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INVESTIGATIONS OF METAMATERIAL-BASED FREQUENCY-SELECTIVE GROUND PLANE INFLUENCE ON PATCH ANTENNA CHARACTERISTICS
Kukharenko Alexander Sergeevich,
Ph. D., head researcher, Branch of "United Rocket and Space Corporation" - "Institute of Space Device Engineering", Moscow, Russia, alexk.05@mail.ru
Keywords: special ground plane, metamaterial, frequency-selective structure, antenna adjustment, antenna characteristics.
A mushroom-type metamaterial construction and physical properties are shortly described. Two constructions of metamaterial-based frequency-selective ground planes, having same dimensions, but different band gaps are presented. With the help of several experimental measurements an influence of the ground planes on patch antenna element characteristics is investigated. A small-size antenna element was placed in the centre of the metamaterial impedance surfaces, which have different band gaps and size same as the size of a metal ground plane, on which the antenna element was first adjusted. Radiation patterns and reflection coefficient were measured each time. Analysis of the obtained data showed, that in case of changing the ground plane to keep the antenna element resonant frequency, adjusted on the metal ground plane, the metamaterial band gap should completely include the antenna element working band. Also it is shown, that a system, containing metamaterial and antenna, is well coupled with a feeder on the frequency, close to the higher border of the frequency-selective ground plane band gap. This effect can be used during a malty frequency radiating system design. It is experimentally demonstrated that additional resonant frequency gain, which is obtained with the help of metamaterial, is equal to the gain of the main resonant frequency. Also it is shown, that as mushroom-type metamaterials have filtering properties, they reduce the influence of the ground plane edge on the antenna diagram and improve multipath mitigating. That means, that using such an antenna constructing method, ground plane size can be reduced compearing to the metal ones, and their length and width should not be quarter wave length for multipath mitigation. Advantages of using mushroom-type metamaterials for patch antenna ground plane design are shown in the paper.
Для цитирования:
Кухаренко А.С. Исследование влияния частотно-селективного экрана на основе метаматериала на характеристики печатной антенны // T-Comm: Телекоммуникации и транспорт. - 2015. - Том 9. - №8. - С. 94-99.
For citation:
Kukharenko A.S. Investigations of metamaterial-based frequency-selective ground plane influence on patch antenna characteristics. T-Comm. 2015. Vol 9. No.8, рр. 94-99.
Т-Сотт Уо!.9. #8-2015
W 3Î2014, 7 J6 РМ
Fig. 3, S2i parameter of the structure with spiral-shape elements vs. frequency structure
»1312014. PM
Fig. 4. S2i parameter of the structure with cross-shape elements vs. frequency
In the center of the top layer of each ground plane a metal square is specially made to place a patch antenna element on the top layer of the constructions. Metal squares are connected to the bottom metal planes with vias on their perimeter. It is important that vias are placed only on the perimeter of the metal squares and not in the center, It is specially made, as vias, placed under the patch antenna element change the antenna element adjustment and destroy its radiation pattern.
2. Antenna parameter experimental
measurement
For this experiment a small (8*8*4 mm.) patch antenna element with one feeding point and linear field polarization was taken. Before installing the element on the construc-
tions, it was placed in the center of a metal square-shape ground plane with the same size as the constructions (100*100 mm) and adjusted to have a resonance at a frequency 2.49 GHz providing the operation on the 802.11 b/g standard 14-th channel (Fig. 5). The radiation pattern of the construction is illustrated on the Fig. 8 (line 1). During the measurement, it was rotated along the antenna axes, which goes thru its center and feeding point.
After the measurements on the metal ground plane, the patch antenna element was replaced to the ground plane with the spiral-shape top elements in the same position and orientation respectively the rotation axis and the feeding cable (Fig. 6a). Sn parameter of this configuration is shown on Fig. 7,
Trc1 ■-SfldBMag 10dBJ RefOdB OITs 1
Ш1 ■M1 2.491 S0< G№ -2 ¡.269 dB
0 — -«
--- л,
\
CM Start 2 2GHJ Pwr 4 8 dBm Stop 27 GHz
1 (28/2014, 6:30 PM
Fig. 5. Sn parameter of the patch antenna element, adjusted on the metal ground plane
a) b)
Fig. 6. Lay-out of the antenna element on ground planes with spiral-shape (a) and cross-shape (b) top elements
It is well seen from the Fig. 7, that in this configuration the system of the patch antenna and the metamaterial ground plane has 2 resonances. One of them is approximately on the same place as It was adjusted on the metal ground plane (a slight difference of 2% is caused by some changes, occurred during the antenna element replacement from one ground plane to another).
The second resonance, which is 200 MHz higher, is caused by the influence of the meta materia I frequency-selective structure of the ground plane.
Trc1-SB dBMag 2dB/ ReMOdB Offis 1
•M 1
мг
2 442001 2 649501 GHz -1
Chi Start 2 2 GHz UW20U, 9:00 PM
Pwi 4.BdBm
Stop 2 8 GHz
Fig. 7. Sn parameter of the patch antenna element, placed on the frequency-selective ground plane with spiral-shape top elements
Gain 5 [dB] 2,
о
-23 -5
-73 -10 - 1AÎ - и -17J -20
TNS
I \
к \
\ ¡\
л J I » / jf V » i *
2 if 1 I \ \ \ » \ 1
J , V*'' < j 't . 1 ■ '/
r1
— 200 -160 -120 -SO -40
0
eB
Fig. 8. Radiation patterns of the patch antenna: 1 - on the meta! ground plane f=2.49 GHz; 2 - on spiral-shape metamaterial ground piane f=2.44 GHz; 3 - on spirai-shape metamaterial ground plane f=2.64 GHz
The radiation patterns, taken on both resonant frequencies, are shown on the Fig. 8 (lines 2 and 3). Analyzing the obtained data it is seen that the gain of the antenna element, placed on the metamaterial ground plane, on the basic frequency is the same as in the case of using a metal ground plane. The gain on the second resonant frequency is 1.25 dB lower.
It is also seen, that regional effects of the ground plane edges on the basic frequency are reduced with the help of using metamaterial ground plane, what is caused by the
metamaterial frequency-selective properties, which provide the space decoupling of the antenna element and the ground plane edge. It should be also mentioned that the second resonant frequency is close to a higher border of the spiral-shape metamaterial structure band gap.
Finally the patch antenna element was replaced on the metamaterial ground plane with the cross-shape top elements in the same position and orientation respectively the rotation axis and the feeding cable as in previous two experiments (Fig. 6b). Sn parameter of this configuration is shown on the Fig. 9.
Trc1-dB Mag 2 dB I Ref-IOtfB Offs
M 1 M 2 3.03720t 3.0000« GHz -1 GHz ^J- S.526jjS-riSt dB
/
j
j
1 1
I
2
CM Start 2.7 GHz
148(2014, S 57 PM
Pwr 4.S[fBm
Stop 3.2 GHz
Fig. 9. Sn parameter of the patch antenna element, placed on the frequency-selective ground plane with cross-shape top elements
Gain 5 [dB], s
о
-2.5 -5 -7.5
-10
-12.5 -15
-17.5
-20
/
/
/ H
* ? » ' *
J.Y ' '/ V1 V.i
3 t f,7 t .1 ' 7 t.'/ V, 1 V 1 V *
■ \ A. * */ V" 1
2 -1
-200 -160 -120 - 30 -JO
0 8°
JO
so
120 160 200
Fig. 10. Radiation patterns of the patch antenna: 1 - on the metal ground plane f=2,49 GHz; 2 - on cross-shape metamaterial ground plane f=3.037 GHz; 3 - on spiral-shape metamaterial ground plane f=2.44 GHz
It is well seen from the Fig. 9 that the resonance of the construction jumped up to the 3.0 GHz. There are still 2 resonances, but they are very close to each other. There is no resonance at the frequency, patch antenna was first adjusted. After a correlation of this result with an S2i parameter of the metamaterial ground piane with cross-shape top elements (Fig. 4) it Is seen that the resonance of the construction is on the top border of the metamaterial band gap. This is the same result as for the second resonance of the construction with a metamaterial ground plane with spiral-shape top elements, which is also close to the top border of the ground plane forming metamaterial band gap.
Analysis of the radiation pattern (Fig. 10)shows, that the gain of the configuration is 0.1 dB lower even the resonant frequency is higher. It should be mentioned that dimensions of the metamaterial ground plain (100*100 mm) are accurate equal to the wave length on the frequency 3.0 GHz.
Conclusion
Summarizing and analyzing the experimental data, provided above, the following advantages of mushroom-type metamaterials usage for patch antenna's ground plane design should be mentioned:
• The antenna element resonant frequency, which was adjusted on a metai ground plane, doesn't change when the antenna element is replaced on a mushroom-type metamaterial ground plane of the same size, in case if the adjusted antenna resonance is completely inside the metamaterial band gap.
• The system of antenna element and a metamaterial ground plane has a good coupling with feeding lines on the frequency close o a top border of the metamaterial band gap. The same time the gain on the additional frequency, which is formed owing to the metamaterial impedance surface influence, is not much less then the gain on the basic antenna element resonant frequency. This effect can be used during the design of multi frequency antenna systems.
• As mushroom-type metamaterials have space filtering properties, they reduce the influence of the ground plane edges on the antenna element radiation pattern and improve the ground plane multipath mitigation properties. That means that in case of using these structures during the antenna and UHF devices design, dimensions of the additional ground plane can be reduced comparing with metal one's, and their width and length shouldn't be equal to a quarter wave length for better multipath mitigation.
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References
ИССЛЕДОВАНИЕ ВЛИЯНИЯ ЧАСТОТНО-СЕЛЕКТИВНОГО ЭКРАНА НА ОСНОВЕ МЕТАМАТЕРИАЛА НА ХАРАКТЕРИСТИКИ ПЕЧАТНОЙ АНТЕННЫ
Кухаренко Александр Сергеевич, к.т.н., с.н.с., Филиал открытого акционерного общества "Объединенная ракетно-космическая корпорация" "Научно-исследовательский институт космического приборостроения", Москва,
Россия, alexk.05@mail.ru
Кратко рассмотрены особенности конструкции и физические свойства грибовидных метаматериалов. Приведены два частотно-селективных экрана на основе этих структур, имеющих одинаковые габаритные размеры, но разные полосы запирания. При помощи ряда экспериментальных измерений рассмотрено их влияние на характеристики печатного антенного элемента. В ходе исследования антенный элемент небольшого размера поочередно устанавливался в центр импе-дансной поверхности метаматериалов, имеющих разные полосы запирания и габаритные размеры, равные размерам металлического экрана, на котором антенный элемент был изначально настроен. В каждом случае были измерены диаграммы направленности и коэффициенты отражения конструкций. Анализ полученных данных показал, что для того чтобы при перестановке антенного элемента с металлического экрана на частотно-селективную поверхность, образованную грибовидным метаматериалом, его резонансная частота осталась прежней, полоса запирания частотно-селективной поверхности должна целиком захватывать рабочий диапазон антенного элемента. Также установлено, что система, состоящая из антенного элемента и метаматериала, согласована с приемо-передающим трактом на частоте, близкой к верхней границе полосы запирания частотно-селективного экрана. Этот эффект может быть использован при проектировании многодиапазонных излучающих систем. Экспериментально показано, что коэффициент усиления на дополнительной резонансной частоте, образованной влиянием импедансной поверхности метаматериала, равен коэффициенту усиления на основной частоте работы антенного элемента. Также продемонстрировано, что, поскольку грибовидные мета-материалы обладают свойствами пространственного фильтра, они снижают влияние края экрана на диаграмму направленности антенного элемента и способствуют подавлению обратного излучения. А это означает, что, в случае использования этих структур при конструировании антенн и СВЧ-устройств, размеры дополнительных экранов могут быть уменьшены по сравнению с металлическими, а их длина и ширина не обязательно должны быть кратны четверти длины волны для лучшего подавления обратного излучения. Таким образом, в работе показаны преимущества использования грибовидных метаматериалов для создания экранов печатных антенных элементов.
Ключевые слова: специальный экран, метаматериал, частотно-селективная структура, настройка антенн, характеристики антенн.
Литература
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2. Веселаго В.Г. Электродинамика материалов с одновременно отрицательными значениями диэлектрической и магнитной проницаемостей // Успехи физической науки. - 1967. - Том 2. - № 3. - С. 517-539.
3. Engheta N., Ziolkowsky R.W. Metamaterials - physics and engineering exploration. - Danvers: John Wiley & Sons Inc., 2006. - 414 p.
4. PendryJ. B., Holden A. J. A., Roberts D. J., Stewart W. J. Magnetism from conductors and enhanced nonlinear phenomena // IEEE Trans. MTT. 1999. vol. 47. No. 11. Pp. 2075-2081.
5. Sievenpiper D., Zhang L., Broas R.J., Alexopolous N.G., Yablonovitch E. High-impedance electromagnetic surfaces with a forbidden frequency band // IEEE Trans. MTT. 1999. Vol. 47. № 11. Р.2059-2074.
6. Бойко С.Н., Елизаров А.А., Закирова Э.А., Кухаренко А.С. Исследование малогабаритного развязывающего СВЧ-фильтра на метаматериале // Материалы международной научно-технической конференции АПЭП-2014. - 2014. - Том. 1. - С. 218-225.
7. Кухаренко А.С., Елизаров А.А. Анализ физических особенностей метаматериалов и частотно-селективных СВЧ-устройств на их основе // T-Comm - Телекоммуникации и транспорт. - 2015. - Том 9. - №5. - С. 36-41.
8. Froozesh A., Shafai L. Investigations into the application of artificial magnetic conductors to bandwidth broading, gain enhancement and beam shaping of low profile and conventional monopole antennas // IEEE Trans. AP. - 2011. - Vol. 59. - № 1. - Рр. 4-20.
9. Zheng Q., Fu Y., Yuan N. A novel compact spiral electromagnetic band-gap (EBG) structure // IEEE Trans. AP. - 2008. - Vol. 56. - No. 6. - Pp. 1656-1660.
