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 5G Vivaldi Tapered Slot Filtering Antenna with Enhanced Bandwidth

Compact fifth-generation(5G)low-frequency band filtering antennas(filtennas)with stable directive radiation patterns,improved bandwidth(BW),and gain are designed,fabricated,and tested in this research.The proposed filtennas are achieved by combining the predesigned compact 5G(5.975–7.125 GHz)third-order uniform and non-uniform transmission line hairpin bandpass filters(UTL and NTL HPBFs)with the compact ultrawide band Vivaldi tapered slot antenna(UWB VTSA)in one module.The objective of this integration is to enhance the performance of 5.975–7.125GHz filtennas which will be suitable for modern mobile communication applications by exploiting the benefits of UWB VTSA.Based on NTL HPBF,more space is provided to add the direct current(DC)biassing circuits in cognitive radio networks(CRNs)for frequency reconfigurable applications.To overcome the mismatch between HPBFs and VTSA,detailed parametric studies are presented.Computer simulation technology(CST)software is used for the simulation in this study.Good measured S11 appeared to be<−13 and<−10.54 dB at 5.48–7.73 and 5.9–7.98GHz with peak realized gains of 6.37 and 6.27 dBi,for VTSA with UTL and NTL HPBFs,respectively which outperforms the predesigned filters.Validation is carried out by comparing the measured and simulated results.

Ultra-wideband low radar cross-section metasurface and its application on waveguide slot antenna array

A novel approach devoted to achieving ultra-wideband radar cross section reduction（RCSR） of a waveguide slot antenna array（WGSAA） while maintaining its radiation performance is proposed. Three kinds of artificial magnetic conductors（AMCs） tiles consisting of three types of basic units resonant at different frequencies are designed and arranged in a novel quadruple-triangle-type configuration to create a composite planar metasurface. The proposed metasurface is characterized by low radar feature over an ultra-wideband based on the principle of phase cancellation. Both simulated and measured results demonstrate that after the composite metasurface is used to cover part of the antenna array, an ultrawideband RCSR involving in-band and out-of-band is achieved for co-and cross-polarized incident waves based on energy cancellation, while the radiation performance is well retained. The proposed method is simple, low-cost, and easy-tofabricate, providing a new method for ultra-wideband RCSR of an antenna array. Moreover, the method proposed in this paper can easily be applied to other antenna architectures.

On the Design of Plus Slotted Fractal Antenna Array

A new technique which is a combination of fractal antenna and array antenna is presented to design Plus Slotted Fractal Antenna Array (PSFAA) in this paper. PSFAA with corporate feed operates at 2.5 GHz frequency. PSFAA is designed on FR4 substrate material with permittivity 4.4 and height 1.6 mm. PSFAA is designed up to 2nd iteration. High Frequency Structure Simulator (HFSS) software is used for simulation of PSFAA. The proposed antenna array operates at three bands with five frequencies 2.5 GHz, 4.1 GHz, 6.9 GHz, 7.4 GHz and 8.2 GHz. Simulated Return losses results of proposed PSFAA are -22.15 dB, -19.44 dB, -25.21 dB, -10 dB, -12.45 dB at above frequencies respectively. It has a gain of 9.22 dB at resonant frequency 2.5 GHz whereas conventional antenna array has a gain of 5.15 dB at resonant frequency 2.5 GHz. Return losses and gain of PSFAA also improved from conventional antenna array at various resonant frequencies.

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.

Design and Analysis of Antipodal Vivaldi Antennas for Breast Cancer Detection

This paper presents the design and analysis of antipodal Vivaldi antennas(AVAs)for breast cancer detection.In order to enhance the antenna gain,different techniques such as using the uniform and non-uniform corrugation,expanding the dielectric substrate and adding the parasitic patch are applied to original AVA.The design procedure of two developed AVA structures i.e.,AVA with non-uniform corrugation and AVA with parasitic patch are presented.The proposed AVAs are designed on inexpensive FR4 substrate.The AVA with non-uniform corrugation has compact dimension of 50×50 mm2 or 0.28λL×0.28λL,whereλL is wavelength of the lowest operating frequency.The antenna can operate within the frequency range from 1.63 GHz to over 8 GHz.For the AVA with parasitic patch and uniform corrugation,the overall size of antenna is 50×86 mm2 or 0.24λL×0.41λL.It can operate within the frequency range from 1.4 GHz to over 8 GHz.The maximum gain for AVA with non-uniform corrugation and AVA with parasitic patch and uniform corrugation are 9.03 and 11.31 dBi,respectively.The corrugation profile and parasitic patch of the proposed antenna are optimized to achieve the desired properties for breast cancer detection.In addition,the proposed AVAs are measured with breast phantom to detect cancerous cell inside the breast and the performance in detecting cancerous cell are discussed.The measured result can confirm that the proposed AVAs can detect unwanted cell inside the breast while maintaining the compact size,simple structure and low complexity in design.

Substrate Integrated Waveguide Based Monopulse Slot Antenna Arrays for 60 GHz Applications

Monopulse slot antenna arrays based on substrate integrated waveguide （SIW） are proposed for the application of 60 GHz mono- pulse tracking systems in this paper. The sum-difference monopulse comparator can provide a high amplitude and phase balance over wide frequency band and no phase delay technique is required for the difference channel. Resonant slot antennas are adopted as the radiating elements since they can be integrated with the sum-difference monopulse comparator in a single layer with a compact size. Two monopulse arrays with 2× 4 and 4×4 slot elements are designed, fabricated, and measured. Measured results show that the proposed antenna arrays have wide bandwidth covering the unlicensed 60-GHz band. The peak sum beam gain is 13.85 dBi for the 2 ×4 element array and 16.24 dBi for the 4×4 element array. The peak difference beam gain is 11.20 dBi for the 2×4 element array and 12.11 dBi for the 4×4 element array and the maximum null depth can reach -40 dB.

Printed elliptical slot UWB antenna for dual-banded application

Based on the analysis of printed elliptical slot (PES) UWB antenna,a dual-banded PES antenna is designed for WLAN and UWB bands at 2.4 GHz.The design cooperates two important wireless commutation system antennas into one printed antenna.In the design,a circular slot structure is presented,which is suitable for the band ejection.Characteristics of the designed antenna are analyzed and key parameters,such as S11,S21 and VSWR are measured.E-field distribution of the surface is simulated and analyzed.

Tri-Band Parallel Slots Loaded Circular Disk Patch Antenna for C and X-Band Applications

This paper presents the tri-band slot loaded patch antenna for mobile communication. The antenna consists of parallel slots loaded circular disk with defected ground structure antenna (DGS). The antenna without DGS, acts like wide band antenna and bandwidth is 34.45% (3.47 - 4.92 GHz) with maximum gain of 4.97 dBi, which can be used in WiMax application. This structure has the following advantages: 1) co-axial feeding technique, which is very simple as compared to other feeding technique, 2) simple and cost effective and 3) it is more efficient than the antenna without DGS. This antenna has been analyzed using IE3D simulation software.

A 2.4 GHz Switched Beam Antenna for Indoor Applications Using Angle of Arrival Estimation

This study introduces a new design of planar antenna array for ISM band applications at 2.4 GHz. This prototype is switched beam antenna, namely planar antenna with four meandered slotted triangular elements (PAFMSTE), which is proposed for wireless indoor applications. The Base Station (BS) equipped with this planar antenna is preferred to be at the center position on the room ceiling to cover all sectors of the room. It is designed to use four directional triangular elements arranged to form a square planar antenna array. The PAFMSTE is used to obtain optimal directivity in four directions in azimuth plane with 3 dB beamwidth of 90°at a specific orientation of 30°in elevation plane. Switched parasitic technique is used to enable PAFMSTE to steer a directional beam through four locations by using four PIN diodes switches. The High Frequency Structure Simulator (HFSS) is used as an efficient simulation tool to optimize the performance of the PAFMSTE antenna. The fabrication and measurements of the PAFMSTE antenna are introduced. The proposed antenna enable radio positioning via Angle of Arrival (AOA) information collected from nearby devices. Then, the Cramér-Rao Bound (CRB) is presented for AOA estimation using identically and equally spaced antenna elements. The CRB depends on the directivity, where the maximum values of CRB are 1.35 × 10-3 and 8 × 10-3 at HPBW of 60° and 90°, respectively.

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.

Frequency notched wide slot antenna for UWB/2.4 GHz WLAN applications

Abstract A compact frequency notched microstrip slot antenna for ultra-wideband （UWB）/2.4 GHz-band wireless local area network（WLAN） applications is proposed. The antenna is similar to a conventional microstrip slot antenna; however, by introducing a cross wide slot and a meandered-slotted stub, both compact size and frequency notched function can be achieved. It has been studied both numerically and experimentally for its impedance bandwidth, surface current distribution, radiation patterns, and gain. As will be seen, an operation bandwidth of over 4.6：1 ranging fi＇om 2.39 to 11.25 GHz for return loss lower than -10 dB having a frequency notched band ranging from 4.75 to 5.85 GHz has been achieved, and good radiation performance over the entire frequency range has also been achieved.

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.