Stripline-fed printed square spiral slot antenna for circularpolarisation

A novel design for a circularly-polarised printed square spiral slot antenna with a stripline feed is demonstrated. The printed slot antenna consists of a square spiral slot of ~1.25 turns, and a total slot length of approximately one free-space operating wavelength. By carefully trimming both ends of the square spiral slot, circular polarisation (CP) operation with a wide operating bandwidth can easily be achieved. A CP bandwidth of >6% has been obtained     

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.      

Low-Cost Broadband Circularly Polarized Printed Antennas and Array

This paper presents the design, simulation, and measurements of two low-cost broadband circularly polarized (CP) printed antennas: an element and an array at 2 GHz. To realize the broadband circularly polarized antenna element, a circular microstrip patch is electromagnetically coupled by crossed slots cut in the ground plane, which is fed by an L-shaped microstrip feed. Two orthogonal modes in the patch are excited by using the crossed slots, and a single L-shaped feed provides a 90deg phase shift between two orthogonal slots. The antenna element achieves a 9.6% bandwidth for an axial ratio (AR) below 3 dB and a voltage standing wave ratio (VSWR) below 1.5. To further improve the performance, a sequentially rotated feed network is designed for a 2 times 2 array. The axial ratio value of the array is below 3 dB within a 27.2% bandwidth, from 1.75 GHz to 2.3 GHz. The return loss is above 10 dB within a 41% bandwidth, from 1.62 GHz to 2.45 GHz. Details of the proposed antenna element and the array design are described, and both the simulation and the experimental results are presented and discussed.     

Broadband circularly-polarised slot antenna array

A stacked slot antenna is proposed and studied to improve the performance of a circularly-polarised (CP) annular-ring slot antenna that has the disadvantages of a narrow bandwidth, a lower gain and bidirectional radiation. The stacked antenna structure is composed of a circular wide slot, a parasitic patch and a metallic reflector, and its CP radiation is excited through the proximity coupling of an L-shaped microstrip line. A 4 times 4 array using the stacked slot antenna as an element is also developed and designed at X-band. Details of the antenna design and obtained results are presented.     

Circularly polarised patch antenna array using proximity-coupledL-strip line feed

A microstrip antenna array for circular polarisation (CP) using a proximity L-strip line feed is proposed and experimentally investigated. By placing a cross-slot with unequal slot lengths on the circular patch, circular polarisation can be excited. Also, a sequential rotation technique is adopted for the design of this CP antenna array to widen the bandwidth. The impedance and axial ratio bandwidth values are 78 and 16.15%, respectively. The boresight axial ratio is 0.4 dB at 1.91 GHz     

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.     

CPW feed circularly polarised microstrip antenna using asymmetric coupling slot

Design of a coplanar waveguide (CPW) feed square microstrip antenna with circular polarisation (CP) radiation is described. This CP design is achieved by using an asymmetric inductively coupling slot in the ground plane of the CPW feed line. Results show that the proposed antenna can have a CP bandwidth of 2.4%, whereas a simple inclined coupling slot case has 1.6% CP bandwidth at a fixed square patch size. Typical experimental results are presented and discussed     

Wide‐Band T‐Shaped Microstrip‐Fed Twin‐Slot Array Antenna

A numerical simulation and an experimental implementation of T‐shaped microstrip‐fed printed slot array antenna are presented in this paper. The proposed antenna with relative permittivity 4.3 and thickness 1.0mm is analyzed by the finite‐difference time‐domain (FDTD) method. The dependence of design parameters on the bandwidth characteristics is investigated. The measured bandwidth of twin‐slot array antenna is from 1.37 GHz to 2.388 GHz, which is approximately 53.9 % for return loss less than or equal to ‐10 dB. The bandwidth of twin‐slot is about 1.06 % larger than that of single‐slot antenna. The measured results are in good agreement with the FDTD results.     

Broadband circularly polarized CPW-fed slot antenna array for millimeter wave application

A broadband and circularly polarized 1×4 linear antenna array composed of CPW-fed slot elements for millimeter wave application is discussed. Through a special short-circuiting stub perturbation method, the circular ring slot element achieves circular polarization and a broad bandwidth. Through a parallel feeding network, the array achieves a broad impedance bandwidth of 19% with VSWR?2 and CP bandwidth of 18.4% with AR?3 dB and has a peak gain of about 6.8 dB.     

一种小型化缝隙圆极化印刷天线

设计了一种小型化的方形缝隙圆极化（CP）平面印刷天线,该天线采用在方形缝隙的四个边上均加载尺寸相同的矩形缝隙,使其具有更低的谐振频率;在方形缝隙的任一个加载缝隙里插入与外围地相连的细金属带条以产生微扰,激励出一对相位差90°的差分正交简并模,从而辐射圆极化波。对天线模型进行了优化设计和实物加工,测试结果表明,缝隙加载后天线谐振频率降低了约10%,验证了该小型化措施的有效性;另外该天线在3%的带宽内轴比<3 dB,具有良好的圆极化特性。     

Circularly polarized antenna array with a new sequential phase feed network utilizing directional coupler

This is a presentation of a new design of circularly polarized (CP) antenna array having a wide axial ratio (AR) bandwidth and high-gain. It uses an innovative feed network which consists of compact directional couplers and a delay line describing a new kind of sequential phase (SP) feed network. Furthermore, in this work, we report and discuss the features of the feed network and single element. In the following, the single element antenna and the 2 × 2 CP antenna array are designed, prototyped and tested. The antenna array is designed by a multilayer microstrip structure with a compact size of 75 × 52 mm². Moreover, a metal reflector is utilized to enhance the antenna gain and achieve a unidirectional radiation pattern over the operating frequency band. According to the experimental results, the CP antenna array has a return loss (RL) bandwidth of 2.42 GHz (5.83–8.25 GHz), AR bandwidth of 1.11 GHz (6.76–7.87 GHz), and peak gain of 12.15 dBic. It seems that the performance of the proposed design is admirable for C-band frequency.     

一种新型单馈点宽带圆极化微带天线的设计

介绍了一种新型单层单贴片圆极化微带天线。该天线采用同轴线单点馈电,通过在圆形贴片上开C型缝的方法实现圆极化辐射并同时展宽了天线的阻抗带宽。仿真结果显示,该新型天线工作于C波段时,3dB轴比带宽为2.6%（124 MHz）,VSWR〈2的阻抗带宽达到10%（477 MHz）。证明了在贴片上开C型缝是展宽带宽和实现圆极化的有效方法。     

Circularly polarised microstrip antenna array using proximitycoupled feed

A 2×2 circularly polarised (CP) microstrip antenna array using a proximity coupled feed and sequential rotation is described. As compared with a previously presented single-element circularly polarised microstrip antenna with a cross-slot, the new array achieves a much wider impedance bandwidth of 11.18% and has an axial ratio bandwidth of 4.1%. The return loss, radiation patterns and axial ratio of the antenna array were measured and are presented     

Meander-slot and U-slot antenna arrays for wide-band spatial power combiners

In this work, we present a multilayered waveguide transition containing several interacting printed antenna arrays for spatial power combining applications. Narrow-band resonant rectangular slot antennas used in earlier designs are replaced by meander-slot antennas and their modifications, in order to increase the frequency bandwidth and efficiency of the system. Numerical results for finite arrays of meander-slot and U-slot antennas show significant advantages in scattering characteristics in comparison to traditionally used rectangular slot antenna arrays.     

2 X 2 etched slot array with corporate slotline feed network

Measured and simulated results for a planar 2times2 slot array corporately fed by a slotline feed network are presented. The antenna array has a coplanar-waveguide input port and the slots are etched on the finite ground plane of a single substrate. The coplanar-waveguide transmission line is transitioned into a four-way slotline feed network, which directly feeds the four half-wavelength slots from the narrow edges of the slots. An experimental array achieved an impedance bandwidth of more than 12%, stable bidirectional radiation patterns with low cross-polarisation, and a maximum gain of more than 8 dBi.     

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.     

A study on wideband gap-coupled microstrip antenna arrays

A method for increasing the bandwidth of microstrip antenna arrays by using gap-coupled patches is described. The input impedance properties of gap-coupled patches are analyzed by the use of the spectral dyadic Green's function for a grounded dielectric slab and the moment method. The dependence of different parameters such as s, L and ϵr on the impedance characteristics is investigated. In considering the effect of feed network, the impedance bandwidth for a VSWR<2 of two-element gap-coupled patch array is as large as 2.5 times that of an ordinary array. The radiation patterns over this bandwidth are measured and discussed. All the microstrip antenna arrays are fabricated on a substrate with ϵr=2.86, h=1.5 mm. A comparison of theoretical and experimental results for both input impedance and radiation patterns are given     

Radiation and scattering analysis of infinite arrays of endfireslot antennas with a ground plane

A Green's function moment-method analysis of infinite arrays of endfire slot antennas is described that includes the constant width slot antenna (CWSA) and the linearly tapered slot antenna (LTSA), with a ground plane. The method utilizes an application of equivalence at a plane in front of the array which facilitates the extension of this analysis to antennas printed on protruding dielectric sheets and/or the addition of a radome. Numerical calculations are compared with waveguide simulator experiments for CWSA and LTSA arrays as well as several less complex problem. Relevant numerical considerations and convergence issues are also discussed     

Broadband circularly polarised crosspatch- loaded square slot antenna

A new design of a circularly polarised square slot antenna loaded with a cross patch is presented. A cross patch inclined diagonally with respect to the square slot is placed at the centre of the square slot. By choosing proper dimensions of the cross patch, two orthogonal resonant modes with a 90deg phase difference for circular polarisation can be excited and feed the square slot antenna using a 50 Omega CPW with a protruded signal strip. 10 dB return loss bandwidth of 846 MHz (39.6%) and 3 dB axial ratio bandwidth of 240 MHz (12.4%) for the proposed antenna are achieved. Gain variation within the CP bandwidth is observed to be less than 1 dB     

Comparison Between Arrays of Rotating Linearly Polarized Elements and Circularly Polarized Elements

The gain and bandwidth characteristics of circularly polarized (CP) arrays comprising of rotated linearly polarized (LP) elements and hybrid-fed CP elements are presented. It is found that for small element spacing, the gain of the LP elements' array is comparable with that of the CP elements' array; however for large element spacing the former shows significantly lower gain than the latter. Furthermore, the bandwidth of a rotating LP elements' array is narrower than that of a CP elements' array. The bandwidth difference is explained invoking Floquet modal theory and the cavity model of a patch antenna. Variations of gain and bandwidth with element spacing are studied using a full wave analysis and the results for slot-fed and probe-fed patch arrays are shown. The advantages and disadvantages of rotating LP elements' arrays are discussed.