Size reduction of cavity-backed slot antennas

A technique for reducing the dimensions of the cavity of a cavity-backed slot antenna (CBSA) is presented, which facilitates proper fabrication and integration of miniaturized slot antennas on multilayer substrates. This is accomplished by replacing the solid metal around the traditional slot antennas with a specific metallic pattern that can be viewed as a series of parallel strip lines placed around the slot antenna. This metallic pattern is then modified by designing the parallel strips in a compact fashion to reduce the overall antenna dimensions and obtain a reduced-size CBSA. It is shown that, for a simple straight slot antenna, the overall occupied volume of the modified cavity backing the slot antenna can be reduced by more than 65% without affecting the high radiation efficiency of the antenna. A number of traditional cavity backed slot antennas and the proposed modified CBSAs are designed, fabricated, and measured. The reduced-size CBSAs show a very low input VSWR, low cross-polarized radiation levels, and high radiation efficiency. Despite their small ground plane size, the proposed cavity backed slot antennas have front-to-back ratio (FTBR) values in the range of 6-7 dB.     

基于HFSS的波导裂缝有源导纳的计算方法

提出一种基于商业软件HFSS仿真得到的开缝波导散射参数来提取辐射缝隙自导纳和有源导纳的方法。根据传输线理论．给出了通过散射参数计算孤立缝隙自导纳的公式．同时给出了考虑互耦的有源导纳方程．利用牛顿迭代法求解此方程得到裂缝的有源导纳值。该方法非常适合于波导天线阵的设计．有效地提高了天线阵的设计效率.     

Determination of the multi‐slot transmission in Bluetooth systems with the estimation of the channel error probability

Bluetooth is an open specification for a technology to enable short‐range wireless communications that operate in an ad hoc fashion. Bluetooth uses frequency hopping with a slot length of 625 μs. Each slot corresponds to a packet and multi‐slot packets of three or five slots can be transmitted to enhance the transmission efficiency. However, the use of multi‐slot packet may degrade the transmission performance under high channel error probability. Thus, the length of multi‐slot should be adjusted according to the current channel condition. Segmentation and reassembly (SAR) operation of Bluetooth enables the adjustment of the length of multi‐slot. In this paper, we propose an efficient multi‐slot transmission scheme that adaptively determines the optimal length of slots of a packet according to the channel error probability. We first discuss the throughput of a Bluetooth connection as a function of the length of a multi‐slot and the channel error probability. A decision criteria which gives the optimal length of the multi‐slot is presented under the assumption that the channel error probability is known. For the implementation in the real Bluetooth system, the channel error probability is estimated with the maximum likelihood estimator (MLE). A simple decision rule for the optimal multi‐slot length is developed to maximize the throughput. Simulation experiment shows that the proposed decision rule for the multi‐slot transmission effectively provides the maximum throughput under any type of channel error correlation. Copyright © 2005 John Wiley & Sons, Ltd.     

波导宽边辐射缝隙的全波分析

使用时域有限差分法 (FDTD法 )对矩形波导上单个辐射缝隙的特性进行了严格分析 ,得出在不同缝隙偏置、缝隙宽度和波导壁厚条件下缝隙的谐振长度、散射参数以及等效归一化导纳等特性 ,并对‘谐振状态’的定义做了讨论 ,为高性能波导缝隙天线阵的设计提供参考     

Analysis of Slot Characteristics in Slotted Single-Mode Semiconductor Lasers Using the 2-D Scattering Matrix Method

We use the two-dimensional (2-D) scattering matrix method (SMM) to analyze the slot characteristics in slotted single-mode semiconductor lasers and compare the results with those calculated by the one-dimensional transfer matrix method (TMM). The analysis shows that the 2-D SMM is required to accurately account for the measured results. Using the 2-D SMM simulation, we find that there is almost no reflection at the interface from slot to waveguide while a large reflection exists at the interface from waveguide to slot, and the power loss is much larger than the power reflected. For a single slot, the slot width has little influence on the slot reflectivity, which coincides with the measured results. The reflection and transmission of the slot are found to be exponentially dependent on the slot depth     

Resonant length of longitudinal slots and validity of circuit representation: Theory and experiment

Pertinent theory for the design of longitudinal slot arrays is reviewed and its dependence on the dominant mode scattering off a single slot is pinpointed. The critical need to know resonant length versus slot offset is emphasized and the desirability of determining this information theoretically rather than experimentally is argued. Then method of moments solutions are used to calculate resonant length versus slot offset for given waveguide dimensions and frequency. These theoretical results are compared to new, carefully obtained experimental data. Agreement is found to be so good, it is concluded that one can dispense with the costly gathering of experimental input data when designing longitudinal slot arrays fed by standard rectangular waveguide. A critical look is taken at the validity of representing the longitudinal slot as a shunt element on an equivalent transmission line. This assumption is found to be more and more questionable as thebdimension is reduced. For quarter-height guide, an alternate design procedure is suggested as being more accurate.     

The design of small slot arrays

The differences in mutual coupling for a central slot and a peripheral slot cannot be ignored in small arrays if good patterns and impedance are to be obtained. A theory has been developed whereby the length and offset of every slot in the array can be determined, in the presence of mutual coupling, for a specified aperture distribution and impedance match. The theory enlarges on Stevenson's method, and uses a modified form of Booker's relation based on Babinet's principle to treat nonresonant longitudinal shunt slots in the broad wall of a rectangular waveguide. A general relation between slot voltage and mode voltage is developed, and then formulas are derived for the active, self-, and mutual admittances among slots. These formulas result in a design procedure. Analogous treatments of inclined series slots in rectangular guide and of strip-line-fed slots are possible. Comparison between various experiments and the theory is presented. Tests of the theory include the resonant length of a zero offset slot, resonant conductance versus offset and resonant conductance versus frequency for a single slot, and self- and mutual admittances for two staggered slots. The design and performance of a two-by-four longitudinal shunt slot array is also described.     

Electromagnetic transmission through narrow slots in thick conducting screens

The general formulas for electromagnetic transmission through an infinitely long slot in a perfectly conducting screen of finite thickness are specialized to the case of a narrow slot. The slot may be filled with a homogeneous isotropic material. A simple equivalent circuit for the narrow slot is developed. It is found that for certain screen thicknesses the slot becomes resonant, and exceptionally large transmission of energy may occur. In fact, as the slot width approaches zero, the transmission width at resonance becomes1/piwavelengths regardless of the actual slot width. The effect of loading the slot with a lossy dielectric is also considered. Computations are given to illustrate the validity of the equivalent circuit model and the accuracy of transmission characteristics computed from it.     

人体中心网络微带缝隙天线设计和研究

设计了一款小型微带缝隙天线.通过电磁仿真软件CST的参数优化功能,对微带缝隙天线缝隙的长度、宽度、馈电点等参数进行优化,得到了工作频率为2.45GHz,带宽100 MHz、阻抗匹配良好、辐射效率较高的用于人体中心网络的微带缝隙小型天线,根据仿真设计,制作了天线,测试结果和仿真结果吻合较好.     

Analysis of an untilted wire-excited slot in the narrow wall of arectangular waveguide by including the actual external structure

The admittance of an untilted slot in the narrow wall of a rectangular waveguide is calculated by including the actual external structure. The slot is excited by two tilted thin wires inside the waveguide. The slot is also allowed to extend into the two broad walls of the waveguide to make it sufficiently long for resonance to occur. The external slot admittance is evaluated by using a spectrum of two-dimensional solutions, a method which can handle the arbitrary cross section of the external structure, The analysis predicts that if both the slot and the wires are tuned to resonance, the transmission coefficient gets constant phase over a wide-frequency band. The results also show that resonance can be obtained for any slot length by adjusting the wire length, and this relation between the lengths is presented. The distance between the slot and the wires needed to maximize the radiated power is also shown; some results are confirmed by measurements     

X 波段加膜片式单脊波导裂缝天线的研究

等效导纳值是波导宽边纵缝天线的关键设计参数。为克服传统波导裂缝天线副瓣偏高、设计效率低下等问题,本文提出了一种单脊波导裂缝天线的改进设计方法,在传统波导裂缝阵列天线设计的基础上,利用等效导纳值对天线等效电路的影响,在裂缝单元下增加金属膜片,通过改变金属膜片的高度,优化裂缝等效导纳值,使得每个裂缝口径场分布更加接近于理论设计值,并在设计过程中使用牛顿迭代法提取导纳进一步缩短设计时间。通过设计实例表明:应用此方法设计单脊波导裂缝天线能够有效抑制副瓣电平,天线方位面副瓣电平可达到-30 dB 以下;在满足主要指标要求的前提下,设计效率显著提升。     

A simple scheme for slot reuse without latency for a dual busconfiguration

A simple scheme for slot reuse without latency for the dual bus configuration is studied. The scheme relies on information read in the previous slot and will be referred to as previous slot information (PSI) slot reuse. The scheme requires a minimal addition to the station hardware and its reliability is high. The efficiency of PSI is checked over a wide range of parameters and is found to be almost as good as destination release. The scheme can be implemented with or without the addition of erasure nodes     

Evaluation of edge effects in slot arrays using the geometricaltheory of diffraction

The geometric theory of diffraction (GTD) is applied to evaluate efficiently the coupling coefficient associated with the design of a waveguide-fed longitudinal shunt slot arrays. The coupling coefficient is proportional to the reaction integral between the field of a slot and the equivalent current distribution of another slot. Using an approximate form of the Green's function for the wedge, it is shown that the edge-diffraction field due to each slot is practically equal to the field of a suitable `mirror image' of such slot. In this way the actual coupling coefficient can be decomposed into a sum of coupling coefficients between slots on an infinite ground plane. The latter can be evaluated very efficiently so that inclusion of edge effects does not slow down the design procedure. The same approach also allows the computation of the relation between the self-admittance with and without the edge. Some test cases are provided which show that the overall error of this approximation can be neglected since it is comparable with the error due to mechanical tolerances     

Circularly-Polarized Wide Slot Antenna Loaded With a Parasitic Patch

A design is described of a broadband circularly-polarized (CP) slot antenna. A conventional annular-ring slot antenna is first analyzed, and it is found that two adjacent CP modes can be simultaneously excited through the proximity coupling of an L-shaped feed line. By tuning the dimensions of this L-shaped feed line, the two CP modes can be coupled together and a broad CP bandwidth is thus formed. The design method is also valid when the inner circular patch of the annular-ring slot antenna is vertically raised from the ground plane. In this case, the original band-limited ring slot antenna is converted into a wide-band structure that is composed of a circular wide slot and a parasitic patch, and consequently the CP bandwidth is further enhanced. For the patch-loaded wide slot antenna, its key parameters are investigated to show how to couple the two CP modes and achieve impedance matching. The effects of the distance between the parasitic patch and wide slot on the CP bandwidth and antenna gain are also presented and discussed in details.      

Simulation Demonstration and Experimental Fabrication of a Multiple-Slot Waveguide

A multiple-slot waveguide is presented and demonstrated through theoretical simulation. Taking a double-slot waveguide as an example, the results show a nearly 30% enhancement of optical intensity compared with the traditional single-slot waveguide with the same slot gap width. Therefore, the E-field intensity of the slot can be increased by adding another smaller slot. A double-slot waveguide with oxide and air as low index slot materials is realized experimentally and the formation processes of the slots are analyzed.     

Admittance of a half-wavelength slot antenna radiating into a warm lossy two-layer plasma

The admittance of a half-wavelength slot antenna in a two-layer lossy plasma is shown to be greatly affected by moderate electron temperatures (T_{e} leq 1 eV) when the plasma is overdense. The effects of slot width and electron collision frequency upon the slot admittance also are investigated.     

基于缝隙效应的几种宽带微带天线的设计

利用缝隙对天线带宽的影响设计了四种宽带微带天线。主要研究了缝隙的形状和大小以及与馈电的距离对天线带宽的影响。首先,宽缝机构可以较大的展宽天线的频带,如果同时配合在贴片上适当的开缝,带宽将进一步展宽;其次,相同缝隙结构的嵌套可使天线同时谐振在很多的频率,从而增加带宽。设计表明这几种微带天线都具有宽带特性,尤其是前两种天线具有超宽带（UWB）的特性,后两种天线的带宽也达到了48％以上。     

Waveguide slot element

A waveguide slot element, excited by a thin strip, printed and kept behind the slot is presented. The slot is vertical and non-wrap around, whereas the strip is inclined with respect to the slot or takes an L-shape. The strip and the slot are printed simultaneously on a dielectric substrate and replaces the narrow wall of the guide. The use of printed circuit technique leads to good accuracy and square ended slots. A wide range of admittance can be realised by choosing the strip parameters     

The inclusion of wall loss in finite-difference time-domainthin-slot algorithms

The authors present two methods for incorporating slot wall loss into the finite-difference time-domain (FDTD) calculations. The walls are assumed to be good conductors. Loss is only applied to the current component that flows axially along the slot walls, which is generally the dominant component for slots that are long and narrow. The first method modifies an FDTD equation internal to the slot to include a surface-impedance contribution. This method is appropriate for the usual FDTD thin-slot formalisms. The second method includes the losses into a half-space integral equation that can be used by the recently introduced hybrid thin-slot algorithm. Results based on the two methods are compared for a variety of slot parameters and wall conductivities     

Slot apertures having depth and losses described by local transmission line theory

The problem of electromagnetic penetration of a narrow slot aperture in a thick conducting plane is considered when the conductivity of the plane (and slot walls) is large but not necessarily infinite and when somewhat lossy gaskets are placed in the slot. The problem is partitioned into a local region, where transmission line theory is used to describe the antenna modes along the slot, and a nonlocal region, where a filament-type integral representation is used. The result is a modified Hallen-type integro-differential equation for the slot voltage (or magnetic current). The local transmission line theory allows the effects of wall loss and gaskets to be included in a simple and intuitive manner. Examples involving a rectangular slot aperture are given. The finite conductivity of the conducting plane, even for good conductors, reduces the penetration when realistic slot dimensions are used. Gaskets, even with relatively small loss tangents, also reduce the penetration when realistic slot dimensions are used.<>