Input impedance and resonance characteristics of superstrate-loaded triangular microstrip patch

The input impedance and resonance characteristics of an equilateral triangular microstrip patch in the presence of a dielectric superstrate loading have been studied both theoretically and experimentally. A simplified cavity model is used to analyse the structure and is validated using a series of experiments. Different patch sizes and substrate-superstrate combinations are used to demonstrate their effects.     

Metamaterial superstrate-loaded meandered microstrip-based radiating structure for bandwidth enhancement

We have introduced metamaterial superstrate in microstrip-based radiating structure to increase its bandwidth. Split ring resonators are added as metamaterial metallic inclusion in superstrate of the conventional design. This changes the basic structure of the material. Material properties such as permittivity and permeability changed due to change in the structure. The change in its material properties enhances the bandwidth of the antenna. The antenna is meandered to achieve better performance at the edges which in a way improve the radiation path of the patch. Here, the proposed antenna works on three bands in the range 3–8?GHz. Maximum 60% bandwidth is enhanced in the third band. The voltage standing wave ratio and return loss (S₁₁) of the entire three bands are shown in the paper. The antenna works on 3.51, 4.86 and 7.8?GHz. Design results are obtained by high-frequency structure simulator which is used for simulating microwave passive components.     

Ultra wideband patch antenna with a novel folded-patch technique

The authors present the results of a polygonal patch antenna for ultra-wideband applications covering a frequency band from 4.14 to 13.50 GHz. The fabricated antenna achieved a 210 dB impedance bandwidth in excess of 125% with an antenna size of 0.373λo/sub / x 0.373 xλo/sub /0.149λ/spl o/ at its centre frequency. The antenna?s impedance bandwidth is 64% higher than what is currently obtainable with state-of-the-art folded-patch techniques. The proposed patch antenna has a polygonal-shape with a rectangular slot and shorting pins. The analysis of this antenna shows that bandwidth broadening is achieved by using a rectangular slot on the patch that is fed from a folded-patch feed, whereas the reduction in antenna size is achieved through the use of two shorting pins strategically located on the radiating patch.     

Dual layer stacked rectangular microstrip patch antenna for ultra wideband applications

An antenna consisting of a U-slotted rectangular microstrip patch stacked with another patch of a different size on a separate layer is presented and its performance results are investigated. An equivalent circuit model of this stacked patch design structure is also presented based on an extended cavity model to predict the input impedance. The theoretical input impedance is evaluated from this circuit model and the experimental results support the validity of the model. In this case, stacking with a simple patch adds another resonance to the antenna thus providing a wider bandwidth. The dimension of the top patch is optimised to achieve ultra wide bandwidth. A maximum impedance bandwidth of 56.8% is achieved using this structure, and the return loss |S₁₁|of the antenna is less than -10 dB between 3.06 and 5.49 GHz and the radiation patterns are found to be relatively constant throughout the band. A coaxial feed with Gaussian modulated pulse is used for this antenna.     

Dual-broadband multistandard printed slot antenna with a composite back-patch

A square slot antenna fed by a coplanar waveguide for dual-band multistandard applications is presented. Printed on the back of the square slot is a composite patch formed by an annular metal ring inscribed by a circular patch. Appropriate design of the composite back-patch resulted in five resonant bands, the first (last) two of which were combined to form a lower (upper) operating band. The ratio of the two operating band centre frequencies can be tuned larger than 2.5. A pair of notches was embedded in the annular metal ring to further broaden the lower (upper) operating band up to a fractional bandwidth of 37% (20%). The measured results indicate that the proposed antenna can cover the frequency bands of the following wireless communication standards: digital communication system, personal communication services, universal mobile telecommunications system and 2.4/5-GHz wireless local-area networks.     

Resonator Rectenna Design Based on Metamaterials for Low-RF Energy Harvesting

In this paper, the design of a resonator rectenna, based on metamaterials and capable of harvesting radio-frequency energy at 2.45 GHz to power any low-power devices, is presented. The proposed design uses a simple and inexpensive circuit consisting of a microstrip patch antenna with a mushroom-like electromagnetic band gap (EBG), partially reflective surface (PRS) structure, rectifier circuit, voltage multiplier circuit, and 2.45 GHz Wi-Fi module. The mushroom-like EBG sheet was fabricated on an FR4 substrate surrounding the conventional patch antenna to suppress surface waves so as to enhance the antenna performance. Furthermore, the antenna performance was improved more by utilizing the slotted I-shaped structure as a superstrate called a PRS surface. The enhancement occurred via the reflection of the transmitted power. The proposed rectenna achieved a maximum directive gain of 11.62 dBi covering the industrial, scientific, and medical radio band of 2.40–2.48 GHz. A Wi-Fi 4231 access point transmitted signals in the 2.45 GHz band. The rectenna, located 45 anticlockwise relative to the access point, could achieve a maximum power of 0.53 μW. In this study, the rectenna was fully characterized and charged to low-power devices.     

Aperture-coupled asymmetrical c-shaped slot microstrip antenna for circular polarisation

A novel aperture-coupled, asymmetrical C-shaped slot, square microstrip antenna is proposed for circular polarisation (CP). A narrow and asymmetrical C-shaped slot, microstrip antenna is fed at the centre using an aperture coupling to obtain a CP operation. The compactness of the antenna is easily obtained by inserting a C-shaped slot. Wide CP radiation is achieved simply by making the C-shaped slot asymmetrical. With this antenna, the measured 3 dB AR bandwidth is around 3.3% and the 10 dB return loss bandwidth achieved is 16.0%. The overall antenna size is 0.48λo x 0.48λo x 0.092λo at 2.4 GHz. The proposed slot microstrip patch technology is useful to design compact, broadband, circularly polarised antennas and arrays.     

Small modified monopole antenna for UWB application

In this paper, we present a novel modified printed monopole antenna (PMA) for ultra-wideband (UWB) applications. The proposed antenna consists of a truncated ground plane and radiating patch with two tapered steps, which provides wideband behaviour and relatively good matching. Moreover, the effects of a modified trapezoid-shaped slot inserted in the radiating patch, on the impedance matching and radiation behaviour is investigated. The antenna has a small area of 14 x 20 mm² and offers an impedance bandwidth as high as 100% at a centre frequency of 7.45 GHz for S₁₁ < -10 dB, which has a frequency bandwidth increment of 18% with respect to the previous similar antenna. Simulated and experimental results obtained for this antenna show that it exhibits good radiation behaviour within the UWB frequency range.     

Miniaturised coplanar waveguide-fed antenna and band-notched design for ultra-wideband applications

A miniaturised coplanar waveguide-fed ultra-wideband (UWB) antenna is presented here. The wideband operation is obtained through an optimised curvature of the radiating element. The input impedance of the antenna is matched using an elliptically tapered coplanar waveguide line. A high-band rejection characteristic at wireless local area network frequencies is achieved by inserting an v-shaped slot on the antenna surface. The frequency domain dispersion characteristic is studied by means of the antenna transfer function both numerically and experimentally. Time domain characteristic of the antenna is investigated in detail for both UWB single-band and multiband schemes. In order to efficiently characterise the antenna system for an arbitrary pulse source excitation, the pole/residue model of the antenna system transfer function is presented using the matrix-pencil method.     

Multiple band-stop bow-tie slot antennas for multiband wireless systems

A novel and simple design of wideband coplanar waveguide (CPW)-fed bow-tie slot antennas with multiple band-stop characteristics featuring multi-network applications is presented. A frequency stop band can be created by embedding the slot with a pair of stubs, which causes the resultant magnetic fields almost counterbalance in the slot and to be non-responsive at the desire stop band. The effects of the dimensions of the stub on the stop band are also analysed. Dual band-stop characteristic is also accomplished by embedding two pairs of stubs in the slot. Details of the proposed designs and experimental results of the constructed prototypes are presented.     

An Improved Super-Resolution Source Reconstruction Method

The source reconstruction method (SRM) is a technique developed for antenna diagnostics and for carrying out near-field (NF) to far-field (FF) transformation. The SRM is based on the application of the electromagnetic equivalence principle, in which one establishes an equivalent current distribution that radiates the same fields as the actual currents induced in the antenna under test (AUT). The knowledge of the equivalent currents allows the determination of the antenna radiating elements, as well as the prediction of the AUT-radiated fields outside the equivalent currents domain. The unique feature of the novel methodology presented in this paper is that it can resolve equivalent currents that are smaller than half a wavelength in size, thus providing super-resolution. Furthermore, the measurement field samples can be taken at field spacings greater than half a wavelength, thus going beyond the classical sampling criteria. These two distinctive features are possible due to the choice of a model-based parameter estimation methodology where the unknowns are approximated by a continuous basis and, secondly, through the use of the analytic Green's function. The latter condition also guarantees the invertibility of the electric field operator and provides a stable solution for the currents even when evanescent waves are present in the measurements. In addition, the use of the singular value decomposition in the solution of the matrix equations provides the user with a quantitative tool to assess the quality and the quantity of the measured data. Alternatively, the use of the iterative conjugate gradient (CG) method in solving the ill-conditioned matrix equations can also be implemented. Two examples of an antenna diagnostics method are presented to illustrate the applicability and accuracy of the proposed methodology.     

基于LTCC宽频带双频差分天线的研究与设计

提出了一种新型宽频带双频差分天线.该天线基于低温共烧陶瓷(Low Temperature Co-Fired Ceramies,简称LTCC)技术,采用矩形环状贴片,并使用两条叉形微带馈线进行差分馈电,是一种具有平衡结构的宽缝隙天线,该结构使得天线拥有很宽的频带宽度.天线两频段的中心频率为2.63 GHz和5.13 GH...     

Ultra-wideband CPW-fed antenna with round corner rectangular slot and partial circular patch

Abstract: A novel coplanar waveguide (CPW)-fed ultra-wideband wide slot antenna is proposed. Because of the round corner of the rectangular slot and partial circular patch, the bandwidth of the antenna is enhanced largely. Good agreement between the measurement and simulation has been achieved. The results show that the impedance bandwidth of the antenna reaches up to 4.5-15.5 GHz for S₁₁ < -15 dB and 2.5-18 GHz for S₁₁ < -10 dB. Meanwhile, a good omni-directional radiation performance has also been achieved.     

低交叉极化高隔离的双极化天线

设计了一种应用于WLAN的具有低交叉极化和高隔离度的双极化天线.天线由3层功能层和2层介质基板间隔层叠而成.3层功能层分别为1个方形辐射贴片,2个带有发夹谐振器的馈电网络和1个刻蚀H形缝隙的接地板.发夹谐振器和辐射贴片构成一个二阶滤波天线用以展宽天线的带宽.通过在接地板上蚀刻H形缝隙降低了天线端口间的耦合电流,改善了天...     

Broadband designs of coplanar capacitivelyfed shorted patch antennas

The author presents a coplanar capacitively fed shorted patch antenna for easy fabrication and providing a very wide impedance bandwidth. In this design, a feeding strip is located on the same plane as that of the radiating patch and used to excite the antenna by electromagnetic coupling. Experimental results reveal that the impedance bandwidth of the proposed antenna depends not only on the length and location of the feeding strip but also on the width of the radiating patch. For the optimal result obtained in the design, the 10 dB return-loss impedance bandwidth is as large as 78%. The radiation characteristics of the operating frequencies within the obtained wide bandwidth are also studied and presented.     

CPW-fed ultra wideband slot antenna with arc-shaped stub

An ultra wideband coplanar waveguide (CPW) fed slot antenna is presented. A rectangular slot antenna is excited by a 50-CPW with an arc-shaped tuning stub. For the proposed antenna, the 210 dB return loss bandwidth could reach 15.6 GHz (3.7-19.3 GHz), which is about 135% with respect to the centre frequency of 11.5 GHz. Details of the antenna design, simulation and measured results on the return loss and the E-and H-plane radiation patterns of the proposed antenna are presented.     

Circularly polarised proximity-fed microstrip antenna with polarisation switching ability

The authors propose a design of a circularly polarised proximity-fed microstrip antenna having polarisation switching ability. The proposed antenna has a simple structure, consisting of a truncated-corners square patch in the same plane with a microstrip feed line extended beyond the patch edge, pin diode and a pad connected to a ground by a conducting post. The diode, which is inserted between the end of the feed line and a pad, is used to control feed line termination. By turning the diode on or off, this antenna can radiate either right hand or left hand circular polarisation. Furthermore, we present a technique to improve the input characteristics of the antenna. It involves two diode-controlled tuning stubs connected in shunt with the feed line. Finally, a discussion on how the diode characteristics affect the structure and results of the antenna is given. All analyses are carried out using finite-difference time-domain technique and confirmed by measurements in the 5 GHz band. A good agreement between the simulated and measured results was obtained     

Application of dual-mode filter techniques to the broadband matching of microstrip patch antennas

Structures such as square or circular microstrip patch antennas may support two orthogonal resonant modes. The paper presents a new method of utilising the dual-mode property to increase the bandwidth of microstrip antennas. The input impedance of such a dual-mode antenna may be represented as a second-order ladder network of coupled resonators, where each resonator is coupled to a load resistor. A theoretical method for evaluating the coupling values in the network is presented, enabling the bandwidth of a dual-mode antenna to be maximised. A theoretical bandwidth improvement of up to 3:1 is achieved when compared to a single-mode antenna. This is confirmed with an experimental dual-mode circular microstrip patch antenna     

Zero-Index Metamaterial Superstrates UWB Antenna for Microwave ImagingDetection

Metamaterials (MTM) can enhance the properties of microwaves and also exceed some limitations of devices used in technical practice. Note that the antenna is the element for realizing a microwave imaging (MWI) system since it is where signal transmission and absorption occur. Ultra-Wideband (UWB) antenna superstrates with MTM elements to ensure the signal transmitted from the antenna reaches the tumor and is absorbed by the same antenna. The lack of conventional head imaging techniques, for instance, Magnetic Resonance Imaging (MRI) and Computerized Tomography (CT)-scan, has been demonstrated in the paper focusing on the point of failure of these techniques for prompt diagnosis and portable systems. Furthermore, the importance of MWI has been addressed elaborately to portray its effectiveness and aptness for a primary tumor diagnosis. Other than that, MTM element designs have been discussed thoroughly based on their performances towards the contributions to the better image resolution of MWI with detailed reasonings. This paper proposes the novel design of a Zeroindex Split Ring Resonator (SRR) MTM element superstrate with a UWB antenna implemented in MWI systems for detecting tumor. The novel design of the MTM enables the realization of a high gain of a superstrate UWB antenna with the highest gain of 5.70 dB. Besides that, the MTM imitates the conduct of the zeroreflection phase on the resonance frequency, which does not exist. An antenna with an MTM unit is of a 7 × 4 and 10 × 5 Zero-index SRR MTM element that acts as a superstrate plane to the antenna. Apart from that, Rogers (RT5880) substrate material is employed to fabricate the designed MTM unit cell, with the following characteristics: 0.51 mm thickness, the loss tangent of 0.02, as well as the relative permittivity of 2.2, with Computer Simulation Technology (CST) performing the simulation and design. Both MTM unit cells of 7 × 4 and 10 × 5 attained 0° with respect to the reflection phase at the 2.70 GHz frequency band. The first design, MTM Antenna Design 1, consists of a 7 × 4 MTM unit cell that observed a rise of 5.70 dB with a return loss (S11) −20.007dB at 2.70 GHz frequency. The second design, MTM Antenna Design 2, consists of 10 × 5 MTM unit cells that recorded a gain of 5.66 dB, having the return loss (S11) −19.734 dB at 2.70 GHz frequency. Comparing these two MTM elements superstrates with the antenna, one can notice that the 7 × 4 MTM element shape has a low number of the unit cell with high gain and is a better choice than the 10 × 5 MTM element in realizing MTM element superstrates antenna for MWI.     

A Novel Broadband Microstrip Antenna Based on Operation of Multi-Resonant Modes

A novel broadband microstrip antenna under operation of TM_1/2,0, TM₁₀ and TM₁₂ modes through a shorting wall and slots is proposed in this paper. Initially, an inverted U-shaped slot is adopted around the feeding point, which achieves a good impedance matching on TM₁₀ mode and separates the patch into two parts. Additionally, a shorting wall is added underneath the edge of smaller patch to excite another one-quarter resonant mode, i.e., TM_1/2,0 mode of smaller patch close to TM₁₀ mode to expand the impedance bandwidth. Further, the antenna width is enlarged and two symmetrical vertical rectangular slots are cut on the patch to reduce the frequency of TM₁₂ mode to form a broadband. Based on the arrangements above, a wide impedance bandwidth with three minima can finally be achieved. The results show that the impedance bandwidth of proposed antenna for |S11|<-10 dB is extended to 26.5% (23.5-30.67 GHz), which is three times of the conventional antenna at same profile. Moreover, a stable radiation pattern at broadside direction is realized over the operating band.