Xin-Huai Wang

RCS Reduction of Array Antenna by Using Bandstop FSS Reflector

This paper investigates the application of a novel frequency selective surface (FSS) reflector for 4×2 dipole array antenna to reduce radar cross section (RCS) out of operating band. The proposed FSS adopting a regular hexagon quasi-fractal structure has good bandstop characteristic. By replacing the metal reflector with this bandstop FSS sheet, the in-band radiation performance of the proposed array antenna is preserved, while the out-of-band backward RCS is significantly reduced. Due to the good angle stability of the given FSS, the monostatic RCS peaks at oblique angle ( = 60°, ϕ = 0°) are also controlled. The measured results demonstrate the feasibility of antenna RCS reduction by this method.

Novel Wideband Bandpass Filter Integrating HMSIW with DGS

In this paper, a novel method is proposed to design wideband bandpass filters with compact size. Combining half mode substrate integrated waveguide (HMSIW) and periodic dumbbell-shaped defected ground structure (DGS), two compact wideband bandpass filters with different HMSIW-microstrip transitions are fabricated and measured. The filters are found to possess wide passband bandwidth and compact size. Good agreement between the measured and simulated results demonstrates the validity of this technique.

A Novel Low RCS Mobius-Band Monopole Antenna

A novel mobius-band monopole antenna (MBMA) using several metallic via holes, which is based on the concept of topology, is designed to realize radar cross section (RCS) reduction compared to a common printed circular-disc monopole antenna (PCDMA). The characteristic of mobius-band realizes antenna RCS reduction. UWB-related characteristics of the proposed antenna including the return loss and radiation patterns are simulated and experimentally verified. Mobius-band antenna and the reference antenna are both UWB antennas whose RCS performances under different loads are studied and compared. The results show that the proposed antenna has lower RCS than the reference antenna in the whole frequency band while maintaining good radiation performances, which illuminates that MBMA is a good candidate for antennas with or without a requirement of RCS control.

Design of Compact Quad-Frequency Impedance Transformer Using Two-Section Coupled Line

This paper presents a compact quad-frequency impedance transformer that is composed of a two-section coupled line to achieve ideal impedance matching at three arbitrary frequencies and a related frequency. The exact closed-form equations and design procedures are given based on strict theoretical analysis. After demonstrating the bandwidth performance and symmetry properties of different impedance transform ratios, we fabricated a circuit to show the validity of practical applications. Good agreement between the measured data and anticipated results is achieved.

Smart antenna design for GPS/GLONASS anti-jamming using adaptive beamforming

Smart antenna has the advantage of suppressing jamming in spatial region and improving signal to Interference plus Noise Ratio (SINR) of receive signals, thus it is recognized as the promising technologies and indispensable anti-jamming methods. This paper presents a practical design of smart antenna system for GPS/GLONASS anti-jamming base on adaptive beam-forming. It firstly introduces the basic concepts and principles of the smart antenna, provides the structure of the system, analyses and discusses each component, then designs a anti-jamming smart antenna for GPS and GLONASS, ultimately realizes a flexible hardware platform base on the technology of digital signal processor (DSP), field-programmable gate arrays (FPGA), and software defined radio (SDR).

Planar Dual-Frequency Power Divider using Umbrella-Shaped Resonator

In this paper, a new planar dual-frequency power divider based on umbrella-shaped dual-mode resonator is presented. The topology of the circuit, different from conventional Wilkinson power divider, is the couple lines and resonators instead of the transmission lines. It can provide not only dual band, but also direct current (DC) block characteristic and compact size, which fits for microwave intergraded circuit application. The proposed structure is analyzed and simulated. To certify the validity of the technique, two proposed power dividers are fabricated and measured at 1.85/4.85 GHz and 1.57/3.5 GHz. Good experimental performances at both frequencies are obtained, which are in good agreement with the simulated results.

A Hybrid Genetic-Algorithm Space-Mapping Method for the Optimization of Broadband Aperture-Coupled Asymmetrical U-Shaped Slot Antennas

In this study, a novel hybrid genetic-algorithm space-mapping method (GA-SM) is used in conjunction with method-of-moments (MoM) to design a broadband aperture-coupled asymmetrical U-shaped slot antenna. This hybrid method consists of the application of a genetic algorithm (GA) that employs coarse models in the simulations and an additional space mapping (SM) method that refines the solution found in the previous stage. As a comparison, the single application of GA with a fine model is also used to design the antenna. Compared with GA, the GA-SM method is much more efficient in reducing the computational time and can successfully achieve the same design goal as GA does. Finally, the proposed antenna is fabricated based on GA-SM optimization, and measured results show that the impedance bandwidth reaches 2.22 GHz (2.23 GHz–4.45 GHz) (VSWR < 2.0), which means that the relative impedance bandwidth is expanded up to 66.6%. Hence, GA-SM method is an efficient and practical technique for designing antennas, especially for large antenna array design in which long computational time is required.

A Compact Dual-Frequency Three-Way Unequal Power Divider

In this paper, a compact dual-frequency three-way unequal power divider is presented. The design of the proposed power divider is accomplished by transforming the length and impedance of each quarter-wave branch into two sections with the characteristic impedance of Z 1 and Z 2, the length of λ/4 and four resistors which provide enough isolation at two frequencies. The configuration of the proposed power divider and formulas used to determine the design parameters are given. To verify the validity of the formulas, a three-way power divider with a power split ratio of 1 : 1.5 : 3 for two frequencies of 915 MHz and 2450 MHz is fabricated and measured. The size of the proposed power divider is about two thirds of that of the conventional one. The measured results show good agreement with the simulated ones. Good experimental performances of the proposed power divider, including an unequal power split, low return loss, and good isolation at the two frequencies between the output ports, are obtained.

Compact Multiband Slot Antenna for WLAN/WiMAX Operations

A novel compact triple-band slot antenna is proposed for WLAN/WiMAX applications. With the use of three L-shaped slots and an open-ended slot on the ground plane, three resonant modes centered at 2.4/3.5/5.8 GHz are excited. These modes cover the standards of 3.5 GHz WiMAX and 2.4/5.8 GHz WLAN, three useful frequency bands for present wireless communication systems. The proposed antenna fed by L-shaped microstrip line has a small overall dimension of mm2. The numerical and experimental results show that acceptable radiation characteristic is obtained over the operating bands.

Compact electronically tunable microstrip dual-band filter using stub-loaded SIRs

A compact electronically tunable dual-bandpass filter (BPF) with harmonic suppression is investigated in this paper. The BPF is composed of a step-impedance resonator, a T-stub with a varactor diode and a filtering network. The second passband can be independently tuned by varying the bias voltage across the varactor, whereas the first passband is fixed. The proposed filter exhibits wide stopband due to the introduction of the filtering network suppressing harmonics. A prototype of a tunable dual-band BPF, in which the second passband is tuned from 1.58 to 2.21 GHz and the first passband is fixed at 0.98 GHz, is designed and fabricated. The simulated and measured results are in good agreement with each other.