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Wide-angle scanning wide-band phased array antennas
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis considers problems related to the design and the analysis of wide-angle scanning phased arrays. The goals of the thesis are the design and analysis of antenna elements suitable for wide-angle scanning array antennas, and the study of scan blindness effects and edge effects for this type of antennas. Wide-angle scanning arrays are useful in radar applications, and the designs considered in the thesis are intended for an airborne radar antenna.After a study of the wide-angle scanning limits of three candidate elements, the tapered-slot was chosen for the proposed application.A tapered-slot antenna element was designed by using the infinitive array approach and the resulting element is capable of scanning out to 60° from broadside in all scan planes for a bandwidth of 2.5:1 and an active reflection coefficient less than -10 dB. This design was implemented on an experimental antenna consisting of 256 elements.The predicted performance of the antenna was then verified by measuring the coupling coefficients and the embedded element patterns, and the measurements agreed well with the numerical predictions.Since the radar antenna is intended for applications where stealth is important, an absorbing layer is positioned on top of the ground plane to reduce the radar cross section for the antenna's cross-polarization.This absorbing layer attenuates guided waves that otherwise lead to scan blindness, but does not adversely affect the antenna performance for the desired scan directions and frequencies.The highest frequency limit of the tapered-slot element is set by scan blindnesses. One of these scan blindnesses is found to be unique to tapered-slot elements positioned in triangular grids. This scan blindness is studied in detail and a scan blindness condition is presented and evaluated.The evaluation of the experimental antenna shows that edge effects reduce the H-plane performance of the central elements.These edge effects are further studied and characterized, by comparing the scattering parameters for finite-by-infinite arrays and infinite arrays.In this way it is possible to divide the edge effects into two categories: those caused by finite excitation, and those caused by perturbed currents due to the geometry of the edge. A finite difference time domain code with time shift boundaries is used to compute the active reflection coefficients needed to compute the scattering parameters, but this code cannot directly compute the active reflection coefficient for all the required phase shifts.Hence, an additional method is presented that makes it possible to compute arbitrary phase shifts between the elements using any numerical code with limited scan directions.

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , viii, 62 p.
Series
Trita-EE, ISSN 1653-5146 ; 2009:017
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-10225ISBN: 978-91-7415-291-3 (print)OAI: oai:DiVA.org:kth-10225DiVA: diva2:211543
Public defence
2009-05-08, F3, Lindstedtsvägen 26, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20100712Available from: 2009-05-07 Created: 2009-04-16 Last updated: 2010-07-12Bibliographically approved
List of papers
1. Study of Rectangular Waveguide Elements for Planar Wide-Angle Scanning Phased Array Antennas
Open this publication in new window or tab >>Study of Rectangular Waveguide Elements for Planar Wide-Angle Scanning Phased Array Antennas
2005 (English)In: Antennas and Propagation Society International Symposium, 2005 IEEE, 2005, 815-818 p.Conference paper, Published paper (Refereed)
Abstract [en]

Rectangular waveguide elements in an infinite planar phased array are analysed with respect to wide-angle scanning. Three waveguide geometries are considered: two dual polarized square waveguides and one rectangular waveguide. The waveguides are matched for minimum average reflected power over the scan range. This cost function is shown to give a match suitable for wide-angle scanning

 

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-10218 (URN)10.1109/APS.2005.1551689 (DOI)2-s2.0-33846859111 (Scopus ID)0-7803-8883-6 (ISBN)
Note
QC 20100712Available from: 2009-04-16 Created: 2009-04-16 Last updated: 2010-07-12Bibliographically approved
2. Characteristics of a broad-band wide-scan fragmented aperture phased array antenna
Open this publication in new window or tab >>Characteristics of a broad-band wide-scan fragmented aperture phased array antenna
2006 (English)Conference paper, Published paper (Refereed)
Abstract [en]

In this paper a phased array antenna is described that is designed with the help of a genetic algorithm for scan angles out to 60° from broadside. The focus is on simplifying the manufacturing of the diagonally adjoining pixels and on numerical results for thin antennas. The effects of the corner to corner contacts are studied and results for two synthesized elements ar Test and measurement requirements on wireless devices

Series
European Space Agency, (Special Publication) ESA SP, ISSN 0379-6566
Keyword
Broad-band; Fragmented aperture; Phased array; Wide-scan
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-10219 (URN)10.1109/EUCAP.2006.4584710 (DOI)2-s2.0-33847372169 (Scopus ID)978-92-9092-937-6 (ISBN)
Conference
European Conference on Antennas and Propagation: EuCAP 2006; Nice; France; 6-10 November 2006
Note

QC 20141125

Available from: 2009-04-16 Created: 2009-04-16 Last updated: 2017-03-24Bibliographically approved
3. Effects on scan blindnesses of an absorbing layer covering the ground plane in a triangular grid single-polarized tapered-slot array
Open this publication in new window or tab >>Effects on scan blindnesses of an absorbing layer covering the ground plane in a triangular grid single-polarized tapered-slot array
2008 (English)In: Antennas and Propagation Society International Symposium, 2008. AP-S 2008. IEEE, 2008, 2966-2969 p.Conference paper, Published paper (Refereed)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-10220 (URN)10.1109/APS.2008.4619660 (DOI)000261440601354 ()2-s2.0-55649121433 (Scopus ID)978-1-4244-2041-4 (ISBN)
Note
QC 20100712Available from: 2009-04-16 Created: 2009-04-16 Last updated: 2010-12-03Bibliographically approved
4. A Scan Blindness Model for Single-Polarized Tapered-Slot Arrays in Triangular Grids
Open this publication in new window or tab >>A Scan Blindness Model for Single-Polarized Tapered-Slot Arrays in Triangular Grids
2008 (English)In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 0096-1973, Vol. 56, no 9, 2937-2942 p.Article in journal (Refereed) Published
Abstract [en]

A simple model is presented that predicts scan blindness in the E-plane for single polarized tapered-slot arrays where the elements are positioned in a triangular grid. The blindness occurs when the phase progression along the dielectric substrates is equal to the phase progression of a leaky mode in the structure. A simple equation is presented that estimates the frequency at which the scan blindness occurs for a given angle in the E-plane. This equation is derived from a simple representation of the phased array antenna, but includes the dominant effect of this particular class of scan blindness. The method is shown to agree well with computed results obtained with two different numerical codes.

Keyword
array, broadband-antennas, scan blindness, tapered-slot, triangular grid
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-10221 (URN)10.1109/TAP.2008.928780 (DOI)000259407100017 ()2-s2.0-51749093123 (Scopus ID)
Note
QC 20100712Available from: 2009-04-16 Created: 2009-04-16 Last updated: 2011-11-08Bibliographically approved
5. A single polarized triangular grid tapered-slot array antenna
Open this publication in new window or tab >>A single polarized triangular grid tapered-slot array antenna
2009 (English)In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 0096-1973, Vol. 57, no 9, 2599-2607 p.Article in journal (Refereed) Published
Abstract [en]

A triangular grid single polarized tapered-slot array antenna for radar applications is studied. Compared with a rectangular grid an equilateral triangular grid allows a larger unit cell without any onset of grating lobes. Since single polarized tapered-slots in triangular grids support guided modes, which cause scan blindness, the increase in unit cell size is smaller than the optimal 15%. The design presented in the paper is capable of scan angles out to 60° from broadside in the E and H planes. To improve the match over the radar band a local minimum in the active reflection coefficient is positioned at the most critical scan direction, resulting in a reflection coefficient that is less than -12 dB in the X-band. To reduce the radar cross section for the cross-polarization an absorbing layer is positioned above the ground plane, which affects some of the guided modes that lead to scan blindnesses. An experimental antenna with 16×16 elements was built, and it was found that the H-plane performance for large scan angles for the finite antenna deviates more than expected from the infinite array approximation. Otherwise both mutual coupling measurements and embedded element patterns agrees well with the numerical results.

Keyword
Broadband antennas; phased arrays; scan blindness; tapered-slot; triangular grid; Vivaldi antennas
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-10222 (URN)10.1109/TAP.2009.2027044 (DOI)000269513300010 ()2-s2.0-70349257599 (Scopus ID)
Note

QC 20150727

Available from: 2009-04-16 Created: 2009-04-16 Last updated: 2015-07-27Bibliographically approved
6. Computing return loss for arbitrary scan directions using limited scan codes for infinite phase arrays
Open this publication in new window or tab >>Computing return loss for arbitrary scan directions using limited scan codes for infinite phase arrays
2009 (English)In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 45, no 13, 660-662 p.Article in journal (Refereed) Published
Abstract [en]

Analyzing large phased array antennas using time domain codes is favourable when looking into wideband solutions. This is often done by assuming an infinite array, i.e. a unit cell approach is used. Unfortunately, unit cell based time domain codes using time shifts between cell boundaries have a disadvantage of only being able of analyzing phase shifts corresponding to a beam scanned in the visible space. However, in order to fully characterize the infinite array antenna it is sometimes necessary to compute the active reflection coefficient also for scan directions/phase shifts corresponding to invisible space. Presented in this letter is a new approach on how to do this in a simple manner using unit cell based time domain codes. By extending the size of the computational domain, and include more than one element, phase shifts corresponding to invisible space are included.

Keyword
PERIODIC BOUNDARY-CONDITIONS
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-10223 (URN)10.1049/el.2009.0272 (DOI)000267820600002 ()2-s2.0-67650085552 (Scopus ID)
Note
QC 20100712Available from: 2009-04-16 Created: 2009-04-16 Last updated: 2010-12-08Bibliographically approved
7. A study of edge effects in triangular grid tapered-slot arrays using coupling coefficients
Open this publication in new window or tab >>A study of edge effects in triangular grid tapered-slot arrays using coupling coefficients
2010 (English)In: Radio Science, ISSN 0048-6604, E-ISSN 1944-799X, Vol. 45, RS2005- p.Article in journal (Refereed) Published
Abstract [en]

Edge effects for tapered-slot elements in triangular grid array antennas are studied by using finite difference time domain codes. The S parameters for finite-by-infinite arrays are computed and evaluated for two different edge models and, to evaluate the edge effects, the results are compared with the S parameters for the infinite array. As expected, the largest difference between the results occurs for the elements closest to the edges, because of the missing coupling from nearby elements and the perturbed element currents due to the edge geometry. By using the proposed method it is possible to distinguish between these two edge effects. A method to combine the finite-by-infinite array results and the infinite array results is presented and used to characterize the perturbation caused by the truncation of the infinite array.

Keyword
ANTENNA-ARRAYS, PHASED-ARRAYS, FINITE, DIRECTIONS
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-10224 (URN)10.1029/2009RS004174 (DOI)000276831400001 ()2-s2.0-77954321672 (Scopus ID)
Note
QC 20100712 Uppdaterad från submitted till published (20110114).Available from: 2009-04-16 Created: 2009-04-16 Last updated: 2011-01-14Bibliographically approved

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Citation style
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  • en-US
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  • Other locale
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Output format
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