Huiqing Zhai

Compact UWB Band-Notched Antenna Design Using Interdigital Capacitance Loading Loop Resonator

In this letter, a new compact ultrawideband (UWB) antenna with band-notched characteristic is proposed for UWB communication applications. By using a C-shaped ground, the overall dimension of the proposed antenna is dramatically decreased to 24 × 28 × 1 mm3. To avoid potential interferences, interdigital capacitance loading loop resonator (IDCLLR) is utilized to reject certain bands within the passband of the antenna. Due to its high capacitance, the resonator has a smaller size and forms a narrower notched band than many other structures, thus the present design effectively saves many more useful frequencies. Good agreement is achieved between the simulation and measurement, which shows that the proposed antenna has an operation frequency band from 3 to 13 GHz with good rejection to the wireless local area network bands (WLANs) (5.2- and 5.8-GHz bands).

A Triple-Band Ultrathin Metamaterial Absorber With Wide-Angle and Polarization Stability

This letter presents a triple-band compact and efficient ultrathin metamaterial absorber with wide-angle and polarization stability. The compact single unit cell includes a metallic background plane, four groups of dipoles lying around a metallic ring connected by four groups of pins, and only 1-mm low-cost dielectric layer. In addition, the main parameters of the designed absorber are investigated and optimized to show that each of three absorption frequency points can be effectively separately adapted, respectively. The simulation results demonstrate that this absorber has good absorption rates and polarization-insensitive characteristic over wide angles of incident waves for both transverse electric (TE) and transverse magnetic (TM) in three frequency bands. The waveguide measurement method is utilized to test the simulated results of three good absorption peaks.

CPW-Fed S-Shaped Slot Antenna for Broadband Circular Polarization

In this letter, a new broadband circularly polarized (CP) printed-slot antenna fed by a coplanar waveguide (CPW) is designed and fabricated. To achieve a broadband CP wave, an S-shaped slot is employed in the ground to produce orthogonal surface currents for right-hand circular polarization (RHCP). Furthermore, an L-shaped radiator is introduced to obtain a broad impedance bandwidth that can cover the whole CP bandwidth completely. Good agreement is achieved between the simulation and measurement, which shows that the presented antenna covers an impedance bandwidth (S11 <; -10 dB) of 104% from 1.78 to 5.64 GHz, and a 3-dB axial-ratio bandwidth (ARBW) of 58.6% from 2.85 to 5.21 GHz. The surface current analysis and a parametric study of the design are also carried out to explain the mechanism of circular polarization.

Compact UWB Antenna With Tunable Band-Notched Characteristic Based on Microstrip Open-Loop Resonator

A compact ultrawideband (UWB) antenna with an electronically tunable notched band is proposed for UWB communication applications. The proposed antenna utilized a C-shaped ground to realize miniaturization and a pair of open-loop resonators (OLRs) to create notched band. The center frequency of the notched band can be electronically tuned by changing the effective electrical length of the OLRs, which is achieved by employing varactor diodes. A prototype with an overall size of 24 × 28 mm2 was constructed, and good agreement has been obtained between simulation and measurement. The experimental results show that, for a varactor diode capacitance approximately ranging from 0.63-2.67 pF, a continuous tuning notched band range from 5.1 to 5.9 GHz is achieved.

A Compact Antenna With Broad Bandwidth and Quad-Sense Circular Polarization

A new compact antenna design with broad bandwidth and quad-sense circular polarization (CP) is presented in this letter. The broadband property is achieved based on a compact monopole structure. Furthermore, the quad-sense CP wave is obtained by a ground plane embedded with a T-shaped slit (TSS) and an annular patch etched by an X-shaped slit (XSS). Good agreement is achieved between the simulation and measurement, which shows that the presented antenna covers the impedance operations from 3.1 to 22.2 GHz ( S11 <; -10 dB), reaching the particularly broad bandwidth of 150%. Moreover, the design achieves good CP waves at Worldwide Interoperability for Microwave Access (WiMAX) (3.626-3.772 GHz) for left-hand CP (LHCP), the wireless local area network band (WLAN) (4.951-5.18 GHz) for right-hand CP (RHCP), X-band (10.9392-11.0456 GHz), and Ku-band (15.14-17.2 GHz) for LHCP. Simulated and measured results show that the CP 3-dB axial-ratio (AR) bandwidths are 4.02%, 4.51%, 1%, and 12.74% with a parasitic notch at the frequency of 17.75 GHz to realize good CP characteristics in quad bands.

DESIGN OF A COMPACT UWB ANTENNA INTEGRATED WITH GSM/WCDMA/WLAN BANDS

In this research, a compact printed antenna design operating on ultra-wideband (UWB) and three extra wireless communication bands is proposed. An ellipse-shaped monopole is utilized to realize UWB application (3.1{10.6GHz). The modifled ground employs three folded Capacitive Loaded Line Resonators (CLLRs) to obtain triple relatively lower communication bands, including parts of global System for Mobile Communications (GSM) band at the centre frequency of 1.78GHz, Wideband Code Division Multiple Access (WCDMA) band at the centre frequency of 2.15GHz, and Wireless Local Area Networks (WLAN) band at the centre frequency of 2.4GHz. The CLLRs are designed with quarter- wavelength to control the corresponding frequencies independently. Good agreement is achieved between the simulation and measurement to verify our presented design. The basic, dual-, triple-band UWB antennas are also simulated and good results are obtained. Small group delay variations across UWB frequencies are obtained for the presented antenna and reference antennas, with some level of distortion observed.

Frequency-Reconfigurable Bow-Tie Antenna for Bluetooth, WiMAX, and WLAN Applications

A frequency-reconfigurable bow-tie antenna for Bluetooth, WiMAX, and WLAN applications is proposed. The bow-tie radiator is printed on two sides of the substrate and is fed by a microstripline continued by a pair of parallel strips. By embedding p-i-n diodes over the bow-tie arms, the effective electrical length of the antenna can be changed, leading to an electrically tunable operating band. The simple biasing circuit used in this design eliminates the need for extra bias lines, and thus avoids distortion of the radiation patterns. Measured results are in good agreement with simulations, which shows that the proposed antenna can be tuned to operate in either 2.2-2.53, 2.97-3.71, or 4.51-6 GHz band with similar radiation patterns.

Isolation-Improved Dual-Band MIMO Antenna Array for LTE/WiMAX Mobile Terminals

A compact dual-band multiple-input-multiple-output (MIMO) antenna array with eight elements is proposed for the Long Term Evolution (LTE)/Worldwide Interoperability for Microwave Access (WiMAX) mobile applications. The dual-band MIMO array consists of four U-slit etched planar inverse-F antennas (PIFAs) and four L-slit etched PIFAs. The two types of PIFAs are placed orthogonally to reduce mutual coupling between them. With the presented decoupling methods in the design including the disconnection of ground plane, the parasitic resonant strips, and also the modified PIFAs, the excellent element isolation (above 20 dB) and other good MIMO performance are achieved. The overall dimension of the MIMO system is only 140 × 70 × 9.55 mm 3, and good return loss (above 10 dB) is achieved across the operating bands (2.6-2.8 and 3.4-3.6 GHz) for all the PIFA elements. The radiation patterns and envelope correlation coefficient (ECC) of MIMO system are also studied, showing quasi-omnidirectional radiation and accepted envelope correlation coefficient across the dual-band operation for mobile communications.

AMC-Loaded Wideband Base Station Antenna for Indoor Access Point in MIMO System

Wideband indoor base station antenna (operating at 5.2 /5.8 GHz WLAN and 5.5 GHz WiMAX), loaded with artificial magnetic conductor (AMC), is proposed for multiple-input multiple-output (MIMO) system. The MIMO system has sixteen elements, and each element has a pair of folded dipoles, fed by a coupling E-shape microstrip feedline. Periodical AMC surfaces are introduced underneath the dipole elements to achieve unidirectional radiation and low profile. They also contribute to antenna miniaturization and bandwidth enhancement. The MIMO system has the advantages of wide bandwidth, good isolation, enhanced radiation, and low correlation, all within a compact volume. The MIMO array was fabricated and tested, and the results are in good agreement with those of the simulations.

Frequency-Reconfigurable Quasi-Sierpinski Antenna Integrating With Dual-Band High-Impedance Surface

This paper proposes a new frequency-reconfigurable antenna (FRA) which consists of quasi-Sierpinski fractal dipoles integrating with a dual-band high-impedance surface (HIS). The antenna can operate in three frequency bands, i.e., X-band, Ku-band, and Ka-band, by changing the states of two switches. In order to achieve a low-profile design and good front-to-back radiation ratio, a dual-band HIS is presented as a reflector. The HIS is composed of an array of square patches with etching square slots, which has two in-phase reflection bands for X-band and Ku-band and can be viewed as an artificial magnetic conductor, while as a metallic electric conductor in Ka-band. So the antenna has a unified profile of 2 mm for different reconfigurable frequency bands. An ideal switch prototype of FRA was simulated, and practical PIN switch models of FRA and 2 × 2 FRA array with bias lines were fabricated and tested to verify the reconfigurable property of the proposed antenna.