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Low-sidelobe phased array antenna characteristics using the planar near-field scanning technique: theory and experiment

February 14, 1990
  |
Technical Report
Author:
Alan J. Fenn
…
Published in:
MIT Lincoln Laboratory Report TR-870
Topic:
antennas
R&D area:
R&D group:

Summary

Characteristics of a low-sidelobe phased array antenna are investigated using the technique of planar near-field scanning. The theory associated with the planar near-field scanning technique, with and without probe compensation, is reviewed and an application of the theory is made. The design of an experimental low-sidelobe phased array antenna consisting of monopole elements which are corporate-fed using high precision transmit/receive modules is described. Accurate array radiation patterns are obtained both theoretically and experimentally using centerline scanning at less than one wavelength distance from the antenna. The effects of the antenna probe on the array near-field pattern, plane-wave spectrum, and far-field pattern are demonstrated theoretically using a method of moments numerical simulation. Comparisons of the array theoretical near-zone electric field and array received voltage due to a V-dipole near-field transmitting probe are made. It is shown that a V-dipole theoretical probe antenna can accurately model a practical near-field measurement probe consisting of an open-ended rectangular waveguide surrounded with anechoic material.
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Summary

Characteristics of a low-sidelobe phased array antenna are investigated using the technique of planar near-field scanning. The theory associated with the planar near-field scanning technique, with and without probe compensation, is reviewed and an application of the theory is made. The design of an experimental low-sidelobe phased array antenna consisting...

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Low-sidelobe phased array antenna characteristics using the planar near-field scanning technique: theory and experiment

Very low grazing angle backscatter from the ocean surface

January 4, 1990
  |
Conference Paper
Author:
Henry F. Helmken
…
Published in:
IEEE Int. Radar Conf. 1990, 6-9 May 1990, pp. 181-188.
Topic:
radar
R&D area:
R&D group:

Summary

A very low grazing angle (
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Summary

A very low grazing angle (

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Very low grazing angle backscatter from the ocean surface

Miss distance analysis for command guided missiles

December 1, 1988
  |
Journal Article
Author:
Joel Alpert
Published in:
J. Guid. Control Dyn., Vol. 11, No. 6, November-December 1988, pp. 481-487.
Topic:
missile defense
R&D area:
R&D group:

Summary

A concise theoretical technique is presented for estimating the minimum miss distance capability of command guided missile systems using synthetic proportional navigation. The effect of the parameter values on the system capability is shown to be a function of range-to-intercept; the technique enables the system designer and analyst to quantify system performance and to develop a systematic understanding of the performance limitations of command guidance systems at each intercept range. New analytical equations based upon adjoint theory are developed for statistical miss distance caused by target maneuver, range-dependent, servo, glint and atmosphere noises for command guided systems. An optimal total system time constant is derived which yields the minimum statistical miss distance. Realistic constraints on the minimum achievable system time constant are considered. The equations derived for the optimal total system time constant are valuable to the system designer for minimizing miss distance over the ranges of system parameters and limitations, and intercept conditions.
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Summary

A concise theoretical technique is presented for estimating the minimum miss distance capability of command guided missile systems using synthetic proportional navigation. The effect of the parameter values on the system capability is shown to be a function of range-to-intercept; the technique enables the system designer and analyst to quantify...

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Miss distance analysis for command guided missiles

Rain rate climatologies over marine regions

May 1, 1984
  |
Project Report
Author:
Andreas K. Goroch
…
Published in:
no published logic to cover case - index 63
Topic:
weather
R&D area:
R&D group:

Summary

A method to relate archived marine meteorological observations to two-minute average rain rates is described. The method is used to produce maps that indicate the frequency of observation of critical rain rates (5, 8, and 15 mm/hr) for the Atlantic, North Pacific and Indian Oceans.
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Summary

A method to relate archived marine meteorological observations to two-minute average rain rates is described. The method is used to produce maps that indicate the frequency of observation of critical rain rates (5, 8, and 15 mm/hr) for the Atlantic, North Pacific and Indian Oceans.

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Rain rate climatologies over marine regions

Classes of functions with explicit best uniform approximations

January 1, 1982
  |
Journal Article
Author:
Harold Z. Ollin
…
Published in:
J. Approx. Theory, Vol. 34, No. 3, 1982, pp. 264-276.
Topic:
algorithms
R&D area:
R&D group:

Summary

This paper concerns the construction of forms of the error function, en(x) = f(x)- p*n(x), where p*n is the best uniform polynomial approximation of degree n to a continuous function f on [-1, +l]. We show that it is always possible and, from the viewpoint of obtaining explicit results, expedient to write the error as en= a cos(n(Theta + phi), where x =cos Theta, |a|= En(f), the uniform norm of en(x), and the phase angle phi is a continuous function of Theta, depending on f and n. Our classes of explicit best approximations arise from a novel method of determining suitable phase angles in this representation of en(x).
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Summary

This paper concerns the construction of forms of the error function, en(x) = f(x)- p*n(x), where p*n is the best uniform polynomial approximation of degree n to a continuous function f on [-1, +l]. We show that it is always possible and, from the viewpoint of obtaining explicit results, expedient...

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Classes of functions with explicit best uniform approximations

On best approximation by truncated series

May 1, 1981
  |
Journal Article
Author:
Harold Z. Ollin
Published in:
J. Approx. Theory, Vol. 32, May 1981, pp. 82-84.
Topic:
algorithms
R&D area:
R&D group:

Summary

Let T, be the Chebyshev polynomial of the first kind of degree k.
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Summary

Let T, be the Chebyshev polynomial of the first kind of degree k.

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On best approximation by truncated series

Modes of crossed rectangular waveguide

March 1, 1976
  |
Journal Article
Author:
Henry J. Stalzer Jr
…
Published in:
IEEE Trans. on Antennas Propag., Vol. 24, No. 2, March 1976, pp. 220-223.
Topic:
antennas
R&D area:
R&D group:

Summary

The cutoff frequencies and model fields of dually polarized crossed rectangular waveguide are calculated numerically and the cutoff frequencies verified experimentally. Symmetry arguments and group theory are used to explain mode degeneracies and mode splitting. The single mode bandwidth is 38 percent of center frequency for both polarization when the guide dimensions are chosen appropriately. For applications where symmetric excitation is assured, bandwidths in excess of 2:1 can be obtained.
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Summary

The cutoff frequencies and model fields of dually polarized crossed rectangular waveguide are calculated numerically and the cutoff frequencies verified experimentally. Symmetry arguments and group theory are used to explain mode degeneracies and mode splitting. The single mode bandwidth is 38 percent of center frequency for both polarization when the...

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Modes of crossed rectangular waveguide

Frequency scan antenna design for RPV radar sensors

October 22, 1975
  |
Project Report
Author:
Francis G. Willwerth
…
Published in:
MIT Lincoln Laboratory Report TT-5
Topic:
antennas
R&D area:
R&D group:

Summary

A small program to explore the feasibility of a frequency-scanned antenna as a low-cost, light-weight answer to the requirements of the mini- RPV radar system for the HCWLS program resulted in construction and study of a slotted-waveguide laboratory embodiment of the device. A general formulation of the relationships connecting design parameters was carried out and employed for guidance in selection of waveguide size, band center, and slot spacing. A 301 band from 14.8 to 20.3 GHz in empty WR-42 waveguide was selected. The beamwidth, sidelobe level, gain, attenuation, and efficiency were studied, including the effectiveness of tapered illumination and the occurrence of spurious cross-polarized radiation, as functions of the frequency-controlled scan direction. Some thought was given to alternatives such as aperiodic-array and subarray techniques as means of reducing the tunable bandwidth requirement, as well as stripline serpentine-waveguide designs, for possible future investigation. The work reported herein has shown that the frequency-scanned antenna will provide a low-cost implementation practical for some system applications. If the limitation, primarily in instantaneous signal bandwidth are acceptable in the applications pursued, further investigation of alternate designs is recommended.
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Summary

A small program to explore the feasibility of a frequency-scanned antenna as a low-cost, light-weight answer to the requirements of the mini- RPV radar system for the HCWLS program resulted in construction and study of a slotted-waveguide laboratory embodiment of the device. A general formulation of the relationships connecting design...

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Frequency scan antenna design for RPV radar sensors
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