Ortogonally-Aranged Center-Feed Single-Layer Slotted Waveguide Array Antennas for ...

109 Pages·2009·2.21 MB·English

Doctoral dissertation

Orthogonally-Arranged Center-Feed
Single-Layer Slotted Waveguide Array
Antennas for Polarization Division Duplex

March 2007.

Under the supervision of
Professor Makoto Ando
Associate Professor Jiro Hirokawa

Presented by
Yasuhiro Tsunemitsu

Department of Electrical and Electronic Engineering
Tokyo Institute of Technology
Contents

Chapter 1. Introduction-------------------------------4
1.1 Microwave applications--------------------------------------------------------4
1.2 Single-layer waveguide slotted array-----------------------------------------5
1.3 Summary of this study---------------------------------------------------------5
References----------------------------------------------------------------------------6

Chapter 2. Isolation between orthogonally
arranged two antennas -------9
2.1 Introductory remarks-----------------------------------------------------------9
2.2 Configuration and Simulation Model for an Array-----------------------10
2.3 Reflection and Radiation Patterns of an Array----------------------------10
2.4 Isolation Characteristics of Orthogonally
Polarized Pair Arrays Arranged Side-by-Side-----------------------12
2.5 Conclusion remarks-----------------------------------------------------------12
References--------------------------------------------------------------------------13

Chapter 3. Reflection characteristics due to
mutual coupling among slots -----------33
3.1 Introductory remarks----------------------------------------------------------33
3.2 Center-Feed Array Antenna--------------------------------------------------34
3.2.1 A center-feed single-layer waveguide array----------------------------------------------------34
3.2.2 A multiple way power divider with a series of cross-junctions------------------------------34
3.2.3 A radiation waveguide - linear array of reflection canceling units
consisting of a slot and a wall------------------35
3.3 Reflection Characteristics----------------------------------------------------36
3.3.1 Reflection from components---------------------------------------------------------------------36
-1 -
3.3.2 Overall reflection from the array-----------------------------------------------------------------36
3.4 Mechanism extraction of accumulated reflection
in overall array---------------37
3.4.1 Slot mutual coupling between adjacent radiation waveguides.-----------------------------37-
3.4.2 Localization of mutual coupling in the aperture
as functions of illumination distribution-------------------------38
3.5 Conclusion remarks-----------------------------------------------------------39
References--------------------------------------------------------------------------40

Chapter 4. Blocking free center-feed E-to H-plane
and ridged cross-junction----------------------------57
4.1 Introductory remarks----------------------------------------------------------57
4.2 Design of a Cross-Junction Power Divider -------------------------------58
4.3 SUPPRESSION OF THE SIDELOBES
DUE TO BLOCKAGE OF FEED WAVEGUIDE -----------------59
4.4 An Alternating-phase fed Single-Layer Slotted Waveguide Array
Fed By the Center Feed
with the E- to H-Plane Cross-junctions ----------60
4.5 Conclusion remarks-----------------------------------------------------------62
References--------------------------------------------------------------------------62

Chapter 5. Aperture efficiency enhancement
Reflection canceling stair ----------78
5.1 Introductory remarks----------------------------------------------------------78
5.2 Structure -----------------------------------------------------------------------79
5.3 Analysis of a linear array and full model ----------------------------------79
5.4 Conclusion remarks-----------------------------------------------------------80
References--------------------------------------------------------------------------81

-2 -
Chapter 6. Slot arrays
with Interchangeable slot plates -------90
6.1 Introductory remarks----------------------------------------------------------90
6.2 Structure -----------------------------------------------------------------------90
6.3 Analysis of Full Models -----------------------------------------------------91
6.4 Conclusion remarks-----------------------------------------------------------92
References--------------------------------------------------------------------------92

Chapter 7. Transmission experiments for
evaluating Propagation Isolation and XPD ----101
7.1 Introductory remarks--------------------------------------------------------101
7.2 Measurements----------------------------------------------------------------101
7.3 Conclusion remarks---------------------------------------------------------101

Chapter 8. Conclusion------------------------------104
8.1 Summary of proceeding chapters------------------------------------------104
8.2 Remarks for future studies--------------------------------------------------104

Acknowledgement--------------------------------------------------------------105

List of publication--------------------------------------------------------------106

-3 -
Chapter 1
Introduction

1.1 Microwave applications

Fixed Wireless Access (FWA) systems in the 26 GHz band have been
commercialized in Japan for high-speed Internet connections between subscribers and
base stations. Compact and low cost user terminals are realized by adopting alternating
phase fed single-layer waveguide slot arrays [1-1]. This unique antenna consists of two
parts, a slot plate and a base plate with corrugations screwed to each other, which
dispenses with electrical contact in the strict sense. All the components in the array such
as power dividers and slots are designed so that the reflection is suppressed in each
component; the array works in traveling wave operation for widening the bandwidth of
the array even in large size and high gain applications. A Time Division Duplex (TDD)
technique is adopted, and the same frequency is used for transmission and reception.
To double the frequency efficiency, we proposed the system which utilizes orthogonal
polarization [1-2] [1-3] [1-4]. Challenges for full frequency reuse based upon high
polarization purity, which is inherent to planar slotted waveguide arrays, are now
underway. This system shows an example of orthogonal arrangement of two arrays; the
antenna is for transmitting while the antenna is for receiving or vice versa. An
alternating phase fed array with a new feeding structure named center-feed single-layer
waveguide arrays was developed for this system [1-5]. In this array, the feed waveguide
is not at the end but is in the center of the array aperture; the bandwidth doubling of the
array and the frequency-independent boresite beam without tilting are the two important
design objectives of this array. The grating lobes due to blockage are remedied by
adopting a tapered aperture illumination [1-6]. As is usual in the case of such an
electrically-large structure, overall reflection can not be designed in strict sense and is
assessed roughly by the simple sum of the reflections from components, which are
electrically much smaller. Unfortunately, it turns out that the measured reflection is
much higher than this primitive prediction and that the accumulation of reflection at the
input port becomes notable as the size of the array increases.
In this chapter, we diagnose the reflection in large center-feed single-layer
waveguide arrays. The FEM analysis using HFSS is conducted for the whole structure
-4 -
of this large array, which has more than 30 dBi of gain. Although the structure is very
large in terms of the wavelength, the predicted reflection shows remarkable agreement
with the experiments. The mechanism of reflection accumulation in the overall array is
discussed. It is concluded that the external mutual coupling between slots in adjacent
alternating phase radiation waveguides results in increased reflection at the design
frequency. Amongst all, the dominant contributions are coming from strongly excited
slots; for tapered illumination to produce low sidelobes, slots in the central part of the
aperture cause considerable degradation.

1.2 Single-layer waveguide slotted array

the structure of a center-feed single-layer waveguide array is below. The design
frequency is 25.3 GHz. It has 32 (=16x2) radiation waveguides. The 32-way power
divider at the center of the antenna aperture consists of 14 cross-junctions and 2
terminal-junctions; 7 cross junctions are arrayed in series on each side of the antenna
input. Each cross- junction has 4 inductive posts and two ports coupling to radiation
waveguides [1-8] [1-9] [1-10] [1-11] [1-12]. One radiation waveguide has 10 slots, each
with a reflection canceling sidewall; the total number of slots in the array is 320 (10x32).
Each part of the antenna is analyzed and designed by the method of moments [1-13]
[3-14]. This antenna mechanically consists of a slotted plate and a waveguide base
joined by a screw. The test antenna is fabricated for a FWA system at 25.3 GHz.

1.3 Summary of this study
The dissertation investigates the design of center-feed waveguide slotted array antenna and its
application for Polarization Division Duplex (PDD) system. The center-feed waveguide slot array
enhances the frequency band-width in high gain range, where a conventional center-feed array
suffers fro m serious efficiency reduction. The orthogonally arranged center-feed waveguide array is
able to adapt to new communication system. That will realize “Wireless Fiber” cover all over the
world in near feature with several other systems.
Figure 1.1 summarizes the structure of this dissertation. The relation between general
investigative topics for micrometer-wave antennas, study topics for orthogonally arranged
center-feed single-layer waveguide slot antenna.
At first, isolation between two antennas is reviewed in Chapter 2. Measurements and
-5 -
Calculations are isolation between two orthogonally arranged center-feed waveguide slot array
antenna. Slot array symmetry arrangement is most important for obtain high isolation over 80dB.
Chapter 3 describes reflection characteristics of mutual coupling among slots. Single-layer
center-feed waveguide array has a blocking area at the center of the aperture. It causes high side-lobe
level and decrease aperture efficiency. So, first we adopt GA taper (almost Tailar distribution) on the
amplitude illumination. This design does not account of mutual coupling in adjacent radiating
waveguide slot. So, each component has a good reflection characteristics at the design frequency
(almost -20dB), but combination of the components has different reflection (almost -10dB). We
adopt the PEC for adjacent direction. Our study reveals almost effects of mutual coupling with slots
include calculation this method.
Chapter 4 describes blocking free center-feed E- to H-plane and ridged cross-junction. It can run all
over the aperture. So blocking area is decrease. And reflection characteristics is wider than
conventional H-plane cross-junction.
Chapter 5 describes aperture efficiency enhansement:reflection canceling stair. It can improve
aperture efficiency and decrease side-lobe level. Slot and reflection canceling wall’s combination is
one unit. And narrow wall of radiating waveguide is graduatelly change to reduce. So, radiation
power from slots increase, slot offset is set to small. We confirm by simulation and measearment.
Chapter 6 shows interchangeable slot plate. Waveguide slots array has relatively narrow
bandwidth. Base plate is made by die-casting for mass-production. If small amout, does not good for
costs. So Base plate is using common frequency range, only slot plate is change for required
frequency band. It is reasonable to cover wider frequency range.
Chapter 7 describes Propagation Isolation, XPD, and data transmission. Experimental
environment is almost 100m, 200m and 300m distance. In the case of 100m experiments, isolation
and XPD is a little change. Data transmission experiments operate using QPSK, 16QAM, and
64QAM. Max Data ratio is Tx 120Mbps and Rx 120Mbps. PDD realizes 240Mbps data ratio using
20MHz band width in 26GHz band.
Chapter 8 summarizes the results of this study, and presents the future problems of the work.

References

[1-1] N. Goto, “A waveguide-fed printed antenna,” IEICE Technical Report, AP89-3,
Apr. 1989.
[1-2] Y. Tsunemitsu, Y. Miura, Y. Kazama, S. H. Park, J. Hirokawa and M. Ando,
“Polarization Isolation between Two High-gain Slotted Waveguide Arrays
Arranged Side-by-side,” IEICE General Conv., B-1-210, Sept. 2003.
-6 -
[1-3] Y. Tsunemitsu, Y. Miura, Y. Kazama, S. H. Park, J. Hirokawa, M. Ando and N.
Goto, “Polarization Isolation between Center Feed Waveguide Arrays Arranged
Side-by-side,” IEICE General Conv., B-1-172, Mar. 2004.
[1-4] Y. Tsunemitsu, Y. Miura, Y. Kazama, S. H. Park, J. Hirokawa, M. Ando and N.
Goto, “Polarization Isolation between Two Center-Feed Single-Layer Waveguide
Arrays Arranged Side-by-side,” IEEE AP-S Int. Symp. Dig., vol.3, pp. 2380-2383,
June. 2004.
[1-5] S. H. Park, J. Hirokawa and M. Ando, “A Planar Cross-Junction Power Divider
for the Center Feed in Single-Layer Slotted Waveguide Arrays,” IEICE Trans.
Commun., vol. E85-B, no.11, pp.2476-2481, Nov.2002.
[1-6] S. H. Park, A study of center feed for single layer waveguide arrays, Doctoral
Dissertation, Dept. of Electrical and Electronic Eng., Tokyo Institute of
Technology, 2003.
[1-7] S. H. Park, J. Hirokawa and M. Ando, “Analysis of a waveguide slot and a
reflection-canceling inductive wall,” 2003 IEEE Topical Conference on Wireless
Communication Technology, Hawaii, s23p08, Oct. 2003.
[1-8] S. H. Park, J. Hirokawa and M. Ando, “Design of a Multiple-Way Power Divider
for Center feed Single Layer Waveguide Arrays,” 2003 IEEE AP-S Int. Symp.
Dig., vol.2, pp. 1165-1168, June. 2003.
[1-9] S. H. Park, J. Hirokawa and M. Ando, “Planar Cross-Junction for the Center Feed
in Single-Layer Slotted Waveguide Arrays,” 2002 IEEE AP-S Int. Symp. San
Antonio, Texas, Dig., vol.3, pp. 416-419, June. 2002.
[1-10] S. H. Park, J. Hirokawa and M. Ando, “Single-layer cross-junction power divider
for the center feed in slotted waveguide arrays,” IEICE Tech. Rep., EMCJ2001,
vol.101, No.392, 143-147.
[1-11] S. H. Park, J. Hirokawa and M. Ando, “Design of a Center-Feed Multiple-Way
Circuit for a Single-Layer Waveguide Array,” IEICE General Conv., B-1-87,
March. 2003.
[1-12] S. H. Park, J. Hirokawa and M. Ando, “Single-Layer Cross-Junction Power
Divider for the Center Feed in Slotted Waveguide Arrays,” IEICE General Conv.,
B-1-167, Sept. 2001.

-7 -
Orthogonally arranged Center-Feed Single-Layer Slotted
Waveguide Array antennas for Polarization Division Duplex
Chapter 1
Center-feed alternating
Introduction
phase fed array
Chapter 2
Chapter 3
Isolation between
Reflection characteristics due to mutual coupling
orthogonally arranged two
among slots
antennas
Chapter 4 Blocking free center-feed E-to H-
plane and ridged cross-junction
Chapter 5 Aperture efficiency enhancement
Reflection canceling stair
Chapter 6 Slot arrays with Interchangeable slot
Chapter 7
plates
Transmission experiments for
evaluating Propagation
Isolation and XPD
Chapter 8 Conclusion

Figure 1-1. Outline of Thesis

-8 -
Chapter 2
Isolation between orthogonally

arranged two antennas

2.1 Introductory remarks

Millimeter-wave applications [2-1] have been highlighted and intensively
developed for high-speed and broadband communication due to their extensive
frequency resources. To overcome serious attenuations due to rain, snow, etc., relatively
short-range FWA (Fixed Wireless Access) systems in the 26GHz band are in
commercial use in Japan [2-2] where extremely small size and low-cost wireless
terminals have been realized. Single-layer slotted waveguide arrays [2-3] are one of the
key components in this system since they have a high gain of about 32dBi, high
efficiency of more than 70%, and mass producible structures. One difficulty, however,
of this antenna is the relatively narrow bandwidth due to its traveling wave operation.
Polarization re-use is attractive and effective for mitigating this difficulty since linear
polarized slot arrays have inherently high XPD and the polarization purity does not
deteriorate greatly in short range propagation.
This paper demonstrates the feasibility of a challenging system where frequency is fully
re-used by the use of polarization isolation only [2-4]. An FWA system with this concept
is presented in Figure 1. Figure 2 presents two center-feed single-layer slotted
waveguide arrays with orthogonal polarization in exactly the same frequency band for
transmission and reception. In order to completely reuse the frequency two times [2-5,
2-6], approximately 100dB of transmission-reception isolation is required. A
preliminary scenario is to realize this isolation by the combination of an antenna
isolation of 50dB and a cross-polarization compensating algorithm circuit of 50dB. The
latter dispenses with the diplexer, and the use of Microwave Integrated Circuits realizes
the miniaturization and economization of equipment. This paper assesses and verifies
the isolation between two pairs of arrays in orthogonal polarization by simulation using
Ansoft HFSSTM (High-Frequency Structure Simulator) and measurement.
We prepared two center-feed single-layer waveguide arrays [2-7] which have
-9 -