Dual slot-coupled microstrip antenna for dual frequency operation

A new dual slot-coupled circular antenna for dual frequency or dual polarisation operation is proposed. By optimising the placement of the two slots, high isolation between two ports is achieved. Experimentally, an isolation of more than 35 dB is obtained at L-band.<>     

Dual-polarized slot-coupled planar antenna with wide bandwidth

A new dual-polarized slot-coupled microstrip patch antenna is presented, which can achieve high-isolation, low cross-polarization levels, a wide bandwidth, and low backward radiation levels. The coupling slot is an H-shaped slot. For wide bandwidth and easy integration with active circuits, it uses slot-coupled stacked microstrip patches. The theoretical analysis is based on the finite-difference time-domain (FDTD) method. First, a parametric study on the input impedance of the antenna with a single input port is presented. Based on the results, a dual-polarized microstrip antenna is designed, fabricated, and then measured. The measured return loss exhibits an impedance bandwidth of over 20.9% and the isolation between two polarization ports is better than 36 dB over the bandwidth. The cross-polarization levels in both E and H planes are better than 22 dB. The front-to-back ratio of the antenna radiation pattern is better than 21 dB. Both theoretical and experimental results of return loss, isolation, and radiation patterns are presented and discussed.     

Dual-frequency microstrip antenna with dual circular polarisation

A single-feed dual-frequency microstrip patch antenna that can produce dual circular polarisations (CP) is presented. The microstrip antenna has an annular-ring patch and is excited by an L-shaped microstrip line through the coupling of a ring slot in the ground plane. The occurrence of the dual CP is because the magnetic currents circulating along the ring slot at two specific frequencies have opposite flowing directions. Both simulated and measured results are provided to validate the CP performance of the proposed antenna     

Dual aperture-coupled microstrip antenna for dual or circular polarisation

A new method for radiating dual or circular polarisation with a printed circuit antenna element is described. A square microstrip patch on one substrate is coupled to a pair of microstriplines on another substrate via two orthogonal, rectangular apertures in a common ground plane. Quadrature excitation of the system results in circularly polarised radiation.     

Compact microstrip-T coupled patch antenna for dual polarisation and active antenna applications

A novel way of feeding single-layer microstrip patch antennas using electromagnetically coupled microstrip-T junctions is proposed. The measured isolation and 10 dB bandwidth of an X-band dual polarised antenna are /spl sim/32 dB and 2.1%, respectively, on an /spl epsiv//sub r/ 3.0 substrate. Since both ports of the antenna are electromagnetically coupled, the proposed antenna eliminates the need for capacitors in the RF path for active antenna applications.     

Passive filter for increasing directivity in dual polarisation antenna systems

A novel design for a passive microwave filter is presented. The filter consists of a stacked array of low loss dielectric layers, whose permittivity profile alters in a near sinusoidal manner. The radiation property of the filter is investigated for both co- and crosspolarisation and it is shown that the filter acts as an apodiser and a beam shaper.<>     

Annular slot-coupled dielectric resonator antenna

An annular slot-coupled dielectric resonator antenna is investigated experimentally. As compared with the previous rectangular-slot version, the new configuration offers a much wider bandwidth of 18%. The return loss, radiation patterns, and antenna gain of the configuration have been measured and are discussed     

Coplanar-waveguide-fed slot-coupled rectangular dielectric resonator antenna

A novel coupling scheme to a rectangular dielectric resonator antenna is proposed and investigated. In particular, coupling to the resonator is achieved through a narrow slot at the end of a coplanar waveguide (CPW). The objectives of this design are to maximize the coupling, match the dielectric resonator to the CPW feed line, achieve resonance at the desired frequency, obtain linear polarization with low cross polarization components, and minimize back radiation without using a back conductor. An approximate and quick design approach is given followed by more accurate design and analysis using commercial software. The antenna was fabricated and tested. Measurements match well with simulation results.     

一种新型平面结构的双陷波超宽带天线设计

为了避免现存的一些窄带通信系统对超宽带天线的干扰,提出了一种具有双陷波特性的超宽带天线结构。由于采用了渐变式阶梯阻抗匹配结构作为超宽带基础天线的馈电,使天线具有了宽阻抗匹配能力。通过在基础天线背面附加双偏T寄生单元和在辐射贴片上开窗的联合方法,实现了超宽带天线的双陷波特性。天线电流分布结果可以完全反映出在陷波频率下两种方法的谐振抑制作用,而且实验结果表明该结构的天线对 WLAN(5.15～5.825 GHz) 和WiMAX(3.4～3.69 GHz)频段的信号起到了有效的抑制作用,同时在工作频段内表现出较好的全向辐射特性。     

Modal expansion method of analysis for slot-coupled microstrip antenna

A modal field expansion technique together with the Poynting theorem are used to derive the input impedance of a slot-coupled microstrip antenna. The approach leads to easier and lower computational requirements. Predicted values of input impedance are compared with previous theoretical and experimental results.<>     

低剖面双频双圆极化平板缝隙天线的设计

提出一种新型双频(Ku/Ka)双圆极化平板缝隙天线.三层平行平板构成双层的径向波导,缝隙对螺旋排布于最上层平板,低频与高频缝隙对分别逆时针和顺时针排布,对应实现右旋圆和左旋圆极化辐射.低频与高频段分别采用单根探针与多根探针的馈电形式.在组成高频径向波导的平板外围加上一圈金属通孔使低频馈电端口易于阻抗匹配.仿真结果表明:该新型双频天线在Ku和Ka频段最高的辐射效率达到60.5％和55.7％,-1 dB增益带宽分别为8.3％和6.2％,具有较宽的轴比带宽以及较高的端口隔离度,该天线具有很好的工程应用价值.     

Slot-coupled microstrip antenna for broadband circular polarisation

A microstrip antenna with broadband circular polarisation (CP) is presented. The proposed microstrip antenna has a circular patch and is excited by a series microstrip-line-feed configuration through the coupling of a ring slot in the ground plane. The broadband operation is achieved by coupling two CP resonant elements, which are due to the circular patch and the ring slot, respectively. A typical prototype using foam material of thickness 5 mm as the antenna substrate is constructed. Measured results show the 3 dB-axial-ratio bandwidth centred at 2500 MHz is more than 10%.     

Slot-coupled microstrip antenna for broadband circular polarisation

Broadband circular polarisation (CP) operation of single-feed slot-coupled microstrip antennas is achieved using an inclined nonlinear coupling slot. This nonlinear slot, end-loaded with two V slots, significantly broadens the CP bandwidth to about 2.1 times that obtained using a simple inclined coupling slot for CP operation. Details of the antenna design are described, and experimental results of the CP performance are presented     

Circular polarisation design of a single-feedequilateral-triangular microstrip antenna

By inserting a narrow slit at the edge of an equilateral-triangular microstrip patch, circular polarisation (CP) radiation can be obtained using a single probe feed. This CP design is easy to implement. Details of the antenna design are described, and experimental results of the axial ratio and radiation pattern are presented and analysed     

Cavity-backed slot-coupled dielectric resonator antenna excited bya narrow strip

The input impedance of the cavity-backed slot-coupled dielectric resonator antenna excited by a slender strip is investigated theoretically and experimentally. The effect of the cavity size and strip length on the input impedance are studied and discussed     

Design of square-ring microstrip antenna for circular polarisation

The design of a square-ring microstrip antenna with circular polarisation (CP) is presented. To compact the antenna size and overcome the high impedance problem, the CP antenna is excited by a coupling strip located inside the square-ring patch. Several prototypes of the square-ring CP antennas with various substrate thickness (0.013-0.09/spl lambda//sub 0/) have been constructed and studied experimentally, and their coupling-strip designs and CP performance are described.     

Dual polarisation of microstrip reflectarray antenna

Dual polarisation of a microstrip reflectarray was demonstrated for the first time. A 16 element array of square microstrip patch antennas operating in the X-band was used to reflect the main beam 20" off broadside in both the E-plane and H-plane     

The slot-coupled hemispherical dielectric resonator antenna with a parasitic patch: applications to the circularly polarized antenna and wide-band antenna

The aperture-coupled hemispherical dielectric resonator antenna (DRA) with a parasitic patch is studied rigorously. Using the Green's function approach, integral equations for the unknown patch and slot currents are formulated and solved using the method of moments. The theory is utilized to design a circularly polarized (CP) DRA and a wide-band linearly polarized (LP) DRA. In the former, the CP frequency and axial ratio (AR) can easily be controlled by the patch location and patch size, respectively, with the impedance matched by varying the slot length and microstrip stub length. It is important that the AR will not be affected when the input impedance is tuned, and the CP design is therefore greatly facilitated. For the wide-band LP antenna, a maximum bandwidth of 22% can be obtained, which is much wider than the previous bandwidth of 7.5% with no parasitic patches. Finally, the frequency-tuning characteristics of the proposed antenna are discussed. Since the parasitic patch can be applied to any DRAs, the method will find applications in practical DRA designs.     

Compact polarisation selectable radial cavity antenna

The generation of both hands of circular (CP) in addition to vertical and horizontal linear (LP) polarisation from a 6.5 mm-deep radial cavity antenna is demonstrated in the frequency range 8.1-8.6 GHz by incorporating a compact four port coaxially fed polariser, thus removing the need for an orthomode transducer. The polariser is realised using metal post inserts positioned inside a circular waveguide; its length is 59 mm.