Radiation from a slot in an impedance surface

The effects of a lossy-ground plane on the radiation from a slot are analyzed by using a Green's function of an impedance surface. Numerical results of the radiation field, radiated power, and loss power are presented for various lossy ground planes. In particular, the radiation field and the radiated power from a short slot are given by simple closed expressions. The analytical model of a slot in an impedance surface is validated by radiation field measurements     

Subtraction of edge-diffracted fields in antenna radiation patterns for simulation of infinite ground plane

A measurement technique is introduced to simulate the radiation pattern of an antenna mounted on an infinite sized ground plane. The edge diffracted fields from a finite ground plane are measured and then subtracted from the total field to yield only the direct radiation from the antenna that would be present if the antenna were mounted on an infinitely large ground plane. Comparisons with theory are also presented.<>     

Radiation characteristics of dielectric-coated coaxial waveguideperiodic slot with finite and zero thickness

The leaky wave radiated from the dielectric-coated coaxial waveguide periodic slot with finite and zero thickness is investigated theoretically for the infinite and finite periodic structures. For the infinite periodic structure, mode-matching technique and integral equation method are applied to the analysis of finite and zero thickness slot cases, respectively. The integral equations are derived for the finite periodic structure by use of the Fourier transform and mode expansion and simultaneous linear equations are obtained. The effects of the slot thickness, the finite slot number and the dielectric coating are analyzed. Results for finite periodic slots are compared with those of the infinite extent structure and good agreement is found     

A physical optics based plane wave spectrum approach to theanalysis of finite planar antennas

An efficient physical optics based method of analysis of antennas over finite ground planes is presented. The far field radiated by the current on the finite ground plane is expressed as the convolution integral of the far field of the antenna above the infinite ground plane with the Fourier transform of the polygonal ground plane shape. The convolution integral is simplified by applying the sampling theorem     

Effects of finite ground plane on the radiation characteristics ofa circular patch antenna

An analytical technique to determine the effects of finite ground plane on the radiation characteristics of a microstrip antenna is presented. The induced currents on the ground plane and on the upper surface of the patch are determined from the discontinuity of the near field produced by the equivalent magnetic current source on the physical aperture of the patch. The radiated fields contributed by the induced current on the ground plane and the equivalent sources on the physical aperture yield the radiation pattern of the antenna. Radiation patterns of the circular patch with finite ground plane size are computed and compared with the experimental data, and the agreement is found to be good. The radiation pattern, directive gain and input impedance are found to vary widely with the ground plane size     

导体半平面上双边激励缝隙的并矢格林函数

将导体半平面上的缝隙分解为无限小的水平缝和轴向缝，根据导体半平面上单边激励的无限小缝隙的辐射场，利用求积分的鞍点法，得到了导体半平面上双边激励的缝隙的并矢格林函数在远区的渐近解。根据该并矢格林函数，就可以分析TSA天线的极化及交叉极化特性。     

Textured surface slot antenna with reduced radar cross-section

Provided is experimental verification that a textured surface slot antenna is capable of producing usable far-field radiation patterns with preferential radiation into the forward half-space, at better than -16 dB return loss. In addition, it is shown that the antenna when connected to a 50 Omega load yields a backscattered return of only -17 dB compared to a matched slot antenna constructed on a perfectly conducting (PEC) ground plane, which returns -3 dB. The gain of the textured slot antenna structure was measured to be 3.35 dBi at 4.77 GHz     

Slot antenna impedance for plasma layers

The rectangular cavity or waveguide backed slot is covered by a plasma layer of finite thickness. The longitudinal variation of the voltage across the slot is obtained from the variational solution of an integral equation. The solution for plasma layer of finite thickness is obtained from the free space Green's function by the method of images. The fields outside the slot depend on the surface integral of the fields over the slot plane and over the surface of the plasma layer. If the thickness of the plasma layer is large compared with the wavelength, the fields on the surface of the plasma may be related to the voltage distribution along the slot by plane wave reflection coefficients. This leads to an integral equation that is reduced to a form suitable for machine computations. These calculations show the slot admittance to remain almost constant for plasma layers of various thicknessesh. The slot conductance tends to increase forh/ lambda <0.5. The presence of a plasma layer affects the voltage distribution along the slot for a center excited slot. The field distribution along the waveguide excited slot differs only slightly from the principal mode field distribution in the guide.     

Investigation of wide-band microstrip slot antenna

This paper presents the simulation and experimental investigations of a printed microstrip slot antenna. It is a quarter wavelength monopole slot cut in the finite ground plane edge, and fed electromagnetically by a microstrip transmission line. It provides a wide impedance bandwidth adjustable by variation of its parameters, such as the relative permittivity and thickness of the substrate, width, and location of the slot in the ground plane, and feed and ground plane dimensions. The ground plane is small, 50 mm/spl times/80 mm, and is about the size of a typical PC wireless card. At the center frequency of 3.00 GHz, its width of 50 mm is about /spl lambda//2 and influences the slot impedance and bandwidth significantly. An impedance bandwidth (S/sub 11/=-10 dB) of up to about 60% is achieved by individually optimizing its parameters. The simulation results are confirmed experimentally. A dual complementary slot antenna configuration is also investigated for the polarization diversity.     

Frequency-adjustable circularly polarised dielectric resonator antenna with slotted ground plane

Circularly polarised (CP) dielectric resonator antennas (DRAs) with a slotted ground plane are proposed. The proposed CP design is achieved by embedding two pairs of unequal slots in the finite ground plane of the feed substrate, which results in the excitation of two near-degenerate orthogonal modes and leads to CP radiation. For the proposed design, a large CP bandwidth, determined from 3 dB axial ratio, as high as 2.7% is also obtained. The resonant frequency can be tuned by changing the slot length. This proposed design is applicable to DR antennas where post-manufacturing trimming is required. Details of the proposed designs and experimental results of the constructed prototypes are presented.     

Ground plane impact on quadrifilar helix antenna performance with respect to deployment heights

Quadrifilar helix antenna (QHA) has its applications in satellite communications. This paper presents the performance optimisation of input and radiation characteristics of QHA in the presence of infinite and finite metallic ground planes. For the infinite ground plane, it has been observed that input parameters such as impedance and voltage standing wave ratio (VSWR) are stable, and the antenna has broader half power beamwidth (HPBW). Smaller metallic platforms that act as finite ground planes produce better 3‐dB axial ratio beamwidth and boresight axial ratio. Deployment of QHA on smaller metallic platforms such as nanosatellites and CubeSats enhances the circularly polarised beamwidth of the antenna with improved boresight axial ratio. However, on large low earth orbit (LEO) satellites, stable input characteristics and broader HPBW have been achieved at the cost of narrow circularly polarised beamwidth and degraded boresight axial ratio.     

Theoretical and Experimental Study of a Novel H-Guide Transverse Slot Antenna (Short Papers)

Transverse slots in the "upper" plate of a dielectric-loaded parallel plane waveguide (H-guide) operating in the dominant mode (zero cutoff frequency) are proposed as slot antennas. A new theoretical approach to the analysis of a single-slot antenna is presented, leading to explicit expressions for the antenna input impedance and radiation efficiency. The computed values of the VSWR and radiation efficiency are in good agreement with laboratory measurements. The radiation efficiency of a single slot exceeds 10 percent in the 8-11-GHz frequency band, reaching a 50-percent theoretically predicted maximum at the slot resonance frequency, when the guide is terminated by a matched load. Experimental checks prove that the leakage, or parasitic, radiation power level is less than -40 dB relative to the measured radiated power.     

Radiated emissions and immunity of microstrip transmission lines:theory and reverberation chamber measurements

The increasing complexity of electronic systems has introduced an increased potential for electromagnetic interference (EMI) between electronic systems. We analyze the radiation from a microstrip transmission line and calculate the total radiated power by numerical integration. Reverberation chamber methods for measuring radiated emissions and immunity are reviewed and applied to three microstrip configurations. Measurements from 200 to 2000 MHz are compared with theory, and excellent agreement is obtained for two configurations that minimize feed cable and finite ground plane effects. Emissions measurements are found to be more accurate than immunity measurements because the impedance mismatch of the receiving antenna cancels when the ratio of the microstrip and reference radiated power measurements is taken. The use of two different receiving antenna locations for emissions measurements illustrates good field uniformity within the chamber     

Radiation characteristics of cavity backed aperture antennas infinite ground plane using the hybrid FEM/MoM technique and geometricaltheory of diffraction

A technique using the hybrid finite element method (FEM)/method of moments (MoM) and geometrical theory of diffraction (GTD) is presented to analyze the radiation characteristics of cavity fed aperture antennas in a finite ground plane. The cavity which excites the aperture is assumed to be fed by a cylindrical transmission line. The electromagnetic (EM) fields inside the cavity are obtained using finite element method (FEM). The EM fields and their normal derivatives required for FEM solution are obtained using: (1) the modal expansion in the feed region and (2) the MoM for the radiating aperture region (assuming an infinite ground plane). The finiteness of the ground plane is taken into account using GTD. The input admittance of open-ended circular, rectangular, and coaxial line radiating into free space through an infinite ground plane are computed and compared with earlier published results. Radiation characteristics of a coaxial cavity-fed circular aperture in a finite rectangular ground plane are verified with experimental results     

EM pickup and scattering by a wire

This article treats pickup and scattering by a single wire in free space or over a ground plane. The wire may be uniform or nonuniform and infinite or finite. We only treat the case where wire radius is so small compared to a wavelength and the other problem dimensions that scattering by the wire is independent of azimuth. Solutions based directly on Maxwell's equations are compared with solutions based on the telegrapher's equations; for 1 mm radius Cu wire at 1 GHz, equilibrium CW currents as computed from the two models, for a uniform, infinite wire, differ by 6 dB. In general, the wire-current solutions are separated into a homogeneous part and a particular or driven part. The driven part couples and scatters fields, while,at least on an infinite wire in the far field, the homogeneous part does not     

Miniaturized wideband dual linearly and circularly polarized printed square slot antenna for multiradio wireless systems

A dual symmetrical coplanar waveguide (CPW)-fed small size wideband printed square slot antenna (SSA) with dual linearly and circularly polarized radiation capability is presented. The antenna is composed using a square slot, two symmetrical orthogonal CPW feed lines connected to horizontal and vertical arm of L-shaped radiator, an embedded parasitic inverted-L strip at the lower left corner of the square ground slot and engraving slots in the ground plane. Circular polarization (CP) is achieved due to two orthogonal CPW feed lines and a common L-shaped radiator. Isolation between ports is improved by engraving slots at the lower left corner of ground plane and embedded parasitic inverted-L strip. The sense of dual-polarization can be changed in pass-band by changing the port excitation. Measured antenna reveals that an 84.4% (4.6 GHz, 3.15–7.75 GHz) −10 dB impedance bandwidth (IBW) and about 33% (2.03 GHz, 5.12–7.15 GHz) 3-dB axial ratio bandwidth (ARBW). Isolation between ports <−16 dB is achieved over usable CP band.     

Peano分形加载单极子辐射性能的研究

对有限地板尺寸和介质填充情况下Peano分形加载单极子天线的辐射特性进行了研究.利用HFSS分析了地板尺寸和填充介质材料对天线反射系数、辐射方向图和增益的影响.仿真表明:随着地板尺寸的减小,天线的阻抗带宽和增益明显减小,H面方向图变化不大,而E面方向图的半功率波束宽度增大,波束仰角减小;填充材料的介电常数过大会导致天线性能的恶化.在分析研究的基础上,设计并研制了地板尺寸为220mm×220mm的一阶和二阶Peano分形加载单极子天线.天线分别实现了45°和36°的波束仰角,50°和45°的半功率波束宽度.仿真与实测结果均表明凋节地板尺寸是控制Peano分形加载单极子天线E面半功率波束宽度和波束仰角的一种简单而有效的方法.     

CPW馈电缝隙耦合蝶形毫米波贴片天线

该文研究了一种工作在Ka波段共面波导(CPW)馈电缝隙耦合的蝶形贴片天线。耦合缝隙位于接地板上,而不需要额外的缝隙耦合层,使天线更易与电路相集成。耦合缝隙的存在改变了接地板上原有表面电流的分布,使电流沿着缝隙边缘流动,因此馈线与辐射源的电磁耦合效率得到提高。用有限元分析软件(Ansoft HFSS)对衬底厚度、贴片角度、耦合缝隙大小等参数变化时的天线性能进行了仿真。比较并分析了S11,增益等天线性能参数的变化规律,并在带宽最优的条件下给出了一组参数值,此时天线的工作频率为35.5GHz,带宽为1.22GHz,增益为6.38dB。     

Radiation from an aperture in a conducting cylinder coated with a moving plasma sheath

The electromagnetic radiation from an aperture on a conducting cylinder coated with a moving isotropic plasma sheath is considered. Numerical results are presented to illustrate the radiation patterns as functions of sheath velocity and plasma frequency for the circumferential slot and axial slot apertures. It is found for the circumferential slot aperture that the radiation is enhanced in the direction of sheath motion when the plasma is overdense and that relatively little change occurs when the sheath is underdense. For the axial slot, it is found that an electromagnetic field is radiated whose polarization is normal to that of the field radiated under stationary conditions, in addition to a field of the usual polarization. Significant alterations of radiation patterns from their form when the sheath is stationary can occur at relatively small velocities if the wave frequency is near the plasma frequency.     

The finite ground plane effect on the microstrip antenna radiation patterns

The uniform geometrical theory of diffraction (GTD) is employed for calculating the edge diffracted fields from the finite ground plane of a microstrip antenna. The source field from the radiating patch is calculated by two different methods: the slot theory and the modal expansion theory. Many numerical and measured results are presented to demonstrate the accuracy of the calculations and the finite ground plane edge effect.