Edge-fed cavity backed patch antennas and arrays

A new edge-fed patch antenna that mitigates spurious radiation issues when thick substrates are used to create the antenna is presented. The radiator can be classified as an edge-fed cavity backed patch. Here, a thin substrate is used to develop the microstrip feed line, thereby ensuring the track widths are small and subsequently decreasing spurious feed radiation. The patch radiator utilises the thick substrate employed in the cavity ensuring reasonable return loss bandwidth can be achieved. A single element and a 2 x 2 array have been designed, fabricated and tested using the proposed technique and it has been shown that significant reduction in pattern distortion and increase in gain can be achieved compared to conventional edge-fed microstrip patch configurations. Because of the thin tracks used to feed the radiators, the new technique is very applicable to large arrays of microstrip patches where the area consumed by the distribution network must be minimised to ensure good radiation performance.     

Computation of resonant frequency of annular microstrip antenna loaded with multiple shorting posts

Shorting post loaded annular microstrip antenna is of considerable interest. Recent works have presented formulations for annular microstrip patch with a shorting post located at the centre of a circular disc, thereby converting the structure to an annular ring with a centre shot. A theoretical formulation for multiple post loading (up to ten posts) of an annular patch is presented. The posts are located away from the centre of the patch and are thin in diameter with respect to the diameter of the ring. The formulation accurately predicts resonant frequency. For an accurate formulation, the shorting posts have been considered as inductive impedances at the frequency of interest. It is shown that for a short loaded ring, TM₀₁ is the dominant mode. The simple tool presented can be suitably modified to incorporate switching diodes or varactor diodes.     

Superstrate effects on slot-coupled microstrip antennas

An analysis for studying the superstrate (cover) effects on the slot-coupled microstrip antennas is presented. The approach is based on the reciprocity theorem and uses the grounded double- and single-layer dielectric slab Green's functions in a moment method solution for the unknown slot fields and patch currents. From these fields and currents, various characteristics of the antenna can be extracted, such as the radiation efficiency, directivity, input impedance, and resonant frequency. Numerical calculations showing superstrate effects on these antenna characteristics are presented. The input matches obtained from proper adjustment of the slot and patch dimensions are discussed.<>     

Analysis and design of broadband U-slot cut rectangular microstrip antennas

Broadband microstrip antenna using variations of U-slot has been widely reported. However, in most of the reported work, an in-depth explanation about the mode introduced by U-slot and procedure to design U-slot cut antennas at any given frequency is not explained. In this paper, first an extensive analysis to study the broadband response in symmetrical and a new configuration of asymmetrical U-slot cut rectangular microstrip antennas is presented. The U-slot tunes higher-order orthogonal mode resonance frequency of the patch with respect to fundamental mode to realise wider bandwidth. Further formulation in resonant length at modified patch modes in symmetrical U-slot cut antenna is proposed. Frequencies calculated using these formulations show closer agreement with simulated and measured results. Using proposed formulations, a procedure to design U-slot cut antenna at different frequencies over 800–4000 MHz range which shows broadband response is explained. Thus, the proposed work gives an insight into the functioning of widely used U-slot cut antennas and the formulations will be helpful for designing at any given frequency.     

Stub loaded multi-band slotted rectangular microstrip antennas

The multi-band rectangular microstrip antennas (MSAs) realised by placing an open-circuit stub on the edges of the patch and by cutting resonant slots inside the patch are proposed. The multi-port network models for these multi-band rectangular MSAs are also proposed which helps in analysing the voltage distributions at various frequencies. Also the multi-band frequency response of these configurations is experimentally verified.     

Effect of conductive yarn crimp in radiation patch on electromagnetic performance of 3D integrated microstrip antenna

A three-dimensionally integrated microstrip antenna (3DIMA) is a microstrip antenna woven into the three-dimensional woven composite for load bearing while functioning as an antenna. In this study, the effect of conductive yarn crimp on electromagnetic performance of 3DIMAs are investigated by designing, simulating and experimental testing of two microstrip antennas with different patch woven structures: one woven in plain weave pattern with most yarn crimp and the other woven orthogonally without yarn crimp. The measured voltage standing wave ratio (VSWR) of the crimp free 3DIMA was 1.05 at the resonant frequency of 1.31 GHz; while that of the crimped 3DIMA was 1.78 at the resonant frequency of 1.41 GHz. In addition, the measured radiation pattern of the crimp free 3DIMA in its radiating patch has smaller back lobe and side lobes than those of the crimped 3DIMA. This result indicates that yarn crimp may have a negative impact on electromagnetic performance of textile structural antennas.     

Segmentation analysis of loaded microstrip antenna

Abstract

A microstrip antenna for dual‐frequency operation has been investigated. The frequency can be controlled by placing PIN diodes at appropriate locations in the patch. The cavity model and segmentation method are used to analyze the operation frequency, input impedance, and radiation pattern. Finally, experimental data are compared with theoretical predictions.     

Scattering and radiation analysis of cavity-backed microstrip patch antennae with anisotropic slabs via a variational formulation

Abstract

In this paper we examine an arbitrarily shaped cavity-backed microstrip patch antenna with a very general anisotropic grounded slab. We apply a hybrid finite-element-boundary-integral method. We use the finite-element method to solve the Helmholtz equation in the interior of the micro-strip antenna and use the boundary-integral method, together with the dyadic Green function approach, to determine the fields exterior to the microstrip patch antenna. We couple the two methods at the interface plane by enforcing the field continuity conditions. Several numerical results are presented demonstrating the validity, efficiency and capability of this technique.     

Analysis technique for frequency-switchable and microelectromechanical systems-based multi-mode parasitic patch arrays

Multi-mode parasitic patch arrays have multiple resonant frequencies, each with an associated high-gain radiation pattern. The authors present a novel analysis technique that combines existing well-established models to characterise the structures and reduce the design cycle time. Passive radio frequency (RF) identification tags will benefit from this technology to improve the inherently limited range, since they derive their power from the incident RF signal and modulate the backscatter. Additional applications of these structures include microelectromechanical systems-based adaptive arrays that have additional beam-steering capabilities at each frequency. Hardware has been fabricated and tested for both applications, with good correlation between simulated and measured results.     

新型宽频带微带贴片天线的设计

提出了一种新颖的展宽三角形微带贴片天线工作频带的设计方法．通过在三角形微带贴片侧边附近加载与之平行的缝隙来实现双频工作,并添加一对平行于底边的缝隙使两个频点靠近,利用仿真软件进行优化,有效地展宽了贴片天线的频带．制作了实际的贴片天线,结果表明所设计天线的工作带宽(VSWR<2)是普通三角形微带天线的4.46倍,且天线尺寸与同频率的常规贴片天线相比缩小了9.3%．测量结果与仿真结果吻合,证明了所提方法的有效性．     

Modelling of Wideband Concentric Ring Frequency Selective Surface for5GDevices

Frequency selective surfaces (FSSs) play an important role in wireless systems as these can be used as filters, in isolating the unwanted radiation, in microstrip patch antennas for improving the performance of these antennas and in other 5G applications. The analysis and design of the double concentric ring frequency selective surface (DCRFSS) is presented in this research. In the sub-6 GHz 5G FR1 spectrum, a computational synthesis technique for creating DCRFSS based spatial filters is proposed. The analytical tools presented in this study can be used to gain a better understanding of filtering processes and for constructing the spatial filters. Variation of the loop sizes, angles of incidence, and polarization of the concentric rings are the factors which influence the transmission coefficient as per the thorough investigation performed in this paper. A novel synthesis approach based on mathematical equations that may be used to determine the physical parameters of DCRFSS-based spatial filters is presented. The proposed synthesis technique is validated by comparing results from high frequency structure simulator (HFSS), Ansys electronic desktop circuit editor, and an experimental setup. Furthermore, the findings acquired from a unit cell are expanded to a 2 × 2 array, which shows identical performance and therefore proves its stability.     

High precision phase measurement using adaptive sampling

The conventional phase measurement techniques introduce error in the phase when the input signals are distorted by harmonics. A novel technique, known as adaptive sampling, for high-precision phase measurement is introduced. A digital signal-processing approach is used in this technique. The maximum sampling rate required for this technique is h+2 samples/cycle of the input signals, i.e. (h+2) f sampless, where h, is the highest harmonic present in the signals and f is the fundamental frequency of the signals. This sampling rate is way below the Nyquist sampling rate (more than 2hf samples/s) when h is a large number. In the adaptive sampling technique the sampling rate is started from three samples/cycle and then is gradually increased until the phase is correctly measured. This phase measurement technique has been verified using synthesized signals     

Design of circular polarisation microstrip patch antennas with complementary split ring resonator

A novel design of circular polarisation microstrip patch antennas based on the complementary split ring resonator is numerically evaluated and experimentally verified. The non-resonant property of complementary split ring resonator is used as an asymmetric perturbation to excite the square microstrip patch antenna for circular polarisation radiation. The detailed parameters of the complementary split ring resonator on the circular polarisation radiation are studied.     

Wideband microstrip antennas with sandwich substrate

A broadband microstrip antenna with low?high?low (sandwich) dielectric constant substrate combination using a microstrip line-via feed is presented for ultra-wideband applications. The proposed antenna consists of three dielectric substrates; low dielectric constant substrates that contain the microstrip feed line as well as parasitic patches and a high dielectric constant substrate that contains the driven patch. To achieve a large impedance bandwidth, parasitic patches and microstrip line-via combination feed to the driven patch in the multilayered microstrip antenna are used. The proposed antenna designed, fabricated and measured on the sandwich substrate. The antenna has measured 10 dB return loss bandwidth of 46.9% and directive gain .5.2 dBi at boresight across the impedance bandwidth. The total height of antenna is 5.77 mm or 0.077λ ^{at 4 GHz.}     

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     

Neural network method for direction of arrival estimation with uniform cylindrical microstrip patch array

In this study, a new neural network algorithm is proposed for real-time multiple source tracking problem with cylindrical patch antenna array based on a previously reported Modified Neural Multiple Source Tracking (MN-MUST) algorithm. The proposed algorithm, namely cylindrical microstrip patch array modified neural multiple source tracking (CMN-MUST) algorithm implements MN-MUST algorithm on a cylindrical microstrip patch array structure. CMN-MUST algorithm uses the advantage of directive pattern of microstrip patch elements by considering only a part of array elements for a chosen sector. This reduces neural network sizes and also improves the spatial filtering performance. The proposed algorithm improves MN-MUST algorithm in the sense of accuracy and speed while covering the full azimuth range.     

Design of fractal patch antenna for size and radar cross-section reduction

This research study presents a novel design of star-shaped fractal patch antenna for miniaturisation and backscattering radar cross-section (RCS) reduction. The proposed fractal antenna gives 50% size reduction compared with a conventional circular microstrip patch (CCMP) antenna. The antenna is studied experimentally for return loss behaviour using vector network analyser R&S ZVA40. It can be useful for wireless application in 0.85-4 GHz frequency band. Further, the study focuses on backscattering RCS (both monostatic and bistatic) reduction by the proposed antenna compared with the CCMP antenna. It is found that increase in number of fractal iterations included in the conventional patch to design fractal antenna geometry reduces backscattering RCS at multiband compared to the conventional patch antenna. This reduction in backscattering RCS by the antenna is observed at multiband. The antenna can be tuned for low backscattering by variation in the substrate dielectric constant and thickness and the superstrate dielectric constant and thickness. For maximum RCS reduction by the antenna, optimisation of substrate thickness becomes necessary. The study also deals with effect of frequency and aspect angle variation on backscattering RCS reduction.     

Design of a Mechanical Tuning for Superconducting Microwave Power Filters

We have been studying microwave superconducting power filters with dynamic tunable mechanism. This paper reports estimation of superconducting microstrip patch resonators using piezoelectric actuators as parts of the electrically tunable mechanism. We carried out electromagnetic (EM) simulations on the proposed tunable patch resonators. The main conditions of the EM simulations were that the superconducting material was YBCO, the patch pattern with TM₁₁ or TM₀₁-resonant mode was disk shape, and so on. From the EM simulation results, it was estimated that the resonant mode differences of the unloaded-Q, the power handling capability, and the resonant frequency tunability related with the PZT bimorph element as the actuator candidate.     

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     

Gyro-Chirality Effect of Bianisotropic Substrate on the Resonant Frequency and Half-power Bandwidth of Rectangular Microstrip Patch Antenna

In this paper, the gyrotropic bi-anisotropy of the chiral medium in substrate constitutive parameters (xc and hc) of a rectangular microstrip patch antenna is introduced in order to observe its effects on the complex resonant frequency and half-power bandwidth. The analysis is based on the full-wave spectral domain approach using the Moment Method, with sinusoidal type basis functions. The numerical calculations related to the dominant mode have been carried out, and it has been observed that the resonant frequency and the bandwidth are directly linked to the medium chirality. The new results can be considered as a generalisation form of the previously published work.