Q.-Z. Liu

A Swallow-tailed Wideband Planar Monopole Antenna with Semi-elliptical Base

A novel swallow-tailed wideband planar monopole antenna with semi-elliptical base is presented. The impedance and radiation properties of the proposed monopole antenna are investigated experimentally. The study indicates that the proposed monopole antenna yields the maximum bandwidth from 1.22 GHz to more than 15 GHz for VSWR<2 with the optimum ellipticity ratio of the antennas semi-elliptical base and the height of the feeding post. The radiation performance is also discussed and shown to be acceptable over a wide frequency range.

The Tri-Band Performance of Sleeve Dipole Antenna

In this paper broadband characteristics of sleeve antenna are analyzed using the Method of Moments. The sleeve antennas property of three frequency bands is investigated. The first and third operating bands come from the driven dipole, while the second operating band is due to the height of the sleeve and the distance between the driven dipole and the sleeve. Some numerical results are presented and discussed.

A Wideband Circularly Polarized Candy-Like Patch Antenna

The paper demonstrates a new means to achieve a broad impedance bandwidth and circularly polarized bandwidth with a suspended candy-like antenna and a T-shaped feeding probe. By incorporating a long probe inside a high substantial cavity (∼ 0.16λ), a circularly polarized (CP) antenna in broadside direction is achieved. The horizontal arm of the probe is implemented by means of a printed monopole that is diagonally coupled to a small candy-like copper plate. The CP antenna features a wide operating bandwidth of 15.2% ranging from 1.47 Hz to 1.71 GHz (VSWR < 2 and axial ratio < 3 dB). The maximum gain of this antenna is recorded as no less than 7.2 dBic across the bandwidth. The dimension of the candy-like patch is 0.3λ × 0.3λ, whereas the ground plane size is 1.8λ × 1.8λ. The measured results are presented.

Analysis of Antenna Array with Arbitrarily Shaped Radomes Using Fast Algorithm Based on VSIE

The moment method (MoM) based on volume-surface integral equation (VSIE) combined with the adaptive integral method (AIM) is applied to analyze antenna array radiation in the presence of arbitrarily shaped radomes. The application of AIM reduces the computational complexity of MoM, which leads eclectically large-sized radomes with metal reflecting ground can be analyzed accurately and efficiently. Some radomes terminated by metal plane is presented and the effect of the metal plane on the radiation of antenna is analyzed.

RECONFIGURABLE DUAL CIRCULARLY POLARIZED MICROSTRIP ANTENNA WITHOUT ORTHOGONAL FEEDING NETWORK

A polarization reconfigurable microstrip antenna is proposed without orthogonal feeding network. The antenna is composed of a suspended patch, two printed probes and a simple switch circuit. Reconfigurable circularly polarization, i.e., right-hand circular polarization (RHCP) or left-hand circular polarization (LHCP), is produced by controlling the states of the switch circuit. A prototype is designed and tested. The simulation and measurement results show that the proposed antenna demonstrates wide impedance bandwidth and a good axial ratio in the circularly polarized states.

Electromagnetic analysis of coupled conducting and dielectric targets using MoM with a PRE-conditioner

An effective pre-conditioner for the method of moments (MoM) solution to the coupled volume-surface integral equation is presented to calculate electromagnetic scattering from conducting and dielectric targets. In this MoM solution to the integral equations, the target is discretized using triangular patches for conducting surfaces and tetrahedral cells for dielectric volume. Based on the characteristics of impedance matrix, an accurate method is used to improve the convergence speed when the iterative solver is employed. In comparison with other pre-conditioners, some numerical examples are also presented with high efficiency.

Fast Analysis of Body-of-Revolution Radomes with Method of Moments

By taking advantage of the rotational symmetry, the electromagnetic characteristic of the body of revolution (BOR) radome is fast analyzed by the method of moments (MoM) based on the mode decomposition technique. First, the MoM matrix equation governed by the surface integral is established and the theoretical model is reduced in dimension by using the mode decomposition technique in view of the objects structure characteristic. Then, the integrals in the mode decomposition of the incident field are replaced by the fast Fourier transform (FFT), thus the decomposition coefficients of all modes on a given annulus can be fast and easily obtained through one FFT. Due to the surface equivalent electric and magnetic currents gotten by solving the matrix equations having the form of superposition of mode components, the analytical approach is used to substitute for the integral in the calculation of the far field pattern, so the computing time is greatly reduced. Examples are presented to demonstrate the accuracy and efficiency of the proposed method in this paper.

A NOVEL WIDE BAND AND BROAD BEAMWIDTH CIRCULARLY POLARIZED ANTENNA

A novel printed crossed dipole with broad axial ratio (AR) bandwidth and enhanced beamwidth is proposed. the proposed antenna consists of two dipoles crossed through a 90° phase delay line, which produces one minimum AR point due to the sequentially rotated configuration and 4 parasitic ring loops, which generate one additional minimum AR point. By combining these two minimum AR points, the proposed dipole achieves a broadband circularly polarized (CP) performance. under the dipoles are 8 erect parasitical monopoles and a reflector, which are placed to broaden the beamwidth. the proposed antenna has not only a broad 3 db AR bandwidth of 9.84% (155 MHz, 1.495–1.650 GHz) with respect to the CP center frequency 1.575 GHz, but also a broad 3 db beamwidth of about 180. this paper deals with the designs and experimental results of the proposed crossed dipole with parasitic ring loops and erect monopoles.

Research on a Sleeve Antenna Mounted on Metallic Cylinder

A sleeve antenna mounted on metallic cylinder is analyzed by a new moment method. The electric characteristic parameters of this novel sleeve antenna are calculated, including the input impedance, the voltage standing wave ratio (VSWR), the horizontal gain and radiation pattern. The calculated data is in good agreement with the experimental data.

Scan Blindness of Tapered-Slot Array Optimized with Tapered-Aerosubstrate in the Triangular Elements Grids

Tapered-aerosubstrate is applied to optimize the scan blindness of tapered-slot antenna array where elements are positioned in a triangular grid. The blindness occurs when the steering phase progression in the E-plane is equal to the phase progression of a leaky mode in the structure and could be optimized by the tapered-aerosubstrate which elevates the resonance positions of dominant radiator modes. Character analysis of tapered-aerosubstrate is shown to be agreed well with the compute and experiment results, and scan blindness is moved 12.5% toward the upper frequency.