Microstrip Leaky-Wave Antenna for Radar Applications

The work in this article focuses on developing and improving the performance of new leaky-wave antenna configurations that can be adapted for use in radar systems. The study focused on the W-band, where we demonstrated the possibility of modifying resonant frequencies and reducing the number of patches required. The antenna was designed using HFSS, based on the finite element method. It we designed enabled us to observe the influence of the number of patches on the radiation pattern, and also to achieve low levels of minor’s lobes. and good directivity at the operating frequency. These patches are arranged in the shape of an inverted T. The interest of this study is to meet the requirements of radar antennas dedicated to detection.

Differential Quasi-Yagi Antenna and Array

A novel differential quasi-Yagi antenna is first presented and compared with a normal single-ended counterpart.The simulated and measured results show that the differential quasi-Yagi antenna outperforms the conventional single-ended one.The differential quasi-Yagi antenna is then used as an element for linear arrays.A study of the coupling mechanism between the two differential and the two singleended quasi-Yagi antennas is conducted,which reveals that the TE0 mode is the dominant mode,and the driver is the decisive part to account for the mutual coupling.Next,the effects of four decoupling structures are respectively evaluated between the two differential quasi-Yagi antennas.Finally,the arrays with simple but effective decoupling structures are fabricated and measured.The measured results demonstrate that the simple slit or air-hole decoupling structure can reduce the coupling level from−18 dB to−25 dB and meanwhile maintain the impedance matching and radiation patterns of the array over the broad bandwidth.The differential quasi-Yagi antenna should be a promising antenna candidate for many applications.

Designing a Dual-Feed Circular Polarization Antenna

This paper describes a novel dual-feed circularly polarized antenna,and the dual feeding mode is realized by grooving on the antenna radiator.The antenna utilizes air dielectric material to meet the requirements of low weight and cost.Test results demonstrate that the antenna exhibits capacitive loading between the metal antenna patch and the ground floor,allowing for adjustment of the working frequency of the dual-feed circularly polarized microstrip antenna.Specifically,the original center frequency of 2.264 GHz was reduced to 1.582 GHz,facilitating antenna miniaturization and broad bandwidth.With a return loss(S11)below-10 dB,a bandwidth of 72 MHz(1.552-1.624 GHz)was obtained.Additionally,the dual-feed microstrip antenna incorporates a 90°bridge,resulting in circular polarization gains of 2.26 dBi at 1.561 GHz and 2.45 dBi at 1.575 GHz.Overall,the antenna design offers a large working bandwidth and excellent circular polarization characteristics,making it suitable for a wide range of applications in satellite navigation and positioning terminals.

Study of multi-band property of rectangular microstrip patch antenna having different numbers of wide slots

The property of multi-band operation has been studied and investigated analytically through the design of a rectangular patch microstrip antenna having different numbers of wide slots arranged at both the radiating edges. The analyses were carried out using the method of moments simulation software. It is shown that a patch with three slots has a multi-band feature with four resonant frequencies at 1.6, 1.8, 2.65, and 4.83 GHz and adequate values of return loss and gain. It is also shown that a patch with two pairs of wide slots arranged at both the radiating edges has the dual band feature with resonant frequencies at 1.64 and 1.8 GHz and good values of return loss and gain.

Dual-Polarized Slot-Coupled Microstrip Antenna with Very High Isolation

A wideband dual-polarized slot-coupled stacked microstrip antenna with very high isolation and low cross-polarization is presented. To improve isolation between two poiarization ports, the stacked patches are excited by an open-ended and a T-shaped microstrip lines both via two H-shaped slots placed in a ＂T＂ configuration. The measured isolation is better than 40.5 dB over the bandwidth from 8.8 to 9.8 GHz with cross-polarization level less than - 28.5 dB. The measured VSWR ≤ 2 bandwidths reach 20.7 96 and 19.196 at the verrical and horizontal polarization ports, respectively. This antenna is suitable to be used as array elements in spacebome synthetic aperture radars （SAR） and active phased array radars.

Metamaterials and metasurfaces for designing metadevices:Perfect absorbers and microstrip patch antennas

In the past twenty years, electromagnetic metamaterials represented by left-handed metamaterials（LHMs） have attracted considerable attention due to the unique properties such as negative refraction, perfect lens, and electromagnetic cloaks. In this paper, we present a comprehensive review of our group＇s work on metamaterials and metasurfaces. We present several types of LHMs and chiral metamaterials. As a two-dimensional equivalent of bulk three-dimensional metamaterials, metasurfaces have led to a myriad of devices due to the advantages of lower profile, lower losses, and simpler to fabricate than bulk three-dimensional metamaterials. We demonstrate the novel microwave metadevices based on metamaterials and metasurfaces： perfect absorbers and microwave patch antennas, including novel transmission line antennas,high gain resonant cavity antennas, wide scanning phased array antennas, and circularly polarized antennas.

Wireless Strain Measurement Based on a Microstrip Patch Antenna

Wireless interrogation of a rectangular microstrip patch antenna for strain measurement is investigated by simulations.To analyze the antenna performance,a microstrip line-feeding patch antenna at 10 GHz is designed.A patch antenna wirelessly fed by a horn is proposed to measure the strain.The direction information of strain detected by the patch antenna is also considered.The strain can be detected both in the width and length directions.It is shown that the strain can be measured wirelessly using a standard horn antenna.This kind of wireless strain-sensing technique offers significant potential for wireless structural health monitoring(SHM),especially for high-end equipment.

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.

Design and Analysis of Microstrip Antenna Arrays in Composite Laminated Substrates

In high performance aerospace systems where weight and aerodynamics are of major concern, fiber reinforced composite laminates can be tailored to achieve desirable mechanical properties and accommodate low-profile microstrip antenna. This work aims at the analysis of microstrip antenna array embedded in composite laminated substrates. The size of a single antenna is first calculated by spectral domain analysis to model the effects of the substrate’s electromagnetic property and the orientation of the laminate layers. The antenna array as well as the feed network, composed of microstrip transmission lines, quarter wave-length impedance transformers, and T-junction power dividers, is then tuned to accommodate the effects of the coupling between the antenna elements and the feed network loss. The performance of the 1 × 2, 1 × 4, and 1 × 8 linear array and 2 × 2 and 2 × 4 planar array are shown to have better directivity when embedded in composite laminated substrate compared with those when attached on isotropic substrate. Both 1 × 2 and 1 × 4 arrays at 2.4 GHz are validated experimentally to achieve better coverage.

A BROADBAND APERTURE-COUPLED STACKED MICROSTRIP ANTENNA WITH BOTH PATCHES NOTCHED AND OFFSET

This paper proposes a new approach to further improving the bandwidth of a typical aperture-coupled stacked microstrip antenna by cutting triangular notches in the radiating sides of both radiating patches together with offsetting both patches. An antenna applying this new approach is designed,fabricated,and tested. The experimental antenna could achieve a measured impedance bandwidth of about 37.5% for the Voltage Standing Wave Ratio(VSWR) ≤ 2in X-band.

Compact wideband microstrip array antenna with beam squint

A compact wideband microstrip array antenna with a squint beam is introduced without the matched load. Its measured beam is at 10° offset to the broadside with a measured gain of 12 dB at 10 GHz. The measured impedance bandwidth （voltage standing wave ratio （VSWR）≤2） is over 16%, which agrees well with the simulated one. It is a low-cost wideband design with compact simple structure, suited for military and commercial application.

Strain-Insensitive Hierarchically Structured Stretchable Microstrip Antennas for Robust Wireless Communication

As the key component of wireless data transmission and powering,stretchable antennas play an indispensable role in flexible/stretchable electronics.However,they often suffer from frequency detuning upon mechanical deformations;thus,their applications are limited to wireless sensing with wireless transmission capabilities remaining elusive.Here,a hierarchically structured stretchable microstrip antenna with meshed patterns arranged in an arched shape showcases tunable resonance frequency upon deformations with improved overall stretchability.The almost unchanged resonance frequency during deformations enables robust on-body wireless communication and RF energy harvesting,whereas the rapid changing resonance frequency with deformations allows for wireless sensing.The proposed stretchable microstrip antenna was demonstrated to communicate wirelessly with a transmitter(input power of−3 dBm)efficiently(i.e.,the receiving power higher than−100 dBm over a distance of 100 m)on human bodies even upon 25%stretching.The flexibility in structural engineering combined with the coupled mechanical-electromagnetic simulations,provides a versatile engineering toolkit to design stretchable microstrip antennas and other potential wireless devices for stretchable electronics.

Rectangular Microstrip Antenna with Air Cavity for High Gain and Improved Front to Back Ratio

A rectangular microstrip patch antenna using conventional Poly Tetra Fluride Ethelene (PTFE) substrate with air cavity is proposed and theoretically investigated. Considerably high gain along with improved front to back radiation isolation is demonstrated using such proposed antenna. The radiation performance of this new antenna has been compared to a conventional microstrip patch for some commonly used aspect ratios (width to length ratio). Compared to conventional microstrip antenna the proposed configuration shows more than 12% increment in peak gain and more than 10% increment in front to back radiation performance in each set of aspect ratio. The elucidation of such improvement in the radiation characteristics of the proposed antenna is also presented.

Effect of Partial Ground Plane Removal on the Radiation Characteristics of a Microstrip Antenna

This study presents a new, simple method for reducing the back-lobe radiation of a microstrip antenna (MSA) by a partially removed ground plane of the antenna. The effect of the partial ground plane removal in different configurations on the radiation characteristics of a MSA are investigated numerically. The partial ground plane removal reduces the backlobe radiation of the MSA by suppressing the surface wave diffraction from the edges of the antenna ground plane. For further improving the front-to-back (F/B) ratio of the MSA, a new soft-surface configuration consisting of an array of stand-up split ring resonators (SRRs) are placed on a bare dielectric substrate near the two ground plane edges. Compared to the F/B ratio of a conventional MSA with a full ground plane of the same size, an improved F/B ratio of 9.7 dB has been achieved experimentally for our proposed MSA.

Different Feeding Techniques of Microstrip Patch Antennas with Spiral Defected Ground Structure for Size Reduction and Ultra-Wide Band Operation

Different feeding techniques of microstrip patch antennas with different spiral defected ground structures are presented in this paper. The investigated structures illustrate some merits in designing multi-electromagnetic band-gap structures by adjusting the capacitance and changing the inductance through varying the width and length of spiral defected ground structure. Then by applying the three different spirals shapes (one, two and four arms) as the ground plane of microstrip patch antenna with different feeding techniques to create multi or ultra wide-band, improve the antenna gain and reduce the antenna size, it is found that the four arms spiral defected ground structure of microstrip patch antenna with offset feed gives good performance, electrical size reduction to about 75% as compared to the original patch size and ultra-wide bandwidth extends from 2 GHz up to 12 GHz with ?8 dB impedance bandwidth.

Broadband Quasi-Yagi Antenna for WiFi and WiMax Applications

In this paper, we present a broadband quasi-Yagi antenna. Good impedance matching is obtained by using parasitic elements. The antenna has been designed and successfully measured. Experimental results show that the 10 dB return loss bandwidth of this antenna is 50% operating from 2.3 GHz to 3.8 GHz. We obtain very flat gain (around 5 dB) over the entire bandwidth. For the design and optimization of antennas, we use HFSS CAD software from ANSOFT.

Mutual coupling suppression of aperture coupled microstrip antenna array

A mutual coupling suppression method is proposed for microstrip antenna array by cutting four small semi-circle annular apertures on the metal plate. The structure of antenna array is composed of 2 × 2 four elements. The antenna consists of double layer dielectric, and it realizes circular polarization characteristics by cutting rectangular slot on circular patch in the direction of 45°, by using aperture coupling feeding and reverse feeding principle. There is 90＊ phase difference between adjacent antenna elements. Thus, it cuts off the coupling current field between the elements, suppresses the surface wave and reduces the mutual coupling by cutting four semi-circle annular apertures symmetrically on the metal plate. The simulation results show that after cutting four semi-circle annular apertures, the antenna array coupling coefficients decrease significantly, and the side and back lobe levels are suppressed effectively with the gain of antenna improved. So the proposed method is effective to suppress microstrip antenna array mutual coupling.

Microstrip Antennas Loaded with Shorting Post

In this paper, a technical review with recent advances of the microstrip antennas loaded with shorting posts is presented. The overall size of the antenna is significantly reduced by a single shorting posts and the effect of the various parameters of shorting posts on short-circuit microstrip antenna is also discussed.

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.

Corner Fed Microstrip Antenna Analysisfor Dual Polarization

This paper investigates a corner fed microstrip patch antenna by means of the cavity model with proposed feed modeling. The input impedance and radiation patterns for a corner feed are calculated. The mutual coupling between two corner feeds is investigated. An improvement in mutual coupling has been found for corner feeds relative to edge feeds, which is helpful for the design of dual polarized antenna arrays in wireless communication and radar applications.