Broadband printed antennas and dual-polarized microstrip and waveguide slot antenna arrays

In order to meet the urgent needs in wireless communications, microwave image synthetic aperture radars （SAR）, and electronic warfare systems, this dissertation studies several types of broadband dual-polarized planar antenna elements and arrays, and proposes a few of novel designs with experimental verification. The main accomplishments reported in the dissertation are as follows.

Compact wideband cavity-backed slot antenna

A wideband cavity-backed slot antenna operated in the ultra-high frequency （UHF） band is introduced. The antenna has a compact structure and low profile with the size ratio of the ground plane to the slot only 1.6：1. The measured impedance bandwidth of VSWR≤3 achieves 85.3%, covering a frequency range from 390 MHz to 970 MHz. The measured gain is about 5.5-7.5 dB.

On the Design of Slot Cut Circularly Polarized Circular Microstrip Antennas

Circularly polarized microstrip antenna is frequently realized by cutting the slot inside the patch and feeding it along the diagonal axis. In the reported literature, procedure to design them at any given frequency is not available. In proposed work, circularly polarized slot cut circular microstrip antenna at 900 MHz is discussed. By studying the surface current distributions at two orthogonal modes, formulations in their resonant length are proposed. The frequencies calculated using them closely agree with simulated results. Using proposed formulation, procedure to design circular polarized antennas at different frequencies is presented that gives circular polarized response. Thus, proposed work will be helpful to design similar circular polarized circular microstrip antenna at any desired frequency.

Wideband dual-polarized slot-coupled microstrip array for synthetic aperture radar application

An 8 × 1-element wideband dual-polarized slot-coupled microstrip antenna array with high isolation and low crosspolarization in X-band is presented. The array antenna offers an impedance bandwidth （VSWR≤2） of 23% and 21% for dual polarization ports, respectively. The measured isolation between two polarization ports is better than 35 dB and the measured cross-polarization level below -25 dB in the main beam over the operation frequency band of 9.35 GHz to 9.75 GHz. This array is well suitable for X-band SAR （synthetic aperture radar） antenna apphcation.

A NOVEL WIDEBAND ANTENNA DESIGN USING U-SLOT

U-slot patch antennas with П-shaped feed slot are studied, and numerical results based on the FDTD method are presented. The effects of varying physical parameters are investigated with a goal of understanding the coupling among different resonators. It is found that the U-slot patch antenna can be designed to attain 50% impedance bandwidth as well as 30-40% gain bandwidth. By altering the sizes of U-slot and feed slot, the wideband characteristic can be changed into a duai-frequency char- acteristic.

MODIFIED ULTRA WIDEBAND CIRCULAR PRINTED MONOPOLE ANTENNA

A simple and compact microstrip-fed ultra wideband （UWB） printed monopole antenna is presented. The antenna is composed of a circular radiator and a finitely grounded plane. The antenna occupies about 16.62 GHz absolute bandwidth and 142.7% relative bandwidth covering from 3.38 GHz to 20 GHz with voltage standing wave ratio （VSWR） below two. A quasi-omnidirectional and quasi-symmetrical radiation pattern in H plane is obtained in the whole bandwidth. The high performance of the antenna is validated with measured and simulated results given. The antenna can be applied for the system design of UWB wireless communication.

Increasing Microstrip Patch Antenna Bandwidth by Inserting Ground Slots

Microstrip patch antenna (MPA) is widely implemented in different communication systems. One of the main disadvantages of MPA which limits its applications is its narrow bandwidth. In this paper I enhanced the bandwidth of MPA by inserting multiple slots in its ground plane. I used FR-4 substrate to design this antenna. The dimensions of this antenna are 59 mm and 79 mm. The dielectric constant is 4.4 and the height is 1.6 mm. I inserted up to 15 slots in ground plane with 1mm width. The spacing between slots is 3 mm. I investigated two designs. In the first design, slots were arranged in parallel to the feeding line. In the second one, slots were arranged horizontally to the feeding line. The main objective of this paper is to design and simulate MPA suitable for wide number of applications. Antenna bandwidth improvement is 18%. All the simulations were obtained by using HFSS simulator.

A method of elimination of undesired resonant points of microstrip antenna by cutting U-shaped slot on the ground

A method is proposed to eliminate undesired resonant points of a dual-layer circular polarization microstrip antenna, the frequency of which is 2.42 GHz. The simulation results show that there are two undesired resonant points, the frequencies of which are both greater than the resonant frequency. One is around 4.4 GHz, while the other is around 5.8 GHz. As they would disturb the proper functioning of the antenna, the paper will eliminate the undesired resonant points by cutting U-shaped slots on the ground, Size of the slot is half of the wavelength of corresponding frequency point if slot is cut on the patch, while it is a quarter of the wavelength if there is a opening port on the slot. The simulation results show that it＇s effective to eliminate the undesired resonant points in this way.

Resonant Length Formulations for Dual Band Slot Cut Equilateral Triangular Microstrip Antennas

The dual band equilateral triangular microstrip antennas are realized by cutting the slots of either quarter wave or half wave in length, inside the patch. In this design, however these simpler approximations of slot length against the frequency do not give closer results for different slot lengths and there positions inside the patch. In this paper, the modal variations of slot cut patch antennas over wide frequency range are studied. It is observed that the slot does not introduce any mode but reduces the higher order mode resonance frequency of the patch and along with the fundamental mode realizes dual band response. The formulations of the resonant length for the mode introduce by the slots in these antennas are proposed. The resonance frequencies calculated using proposed formulations agree well with the simulated results with an error of less than 5%.

Performance Optimization of Microstrip Antenna with Different Slot Configurations and Various Dielectric Materials

The probe-fed patch antennas were proposed by changing the parameters such as dielectric materials and dimensions of patch for detail investigation of changes in output characteristics. Four rectangular slots were introduced separately for optimizing the antenna design and characteristics. This study illustrated the changes of output characteristics of an antenna with respect to the number of introduced slots on the radiating patch in addition to the effect of various dielectric materials on antenna performances. The antenna performances were analyzed by plotting the observation of various dielectric materials. The changes of antenna characteristics were also observed by introducing four numbers of slots on each edge of the patch to improve radiation characteristics with a wider impedance bandwidth.

Design and Implementation of Step-Constant Tapered Slot Antennas for UWB Application

This paper presents the analytical design and high performance of step-constant tapered slot antenna (STSA) for ultra-wideband application. The return loss, radiation pattern, antenna gain, and level of cross polarization of this antenna are presented and analyzed. Utilizing Rogers (RO3006) substrate having a relative permittivity of 6.15, the proposed antenna provides the ultra-wideband (UWB) from 3.1 GHz to 10.6 GHz. It is observed that the return loss and gain are increased with increasing the step size. It has been observed from the simulation results incorporating CST microwave studio commercial software version 2015, the optimum return loss, directivity and gain are ?43 dB, 10.52 dBi and 10.20 dB, respectively, for 15 step size. Therefore, the newly proposed antenna will be a decent candidate for ultra-wideband application.

Broadband Feed for Low Cross-Polarization Uniplanar Tapered Slot Antennas on Low-Permittivity Substrate

A broadband feeding technique for the uniplanar tapered slot antenna (TSA) is presented. The TSA operates at a center frequency of 6.5 GHz with a 7 GHz bandwidth (107 percent). The antenna and feed are realized with a broadband microstrip-to-slotline transition on a low permittivity high frequency substrate, Rogers RT/Duroid 5880. The input impedance of the system is designed for 50 Ω compatibility with other system components, and the cross polarization is kept below –30 dB. The developed TSA system was simulated with commercially available electromagnetic software and manufactured. Measured results validate the design process and the antenna’s performance.

Wideband Microstrip Antenna in Small Volume Without Using Fundamental Mode

Microstrip antennas are of significant interest and extensively utilized in communication systems because of their unique low profile.However,the general difficulty in microstrip antenna design lies in its wideband electromagnetic radiation within a low-profile structure.To enhance the bandwidth,superposing the fundamental mode and other high-order modes is the most common method,but this occupies a larger footprint than regular narrow-band modes.Here,as a counterintuitive way to broaden the bandwidth,a wideband miniaturized microstrip antenna is proposed by using two high-order modes.The avoidance of the fundamental mode allows for footprint miniaturization without decreasing the bandwidth,providing a different but feasible design strategy for wideband microstrip antennas.Compared with other microstrip antennas at the same profile,the proposed antenna achieves wider bandwidth and a smaller footprint.The experimental result shows a bandwidth of 4.81–6.01 GHz is achieved with a volume of 0.47×0.47×0.043 λ_(0)^(3),whereλ0 represents the in-vacuum wavelength at the center frequency.Therefore,the proposed design provides an effective solution to the intrinsic contradiction between wideband electromagnetic radiation and compact antenna dimensions,not only in a low profile but in a small footprint,contributing to the fundamental development of microstrip antennas.

Analysis and Design of Tapered Slot Antenna for Ultra-Wideband Applications

The tapered slot antenna, such as Vivaldi, has been widely used due to its ultra-wideband, high gain, simple feed structure, and easy fabrication. However, there is no rigorous analytical theory for this type of antenna. This paper analyzed the metal parts of a tapered slot antenna in a conical coordinate system with the medium analyzed in rectangular coordinates. This mixed mode gave an approximate analytical form for the tapered slot antenna with the field distribution and radiation characteristics. A planar tapered slot antenna was proposed according to the results of the analysis methods. Measured and simulated results demonstrate the antenna performance. The antenna shows good impedance matching over a wide bandwidth of 9 GHz, from 2 GHz to 11 GHz, and good radiation patterns. It is suitable for ultra-wideband applications.

Design of hexagon microstrip antenna for vehicle-to-vehicle communication

Considering the shortcomings of the existing vehicle-to-vehicle（V2V） communication antennas, this paper proposes a regular hexagon broadband microstrip antenna. By loading shorting pins and etching V-shape slots with different size at each angle of the regular hexagon patch, it realizes impedance matching and obtains better impedance bandwidth. The simulated results show that the relative bandwidth of this antenna reaches 35.55%, covers the frequency band of 4.74 GHz to 6.79 GHz. The antenna acquires an omni-directional radiation pattern in the horizontal plane whose out of roundness is less than 0.5 d B. In addition, the antenna is manufactured and tested, whose tested results are basically consistent with simulated results. Because the height of antenna is 3 mm, it is easy to be hidden on roof of a vehicle for V2 V communication.

DESIGN OF CPW-FED ASYMMETRIC SLOT UWB ANTENNA FOR WIRELESS APPLICATION

A compact Ultra-WideBand(UWB) slot antenna is presented in this paper. The slot is modified rectangular in shape and asymmetrically cut in the ground plane. A hexagonal patch with two stepped CoPlanar Waveguide(CPW) feed is used to excite the slot. Wider impedance bandwidth is achieved due to the extra inductive reactance created by the asymmetric slot which neutralizes the capacitive reactance of the hexagonal patch. The measured impedance bandwidth of the proposed antenna is 11.85 GHz(2.9–14.75 GHz). The radiation patterns of the proposed antenna are obtained and found to be omni-directional in H-plane and bi-directional in E-plane.

Triple Notched Band Characteristics UWB Antenna Using C-Shaped Slots and Slot-Type Capacitively-Loaded Loop (CLL)

Ultra wide bands antennas with notched bands characteristics have recently been considered for efficient communication between devices. In this paper, a compact ultra-wideband antenna (UWB) for UWB applications with triple bandnotched characteristics is presented. The proposed antenna consists of a square patch with four truncated corners and a partial ground plane with a rectangular slit. The operation bandwidth of the designed antenna is from 2.66 GHz to more than 13.5 GHz. Band-notched characteristics of antenna to reject the frequency band of 3.18 - 3.59 GHz and 4.70 - 5.88 GHz, is realized by inserting two C-shaped slots in the patch, the third band of 9.54 - 12.22 GHz is achieved by slottype capacitively-loaded loop (CLL) inserted in the patch near the feed line. Details of the proposed antenna design and simulated results are presented and discussed.

Double U-Shaped Slots Loaded Stacked Patch Antenna for Multiband Operation

The design of a seven-band stacked patch antenna for the C, X and Ku band is presented. The antenna consists of an H-slot loaded fed patch, stacked with dual U-slot loaded rectangular patch to generate the seven frequency bands. The total size of the antenna is 39.25 × 29.25 mm2. The multiband stacked patch antenna is studied and designed using IE3D simulator. For verification of simulation results, the antenna is analyzed by circuit theory concept. The simulated return loss, radiation pattern and gain are presented. Simulated results show that the antenna can be designed to cover the frequency bands from (4.24 GHz to 4.50 GHz, 5.02 GHz to 5.25 GHz) in C-band application, (7.84 GHz to 8.23 GHz) in X-band and (12.16 GHz to 12.35 GHz, 14.25 GHz to 14.76 GHz, 15.25 GHz to 15.51 GHz, 17.52 GHz to 17.86 GHz) in Ku band applications. The bandwidths of each band of the proposed antenna are 5.9%, 4.5%, 4.83%, 2.36%, 3.53%, 1.68% and 1.91%. Similarly the gains of the proposed band are 2.80 dBi, 4.39 dBi, 4.54 dBi, 10.26 dBi, 8.36 dBi and 9.91 dBi, respectively.

New compact UWB microstrip-fed printed planar antenna for wireless applications

A proposed circular patch antenna with notch-cut fed by a simple microstrip line is described in this paper. It is designed for ultra-wideband （UWB） wireless communications and applications over the band 3.1-10.6 GHz. This antenna consists of a circular patch with notch-cut fed by a microstrip line, one transition step, and a partial ground plane. The 2： l voltage standing wave ratio （VSWR） bandwidth （Sll 〈-10dB） of the proposed antenna covers the entire UWB application range specified by Federal Communications Commission （FCC） that is from 3.1 to 10.6GHz. The proposed antenna is able to achieve an impedance bandwidth about 8.6 GHz （2.4-11 GHz）. The return loss, VSWR, radiation pattern, radiation efficiency, gain, distribution of the proposed group delay, and current antenna are included in this paper. The simulation results and proposed antenna design details are presented by CST Microwave Studio.

基于载体环境的宽带微带天线设计与分析

为确保航天环境下载体内的微带天线性能满足通信系统要求,采用多层和多模技术设计了单开槽WiFi频段的宽带微带天线,重点对载体及环境因素下宽带微带天线的性能进行仿真验证,同时分析了对天线性能的影响,并采用迭代补偿方法进行了性能修正。仿真分析结果表明:提出的迭代补偿方法对微带天线性能可以进行有效的校正;实物验证结果表明:载体内的微带天线性能稳定,满足工作频带要求。