Shaoqiu Xiao

Compact UWB Antenna With Multiple Band-Notches for WiMAX and WLAN

In order to prevent interference problem due to existing nearby communication systems within the UWB operating frequency, a compact triple band-notch UWB antenna is presented in this communication. This antenna, designed for the rejection of interference with Worldwide Interoperability for Microwave Access (WiMAX), lower and upper wireless local area networks (WLANs) covering 3.3-3.6 GHz, 5.15-5.35 GHz and 5.725-5.825 GHz, provides three notched bands by only one structure with simple design. Based on simulation and measurement, it shows that the proposed antenna can guarantee a wide bandwidth from 3.03 to 11.4 GHz with triple unwanted band-notches successfully.

Yagi Patch Antenna With Dual-Band and Pattern Reconfigurable Characteristics

This letter presents a slot-loaded Yagi patch antenna with dual-band and pattern reconfigurable characteristics. The beam can scan in the E-plane by switching the modes of the antenna, which is implemented by changing the states of the switches installed in the slots etched on the parasitic patches. Different modes of the antenna have different radiation patterns and operating frequency bands. There are three modes having a common band of 9.15-9.45 GHz and their beams direct to -7deg, +33.5deg, and -40deg in the E-plane. Two among three modes also have another common frequency band around 10.3 GHz and the main beams direct to +58.5deg and -62.5deg, respectively. The third mode also has another frequency band around 10.85 GHz and has a dual-beam pattern. Simulated and measured results are given and they agree well with each other. The antenna can be used in radar, satellite communications, etc

60-GHz LTCC Integrated Circularly Polarized Helical Antenna Array

A 60-GHz wideband circularly polarized (CP) helical antenna array of 4 × 4 elements is designed and fabricated using low temperature cofired ceramic (LTCC) technology. The flexible via hole distribution is fully utilized to achieve a helical antenna array to obtain good circular polarization performance. Meanwhile, grounded coplanar waveguide (GCPW) to stripline is utilized for probe station measurement. Unlike traditional helical antennas, the proposed helical antenna array is convenient for integrated applications. The fabricated antenna array has dimension of 12 × 10 × 2 mm3. The simulated and measured impedance, axial ratio (AR) and radiation pattern are studied and compared. The proposed antenna array shows a wide measured impedance bandwidth from 52.5 to 65.5 GHz for | S11| <; -10dB, wideband measured AR bandwidth from 54 to 66 GHz for AR <;3 dB, respectively.

Wide-Angle Scanning Phased Array With Pattern Reconfigurable Elements

A novel phased array is presented to extend array scanning range by using pattern reconfigurable antenna elements and weighted thinned synthesis technology in this paper. The pattern reconfigurable microstrip Yagi antenna element is used as a basic element in array and it is capable of reconfiguring its patterns from broadside to quasi-endfire radiation by shifting states of the PIN diode switches integrated on parasitic strips. A weighted thinned linear array synthesis technique is analyzed and some interesting conclusions have been made. A linear array composed of eight pattern reconfigurable antenna elements is manufactured to demonstrate the excellent performance of the array. The active element pattern of each element is measured and pre-stored. Based on active element patterns and weighted thinned linear array synthesis technique, the pattern scanning performance of the novel array is synthesized. The results indicate that the array can scan its main beam from φ = -60° to φ = 60° in H-plane with gain fluctuation less than 3 dB while maintaining low side lobes, and the -3 dB beam width coverage is about from φ = -68° to φ = 68°. The performance is superior to the traditional phased array made of wide-beam elements.

An Ultrathin and Broadband Radar Absorber Using Resistive FSS

An ultrathin and broadband radar absorber comprising single-layer resistive frequency selective surface (FSS) is investigated in this letter. The resistive FSS layer constructed from resistive/low-conductivity treble-square loops is backed by a grounded foam material. Numerical results show that the proposed absorber can provide a 10-dB radar cross section (RCS) reduction for the conducting plate over the frequency range of 10.7-29 GHz, which is equivalent to a relative bandwidth of 92.2%. Moreover, the structure has the thickness of 2 mm (only 0.071 to 0.193 at lowest and highest frequencies, respectively). The equivalent circuit model is then used to introduce the working principles of the proposed absorber.

On the Design of Single-Layer Circuit Analog Absorber Using Double-Square-Loop Array

A detailed study of a single-layer circuit analog absorber using double-square-loop array reveals that three resonances can be obtained within its operating frequency band. An equivalent circuit model is proposed to explain how these three resonances can be produced and its absorption bandwidth can be widened. Simple guidelines for the design of this double-square-loop absorber are then formulated. It is shown through measurements that the fractional bandwidth of 126.8% is realized for at least 10 dB reflectivity reduction under the normal incidence. Furthermore, the total thickness of the proposed design is only 0.088λL at the lowest operating frequency. A good agreement between simulated and measured results demonstrates the validity of our design.

A Compact Slow-Wave Microstrip Branch-Line Coupler With High Performance

One compact slow-wave microstrip branch-line coupler is presented. The new structure not only effectively reduces the occupied area to 28% of the conventional branch-line coupler at 2.0 GHz, but also has high second harmonic suppression performance. The measured results indicate a bandwidth of more than 200 MHz has been achieved while the phase difference between S21 and S31 is within 90deg plusmn 1deg. Furthermore, the measured insertion loss is comparable to that of a conventional branch-line coupler. The new coupler can be easily implemented by using the standard printed-circuit-board etching processes and is very useful for wireless communication systems.

Capacitively Loaded Circularly Polarized Implantable Patch Antenna for ISM Band Biomedical Applications

A single-fed miniaturized circularly polarized microstrip patch antenna is designed and experimentally demonstrated for industrial-scientific-medical (2.4-2.48 GHz) biomedical applications. The proposed antenna is designed by utilizing the capacitive loading on the radiator. Compared with the initial topology of the proposed antenna, the so-called square patch antenna with a center-square slot, the proposed method has the advantage of good size reduction and good polarization purity. The footprint of the proposed antenna is 10×10×1.27 mm3. The simulated impedance, axial ratio, and radiation pattern are studied and compared in two simulation models: cubic skin phantom and Gustav voxel human body. The effect of different body phantoms is discussed to evaluate the sensitivity of the proposed antenna. The effect of coaxial cable is also discussed. Two typical approaches to address the biocompatibility issue for practical applications are reported as well. The simulated and measured impedance bandwidths in cubic skin phantom are 7.7% and 10.2%, respectively. The performance of the communication link between the implanted CP antenna and the external antenna is also presented.

A NUMERICAL STUDY ON TIME-REVERSAL ELECTROMAGNETIC WAVE FOR INDOOR ULTRA-WIDEBAND SIGNAL TRANSMISSION

In this paper, the propagation of ultra-wideband (UWB) pulse based on time reversal (TR) technique is studied by finite- different time-domain method in indoor environment. Time compression and spatial focusing of TR waveform are simulated and the propagation of multi-waveform string is analyzed. Then UWB wireless signal transmission based on TR concept is studied numerically. The studied results indicate that the UWB communication based on TR technique can obtain better Inter-Symbol Interference (ISI) and Co- Channel Interference (CCI) performance than traditional one because of its unique property.

Pattern reconfigurable leaky-wave antenna design by FDTD method and Floquet's Theorem

A pattern reconfigurable millimeter-wave coplanar waveguide leaky-wave antenna is designed by using the finite-difference time-domain (FDTD) method combined with Floquets theorem and the simple linear interpolation technique. The concept of equivalent period is presented for mixed-periodic structures. The novel design process results in a reduction in the design time compared with that of the traditional FDTD method.