for receiving radiation emissions from a scene with a flat or known spectrum of emissions over the operating frequency of the array. Different beam directions are addressed by a spectrum analyzer (404). An image coordinate generator (410) may be used where necessary to normalize the image which may be stored or displayed by an appropriate device (406).In one embodiment, the array is planar so as to generate pencil beams. The planar array comprises parallel line-source antenna elements (402), with a common feed (414). The feed has a large "wrap-up" so that frequency-frequency scanning is employed.Alternatively, one-dimensional images can be effected with a single line-source frequency scanning antenna element. Also, one-dimensional frequency scanning may be supplemented by a different scanning approach for resolution orthogonal to that provided by the frequency scanning. In one embodiment, phase gradient scanning is employed.