四分之一波长单极天线在左手金属材料中的实验研究(英文版)

1、Progress In Electromagnetics Research,PIER51,281293,2005 EXPERIMENTAL STUDY OF/4MONOPOLE ANTENNAS IN A LEFT-HANDED META-MATERIALInstitute of ElectricsChinese Academy of ScienceAbstractThe paper focuses on/4monopole antennas located in a meta-material that exhibits simultaneously negative values of e

2、ective permeability and permittivity within a microwave frequency band, as well as our experimental study in an anechoic chamber.The experimental results show that the electromagnetic waves radiated by the monopole are negatively refracted at the interface between the meta-material and the air at ce

3、rtain directions.In addition,the radiation pattern of the monopole in the meta-material is directional while it is non-directional without the meta-material.1Introduction2Experimental Setup and the Structure of Meta-Material3Experiment Results and Explanations3.1Measured S11of Monopoles in Dierent M

4、edia3.2The Frequency Band of Negative Permeability andPermittivity3.3The Radiation Pattern in x-z Plane3.4Verication of Negative Refraction4ConclusionAcknowledgmentReferences282Sui et al.1.INTRODUCTIONIn the past few years,the meta-materials with permittivity and permeability both taking real negati

5、ve values have been considered in many publications.So far,there are several experiments to verify the left-handed properties of these meta-materials.In2000,David Smith of the University of California at San Diego and his colleagues constructed therst LHM based on a periodic array of interspaced con

6、ducting nonmagnetic split-ring resonators and continuous metallicwires.1The negative permeability region begins at4.2G Hz andIn this paper,a type of meta-material composed of periodical arrangement of thin copper strips and split ring resonators(SRRs is studied.The radiation properties of a/4monopol

7、e antenna in the meta-material was measured in an anechoic chamber.2.EXPERIMENTAL SETUP AND THE STRUCTUREOF META-MATERIALThe meta-material was constructed as follows:the wire strips and SRRs were printed on two separate printed circuit boards by etching technique.The thickness and the relative permi

8、ttivity of the boards are 0.5mm and2.65,respectively.The SRRs and wire strips are0.035mm thick.The size of the square board is246×246mm2.The width and length of the strips are0.5mm and238mm respectively.There are48 strips on one board.The distance between the strips is5mm.The conguration of a s

9、ingle SRR has a geometry which is similar to the previously reported structure.2,4The details of a single SRR are shown in Figure1.It consists of two square rings separated by a gap. There are2304(48×48SRRs,which are separated by5mm,on one board of246×246mm2.Study of/4monopole antennas in

10、meta-material283 Figure1.Single SRR with parameters l=3mm,d=t=w= 0.3mm.Three dierent media were fabricated by combining the SRR and the strip boards.The three media are as follows:Medium-1is made by placing50identical SRR boards in parallel arrangement with5mm in distance,Medium-2by placing49identic

11、al strip boards in parallel arrangement with5mm in distance,and Medium-3by stacking49strip boards and50SRR boards in a periodic arrangement with2.5mm in distance.The main instruments used in our experiments were an Agilent 8722ES vector network analyzer,a microwave horn antenna,and a receiving monop

12、ole with conducting ground plane.The assembled dimensions of the horn antenna are27.9cm in width,15.9cm in height, and24.4cm in length.The height of the receiving monopole above the conducting ground plane(250×250mm2is about7.5mm.As seen in Figure2,a/4monopole with ground plane was placed in th

13、e medium.Theat conducting ground plane is made of copper of270×246mm2.The horn antenna or the receiving monopole was placed beside the medium.The Agilent8722ES was connected to the monopole in the medium and the horn antenna or the receiving monopole beside the medium via two coaxial cables.We

14、studied the radiation characteristics of the monopole in the meta-material by measuring the scattering parameters matrix when the monopole is in Medium-1,Medium-2,Medium-3,and the Air respectively.As seen in Figure2,we placed a/4monopole in the media.The at conducting ground plane is made of copper

15、of270×246mm2.The horn antenna or the receiving monopole was placed beside the media.284Sui et al. Figure2.Experiment setup of monopole in meta-material.3.EXPERIMENT RESULTS AND EXPLANATIONSFigure3to Figure6shows the measured S11of the monopoles of dierent lengths in dierent media.The lengths of

16、 the monopoles are about9.3mm,7.5mm,6.2mm,and5.3mm respectively.From Figure3to6,we decide to use the monopoles of h=7.5mm and h=6.2mm in our experiments.rest of the That means the waves canFigures7and8show the measured S21when the monopoles are in dierent media.Eachgure has four curves showing the r

17、esults of the monopole(h=7.5mmin Medium-1(SRRs only,Medium-2(strips only,Medium-3(SRRs&strips,and the Air,respectively.The horn antenna was placed beside the medium.The distance between the monopole and the horn aperture is about20cm.The following facts can be derived from Figures7and8:When the

18、monopole is in Medium-1,electromagnetic waves can not propagate within1010.5GHz,but can propagate in the rest of the frequency band.This means that the eective permeability of Medium-1 within1010.5GHz is negative.When the monopole is in Medium-2,electromagnetic waves cannot propagate in the frequenc

19、y band under test,which means that the eective permittivity of Medium-2is negative.When the monopole is in Medium-3,S21at10.310.8GHz is higher than that at other frequencies.Because the meta-material consisting of50pieces of SRR boards and49pieces of strip boards isStudy of /4monopole antennas in me

20、ta-material285 S 11(V S W R Frequency (GHzFigure 3.Measured S 11of monopoles of dierent length in the Air.S 11(V S W R Frequency (GHzFigure 4.Measured S 11of monopoles of dierent lenth in Medium-1(SRRs only. S 11(V A W R Frequency (GHzFigure 5.Measured S 11of monopoles of dierent length in Medium-2(

21、strips only. S 11(V S W R Frequency (GHzFigure 6.Measured S 11of monopoles of dierent length in Medium-3(SRRs &strips. S 21 (d B Frequency (GHzFigure 7.Measured S 21of h =7.5mm monopoles in dierent media. -70-65-60-55-50-45-40-35-30-25S 21(d B Frequency (GHzFigure 8.Measured S 21of h =6.2mm mono

22、poles in dierent media.The radiation pattern in x -z plane was measured by rotating the Medium-3around the axis of the monopole. 90270Figure 9.Normalized eld pattern of 10.6GHz.to non-propagable gradually.It is clear that the meta-material is anisotropic.In theory,the radiation pattern in x-z plane

23、of monopole with large ground plane in the air should be a circle.Because the ground plane is not very large in our experiment,the measured pattern is approximately a circle and because the framework that holds the strip and SRR boards remains when we tested the monopole without the meta-material,th

24、ere are pits at45±10and135±10.Figure11shows the measured S21of10.6GHz in the test of Figure10.It is because both the eective permeability and permittivity of Medium-3may be negative within10.310.8GHz that we choose the frequency of10.6GHz for the sake of illustration.Figure11has four curve

25、s showing the S21when the transmitting monopoles(h=7.5mm and h=6.2mmare in Medium-3and the Air,respectively. Figure10.Experimental setup for refraction received by monopole. H (cmFigure11.Measured S21s received by monopole.From Figure11,the maximum S21emerges at about H=3cm to H=4cm when the monopol

26、e is in Medium-3,while at about H=0cm to H=0.5cm when the monopole is in the Air.That means that the electromagnetic waves radiated by the monopole antenna in the meta-material are refracted downwards of the interface between Medium-3and the Air.Indeed,if the electromagnetic waves were not refracted

27、 downwards,the maximum S21could not emerge at the lower position than the conducting ground plane of the transmitting monopole.The role of electromagnetic waves diraction at the edge of the ground plane was also considered.The diractive electriceld below the ground plane of the monopole in the air w

28、as calculated.10The ground plane is250×250mm2,and the calculated result along the route of the receiving monopole was shown in Figure12.The diractive electriceld decreases when the position moves downwards below the plane.Therefore,we conclude that the maximum power detected below the ground pl

29、ane(at H=3cm to4cmwhen the monopole is in Medium-3is due to the negative refraction instead of the diraction.Study of /4 monopole antennas in meta-material Normalized diffractive electric field 1.0 291 h=7.5mm h=6.2mm 0.8 0.6 0.4 0.2 0.0 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 H (cm Figure 12. Normalized diractive electric eld. 4. C