Wide-band sleeve-cage and sleeve-helical antennas

A sleeve-cage monopole has parasitic wire elements that form a sleeve around the driven cage antenna. Appropriate placement and dimensions of the wire parasites lead to bandwidth enhancement. Genetic algorithms and an integral equation solver are employed to determine the position and lengths of the parasitic wires in order to minimize voltage standing wave ratio (VSWR) over a band. The cage is replaced by a normal-mode quadrifilar helix for height reduction and the resulting structure is referred to as a sleeve helix. Measured VSWR and input impedance data are in good agreement with computed data. A fabricated sleeve-cage monopole has a bandwidth ratio of 4.4:1 and a sleeve helix has a bandwidth ratio of 3.5:1 for measured VSWR less than 3.5.     

Broadband planar antenna with parasitic radiator

A novel kind of planar monopole broadband antenna with a parasitic radiator is presented. Measurements show that the bandwidth of the monopole antenna has been considerably improved with a parasitic element earthed with a matching inductor. The achieved impedance bandwidth reaches over 85% for VSWR/spl les/2, and the measured radiation patterns have little distortion when the frequency changes. The impedance bandwidth parameters are compared for different dimensions of ground planes     

Single-feed circularly polarized microstrip ring antenna and arrays

An analysis is presented for a microstrip-feed proximity-coupled ring antenna and a four-element array. Interactions between the embedded microstrip feed and the radiating element(s) are rigorously included. Results demonstrate that circular polarization of both senses can be achieved with a ring antenna with proper design of two inner stubs located at angles of ±45° with respect to the feedline. Theory and experiment demonstrate an axial ratio 3-dB bandwidth of 1% and the voltage standing wave ratio (VSWR) <2 bandwidth of 6.1%. The axial ratio bandwidth is typical for a microstrip antenna with perturbations, while the VSWR bandwidth is larger than for the circular or rectangular patch with perturbations. A mutual coupling study between two elements shows that the axial ratio is less than 2 dB for interelement spacing greater than 0.55λ_eff, while the VSWR <2 for all spacings considered. A comparison between theory and experiment is provided for a 2×2 element array. The benefits of sequentially rotating the antenna elements in an array environment are presented. The axial ratio and VSWR bandwidths are both increased to 6.1% and 18% for a four-element array. A single-element antenna with two orthogonal feeds to provide both senses of polarization is demonstrated. The ring antenna is small (D/λ₀=0.325), the substrate thickness is thin (H/λ₀~0.035), and the microstrip feed produces a completely planar antenna system, which is compatible with microwave and millimeter integrated circuits (MICs), and monolithic microwave integrated circuits (MMICs)     

Tilted- and axial-beam formation by a single-arm rectangular spiralantenna with compact dielectric substrate and conducting plane

A single-arm rectangular spiral antenna is analyzed using the finite-difference time-domain method. The spiral is printed on a finite-size dielectric substrate backed by a finite-size conducting plane. Both the substrate and conducting planes are square with a side length L of less than 0.6λ₀ (λ₀: wavelength in free space). The radiation pattern is dependent on the outermost arm peripheral length C. The spiral whose peripheral length is within 2λ_gg (λ_g: the guided wavelength of the current) radiates a tilted beam of circular polarization. When the peripheral length is decreased to λ_gg, the spiral radiates an axial beam. The axial beam has a wide half-power beam width of approximately 102° (for L≈0.369λ₀) with a gain of approximately 6.7 dB. The axial beam shows a 15% frequency bandwidth for a 3 dB axial ratio criterion. Over this bandwidth, the voltage standing-wave ratio (VSWR) is less than two, as desired. The experimental results for the radiation pattern, gain, axial ratio, and VSWR are also presented     

含有寄生单元的倒F天线分析与设计

提出了在普通倒F天线的两侧和底部同时添加寄生单元的改进倒F天线,该天线与普通的倒F天线相比有更宽的带宽.设计了一个工作于中心频率1.2GHz的改进倒F天线.对该天线的电气特性进行了仿真计算,并对天线主要结构参数对谐振频点和阻抗带宽的影响进行了详细分析.该天线相对带宽达到了33%(VSWR<2),约为普通倒F天线阻抗带宽的4倍,有效地展宽了传统倒F天线的工作带宽,在宽带通信系统中有较好的应用前景.     

Bandwidth enhancement of the monopole antenna by using a parasitic normal-mode helix

An innovative monopole antenna coupled with a parasitic normal-mode helix has been designed and studied both experimentally and theoretically. The effects of various dimensions of the monopole and the parasitic helix were investigated extensively. This simple combination can significantly enhance the antenna bandwidth over that of the conventional monopole antenna. It is found that, with suitably chosen antenna dimensions, the VSWR bandwidth (VSWR ≤ 2) of the antenna can be increased to 36%, almost double that of the monopole antenna alone. The far-field pattern of the combined antenna is basically the same as that of the monopole antenna. This antenna is designed to operate at 1.8GHz. The substantially enhanced bandwidth of this simple and small antenna is a useful feature for future mobile communications.     

Compact printed monopole antenna with 24:1 impedance bandwidth

A compact tapered CPW-fed hollowed elliptical printed monopole antenna with extremely wide bandwidth is proposed. The results demonstrate that this antenna achieves a measured impedance bandwidth from 0.44 to 10.6 GHz (24.1:1) for VSWR les 2, and exhibits a nearly omnidirectional radiation pattern, while its area is only about 0.18 times 0.13lambda_l, where lambda_l is the wavelength of the lowest operating frequency.     

A broad-band coupled-strips microstrip antenna

A coupled-strip microstrip antenna with increased bandwidth and increased polarization purity is presented. We have demonstrated the underlying principle of its operation using even/odd modes of the coupled strips. An optimized parameter set for three coupled strips is obtained. The VSWR=2, impedance bandwidth of this antenna is 23% for antenna thickness of 0.083λ₀     

无线局域网应用的接地平面单极天线的设计

提出了一种应用于无线局域网(WLAN)的新型低成本多频段天线,采用斜切角接地的平面单极结构,天线顶部折返成水平面内的两个对称矩形单元来降低高度。同时,通过在垂直辐射单元表面开L形槽的方法,实现了无线局域网高低两个工作频段覆盖的需求。天线在各工作频段内具有良好的全向辐射特性。实测和仿真结果基本吻合,从而验证了这种设计方法的有效性。     

Small eletric monopole mode dielectric resonator antenna

A novel dielectric resonator (DR) antenna is reported. The lowest order mode of the proposed antenna radiates like an electric monopole. The dimensions of the antenna are much smaller than a previously reported structure radiating in a similar mode, e.g. for an antenna fabricated out of ε_r=20 material, the diameter and height of the DR are ~0.08 λ₀ each     

一种宽带电小天线的研制

本文提出了一种天线结构,即用单极子向Γ结构进行电磁耦合馈电.仿真和实测结果表明,和普通单极天线相比,该天线能够将高度降低一半,并将相对带宽展宽到66%,实现了天线的小型化和宽带化.该天线的相频特性为线性,输出信号波形失真较小,可发送宽带信号.经过特殊的设计,还可以改善匹配和增益,使天线在整个工作带宽范围内的驻波比小于2...     

新型小型化的宽带定向天线

设计了一种小型化宽带定向天线。椭圆形的印制单极天线是一种小型化的超宽带天线,通过将该单极天线的地板折叠为字母C的形状,作为单极天线振子的反射腔,不仅实现了天线的定向性,同时进一步减小了天线的高度尺寸（0．13λ0,λ0为工作频率空气波长）。制作了天线样件并进行了测试,实测结果表明,该小型化天线驻波小于3的工作带宽为700～3800MHz,天线的方向图在整个频带内具有良好的定向辐射特性。     

A Novel Compact Printed Antenna Used in TPMS or Other Complex and Variable Environments

A novel compact printed antenna used in tire pressure monitoring system (TPMS) is proposed and analyzed in this paper. The proposed antenna is printed on both sides of the dielectric substrate and the upper side consists of four parts: (1) the meandered radiating sections; (2) the additional strip line, which is used as a shorting connector and an additional radiating portion; (3) the feed microstrip line; and (4) the loading meandered sections, which are mainly used to improve the impedance bandwidth. The lower side consists of a meandered ground plane, which can also act as a balun choke and the extended parallel strap, which acts not only as a shorting connector but also as an impedance-tuning strap. A prototype of the proposed antenna with 0.17 lambda₀ in length, 0.017 lambda₀ in width and 0.0021 lambda₀ in height has been fabricated and tested. The relative impedance bandwidth of the proposed antenna reaches 22% (VSWR < 3.0) and 12% (VSWR < 2.0), and the antenna has an acceptable relative gain and its performance is relatively stable. Therefore, it also can be used in other complex and variable environments besides TPMS. When the length of the antenna is reduced to 0.098 lambda₀, the relative impedance bandwidth exceeds 28% (VSWR < 2.0). But the antenna's performance will become less stable, which may be the same as that of the conventional compact monopole antenna. Design details of the proposed antenna and the results of both simulations and experiments are presented and discussed.     

Height-reduced meander zigzag monopoles with broad-band characteristics

The characteristics of a meander dual zigzag wire monopole antenna are described. The antenna provides low height and broad-band performance. Measured voltage standing-wave ratio (VSWR) and pattern characteristics are compared with a conventional, straight-wire monopole over a 3:1 bandwidth.     

Mesh antennas for dual polarization

Three mesh antennas, all having an extremely small antenna height of approximately 0.06 wavelength above a ground plane, are presented. First, a mesh antenna excited with a balanced feed is analyzed. It is revealed that the mesh antenna radiates a linearly polarized wave with no cross-polarization component in the principal planes. The radiation mechanism is explained using the current distribution. Second, a mesh antenna excited with an unbalanced feed is analyzed. This antenna shows almost the same radiation characteristics as the mesh antenna with a balanced feed. The frequency bandwidth for a VSWR=2 criterion is evaluated to be approximately 3%. Third, a mesh antenna having two perturbation elements is analyzed. It is found that the antenna acts as a radiation element of circular polarization. The frequency bandwidth for a 3-dB axial ratio criterion is calculated to be approximately 1%. The mesh antennas in the first and second analyses can be used as dual linear polarization elements by appropriately switching the feed. Similarly, the mesh antenna in the third analysis can be used as a dual circular polarization element by switching the feed     

Single feed proximity coupled circularly polarized microstripmonofilar Archimedean spiral antenna array

The analysis is presented for a microstrip feed proximity coupled monofilar Archimedean spiral four-element antenna array. Interactions between the microstrip corporate feed and the radiating elements are rigorously included. Results demonstrate that circular polarization can be achieved with proper spiral arm length. Polarization of either sense is controlled by the location of the feedline. The 3-dB axial ratio (AR) and voltage standing wave ratio (VSWR) bandwidths are 9%. The antenna is small (2R/λ₀=0.33) and the interelement spacing is 0.51λ₀. The microstrip feed produces a completely planar antenna system, which is compatible with microwave integrated circuits (MIC) and monolithic microwave integrated circuits (MMIC)     

Small broadband disc-loaded monopole antenna with probe feed and folded stripline

A small broadband disc-loaded monopole antenna with a probe feed and folded stripline is presented. The antenna is composed of a rectangular disc with multiple shorting pins and a probe feed with a folded stripline that are coupled electromagnetically. The dimensions of the proposed antenna are 12/spl times/12/spl times/10 mm, and it has a measured impedance bandwidth of 700 MHz for VSWR <2 with a centre frequency at 2.54 GHz, which is approximately 27.5% of a fractional bandwidth.     

Modified planar inverted F antenna

The design of a modified planar inverted F antenna (PIFA) which is more compact (antenna length <λ₀/8 and antenna height <0.01 λ₀) and has a much wider antenna bandwidth (greater than 10 times that of a simple PIFA) is demonstrated. The reduction in antenna length is achieved by meandering the radiating patch, while the enhanced bandwidth with low antenna height is obtained using a chip-resistor load in place of the shorting post. A typical design of the modified PIFA in the 800 MHz band has been implemented, and experimental results are presented and discussed     

基于开窗结构和寄生单元的双陷波超宽带天线

设计了一种具有双陷波特性的平面超宽带天线。超宽带基础天线的馈电采用渐变式阶梯阻抗匹配结构作,使得天线具有了宽阻抗匹配能力。通过在椭形辐射器内进行开窗,以及在地面添加矩形寄生单元,实现了天线的双陷波特性。测试结果表明,该天线的工作带宽(VSWR<2）为3.1~10 GHz,工作在超宽带(UWB)频率范围,两个陷波分别在3.3~4.0 GHz和5.0~5.85 GHz,可以应用于WiMAX和WLAN频段的信号抑制。仿真与实测结果表明,该天线结构简单、实现了良好的陷波功能,能够较好地应用于超宽带通信系统中。     

Resonance frequency and bandwidth of rectangular microstrip antennaon thick substrate

We report an improved cavity model called modified Wolff model (MWM) to compute the resonance frequency of a rectangular patch antenna on the thick PTFE substrate (0.037λ_g-0.229λ_g). The MWM accounts for the effect of anisotropy and total losses on the resonance frequency, therefore it has a maximum deviation 2% against the experimental results. The previous cavity model, the multiport cavity model, and MOM based commercial software, Ensemble, compute resonance frequency with deviation between 4%-36%. Results on the bandwidth computed by these models have also been compared against the experimental results