Session 2p7 Antenna And Array: Theory And Design

Session 2P7 Antenna and Array: Theory and Design

A Class of Broadband Planar Traveling-wave Antennas and Their Latest Applications Johnson Jenn-Hwa Wang, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 Phase-only Synthesis of the Radiation Pattern of an Antenna Array with Quantized Phase Shifters Alexander S. Kondratiev, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Stage-by-stage Testing Technique of Active Phased Array M. V. Markosyan, Vahan H. Avetisyan, S. G. Eyremjyan, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 Experimental Investigations of Adaptive Reactance Parasitic Antenna Dipole Array Maxim O. Shuralev, A. L. Umnov, A. Mainwaring, M. A. Sokolov, A. U. Eltsov, . . . . . . . . . . . . . . . . . 99 Planar Array Antenna with Parasitic Elements for Beam Steering Control Mohd Tarmizi Ali, Tharek Abd Rahman, Muhammad Ramlee Bin Kamarudin, M. N. Md Tan, Ronan Sauleau, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 Multiband MIMO Antenna with a Band Stop Matching Circuit for Next Generation Mobile Applications Minseok Han, Jae-Hoon Choi, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dual ISM Band Mircostrip Antenna for Satellite Internet Service Byoungchul Kim, Sangwoon Lee, Joongyu Ryu, Hosung Choo, Hojin Lee, Ikmo Park, . . . . . . . . . . . . . Directional GPS Antenna for Indoor Positioning Applications ¨ ˙ Kerem Ozsoy, Ibrahim Tekin, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Printed Dipole Array Fed with Parallel Stripline for Ku-band Applications ¨ M. Do˘gan, Kerem Ozsoy, Ibrahim Tekin, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Circular Disc Monopole UWB Antenna Fed with a Tapered Microstrip Line on a Circular Ground Yangjun Zhang, Masahiro Shimasaki, Toyokatsu Miyashita, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Improved Tapered Slot-line Antennas Loaded by Grating Peng Zhang, Shu Jun Tand, Wen Xun Zhang, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using High Impedance Ground Plane for Improving Radiation in Monopole Antenna and Its Unusual Reflection Phase Properties Maryam Abootorabi, Mohsen Kaboli, Seyed Abdullah Mirtaheri, Mohammad Sadegh Abrishamian, . . The Impact of New Feeder Arrangement on RDRA Radiation Characteristics Ahmed S. Elkorany, A. A. Sharshar, S. M. Elhalafawy, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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101 102 103 104 105 107

108 110

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Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 18–21, 2009

A Class of Broadband Planar Traveling-wave Antennas and Their Latest Applications Johnson J. H. Wang Wang Electro-Opto Corporation (WEO), Marietta, Georgia 30067, USA

Abstract— Classical antenna theory often ignores the practical problem of platform mounting, which can have deadly impact on antenna performance. This is an unavoidable problem since an antenna is invariably inseparable from a transceiver or platform, which the antenna is connected with or mounted on. In the worst scenario, the main radiator is the platform or transceiver, not the antenna per se. The slot antenna and the microstrip patch antenna provide a narrowband solution to this problem. For broadband needs, a class of planar traveling-wave (TW) antennas, as depicted in Figure 1, and TW phased arrays employing such TW elements, emerged in the past two decades [e.g., 1], offering a satisfactory solution. This paper addresses the fundamental theory for this class of planar TW antennas. A common feature of these patented designs is a ground plane placed very close to a planar broadband TW structure, which is preferably a self-complementary surface. The TW is characterized by a radial component of propagation to and from the geometrical center of the planar TW structure. The conducting ground plane on the back side of the antenna enables the antenna to be conformally mounted on any platform, with minimal EMC/EMI problems as well as a stable radiation property fairly independent of the mounting platform. In addition to an octaval bandwidth of 10 : 1 or more, this class of broadband planar TW antenna offers features such as dual-polarization and multifunction rarely available in other antennas. Applications include ultra-wideband conformal body-wearable antennas, air/sea/ground vehicle antennas, handset antennas, planar phased arrays, etc. A recent application is in highperformance low-cost GNSS antennas that cover all three GNSS services (GPS/GLONASS/Galileo), requiring a wide frequency bandwidth of 1.164–1.610 GHz. The TW structure in this design is a planar four-arm spiral, which has an inherently stable phase center nearly independent of spatial and frequency variations. Such a performance is not achievable by conventional GNSS antenna approaches such as the patch antenna and other broadband antennas. Its phase center stability versus frequency and spatial angle is primarily limited by its manufacturing tolerance and the excitation accuracy of its feed network.

Radiation zone ( ρr ~ λ/ 2 π for Mode-1)

Current density

ρr ρ

Top View

0

S

TW element

ρ

z

Outgoing wave

Side View Matching network

ρr

Feed

Reflected wave (from residual outgoing wave)

Ground plane

Figure 1: The planar TW antenna. REFERENCES

1. Wang, J. J. H., D. J. Triplett, and C. J. Stevens, “Broadband/Multiband conformal circular beam-steering array,” IEEE Trans. Antennas and Prop., Vol. 54, No. 11, November 2006.

Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 18–21, 2009

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Phase-only Synthesis of the Radiation Pattern of an Antenna Array with Quantized Phase Shifters Alexander S. Kondratiev Moscow Power Engineering Institute (Technical University), JSC Altair, Russia

Abstract— At present, solution of many radar and communication problems requires application of antennas with shaped radiation patterns and/or pattern nulls or deep gaps in prescribed directions. Antenna arrays, which have many controllable elements, are most suitable candidates for formation of such patterns. In many arrays, only the phases of the amplitude-phase distribution over the array elements can be controlled. In this case, formation of an array pattern with prescribed properties requires solution of the so-called phase-only synthesis problem [1]. Phase-only synthesis problems are inherently nonlinear and, generally, are solved with the use of numerical methods [2, 3]. The most reliable methods are those based on reduction of the initial synthesis problem to the problem of minimization of a nonlinear nonnegative definite function of desired phases and application of numerical optimization techniques to finding the minimum of this function. (In general, the minimum is local and the obtained solution is only approximate.) In most cases, the element excitation phases are controlled with quantized phase shifters that change the excitation phases only stepwise. The value of phase increment ∆ψ is usually determined from the formula ∆ψ = 2π/2K , (1) where K is the number of binary digits. In this case, it is desirable to solve the problem in the domain of discrete values of the desired phases [2, 3]. This approach, in particular, allows formation of deep nulls in prescribed directions. In formation of a shaped pattern, it is often desirable to ensure near uniform approximation of the desired shape. This approximation can be attained with the use of the Chebyshev metric or an approximation of this metric for the difference between the desired and the synthesized patterns. Here, an approach to solution of the phase-only pattern synthesis problem is proposed that involves (i) formation of the objective function with the use of a power approximation of the Chebyshev metric and (ii) iterative minimization of this objective function by means of finite search over discrete phase values at each iteration. A version of this approach is described below. 0 Let us specify the desired radiation pattern by its values at M angular directions Fm , m = 1, . . . , M .

Then, the phase-only synthesis problem is reduced to solution of the following set of equations: N X

0 Fne (θm , ϕm ) · An · exp(jψn ) · exp (j (kxn κxm + kyn κym + kzn κzm )) = Fm ,

n=1

m = 1, . . . , M,

(2)

where Fne (θm , ϕm ) is the radiation pattern of the nth array element in the mth angular direction (θm , ϕm ) in the spherical coordinate system; An and ψn are the amplitude and phase of the excitation of the nth array element; kxn , kyn , and kzn are the Cartesian electric coordinates of the nth array element; k = 2π/λ and λ is the wavelength. Amplitudes An are fixed and system (2) is solved for desired phases ψn taking discrete values according to formula (1). Since the solution domain of this system of nonlinear equations is

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Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 18–21, 2009 generally unknown, system (2) is solved approximately by reducing it to the objective function ¯ N M ¯X X ¯ Q = Wm ¯ Fne (θm , ϕm ) · An · exp(jψn ) ¯ m=1 n=1 ¯l ¯ ¯ 0 · exp(j(kxn κxm + kyn κym + kzn κzm )) − Fm exp(jαm )¯ , (3) ¯ where αm are the phase values whose values are specified during iterative minimization of this objective function [3] and l ≥ 2 is a positive even integer number. The minima of objective function (3) are the approximate solutions to system (2). Analysis of objective function (3) shows that, along each phase ψn , function (3) is periodic with a period divisible by 2π/l. This feature is used to develop a simple iterative minimization technique in which objective function (3) is successively minimized along coordinates ψn . If l= 2, the minimum along each coordinate can be found analytically [2, 3]. If l > 2, the minimum at each iteration is found numerically by means of the search over a finite number of phase values determined by formula (1) within the period [0, 2π]. The advantages of this synthesis procedure are the simplest selection of the search direction and a limited search interval at each iteration. This procedure can be further improved by replacing the coordinatewise search method with one of faster methods, for example, the well-known conjugate gradient method [4]. However, direct application of this method is impossible because phases ψn can take only discrete values determined by formula (1). If the phase values are considered continuous and formula (1) is applied to the solution found with continuous phases, this operation may result in substantial deterioration of the obtained solution, which is most pronounced for the null synthesis problems.

2 1

Figure 1: Initial and synthesized patterns for l = 2.

1

2

Figure 2: Initial and synthesized patterns for l = 4.

Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 18–21, 2009

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To return the linear search performed at each iteration to the search over only the allowed phase values, one can use a technique in which the search direction is adjusted so that the components of the original search vector are approximated by the values that are the multiples of phase increment ∆ψ. A normalization procedure is used to set the maximum vector component to 2π. At each iteration, objective function (3) is simultaneously minimized along the coordinates changed according to the above algorithm and the steps along coordinates ψn take only the discrete values specified by formula (1). In practice, this is a stepwise approximation of the original search direction. An example of application of the coordinatewise version of the proposed method is shown below for the synthesis of a linear equispaced array of 50 isotropic radiators with a flat-top pattern. The synthesis results are shown in Figs. 1 and 2. In all figures, curves 1 correspond to the initial array pattern and curves 2 correspond to the synthesized patterns for l = 2 (Fig. 1) and 4 (Fig. 2), respectively. As seen from the results in Figs. 1 and 2, the synthesized patterns depend on power l. Changing this parameter, it is possible to flatten the ripples on the top of the synthesized pattern. REFERENCES

1. Cheng, D. K., “Optimization techniques for antenna arrays,” Proc. IEEE, Vol. 59, 1664–1674, 1971. 2. Kondrat’yev, A. S., “Method for phase synthesis of antenna arrays with additional requirements on the shape of the directivity pattern taken into account,” Soviet J. Communications Technol. Electron., Vol. 36, 94–102, 1991. 3. Kondrat’yev, A. S. and A. D. Khzmalyan, “Phase-only synthesis of antenna arrays for a given amplitude radiation pattern,” J. Communications Technol. Electron., Vol. 41, 859–866, 1996. 4. Fletcher, R. and C. M. Reeves, “Function minimization by conjugate gradients,” Computer J., Vol. 7, 149–154, 1964.

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Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 18–21, 2009

Stage-by-stage Testing Technique of Active Phased Array M. V. Markosyan, V. H. Avetisyan, and S. G. Eyremjyan Yerevan Telecommunication Research Institute, Yerevan, Republic of Armenia

Abstract— Manufacturing and bringing of the active phased array (APhA) to a readiness for operation (with the goal of reception of the parameters inserted at the APhA designing) demand significant zeal and expenses. At production the step-by-step assembly of component units of the APhA to entire antenna system is carried out. The basic element of APhA is transceiver module (TM), which combines the electronic-controlled discrete attenuator, phase-shifter, switches, power amplifier and low-noise amplifier; N pieces of TM are combined in a cell; M pieces of cells are combined in group; K pieces of groups are combined in subarray and F pieces of subarraies are combined in entire system of the APhA. At assembling of new unit it is possible to disturb an operability of one or more component units. On each stage of such sequential enlargements it is important to eliminate of faulty component units from process of following assembly for avoiding of additional expenditures. With this goal in given article the technique of stage-by-stage testing and electric alignment of the APhA component units is offered at the described assembly process. In the beginning of everyone specifically-observed stage the checking (according to the developed techniques) of the final assembly units of the previous stage is provided. Note, the final assembly units of the previous stage are the component units of the specifically-observed stage unit, which should be tested. The mentioned checking of each final assembly unit of the previous stage is carried out in mode of in-phase and amplitude uniform excitations of its component units. The check testing defines operability of the previous stage assembly units and also deviations of their amplitude and phase transmission characteristics. On the basis of the received data about deviations for each of tested units, the corrections by amplitude and phase are defined for inserting of additional attenuations and phase-shifts, which necessary for their in-phase and amplitude uniform excitations in composition of the observed stage assembly unit. Such excitation condition of the observed stage component unit is final result of its electronic alignment. After that, the correctness of executed electric alignment of the tested unit is checked by corresponding measurements and its certificate on required parameters is made out. It is an end of the specifically-observed stage. Process of the TM testing is carried out on the basis of radiator far-field measurements by means of the developed automatic measurement system, which determines also polarization characteristics of its radiated wave. Testing of groups, subarraies and whole APhA is carried out by the offered near-field automatic measurement system. The offered stage-by-stage testing technique allows clearly and reliably to carry out a process of bringing of the APhA to a readiness for operation in accordance with requirements on its electric parameters.

Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 18–21, 2009

Experimental Investigations of Adaptive Reactance Parasitic Antenna Dipole Array M. O. Shuralev1, 2 , A. L. Umnov1, 2 , A. Mainwaring3 , M. A. Sokolov1, 2 , and A. U. Eltsov1, 2 1

Nizhny Novgorod State University, Nizhny Novgorod 603950, Russia 2 Intel Corporation, Nizhny Novgorod, Russia 3 Intel Research Laboratory at Berkeley, CA 94704, USA

Abstract— This work explores the theory and practice of low-cost beam steering antennas for WiFi, specifically high-gain arrays of interest for long-distance point-to-point and point-tomultipoint links based on WiFi technology operating at 2.4 GHz. The antenna systems are constructed on a basis of tunable impedance mirrors, named as reflectarrays, assembled from periodic array of passive scatterers illuminated by a single, driven RF element, placed at 2.5 wave-lengths from the center of the reflectarray. Although this approach avoids energy losses and unwanted influence between the passive elements through surface wave interactions, the close spacing of the elements leads to mutual coupling. This complicates the theoretical analysis and modeling of these antennas, but these complications can be resolved through a combination of simulation and experiment. Four key aspects of this work are presented: (1) the careful balancing of the amplitude-phase characteristics of the passive scatteres with using special experimental schemes, taking into account most mutual coupling effect, (2) the development of multilayer structures and array assemblies, intended for widening of phase range of the reflected RF radiation from the mirror, (3) an examination of the bandwidth, and (4) experimental measurement of antenna directivity diagrams and pattern integrity. Our results demonstrated that highly directional patterns can be realized while controlling beam orientation in both azimuth and elevation. Prototype antennas achieve 19 to 22 dBi of gain across an operational 120 degrees of azimuth and 20 degrees in elevation, using an array with an aperture of 100 cm × 65 cm (5 rows of 100 elements each).

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Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 18–21, 2009

Planar Array Antenna with Parasitic Elements for Beam Steering Control M. T. Ali1 , T. A. Rahman2 , M. R. Kamarudin2 , M. N. Md Tan1 , and R. Sauleau3 1

Faculty of Electrical Engineering, Universiti Teknologi Mara (UiTM) Shah Alam, Selangor, Malaysia 2 Wireless Communication Center (WCC), Universiti Teknologi Malaysia 81310 UTM Skudai, Johor, Malaysia 3 Institut d’´electronique et de t´el´ecommunications de Rennes, (IETR) UMR CNRS 6164, University of Rennes 1, France

Abstract— A new antenna structure is formed by combining the concept of a reconfigurable planar array antenna with the parasitic elements technique to improve the beam steering. The integration of PIN diode switches to the antenna has enabled to steer the antenna beams in the desired direction. This can be done by changing the switches mode to either switch it ON or OFF. In this work, a number of reflectors have been proposed namely parasitic elements and were placed between the patches which aimed to increase the steering beam angle. By having such configuration, the main beam of the array can be titled due to the effect of mutual coupling between the driven elements and the parasitic elements (reflectors). The unique property of this antenna design is that instead of fabricating all together in the same plane, the antenna’s feeding network is separated from the antenna radiating elements (the patches) by an air gap distance. This will allow the interferences from the feeding line to be minimized. The optimization results for the resonant frequencies of the antennas with variable air gap heights were also studied. The comparison results between antenna with and without parasitic elements were investigated in this paper. The simulation results for the antenna will be compared with measurements, to show that the beam can be steered by controlling the switches mode. Experimental results are presented to demonstrate the excellent performance of this antenna.

Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 18–21, 2009

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Multiband MIMO Antenna with a Band Stop Matching Circuit for Next Generation Mobile Applications Min-Seok Han and Jaehoon Choi Division of Electrical and Computer Engineering, Hanyang University 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea

Abstract— Next generation mobile systems have to satisfy the requirements of high data rates and flexible interfaces for different communication system standards. MIMO (Multiple Input Multiple Output) technology has been regarded as one of practical approaches to accommodate such requirements by increasing wireless channel capacity and reliability. However, it is usually a big challenge to place multiple antennas within a small and slim mobile handset while maintaining the good isolation between antenna elements since the antennas are strongly coupled with each other and even with the ground plane by sharing the surface currents distributed on it. In this paper, a multiband MIMO antenna with a band stop matching circuit for next generation mobile applications is proposed. The proposed multiband MIMO antenna consists of two dual-band PIFAs which provide wideband characteristics. In order to improve the isolation characteristic at the LTE band, a band stop matching circuit was inserted at the corner of each antenna element. The inserted band stop matching circuit is to suppress the surface currents at the specific frequency band and to generate two additional resonances in the 760 MHz band to cover LTE operation and in the 860 MHz band to cover GSM850 operation. In addition, the band stop matching circuit reveals minimal effect on the upper band performance. The proposed MIMO antenna can cover LTE, GSM850, GSM900, GSM1800, GSM1900, WCDMA and M-WiMAX services, simultaneously. Design considerations and experimental results of the multiband MIMO antenna with a band stop matching circuit are presented.

Figure 1: Geometry of the proposed multiband MIMO antenna. without band stop matching circuit

with band stop matching circuit

LTE GSM850/GSM900 GSM1800/GSM1900/WCDMA M-WiMAX 698 ~ 800 MHz 824 ~ 960 MHz 1710 ~ 2170 MHz 2500 ~ 2690 MHz

LTE GSM850/GSM900 GSM1800/GSM1900/WCDMA M-WiMAX 698 ~ 800 MHz 824 ~ 960 MHz 1710 ~ 2170 MHz 2500 ~ 2690 MHz

0

0

Isolation -10 dB

-20

-30

VSWR 3:1

S-parameters

S-parameters

VSWR 3:1

-10

-10

Isolation -10 dB

-20

-30

S11 S21 -40

S11 S21 -40

0.0

0.5

1.0

1.5

2.0

Frequency [GHz]

2.5

3.0

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Frequency [GHz]

Figure 2: Simulated S-parameter characteristics without and with band stop matching circuit.

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Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 18–21, 2009

Dual ISM Band Mircostrip Antenna for Satellite Internet Service Byoungchul Kim1 , Sangwoon Lee1 , Joongyu Ryu2 , Hosung Choo3 , Hojin Lee2 , and Ikmo Park1 1

Department of Electrical and Computer Engineering, Ajou University 5 Wonchun-dong, Youngtong-gu, Suwon 443-749, Korea 2 Broadcasting and Telecommunications Convergence Research Laboratory, ETRI 161 Gajeong-dong, Yuseong-gu, Daejeon 305-700, Korea 3 School of Electronics and Electrical Engineering, Hongik University 72-1 Sangsu-dong, Mapo-gu, Seoul 121-791, Korea

Abstract— In recent years, satellite internet has received much attention for wireless internet applications on high-speed trains. The Korean high-speed train (KTX) network requires antennas that operate at both the 2.4 GHz and 5.8 GHz industrial, scientific, and medical (ISM) bands for simultaneous transmission and receiving of data. Additionally, it should have nearly equal gain with similar radiation patterns in both bands for optimum communication. Microstrip patch antennas have been used in many applications due to their low cost, light weight, low profile, and ease of fabrication. Dual-frequency operation can be obtained by making slots on the microstrip patch, or by placing shorting pins at appropriate locations on the microstrip patch. However, when the higher frequency band is more than twice that of the lower frequency band, the radiation pattern of the higher resonant frequency becomes distorted due to the higher order resonant modes. In this paper, a dual-band microstrip antenna with nearly equal gain and similar radiation patterns at the 2.4 GHz and 5.8 GHz ISM bands is described. The proposed antenna, shown in Fig. 1, has two Y-shaped slots on the microstrip patch. It is fabricated on an RO4003 substrate, which has a dielectric constant of 3.38 and a thickness of 0.508 mm. The size of the antenna is 50 × 47.5 × 6.5 mm3 , and it is fed by a coaxial cable. The measured bandwidth of the antenna is 2.376–2.492 GHz and 5.425–6.055 GHz for VSWR < 2. The measured gain is 8.37 dB and 8.38 dB for the 2.4 GHz and 5.8 GHz ISM bands, respectively.

Feed point

Patch with slots

Ground plane

Figure 1: Antenna structure.

Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 18–21, 2009

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Directional GPS Antenna for Indoor Positioning Applications 1, 2 ¨ Kerem Ozsoy and Ibrahim Tekin1 1

2

Electronics Engineering, Sabancı University, Istanbul, Turkey Vestek Electronic Research & Development Corp., Istanbul, Turkey

Abstract— In this paper, a directional GPS antenna for L1 frequency — 1575 MHz — with RHCP and a high directive gain is proposed for indoor positioning applications. The proposed antenna is made of a standard off the shelf GPS patch antenna with an additional conical reflector to enhance the gain and the beamwidth of the antenna. The angle of the cone reflector is optimized by HFSS 11 software. Finally, the cone is fabricated, integrated with the patch antenna and measured. The measurement results show that the antenna with the reflector has a 9 dBi gain and a beamwidth of 60 degrees with an axial ratio of 1 dB which agrees well with simulation results. Introduction: The Civil Global Positioning System (GPS) has become very popular in recent years and it has wide usage in many areas. With the latest technological advances such as Differential GPS (DGPS), Assisted GPS (AGPS), civil GPS receivers are able to locate themselves with an error of 1–3 meters outdoors [1]. Although GPS is very successful in outdoor areas, it is hard to decode GPS signals indoors due to the additional signal loss caused by the buildings. For indoors, signals go through additional loss of 10–30 dB [2], in which case, signal levels are too low for an off-the shelf GPS receiver to detect the satellite signal. In order to solve indoor coverage problem, we plan to build an indoor positioning system that uses the GPS infrastructure. This indoor positioning system consists of GPS pseudo-satellites (pseudolite) and a GPS receiver with improved positioning algorithms. A pseudolite should be able to pick up the satellite signal only from a given direction in the sky and transmit the amplified signals to an indoor area. There are several ways to design a directional antenna such as Yagi-Uda, horn, log periodic, reflector and parabolic antenna or phased array systems [3]. Along these antennas, a reflector antenna type is chosen since these antennas are simple to manufacture, and also compact and robust in performance and low cost. In this paper, we propose a directional GPS antenna for L1 frequency — 1575 MHz — with RHCP and a high directive gain. A standard off the shelf GPS patch antenna is used in the design, and directivity increase is achieved through the use of a conical reflector. Off-the-shelf microstrip patch antenna has a gain of 4 dBi. When the conical reflector is placed around the microstrip antenna, gain of the microstrip antenna is increased while the beamwidth of the antenna decreases. The cone is optimized by running simulations on HFSS 11 software tool. Finally, the cone is fabricated and integrated with patch antenna and measured. The measurement results show that the antenna has a 9 dBi gain which is 5 dB higher than the original patch antenna and a beamwidth of 60 degrees with an axial ratio of 1 dB. In the conference, design of the conical reflector, the simulation results and the measurements obtained in an anechoic chamber will be presented. REFERENCES

1. Liu, H., H. Darabi, P. Banerjee, and J. Liu, “Survey of wireless indoor positioning techniques and systems,” IEEE Transaction on Systems, Man, and Cybernetics, Vol. 37, No. 6, 1067–1077, November 2007. 2. Peterson, B. B., D. Bruckner, and S. Heye, “Measuring GPS signals indoors,” Proceedings of the Institute of Navigation’s ION GPS-2001, September 2001. 3. Balanis, C. A., Antenna Theory, Analysis and Design, 2nd ed., Wiley, New York, 1997.

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Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 18–21, 2009

Printed Dipole Array Fed with Parallel Stripline for Ku-band Applications 1, 2 ¨ M. Dogan1, 3 , K. Ozsoy , and I. Tekin1

2

1 Electronics Engineering, Sabanci University, Istanbul, Turkey Vestek Electronic Research & Development Corp., Istanbul, Turkey 3 TUBITAK, UEKAE, Kocaeli, Turkey

Abstract— This paper presents the design procedure of a printed dipole antenna and 1D array configurations of the single dipole element in the Ku-Band with its metallic reflector plane parallel to the array plane. The proposed antenna has a natural beam tilt which is useful for some specific applications. Several array configurations in 1D are simulated and tested. The effect of mutual coupling among each array elements is also investigated. Required modifications on the individual array element and the feed structures due to the effect of mutual coupling are examined. The single dipole and array of dipole has measured VSWR values smaller than 2 in the Ku-Band with simulated gains of 5.7 dBi and 12 dBi, respectively. Introduction: Recent studies are highly focused on antenna design in Ku-Band. Since the Ku-band has enough available bandwidth for satellite links, Ku-band systems are widely used in satellite communications, especially in the mobile antenna systems used in vehicles. There are also other application areas of Ku-band systems such as weather radars and fire detection radars. These sort of systems needs highly directive antennas with a very wide frequency band covers the all Ku-Band to transmit signals to the receiver with equal power in the whole frequency range and an automatic tracking systems to capture the maximum power incident from the satellite while the time and place of the receiver changed. In order to provide good tracking system, one can use digital phase shifter technology or mechanical systems to tilt the beam of the receiver both in azimuth and elevation to the specified direction which will increase the cost of the system or decrease the accuracy of the tracking system respectively. In this paper, a printed dipole antenna which operates in the Ku-Band with high gain and tilted beam is proposed. Since the proposed antenna has a tilted beam in elevation, it will be used in mobile satellite communication systems to eliminate the mechanical or digital needs at least in one direction to tilt the beam of the system. Also, arrays of these printed dipoles will be investigated and the gain of the arrays will be both simulated and measured. Simulation & Measurement Results: The single printed dipole element designed in ADS2006A has a VSWR < 2 in the 10.7 GHz–13.1 GHz range. The measurement results show that it has S11 < −10 dB in between 9 GHz–14 GHz. The simulated gain of the single element printed dipole antenna is 5.7 dBi at 11.5 GHz. The characteristics of 1 × 2 printed dipole array is also measured and the preliminary results show us that the array has VSWR < 2 in the Ku-band. We have also simulated 1 × 8 dipole array in Ku band, and results show that the array return loss is less than −10 dB in 10.7–12.7 GHz band. Simulated gain changes between 10–12 dBi in the band of interest. The beam is tilted from the broadside direction such that only azimuthal rotation is necessary for a mobile antenna system. The measurement results and the simulated results of the single dipole element and 1 × 2 and 1 × 8 dipole arrays will be presented at the conference.

Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 18–21, 2009

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A Circular Disc Monopole UWB Antenna Fed with a Tapered Microstrip Line on a Circular Ground Yangjun Zhang, Masahiro Shimasaki, and Toyokatsu Miyashita Department of Electronics & Informatics, Ryukoku University Seta, Ohtsu 520-2194, Japan

Abstract— The printed disc monopole antenna is considered a good candidate for 3.1 to 10.6 GHz UWB systems [1, 2]. This paper presents a miniature circular disc monopole UWB antenna implemented on a FR-4 substrate (εr = 4.4). The antenna was miniaturized by using a tapered microstrip feed line on a circular ground, as shown in Fig. 1. The total size of antenna is 40 × 30 mm2 , and the diameter of radiation disc is 12 mm. The results of measured and simulated return loss are shown in Fig. 2. It indicates there are differences between the simulated and measured return loss, but both the simulated and measured results show that good impedance matching has been obtained as the −10 dB return loss bandwidth covers the whole UWB band from 3.1 to 10.6 GHz. 0.8

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The radiation patterns of the proposed antenna over the UWB frequency band have been measured. The results at 8 GHz are shown in Fig. 3. It is noticed that the measured and simulated radiation patterns agree well, and the omnidirectional pattern was shown at x-y-plane. The time-domain performance of the UWB antenna is shown in Fig. 4, where the group delay of the two UWB antennas placed with a distance of 36 cm was given. Within the frequency range from 3 to 9 GHz, the group delay is about 2 ns. simulation measurement 330

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Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 18–21, 2009

REFERENCES

1. Cho, Y. J., K. H. Kim, D. H. Choi, S. S. Lee, and S.-O. Park, “A miniature UWB planar monopole antenna with 5-GHz band-rejection filter and the time-domain characteristics,” IEEE Trans. on Antennas and Propagation, Vol. 54, No. 5, 1453–1460, 2006. 2. Guo, L., J. Liang, C. C. Chiau, X. Chen, C. G. Parini, and J. Yu, “Performances of ultrawideband disc monopoles in time domain,” IET Microwave Antennas Propag., Vol. 1, No. 4, 955–959, 2007.

Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 18–21, 2009

Improved Tapered Slot-line Antennas Loaded by Grating Peng Zhang, Shu Jun Tang, and Wen-Xun Zhang State Key Laboratory of Millimeter Waves, Southeast University Nanjing, Jiangsu 210096, China

Abstract— The tapered slot-line antenna (TSA) has been used widely as element of phased arrays, feed of reflector or reflectarray, UWB radiator for time-domain systems. It is a travellingwave end-fire antenna with advantages of wideband, uni-directive beam, and thin-sheet structure. However, its gain is less than a broadside antenna with the similar sizes; the cost of enhancing gain will be sharply extending its length; the bandwidth depends on the taper ratio (max./min. of the slot-width) and the length of taper too. Hence, a risen question is how to further improve the performance of Gain or Bandwidth based on a fixed structural frame? The answer should be to utilize sufficiently the frame-space, one scheme is just setting proper grating inside the zone of tapered slot. Correspondingly, two kinds of samples are designed, simulated, and tested with good results as expected. One is a gain enhanced TSA with grating load and symmetric linear taper. It increases gain 2 dB up over the frequency range of 6.0 ∼ 9.5 GHz (45.2%); or 3 dB up over 8.0 ∼ 9.5 GHz (17.1%). However, the bandwidth for VSWR ≤ 2.0 : 1 was slightly decreased from 5.7 ∼ 11.2 GHz (65.1%) to 5.3 ∼ 9.6 GHz (57.7%). In addition, the beam-width in E- and H-planes approaches to the same. Another is a bandwidth broaden TSA with grating load and asymmetric exponential (Vivaldi) taper. It expands the bandwidth 2.0 ∼ 6.0 GHz for VSWR ≤ 2.0 : 1, and also 3.0 ∼ 6.0 GHz (75%) for vertical shaping pattern satisfying the specifications of base-station in mobile communication system. Especially, the VSWR ≤ 1.5 : 1 is over both two WiMAX bands of 3.3 ∼ 3.8 GHz and 5.1 ∼ 5.8 GHz; while the service coverage efficiencies are higher than 69.5% and 73.2% respectively; about 1 dB gain enhancement, and also improved radiation patterns with lower back-lobe and downward null-filling are achieved. Both samples keep planar structure with complete printed technology in fabrication, and maintain the frame sizes. ACKNOWLEDGMENT

This work was supported by the National High-Tech Project (No. 2007AA01Z264).

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Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 18–21, 2009

Using High Impedance Ground Plane for Improving Radiation in Monopole Antenna and Its Unusual Reflection Phase Properties S. M. Abootorabi, M. Kaboli, S. A. Mirtaheri, and M. S. Abrishamian K. N. Toosi University of Technology, Iran

Abstract— In this paper improving radiation characteristics of monopole antenna on a high impedance ground plane has been investigated. For this purpose the properties of periodic electromagnetic band gap (EBG) structures have been used [1, 2]. As we know conductors are used as reflectors or ground plane in many antenna situations. Surface waves or surface currents are bound to the interface of metal and air. Recent researches have dealt with the suppression of surface wave to improve radiation characteristics of monopole antenna

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using high impedance ground plane (HIGP) in high frequencies such as 35 GHz with hexagonal patches on substrate [3, 4]. In this study high Impedance surface (HIS) as ground plane for monopole antenna at lower frequencies such as 6 GHz with square patches in shape have been used. Due to suppression of surface waves in the band gap, a significant amount of power that is wasted in back lobes reduces about 8 dB, also radiation power in forward direction increases about 10 ∼ 25 dB in some directions. Comparison of patterns on normal metal ground plane and HIGP which are obtained by HFSS simulation could be seen in Figure 1. There are good agreements with measurement and simulation results as shown in Figure 2, in 6 GHz frequency. Effect of the ground plane dimension and number of square patches have also been investigated and it has been observed that a bigger ground plane and more number of metal patches will have a better effect of improving radiation pattern. Another property that is confined to EBG structures is their unusual reflection phase which is changing continuously from +180 to −180 [5]. We changed the length of monopole antenna from 0.245λ to 0.27λ and it found that where the monopole antenna has a good return loss is very close to points that the reflection phase has a quantity between 90◦ ± 45◦ . Consequently this HIS may be very useful in a variety of electromagnetic problems and antenna structures. REFERENCES

1. Xu, H.-J., Y.-H. Zhang, and Y. Fan, “Analysis of the connector section between K connector and microstrip with Electromagnetic Band Gap (EBG) structure,” Progress In Electromagnetic Research, PIER 73, 239–247, 2007. 2. Pirhadi, A. and M. Hakkak, “Using electromagnetic band gap superstrate to enhance the bandwidth of probe-fed microstrip antenna,” Progress In Electromagnetic Research, PIER 61, 215–230, 2006. 3. Sievenpiper, D., L. Zhang, R. F. Jimenez Broas, N. G. Alexopolous, and E. Yablonovitch, “High-impedance electromagnetic surfaces with a forbidden frequency band,” IEEE Transactions on Microwave Theory and Technique, Vol. 47, No. 11, November 1999. 4. Sievenpiper, D., “High-impedance electromagnetic surfaces,” PhD Dissertation, UCLA, 1999. 5. Yang, F. and Y. Rahmat Samii, “Microstrip antennas integrated with Electromagnetic BandGap (EBG) structures: A low mutual coupling design for array applications,” IEEE Transactions on Antennas and Propagation, Vol. 51, No. 10, October 2003.

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Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 18–21, 2009

The Impact of New Feeder Arrangement on RDRA Radiation Characteristics A. S. Elkorany, A. A. Sharshar, and S. M. Elhalafawy Department of Electronics and Electrical Comm., Faculty of Electronics Eng. Menoufia University, Menouf, Menoufia 32952, Egypt

Abstract— Dielectric resonator antennas (DRAs) have been extensively investigated after the first paper published by Long et al.. Recently one of the major topics in DRA research is to enhance the impedance bandwidth. The techniques that have been used to widen the impedance bandwidth include, inserting air gap between the dielectric and the ground plane, using different dielectric geometries, using strip fed, using hybrid configuration, and using multi-segment configuration. Rectangular dielectric resonator antenna RDRA with an air gap that inserted between the dielectric and ground plane was previously proposed, and an achievement in the impedance bandwidth in the order of 31% between 4.5 GHz and 6.2 GHz has been obtained. In this work, a further development in the antenna structure has been suggested to get further improvement in the antenna impedance bandwidth. A new feeder arrangement has been proposed and its effect on the impedance bandwidth has been recorded. This is done by inserting a small rectangular metallic patch within the air gap between the ground plane and the dielectric. The metallic batch is connected to the inner of the coaxial probe feeder. This technique was used successfully in a previous work with microstrip patch antenna, in which two metallic patches with different shapes were inserted between the patch and ground plane. In the present research the dimensions of inserted patch have been changed and the impact of that on the impedance bandwidth has been examined. The dielectric that is used is FR4 with εr = 4.5, and its dimensions is 20 mm × 12 mm × 5 mm, the probe diameter is 1.25 mm, and its height is 2.5 mm, the inserted patch height is 1 mm, all theses parameters are held constant in all cases. Unexpected ultrawide impedance bandwidth has been obtained. Some results are recorded here to show the effect of this new feeder on the antenna impedance bandwidth. An impedance bandwidth of about 2.55 : 1 between 10.2 GHz and 26 GHz is achieved when the patch dimensions were 9 mm × 4 mm, while the bandwidth extends from 16 GHz up to a value behind 34 GHz is achieved when the patch dimensions was 16 mm × 3 mm. The maximum radiation is in the broadside direction and is obtained with a suitable cross polarization level.