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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
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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

DABS link performance considerations

April 28, 1975
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Project Report
Author:
Gary J. Schlieckert
Published in:
MIT Lincoln Laboratory Report ATC-41
Topic:
surveillance
R&D area:
R&D group:

Summary

The DABS link performance is computed using the present values for the system operating parameters and the available models that describe environment and aircraft antenna effects. The various fade mechanisms are described, and a statistical determination of performance is proposed. The performance is computed for various sets of conditions including different ground antennas, aircraft maneuvers, antenna obstructions and the performance when aircraft are in the cone of silence. The DABS link is found to have very good overall performance with only small regions of reduced reliability that are at low angles or due to maneuvers. Those missed replies due to maneuvers are found to be sporadic from scan to scan.
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Summary

The DABS link performance is computed using the present values for the system operating parameters and the available models that describe environment and aircraft antenna effects. The various fade mechanisms are described, and a statistical determination of performance is proposed. The performance is computed for various sets of conditions including...

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DABS link performance considerations

Scale model pattern measurements of aircraft L-band beacon antennas

April 4, 1975
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Project Report
Author:
Kimball J. Keeping
…
Published in:
MIT Lincoln Laboratory Report ATC-47
Topic:
L-band
R&D area:
R&D group:

Summary

This report describes the techniques and apparatus used to measure the directional patterns of aircraft ATC transponder antennas (L-Band) using digital techniques and magnetic tapes for data storage. Algorithms involved in data normalization, cross-polarization correction and coordinate conversations are discussed. Some typical applications of the data are illustrated with actual computer outputs obtained from the model measurements.
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Summary

This report describes the techniques and apparatus used to measure the directional patterns of aircraft ATC transponder antennas (L-Band) using digital techniques and magnetic tapes for data storage. Algorithms involved in data normalization, cross-polarization correction and coordinate conversations are discussed. Some typical applications of the data are illustrated with actual...

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Scale model pattern measurements of aircraft L-band beacon antennas

An analysis of aircraft L-band beacon antenna patterns

January 15, 1975
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Project Report
Author:
Gary J. Schlieckert
Published in:
MIT Lincoln Laboratory Report ATC-37
Topic:
L-band
R&D area:
R&D group:

Summary

Radiation patterns are examined for L-Band beacon antennas mounted on aircraft ranging from small, single-engine, general aviation aircraft to the Boeing 747. The data analyzed consists of antenna gain values taken in two degree steps over a spherical surface centered at the antenna location. Data from three representative scale model aircraft are studied in detail and show the effects of various airframe structural members on the radiation lobing patterns and the relative performance of antennas located at a number of positions on each scale model aircraft. Significant observations were that: -Landing gear and flaps complicate the lobing structure but do not introduce many more low gain values. -In general, antennas mounted forward of the leading edge of the wing and on fuselage bottom centerline (not too close to nosewheel) provide the best overall performance. -As an aircraft maneuvers, antenna performance degrades in direct relationship with the severity of the roll or pitch.
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Summary

Radiation patterns are examined for L-Band beacon antennas mounted on aircraft ranging from small, single-engine, general aviation aircraft to the Boeing 747. The data analyzed consists of antenna gain values taken in two degree steps over a spherical surface centered at the antenna location. Data from three representative scale model...

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An analysis of aircraft L-band beacon antenna patterns

Summary of results of antenna design cost studies

February 19, 1974
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Project Report
Author:
Jean-Claude Sureau
Published in:
MIT Lincoln Laboratory Report ATC-22
Topic:
antennas
R&D area:
R&D group:

Summary

Design/cost studies on antenna systems for DABS have been carried out by Texas Instruments and Westinghouse under Lincoln Laboratory sponsorship. For independent, mechanically-rotating systems aperture widths between 10' and 35' and heights between 4' and 16' were considered, with estimated corresponding production costs ranging from $10K to more than $200K. No generally-recommended implementation emerged although the trend was to choose planar arrays for stringent performance requirements and to accept less expensive reflectors when requirements were sufficiently relaxed. Although the aperture size was found to have a significant cost impact on the remainder of the system (pedestal, drive, tower), the antenna usually accounted for less than half of the total antenna installation cost. With the use of off-boresight monopulse direction-finding, agile beam arrays require only slightly more than one beam position per beamwidth. Even with the resulting simplification in the beamforming circuitry, their cost is about twice that of comparable rotators and starts at about $200K. DABS systems which share the same pedestal as primary radars ("co-located") are inherently highly constrained and tend to lead to unique implementations. For an ASR installation, an integral monopulse beacon feed constitutes an economical (less than $5K) and expedient implementation with performance parameters which, though not optimum, are acceptable for DABS (4 degrees beamwidth and 2 dB/degree elevation cut-off rate). A back-mounted antenna of the same (or smaller) aperture size as the AST reflector can also be implemented as a retrofit for about $40K. For ARSR installations, integral monopulse beacon feeds are also feasible at a very nominal cost but some performance compromises have to be accepted. Back-mounted DABS antennas can be accommodated in a large range of aperture sizes.
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Summary

Design/cost studies on antenna systems for DABS have been carried out by Texas Instruments and Westinghouse under Lincoln Laboratory sponsorship. For independent, mechanically-rotating systems aperture widths between 10' and 35' and heights between 4' and 16' were considered, with estimated corresponding production costs ranging from $10K to more than $200K...

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Summary of results of antenna design cost studies

Effects of airborne transponder antenna lobe switching on en route (PCD) and terminal (BDAS) beacon reply processing

January 29, 1974
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Project Report
Author:
Ernest H. Day
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Published in:
MIT Lincoln Laboratory Report ATC-18
Topic:
antennas
R&D area:
R&D group:

Summary

The comparative performances of switching top and bottom transponder antennas versus the bottom antenna alone, in target detection by ARTS III and by PCD, were investigated in order to determine which of the two antenna configurations is preferable. A variety of military aircraft participated, performing climbouts, orbits, straight and level segments, and descents, in order to expose a wide range of aspect angles to the interrogator. Data were collected at Washington, D.C., utilizing the ATCBI at Andrews Air Force Base, and at NAFEC, utilizing the Elwood site. The frequency of occurrence of lost targets, particularly of consecutive lost targets, was found to vary considerably from one aircraft type to another. Analysis of the reduced data provides a reasonable basis, however, for concluding that, to maximize average probability of detection, the bottom antenna is better in the terminal area but switching antennas are better for En Route application. To minimize long sequences of misses which cause track loss on turns, the switching antenna appears more favorable in both flight regimes. The data also suggest that a higher probability of detection can be obtained in both environments, without incurring serious penalties, by reducing the leading edge detection thresholds.
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Summary

The comparative performances of switching top and bottom transponder antennas versus the bottom antenna alone, in target detection by ARTS III and by PCD, were investigated in order to determine which of the two antenna configurations is preferable. A variety of military aircraft participated, performing climbouts, orbits, straight and level...

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Effects of airborne transponder antenna lobe switching on en route (PCD) and terminal (BDAS) beacon reply processing

Final Report: Transponder Test Program

April 12, 1972
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Project Report
Author:
George V. Colby
…
Published in:
MIT Lincoln Laboratory Report ATC-9
Topic:
surveillance
R&D area:
R&D group:

Summary

Performance parameters of transponders installed in aircraft were measured to determine their degree of compliance with current specifications. A mobile van was outfitted with electronic test equipment which simulated the transmitter and receiver sections of a ground interrogator and which allowed measurement of transponder parameters. A horn antenna located near the aircraft under test was used to couple signals to and from the transponder. The results of measuremetns on 504 transponders installed in general aviation aircraft, 17 transponders installed in military aircraft, and 28 transponders installed in air carrier aircraft are reported. Of these, 31 general aviation, 2 military, and one air carrier transponders were inoperative. The results of measurements of reply frequency, squitter, delay, Mode C operation, dead time, P2/P1 ratio required for suppression, suppression time, framing pulse spacing, power output and sensitivity are included.
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Summary

Performance parameters of transponders installed in aircraft were measured to determine their degree of compliance with current specifications. A mobile van was outfitted with electronic test equipment which simulated the transmitter and receiver sections of a ground interrogator and which allowed measurement of transponder parameters. A horn antenna located near...

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Final Report: Transponder Test Program
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