Guihong Li

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).

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.

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.

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.

A Nesting-L Slot Antenna With Enhanced Circularly Polarized Bandwidth and Radiation

In this letter, a new coplanar waveguide (CPW)-fed circularly polarized (CP) antenna with enhanced bandwidth and radiation is proposed for IEEE 802.16 Worldwide Interoperability for Microwave Access (WiMAX) and IEEE 802.11a wireless local area network (WLAN) applications. By protruding a symmetric T-type strip from CPW feedline, a broad input impedance bandwidth is obtained. To widen CP radiation bandwidth, a nesting-L slot (NLS) structure is introduced in the ground. The NLS is formed by an L-shaped perturbation implanted in the corner of an initial L-slot. The CP radiation bandwidth is enhanced by merging the first and second bands. The first band is generated by the initial L-slot, whereas the second band is obtained by the L-shaped perturbation. According to the measured results, the 10-dB return-loss bandwidth is about 110%, and the 3-dB axial-ratio bandwidth (ARBW) is about 60.9%. Finally, by placing a reflector underneath the antenna, one can obtain unidirectional radiation patterns with greatly improved gains.

Novel Dual-Mode Dual-Band Bandpass Filter Using Microstrip Meander-Loop Resonators

A novel dual-mode dual-band bandpass filter using meander-loop resonators is proposed in this letter. Different meander-loop resonators are operated for respective passbands. Several finite attenuation poles in stopbands are realized to improve the selectivity of the proposed bandpass filter and isolation between the two passbands. Compact size, dual band and high selectivity characteristics are realized by this type of filter structure. The filter is evaluated by experiment and simulation with very good agreement.

Novel Design of Dual-Mode Bandpass Filter With Triangular Structure

A novel dual-mode bandpass filter based on conventional triangular structure is designed in this paper. The filter has the characteristics of compact structure, low insertion loss and so on. Several attenuation poles in the stopband are realized to improve the selectivity of the proposed bandpass filter. The experimented results were in good agreement with simulated results.