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Klein, B. J.

Publications and source records attributed to Klein, B. J..

7 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Optical antenna gain. III - The effect of secondary element support struts on transmitter gain

The effect of a secondary-element spider support structure on optical antenna transmitter gain is analyzed. An expression describing the influence of the struts on the axial gain, in both the near and far fields, is derived as a function of the number of struts and their width. It is found that, for typical systems, the struts degrade the on-axis gain by less than 0.4 dB, and the first side-lobe level is not increased significantly. Contour plots have also been included to show the symmetry of the far-field distributions for three- and four-support members.

Klein, B. J.↗
NASA NTRS1974

Optical antenna gain. II - Receiving antennas

Expressions are developed for the gain of a centrally obscured, circular optical antenna used as the collecting and focusing optics in a laser receiver, involving losses due to (1) incoming light blockage by central obscuration, (2) energy spillover at the detector, and (3) the effect of local oscillator distribution in the case of heterodyne or homodyne detection. Numerical results are presented for direct detection and for three types of local oscillator distribution (uniform, Gaussian, and matched).

Degnan, J. J.↗
NASA NTRS1974

Optical antenna gain. I - Transmitting antennas

The gain of centrally obscured optical transmitting antennas is analyzed in detail. The calculations, resulting in near- and far-field antenna gain patterns, assume a circular antenna illuminated by a laser operating in the TEM-00 mode. A simple polynomial equation is derived for matching the incident source distribution to a general antenna configuration for maximum on-axis gain. An interpretation of the resultant gain curves allows a number of auxiliary design curves to be drawn that display the losses in antenna gain due to pointing errors and the cone angle of the beam in the far field as a function of antenna aperture size and its central obscuration. The results are presented in a series of graphs that allow the rapid and accurate evaluation of the antenna gain which may then be substituted into the conventional range equation.

Klein, B. J.↗
NASA NTRS1974

Variable CO2 laser attenuator

An infrared wavelength variable attenuator based on contra-rotating germanium wedges is examined theoretically. The device redirects the paths of internal reflections associated with an optical flat to avoid closely spaced parallel beams at the output. Complementary wedges separated by an air gap compose an optical flat which, when combined with a masking arrangement, restricts unwanted reflections. A model of the device was built and experimentally evaluated. The results compare favorably with the dynamic range of attenuation of 2 to 50 db from theoretical calculations, and show a substantial reduction in the etalon effect associated with pairs of optical flats.

Klein, B. J.↗
NASA NTRS1973

Transmitter and receiver antenna gain analysis for laser radar and communication systems

A comprehensive and fairly self-contained study of centrally obscured optical transmitting and receiving antennas is presented and is intended for use by the laser radar and communication systems designer. The material is presented in a format which allows the rapid and accurate evaluation of antenna gain. The Fresnel approximation to scalar wave theory is reviewed and the antenna analysis proceeds in terms of the power gain. Conventional range equations may then be used to calculate the power budget. The transmitter calculations, resulting in near and far field antenna gain patterns, assumes the antenna is illuminated by a laser operating in the fundamental cavity mode. A simple equation is derived for matching the incident source distribution to a general antenna configuration for maximum on-axis gain. An interpretation of the resultant gain curves allows a number of auxiliary design curves to be drawn which display the losses in antenna gain due to pointing errors and the cone angle of the outgoing beam as a function of antenna size and central obscuration. The use of telescope defocusing as an approach to spreading the beam for target acquisition is compared to some alternate methods.

Klein, B. J.↗
NASA NTRS1972

The BAPE 2 balloon-borne CO2

The systems and techniques which were utilized in the experiment to establish an air-to-ground CO2 laser heterodyne link are described along with the successes and problems encountered when the heterodyne receiver and laser transmitter package were removed from the controlled environment of the laboratory. Major topics discussed include: existing systems and the underlying principles involved in their operation; experimental techniques and optical alignment methods which were found to be useful; theoretical calculations of signal strengths expected under a variety of test conditions and in actual flight; and the experimental results including problems encountered and their possible solutions.

Degnan, J. J.↗