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Nearfield anechoic chamber and farfield on-site antenna calibration pattern comparison of an S-band planar phased array radar

April 27, 2022
  |
Conference Paper
Author:
Christine F. Parry
…
Published in:
IEEE Annual Conf. on Wireless and Microwave Technology, WAMICON, 27-28 April 2022.
Topic:
antennas
R&D area:
R&D group:

Summary

The Advanced Technology Demonstrator (ATD) is an active, S-band, dual-polarization phased array radar developed for weather sensing. The ATD is an active electronically scanned array (AESA) with a 4-m aperture comprised of 4,864 individual transmit/receive (T/R) modules. The antenna was calibrated at the element, subarray, and array levels. Calibration, validation, and verification testing was completed in two main stages, first in an anechoic chamber and second after it was installed on site in its permanent location. This paper describes the procedure used to collect antenna patterns at each stage and compares three key performance metrics: beamwidth, mean-squared sidelobe level (MSSL), and integrated sidelobe level (ISL).
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Summary

The Advanced Technology Demonstrator (ATD) is an active, S-band, dual-polarization phased array radar developed for weather sensing. The ATD is an active electronically scanned array (AESA) with a 4-m aperture comprised of 4,864 individual transmit/receive (T/R) modules. The antenna was calibrated at the element, subarray, and array levels. Calibration, validation...

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Nearfield anechoic chamber and farfield on-site antenna calibration pattern comparison of an S-band planar phased array radar

Effect of a wet spherical radome on the reflected power for an S-band planar phased array radar antenna

October 24, 2021
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Conference Paper
Author:
Christine F. Parry
…
Published in:
2021 Antenna Measurement Techniques Association Symp., AMTA, 24-29 October 2021.
Topic:
antennas
R&D area:
R&D group:

Summary

An active S-band dual-polarized multifunction phased array radar (MPAR), the Advanced Technology Demonstrator (ATD), has recently been developed for weather sensing and aircraft surveillance. The ATD is an active electronically scanned array (AESA) with 4864 transmit/receive (T/R) modules and was installed in a spherical radome. Simulations and a novel phased array measurement technique have been explored to assess the impact of high reflectivity from a wet radome during rain that can potentially induce voltages exceeding the transmit amplifier breakdown voltage. The measurement technique uses array elements radiating one at a time to illuminate the radome, and uses superposition to quantify the received signal power in a reference antenna on the face of the array. It is shown that when the radome surface is wet and highly reflective, certain electronic steering angles sum to a large reflected signal focused on the array face. This measurement technique can be used prior to high-power phased array radar operation to monitor the magnitude of reflections and help avoid element transmit amplifier failures.
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Summary

An active S-band dual-polarized multifunction phased array radar (MPAR), the Advanced Technology Demonstrator (ATD), has recently been developed for weather sensing and aircraft surveillance. The ATD is an active electronically scanned array (AESA) with 4864 transmit/receive (T/R) modules and was installed in a spherical radome. Simulations and a novel phased...

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Effect of a wet spherical radome on the reflected power for an S-band planar phased array radar antenna

Priority scheduling for multi-function apertures with hard- and soft-time constraints

March 6, 2021
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Conference Paper
Author:
Bruce F. McGuffin
Published in:
2021 IEEE Aerospace Conf., 6-13 March 2021.
Topic:
antennas
R&D area:
R&D group:

Summary

A multi-function aperture (MFA) is an antenna array that supports multiple RF signals for a diverse set of activities. An MFA may support multiple activities simultaneously if they are compatible, and platforms may utilize multiple MFAs to meet field-of-regard and frequency range requirements. Efficient MFA utilization requires a Resource Manager (RM) that routes signals to the correct MFA based on field-of-view and other requirements, and schedules MFA access to resolve conflicts based on request priority. An efficient RM scheduler time-interleaves requests from different activities as needed. Requested access events may be hard-time—that is, the event must be scheduled at a specified time or not at all, or soft-time, indicating it may be scheduled anytime in a specified window. Hard-time events include communications channels with assigned time slots, and soft-time events include asynchronous communications channels. This paper describes and evaluates an optimal algorithm to jointly schedule sequences of hard-time requests, maximizing the number of scheduled events while meeting priority requirements. An extension of this algorithm provides near-optimal schedules for sequences of soft-time or mixed hard- and soft-time events. Algorithms are evaluated by simulation, using two conflict models. The first is based on fixed signal paths that conflict if two paths share a common resource. The second model assumes the RM dynamically assigns resources. As implemented, these algorithms are too slow for real-time operation, and further work is required. They do provide insight into the MFA management problem, a useful metric for evaluating resource sharing and scheduling approaches, and may suggest efficient sub-optimal algorithms.
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Summary

A multi-function aperture (MFA) is an antenna array that supports multiple RF signals for a diverse set of activities. An MFA may support multiple activities simultaneously if they are compatible, and platforms may utilize multiple MFAs to meet field-of-regard and frequency range requirements. Efficient MFA utilization requires a Resource Manager...

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Priority scheduling for multi-function apertures with hard- and soft-time constraints

Antennas and RF components designed with graded index composite materials

July 27, 2020
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Conference Paper
Author:
Roberto G. Rojas-Teran
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Published in:
2020 Intnl. Applied Computational Electromagnetics Society Symp., ACES, 27-31 July 2020.
Topic:
additive manufacturing
R&D area:
R&D group:

Summary

Antennas and RF components in general, can greatly benefit with the recent development of low-loss 3D print graded index materials. The additional degrees of freedom provided by graded index materials can result in the design of antennas and other RF components with superior performance than currently available designs based on conventional constant permittivity materials. Here we discuss our work designing flat lenses for antennas and RF matching networks as well as filters based on graded index composite materials.
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Summary

Antennas and RF components in general, can greatly benefit with the recent development of low-loss 3D print graded index materials. The additional degrees of freedom provided by graded index materials can result in the design of antennas and other RF components with superior performance than currently available designs based on...

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Antennas and RF components designed with graded index composite materials

Beamforming with distributed arrays: FY19 RF Systems Line-Supported Program

January 7, 2020
  |
Project Report
Author:
Keith W. Forsythe
…
Published in:
MIT Lincoln Laboratory Report LSP-270
Topic:
antennas
R&D area:
R&D group:

Summary

Spatial beamforming using distributed arrays of RF sensors is treated. Unlike the observations from traditional RF antenna arrays, the distributed array's data can be subjected to widely varying time and frequency shifts among sensors and signals. These shifts require compensation upon reception in order to perform spatial filtering. To perform beamforming with a distributed array, the complex-valued observations from the sensors are shifted in time and frequency, weighted, and summed to form a beamformer output that is designed to mitigate interference and enhance signal energy. The appropriate time-frequency shifts required for good beamforming are studied here using several different methodologies.
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Summary

Spatial beamforming using distributed arrays of RF sensors is treated. Unlike the observations from traditional RF antenna arrays, the distributed array's data can be subjected to widely varying time and frequency shifts among sensors and signals. These shifts require compensation upon reception in order to perform spatial filtering. To perform...

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Beamforming with distributed arrays: FY19 RF Systems Line-Supported Program

CW radar operation in the focused near-field

April 14, 2019
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Conference Paper
Author:
Kristan A. Tuttle
…
Published in:
2019 Intl. Applied Computational Electromagnetics Society Symp., ACES, 14-19 April 2019.
Topic:
antennas
R&D area:
R&D group:

Summary

In this paper we will show by computer simulation and by measurements that the horn antennas of a bi-static radar operating in the near-field have a distinct maximum at a non-zero range. By focusing the antennas on this hot spot a low-powered, continuous-wave Ku-band radar could detect flying mosquitoes at very short range.
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Summary

In this paper we will show by computer simulation and by measurements that the horn antennas of a bi-static radar operating in the near-field have a distinct maximum at a non-zero range. By focusing the antennas on this hot spot a low-powered, continuous-wave Ku-band radar could detect flying mosquitoes at...

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CW radar operation in the focused near-field

Modeling and validation of a mm-wave shaped dielectric lens antenna

July 29, 2018
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Conference Paper
Author:
David C. Mooradd
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Published in:
2018 Int. Applied Computational Electromagnetics Society Symp., ACES, 29 July - 1 August 2018.
Topic:
antennas
R&D area:
R&D group:

Summary

The modeling and validation of a 33 GHz shaped dielectric antenna design is investigated. The electromagnetic modeling was performed in both WIPL-D and FEKO, and was used to validate the antenna design prior to fabrication of the lens. It is shown that both WIPL-D and FEKO yield similarly accurate results as compared to measured far-field gain radiation patterns.
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Summary

The modeling and validation of a 33 GHz shaped dielectric antenna design is investigated. The electromagnetic modeling was performed in both WIPL-D and FEKO, and was used to validate the antenna design prior to fabrication of the lens. It is shown that both WIPL-D and FEKO yield similarly accurate results...

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Modeling and validation of a mm-wave shaped dielectric lens antenna

Polarization ratio determination with two identical linearly polarized antennas

July 9, 2017
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Conference Paper
Author:
Herbert M. Aumann
…
Published in:
2017 IEEE AP-S Symp. on Antennas and Propagation and USNC Radio Science Meeting, 9-14 July 2017.
Topic:
antennas
R&D area:
R&D group:

Summary

This paper describes a method for determining the complex polarization ratio using two identical, linearly polarized antennas. By Fourier transform analysis of s21 measurements with one of the antennas rotating about its axis a circular polarization ratio is derived which can be transformed into an equivalent linear polarization ratio. A linearly polarized reference antenna is not required. The technique was verified by electromagnetic simulations and illustrated by measurements in an anechoic chamber with two 3.3 GHz square patch antennas.
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Summary

This paper describes a method for determining the complex polarization ratio using two identical, linearly polarized antennas. By Fourier transform analysis of s21 measurements with one of the antennas rotating about its axis a circular polarization ratio is derived which can be transformed into an equivalent linear polarization ratio. A...

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Polarization ratio determination with two identical linearly polarized antennas

A rotating source polarization measurement technique using two circularly polarized antennas

October 30, 2016
  |
Conference Paper
Author:
Herbert M. Aumann
…
Published in:
38th Mtg. and Symp. of the Antenna Measurement Techniques Assoc., AMTA 2016, 30 October - 4 November 2016.
Topic:
antennas
R&D area:
R&D group:

Summary

This paper combines the standard two-antenna gain measurement technique with the rotating source method for measuring the polarization ratio and tilt angle of the polarization ellipse of a circularly polarized antenna. The technique is illustrated with two identical helical antennas, one for the source and one for the antenna-under-test (AUT), facing each other. Measurements of the voltage transfer ratio are made over one 360 degree on-axis rotation of the source while the AUT remains stationary. The rotation causes the phase of the electric field of the principal polarization to rotate in one direction and the phase of the cross polarization to rotate in the opposite direction. A Discrete Fourier Transform (DFT) of the data from a single rotation is insufficient to resolve the two polarization components. Leakage from the principal polarization will most likely cover up the low-level opposite polarization signal. However, the DFT resolution can be artificially increased by appending to the measured data, precisely M-1 copies of the data. Now the polarization components will be separated by 2M revolutions. Application of a heavy weighting function to the augmented data and a phase compensation to the DFT allows a clear determination of the amplitude and phase of the on-axis principal and cross polarization components. The technique was verified by electromagnetic simulations and by measurements in an anechoic chamber with two 6-turn 5.8 GHz helical antennas separated by 4 feet. There was very good agreement between the simulations and measurements of the polarization ellipse tilt angle and a -20 dB polarization ratio.
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Summary

This paper combines the standard two-antenna gain measurement technique with the rotating source method for measuring the polarization ratio and tilt angle of the polarization ellipse of a circularly polarized antenna. The technique is illustrated with two identical helical antennas, one for the source and one for the antenna-under-test (AUT)...

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A rotating source polarization measurement technique using two circularly polarized antennas

3D printed conformal array antenna: simulations and measurements

October 18, 2016
  |
Conference Paper
Author:
Alan J. Fenn
…
Published in:
6th Int. Symp. on Phased Array Systems and Technology, PAST 2016, 18-21 October 2016.
Topic:
antennas
R&D area:
R&D group:

Summary

A conformal array antenna has been investigated using a combination of 3D printer and copper plating techniques. Circular patch antenna elements were copper plated onto a 3D printed dielectric substrate made of ABS-M30 material. Measured and simulated element reflection coefficient, element gain patterns, and array scanned beam radiation patterns at L band are in good agreement.
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Summary

A conformal array antenna has been investigated using a combination of 3D printer and copper plating techniques. Circular patch antenna elements were copper plated onto a 3D printed dielectric substrate made of ABS-M30 material. Measured and simulated element reflection coefficient, element gain patterns, and array scanned beam radiation patterns at...

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3D printed conformal array antenna: simulations and measurements
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