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Triangle TCAS antenna

Published in:
MIT Lincoln Laboratory Report ATC-380

Summary

The Traffic Alert and Collision Avoidance (TCAS) provides a pilot display showing the range and bearing of nearby aircraft. TCAS obtains the bearing information by using an angle-of-arrival antenna. In the development of TCAS at Lincoln Laboratory, the first airborne tests were conducted using an Adcock antenna, which is a small square array of four monopole elements. This report describes an alternative antenna for TCAS, using three elements in the shape of a triangle. It is shown that the triangle antenna is less sensitive to receiver noise, and that improvement factor is about 10 dB.
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Summary

The Traffic Alert and Collision Avoidance (TCAS) provides a pilot display showing the range and bearing of nearby aircraft. TCAS obtains the bearing information by using an angle-of-arrival antenna. In the development of TCAS at Lincoln Laboratory, the first airborne tests were conducted using an Adcock antenna, which is a...

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Low-profile dual-polarized UHF array antenna

Published in:
2010 IEEE Int. Symp. on Phased Array Systems & Technology, 12 October 2010, p. 599-602.

Summary

A low-profile dual-polarized UHF array antenna has been developed for wide field-of-view dual sector coverage in the 250 to 450 MHz frequency range for communications or radar applications. The antenna utilizes a pair of parasitically-tuned dipole arrays for horizontal polarization and a pair of parasitically-tuned monopole arrays for vertical polarization, and both arrays are mounted on a common ground plane. The thickness of the antenna is 18.2 cm. Numerical electromagnetic simulations were used to analyze and optimize the antenna parameters prior to fabrication. Measurements of the dual-polarized prototype in an anechoic chamber demonstrate the antenna?s return loss and dual-polarized radiation gain pattern performance.
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Summary

A low-profile dual-polarized UHF array antenna has been developed for wide field-of-view dual sector coverage in the 250 to 450 MHz frequency range for communications or radar applications. The antenna utilizes a pair of parasitically-tuned dipole arrays for horizontal polarization and a pair of parasitically-tuned monopole arrays for vertical polarization...

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Ultrawideband VHF/UHF dipole array antenna

Published in:
2010 IEEE Int. Symp. on Phased Array Systems, 12 October 2010, pp. 79-82.

Summary

A linearly-polarized ultrawideband dipole array antenna has been developed for coverage in the VHF/UHF frequency range for communications or radar applications. The antenna design utilizes a horizontally polarized array of thick tubular dipole elements above a ground plane. Numerical electromagnetic simulations were used to analyze and optimize the antenna parameters prior to fabrication. Measurements of a 24-element ultrawideband dipole array prototype in an anechoic chamber demonstrate the antenna's return loss and gain pattern performance over a wide bandwidth.
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Summary

A linearly-polarized ultrawideband dipole array antenna has been developed for coverage in the VHF/UHF frequency range for communications or radar applications. The antenna design utilizes a horizontally polarized array of thick tubular dipole elements above a ground plane. Numerical electromagnetic simulations were used to analyze and optimize the antenna parameters...

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Ultra-wideband offset bicone/dipole antenna: simulations and measurements

Author:
Published in:
Ann. Rev. of Progress in Applied Computational Electromagnetics, 8-12 March 2009.

Summary

An ultrawideband (UWB) antenna has been developed for operation in the 60 MHz to 18 GHz frequency range. This antenna is a new type--an offset bicone/dipole design that allows for vertically polarized omnidirectional coverage over an instantaneous 300:1 bandwidth. Numerical electromagnetic simulations with the finite-element method (FEM) were used to investigate the antenna concept and optimize geometry prior to fabrication. Measurements both outdoors and in an anechoic chamber confirm the antenna's performance.
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Summary

An ultrawideband (UWB) antenna has been developed for operation in the 60 MHz to 18 GHz frequency range. This antenna is a new type--an offset bicone/dipole design that allows for vertically polarized omnidirectional coverage over an instantaneous 300:1 bandwidth. Numerical electromagnetic simulations with the finite-element method (FEM) were used to...

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Integrated compensation network for low mutual coupling of planar microstrip antenna arrays

Published in:
IEEE Antennas and Propagation Society Int. Symp., 2007 Digest, 9-15 June 2007, pp. 1273-6.

Summary

The unavoidable presence of mutual coupling of antenna elements in an array limits the ability to transmit and receive signals concurrently [1]. In the absence of mutual coupling, it is conceivable although still difficult to transmit and receive at the same frequency at the same time, i.e., FM-CW radars. The reflection from the antenna, leakage through the circulator, and any other possible deleterious paths from the high power amplifier to the low noise amplifier must be cancelled or compensated for in some manner to keep the receiver linear. With a single antenna the signal and noise paths are correlated and therefore cancellation of the signal inherently eliminates the noise. However, in an array environment the mutual coupling of antenna elements cause noise from neighboring high power amplifiers to couple into each channel's receiver. While the signal coupling is coherent, the noise is uncorrelated to a degree that depends on the amplifier gain and noise figure. The use of a low mutual coupling antenna array is a critical element in operating systems in this manner.
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Summary

The unavoidable presence of mutual coupling of antenna elements in an array limits the ability to transmit and receive signals concurrently [1]. In the absence of mutual coupling, it is conceivable although still difficult to transmit and receive at the same frequency at the same time, i.e., FM-CW radars. The...

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Ultra-wideband step notch array using stripline feed

Published in:
IEEE Antennas and Propagation Society Int. Symp., 2007 Digest, 9-15 June 2007, pp. 3361-4.

Summary

Electronically scanned array (ESA) antennas capable of efficiently radiating over an octave of bandwidth provide system designs with more flexibility in multiple mode operation. Communication and radar bands occupy different frequency allocations and the growing research in Ultra-Wideband (UWB) communications make the use of a single ESA to cover these frequencies an area of interest. Array antennas constructed of tapered-slot antennas and TEM horns have been investigated and shown to operate successfully over an octave bandwidth. These antennas use vertical feeds which make them optimal for brick architectures, but less than desirable for tile architectures. Conventional notch antennas require a feed extending vertically away from the notch antenna which makes a flat 2-D connection between antennas difficult. In this work an Ultra-Wideband Step Notch Array (UWSNA) was designed for ESA applications. The array operates over a 6-12 GHz range using a flat, tile-based 2-D feed network making this array optimal for conformal applications with a minimum of vertical distance. Simulation results and measurements on a small prototype demonstrate the concept.
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Summary

Electronically scanned array (ESA) antennas capable of efficiently radiating over an octave of bandwidth provide system designs with more flexibility in multiple mode operation. Communication and radar bands occupy different frequency allocations and the growing research in Ultra-Wideband (UWB) communications make the use of a single ESA to cover these...

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Design of overlapped subarrays using an RFIC beamformer

Published in:
IEEE Antennas and Propagation Society Int. Symp., 2007 Digest, 9-15 June 2007, pp. 1791-4.

Summary

Electronically scanned arrays require a minimum number of controls, Nmin, given by the number of orthogonal beams that fill a prescribed scan sector. Most practical antenna arrays require considerably more than Nmin control elements, but overlapped subarray architectures can approach this theoretical limit. Figure 1 shows a block diagram of an overlapped subarray architecture. The overlapped subarray network produces a flattopped sector pattern with low sidelobes that suppress grating lobes outside of the main beam of the subarray pattern. Each radiating element of the array is connected to multiple subarrays, creating an overlapping geometry. It is possible to scan one beam, or a fixed set of contiguous beams, over the main sector of the subarray with a set of Nmin phase shifters. Alternatively, digital receivers can be connected to the Nmin subarrays and multiple simultaneous beams can be formed digitally. Digital subarray architectures using a combination of element level phase shifters and subarray level receivers makes it possible to scan multiple beam clusters over all space. The conventional approach to the design and manufacturing of the overlapped subarray network shown in Figure 1 is challenging and costly due to the complexity of the microwave network. However, the design of the overlapped subarray beamformer using Radio Frequency Integrated Circuits (RFIC) represents a novel approach for implementing an efficient trade-off between the agility and capability of fully digital arrays and the cost effectiveness of analog arrays.
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Summary

Electronically scanned arrays require a minimum number of controls, Nmin, given by the number of orthogonal beams that fill a prescribed scan sector. Most practical antenna arrays require considerably more than Nmin control elements, but overlapped subarray architectures can approach this theoretical limit. Figure 1 shows a block diagram of...

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A new compact range facility for antenna and radar target measurements

Author:
Published in:
Lincoln Laboratory Journal, Vol. 16, No. 2, June 2007, pp. 381-391.

Summary

A new antenna and radar-cross-section measurements facility consisting of four anechoic chambers has recently been constructed at Lincoln Laboratory on Hanscom Air Force Base. One of the chambers is a large compact range facility that operates over the 400 MHz to 100 GHz band, and consists, in part, of a large temperature-controlled rectangular chamber lined with radar-absorbing material that is arranged to reduce scattering; a composite rolled-edge offset-fed parabolic reflector; a robotic multi-feed antenna system; and a radar instrumentation system. Additionally, the compact range facility includes a gantry/crane system that is used to move large antennas and radar targets onto a positioning system that provides the desired aspect angles for measurements of antenna patterns and radar cross section. This compact range system provides unique test capabilities to support rapid prototyping of antennas and radar targets.
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Summary

A new antenna and radar-cross-section measurements facility consisting of four anechoic chambers has recently been constructed at Lincoln Laboratory on Hanscom Air Force Base. One of the chambers is a large compact range facility that operates over the 400 MHz to 100 GHz band, and consists, in part, of a...

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Design considerations for space-based radar phased arrays

Author:
Published in:
2005 IEEE MTT-S Int. Microwave Symp. Digest, 12-17 June 2005, pp. 1631-1634.

Summary

Space Based Radar (SBR) is being considered as a means to provide persistent global surveillance. In order to be effective, the SBR system must be capable of high area coverage rates, low minimum detectable velocities (MDV), accurate geolocation, high range resolution, and robustness against electronic interference. These objectives will impose challenging requirements on the antenna array, including wide-angle electronic scanning, wide instantaneous bandwidth, large poweraperture product, low sidelobe radiation patterns, lightweight deployable structures, multiple array phase centers, and adaptive pattern synthesis. This paper will discuss key enabling technologies for low earth orbit (LEO) SBR arrays including high efficiency transmit/receive modules and multilayer tile architectures, and the parametric influence of array design variables on the SBR system.
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Summary

Space Based Radar (SBR) is being considered as a means to provide persistent global surveillance. In order to be effective, the SBR system must be capable of high area coverage rates, low minimum detectable velocities (MDV), accurate geolocation, high range resolution, and robustness against electronic interference. These objectives will impose...

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Design considerations and results for an overlapped subarray radar antenna

Summary

Overlapped subarray networks produce flattopped sector patterns with low sidelobes that suppress grating lobes outside of the main beam of the subarray pattern. They are typically used in limited scan applications, where it is desired to minimize the number of controls required to steer the beam. However, the architecture of an overlapped subarray antenna includes many signal crossovers and a wide variation in splitting/combining ratios, which make it difficult to maintain required error tolerances. This paper presents the design considerations and results for an overlapped subarray radar antenna, including a custom subarray weighting function and the corresponding circuit design and fabrication. Measured pattern results will be shown for a prototype design compared with desired patterns.
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Summary

Overlapped subarray networks produce flattopped sector patterns with low sidelobes that suppress grating lobes outside of the main beam of the subarray pattern. They are typically used in limited scan applications, where it is desired to minimize the number of controls required to steer the beam. However, the architecture of...

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