Scientific-atlanta, Inc.

Doren W Hess, Jr

John R Jones

Rezin E Pidgeon, Jr

An optical transmitter (,) includes a distributed feedback semiconductor laser (,) operated in a linear regime below a threshold associated with stimulated Brillouin scattering to generate an optical signal. A resistor (,) or other heater is physically coupled to the semiconductor laser (,), and a modulated current source (,) drives the resistor (,) with a triangle waveform (,), thereby varying an optical wavelength of the optical signal such that the optical signal and a double Rayleigh backscattered signal are characterized, at the optical receiver (,), by different optical frequencies. As a result, interference generated by Rayleigh backscattering is minimized at the optical receiver (,).

Wavelength modulated laser for minimizing effects of Rayleigh backscattering

Methods and apparatus are described for automatically determining correction factors for an electrical device to compensate for variations in the device as a result of mechanical and/or environmental influences, using a 'three cable' method. A primary cable is used to conduct signals between electrical devices, for example a probe antenna and an antenna under test ('AUT') in an antenna test range. The primary cable is subjected to mechanical and/or environmental influences such as cable flexing and temperature changes. A first secondary cable and a second secondary cable are provided alongside the primary cable, and are subjected to similar environmental influences. A switching network connects the primary cable, the first secondary cable, and the second secondary cable in combinations to form three cable pairs during a calibration mode. A computing system determines insertion factors associated with the primary cable at a first time and a second time, using transfer functions associated with the cable pairs. A correction factor is determined using the insertion factors associated with the primary cable at the first time and the second time. The correction factor is applied to data transmitted via the primary cable during use of the primary cable in an antenna measurement mode, to compensate or adjust for the mechanical and/or environmental influences upon the primary cable.

Methods and apparatus for correction of cable variations

Circular open ended waveguide feeds for compact ranges. Feeds according to the present invention employ smaller apertures for a given frequency of operation than a standard compact range feed. According to a first embodiment of the invention, a circular open ended waveguide feed is constructed to operate with its lowest desired frequency of operation at approximately 1.01 times the cutoff frequency. A second embodiment includes a circular open-ended waveguide loaded with ridges to lower the cutoff frequency further and thus further reduce aperture size for a given bandwidth to radiate a broader beamwidth.

Feeds for compact ranges

Method for measuring polarization of antennas utilizing three-antenna methods and far-field scanning techniques where the measured data is processed via digital Fourier transform. In one method, the normalized received phasor voltage for transmission between each of three antennas measured pairwise is digitally recorded as a continuously sampled function of relative roll angle between the antennas as one of the antennas is rolled in a continuous manner. The recorded data is digitally processed via a one-dimensional Discrete Fourier Transform to yield transformed quantities relating to the polarization of the antennas under test. From these quantities, standard polarization parameters including the circular polarization ratio, axial ratio, tilt angle and sense of the electric field polarization ellipse of each antenna may be obtained. In another method, the antenna in each pair which is not continuously rotated is rotated in incremental fashion while the normalized received phasor voltage for transmission between each pair of antennas is digitally recorded. The recorded data for this second method is digitally processed via a two-dimensional Fast, Discrete or other Fourier transform. This step/scan procedure further compensates for test range ambient and reflected noise and for transmitter and receiver RF path variations compared to the single scan procedure of the first method.

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Norcross, GA, United States of America

Doren W Hess, Jr