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2015-03-04 PIER Letters Vol. 51, 127-133, 2015. doi:10.2528/PIERL14121302

Novel Tri-Band Bandpass Filter with High Selectivity

Liangzu Cao and Lixia Yin

This paper presents a tri-band bandpass filter (BPF) consisting of a wide BPF and two narrow bandstop filters (BSFs). BPF is a ninth-order interdigital structure, and BSFs are designed fifth-order series resonators with quarter wavelength transmission line connected. The selectivity of BPF and the bandwidth of BSF are analyzed using simulation software. A tri-band BPF, made of metal cavities, is designed and measured. Three passbands are located in 1.332~1.401 GHz, 1.443~1.458 GHz, 1.506~1.660 GHz, and insertion losses in passbands are less than 2.1 dB. Ratios of Δf40 dBf3 dB are 1.9, 2.67 and 1.33, respectively, and isolation between passbands is more than 75 dB. The good agreement between the simulated and measured results validated the proposed structure.

2015-02-26 PIER Letters Vol. 51, 119-125, 2015. doi:10.2528/PIERL14102105

Experimental Study of a Low-Cost Radiometer for Hostile Scenarios

German Leon and Angel G. Martino

Noncontact temperature measurements in industrial scenarios present great variety of difficulties (dust, vapor...). In this work, the authors study the use of a low-cost microwave power radiometers to measure the temperature of hot metal plate during its cooling with water. Two different radiometer, centred at different frequency bands, have been experimentally considered. The radiometers have been surrounded with a metal box to reduce undesirable radiation. Several experiments have been carried out, showing the ability of these radiometers to detect the cooling of the plates. A recalibration of the radiometers gain can be done to compensate the gain variation of the circuitry of the radiometers.

2015-02-23 PIER Letters Vol. 51, 117-118, 2015. doi:10.2528/PIERL15012108

A Note on DAS's PCA in Online Phases

Yu-Dong Zhang, Shuihua Wang, Genlin Ji, and Jie Yan

PCA was effective and helpful in developing a classification system. However, it was inappropriate to perform two independent PCA models on ground truth images and query image, which was described in Figure 1 in Reference ``BRAIN MR IMAGE CLASSIFICATION USING MULTISCALE GEOMETRIC ANALYSIS OF RIPPLET, Progress in Electromagnetics Research, 137, 1-17, 2013''. In this note, we analyze the reason and revise Figure 1.

2015-02-14 PIER Letters Vol. 51, 109-115, 2015. doi:10.2528/PIERL14121701

An Improved Wideband 180-Degree Hybrid Applied to Balanced Mixer

Wei Zhao, Yong Zhang, Shuang Liu, Li Li, and Rui-Min Xu

In this paper, an improved wideband millimeter-wave 180° hybrid is proposed to apply to balanced mixers and multipliers. The proposed hybrid consists of a transition of standard waveguide to suspended coplanar waveguide (SCPW) and a transition of SCPW to suspended stripline. According to the inherent electromagnetic field characteristics of the two transitions, the proposed hybrid has merits of broadband power distribution and high isolation, which does not rely on resonant circuits. The measured insertion losses and isolation of two transitions at Ka-band are typically 1.4 dB and 25 dB, respectively. To verify the application of the proposed hybrid, A W-band single balanced mixer based on the hybrid has been designed and fabricated. The measured single-sideband (SSB) conversion losses of the fabricated mixer are less than 9.5 dB for the radio frequency (RF) range from 80 to 108 GHz. The presented hybrid has been proven to be efficient for the design of millimeter-wave balanced mixers and could be well applied in multipliers and other integrated circuits.

2015-02-14 PIER Letters Vol. 51, 101-107, 2015. doi:10.2528/PIERL14120902

Analysis of Complex Discontinuities in Circular Waveguides Using Hybrid Finite Element Method and Multimodal Variational Method

Mohamed Yahia, Junwu Tao, and Hedi Sakli

We propose a hybrid multimodal variational method (MVM) and finite element method (FEM) to the analysis of complex 2D discontinuities in circular waveguides. The finite element method characterizes waves in arbitrarily shaped discontinuities, and the total response of the circuit is obtained by applying the multimodal variational method. The proposed hybrid method is successfully applied to the full-wave analysis of discontinuities with great practical interest (i.e., circular, crossshaped, off-centered, ridged, multi-aperture irises, etc.), thus improving CPU time and memory storage against several full-wave finite element method based computer aided design (CAD) tools (i.e. HFSS High Frequency Structural Simulator).

2015-02-14 PIER Letters Vol. 51, 95-99, 2015. doi:10.2528/PIERL14121507

Homogenization of Periodic Objects Embedded in Layered Media

Teng Zhao, Ji-Ming Song, Telesphor Kamgaing, and Yidnekachew S. Mekonnen

An effective medium modeling technique is proposed to homogenize the periodic objects embedded in layered media. The homogenization is based on the same scattering coefficients. An integral equation based approach is adopted to solve the scattering problem of original structures. Our modeling results are compared with Maxwell-Garnett mixing formula and published results. Good agreements have been observed. Periodic metal patches embedding in layered dielectric structure is fabricated and measured to validate the modeling technique. The difference between experiment results and proposed modeling results is less than 3%.

2015-02-05 PIER Letters Vol. 51, 87-93, 2015. doi:10.2528/PIERL15010901

Design of Compact Quad-Channel Diplexer Using Quad-Mode Stub-Loaded Resonators

Lei Lin, Yu-Tong Zhao, Bian Wu, and Chang-Hong Liang

In this paper, a compact quad-channel diplexer utilizing quad-mode stub-loaded resonators (QMSLRs) is proposed. The proposed quad-channel diplexer is composed of two dual-band bandpass filters (BPFs) based on QMSLRs and source-load coupling lines. Due to the symmetry of the proposed quad-mode resonator, its resonance characteristics are analyzed by using the even-odd-mode method twice. All four modes equivalent circuits of the resonator are quarter wavelength resonators, so the circuit size can be very compact, and the first resonance frequencies is three times of the fundamental ones. Stub-to-stub coupling is introduced to split two identical resonance modes, which is in favor of implementing dual-band BPF by using a single quad-mode resonator. By tuning the corresponding physical dimensions of the stubs, the resonant modes can be individually adjusted. The source-load coupling lines are properly designed to provide appropriate external coupling for the passbands and high isolation level between channels. For demonstration, a quad-channel diplexer (0.9/1.2 GHz at Load 1 and 1.5/1.8 GHz at Load 2) using the quad-mode resonator is designed, fabricated and measured. The simulated and measured results with good agreement are presented.

2015-01-30 PIER Letters Vol. 51, 79-85, 2015. doi:10.2528/PIERL14122302

A Novel Compact Dual-Wideband Bandpass Filter with Multi-Mode Resonators

Jun Li, Shan Shan Huang, Hui Wang, and Jian Zhong Zhao

A novel compact dual-wideband bandpass filter (BPF), with two multi-mode resonators (MMRs), a quad-mode one (QMR) and a triple-mode one (TMR), is proposed in this paper. The first passband is generated by a QMR loaded with a short-ended stub and two open-ended stubs, and the second one is realized by a TMR loaded with a square ring and a short-ended stub. Each passband can be tuned separately by controlling the corresponding resonator. The classical even-/odd-mode analysis is applied to characterize the presented MMRs due to their symmetric configurations. In order to validate the design methodology, a dual-wideband BPF prototype centered at 2.34 and 3.46 GHz with fractional bandwidths of 25.6% and 21.4% for WLAN and WiMAX applications is designed, fabricated and measured. Measurements have good agreement with simulations.

2015-01-22 PIER Letters Vol. 51, 73-78, 2015. doi:10.2528/PIERL14122105

Very Compact Open-Slot Antenna for Wireless Communication Systems

Ali A. Al-Azza, Frances Harackiewicz, and Hemachandra Reddy Gorla

A new very compact open slot antenna for wireless communication systems application has been designed and fabricated. With antenna overall dimension of 9.2 x 9.8 mm2, the proposed design can be used in many modern communication devices with size constraints. Experimental measurements have also been performed to validate the performance of the proposed antenna. The measured results show that the antenna provides a wide bandwidth of 48% (5-8.17 GHz) with an average size reduction of about 88% with respect to a conventional microstrip patch antenna.

2015-01-19 PIER Letters Vol. 51, 67-72, 2015. doi:10.2528/PIERL14121510

Wideband Planar Inverted-F MIMO Antenna with High Isolation

Zhaoyang Tang, Bo Wang, Ying-Zeng Yin, and Ruina Lian

A wideband planar inverted-F MIMO antenna with high isolation is proposed in this letter. The proposed MIMO antenna consists of two back-to-back planar inverted-F antennas and a fork-shaped de-coupling stub. The two planar inverted-F antennas are merged together with a shorting strip connected to the ground plane. In order to enhance the isolation, a fork-shaped decoupling stub connected to the ground plane through shorting pins is introduced, and the impedance matching is significantly improved simulta-neously. The proposed antenna prototype is fabricated and measured, and a compact size of 28×26 mm2 makes the proposed antenna be easily integrated in a MIMO system. Measured results show that the measured bandwidth for |S11| less than -10 dB covers from 5.05 GHz to 6.23 GHz, and the measured isolation is higher than 20 dB in the whole working frequency band.

2015-01-16 PIER Letters Vol. 51, 61-66, 2015. doi:10.2528/PIERL14120601

Dual-Band Bandpass Filter with Wide Upper Stopband Using Novel Stepped Impedance Stub-Loaded Quad-Mode Resonator

Lei Lin, Zhenlong Zhang, Shou Jia Sun, and Chang-Hong Liang

This paper presents a wide upper stopband dual-band bandpass filter (BPF) with controllable passband frequencies and bandwidths as well as a high out-of-band rejection level. The proposed filter is realized by utilizing a novel stepped impedance stub-loaded quad-mode resonator. All the four-mode equivalent circuits of the resonator are quarter-wavelength stepped impedance resonators (SIRs), and their fundamental resonance frequencies are used to form the passbands, so the designed filter has a compact circuit size. By controlling the impedance and length ratios of the stubs of the resonator, wide upper stopband performance is obtained. Hook-shape feed-lines and source-load coupling are applied to provide appropriate external coupling and generate three extra transmission zeros, which greatly improve the selectivity of the proposed filter. An experimental filter operating at 1.5 and 3.5 GHz is designed, fabricated, and measured for validation. The measured results have good agreement with the simulated ones.

2015-01-15 PIER Letters Vol. 51, 53-59, 2015. doi:10.2528/PIERL14120906

Omnidirectional Low-Profile Multiband Antenna for Vehicular Telecommunication

Woncheol Lee, Yang-Ki Hong, Jae-Jin Lee, Ji-Hoon Park, and Wonmo Seong

An omnidirectional low-profile multiband antenna is designed and fabricated for vehicular telecommunication applications. The fabricated antenna with a radiator patch size of 0.26λL×0.3λL has a low-profile of 0.022λL and shows multiple resonant frequencies at 1.14, 1.91, and 2.45 GHz. Omnidirectional radiation patterns in the azimuth plane and vertical polarization at all operating frequency bands were obtained. Antenna gains greater than 1.7 dBi were obtained at the three operating frequencies, and the antenna height is 6 mm. Therefore, the proposed antenna is applicable to the vehicular telecommunication system.

2015-01-09 PIER Letters Vol. 51, 47-52, 2015. doi:10.2528/PIERL14120503

Joint Self-Adaptive Correlation Method and Modified Empirical Mode Decomposition for Soft Defect Detection in Cable by Reflectometry

Soumaya Sallem and Nicolas Ravot

In a previous paper, we have introduced an innovative approach called the self-adaptive correlation method (SACM). It consists in treating the reflectogram in order to amplify the signatures of soft defects and make them more easily detectable. This method allows to highlight the soft defect while attenuating the noise present on the reflectogram and has the advantage of reducing the computational complexity compared to the state of the art. We drew attention to the sensitivity of the performance of this method to noise. In this paper, we propose a solution for the pre-denoising of reflectogram before applying the SACM. This solution consists of an adapted version of the empirical mode decomposition algorithm, we called MEMD for Modified Empirical Mode Decomposition which bypasses some limitations of the conventional EMD.

2015-01-08 PIER Letters Vol. 51, 39-45, 2015. doi:10.2528/PIERL14112604

A Simple Nanoscale Plasmonic Square-Shaped Ring Resonator Waveguide

Ya-Li Yan, Guang Fu, Yu Zhang, Shu-Xi Gong, and Xi Chen

A novel surface plasmon based square-shaped ring resonator with bending metaldielectric-metal input/output (I/O) waveguide at optical spectral range is investigated. The influence of various geometric parameters is studied in detail, with parallel finite difference time domain method. The results validate that vertical coupling disturbance can be efficiently suppressed by employing the modified I/O structure. The transmittance performance has all the resonant frequencies workable with better extinction ratios, higher finesse and higher Q-factors compared to the original plasmonic micro-ring resonator. From these analyses, it is found that the proposed waveguide is outstanding in aspects of the total field extinction and frequency selectivity characteristic.

2015-01-04 PIER Letters Vol. 51, 33-37, 2015. doi:10.2528/PIERL14101602

Compact Balanced UWB BPF Based on HMSIW and D-DGS

Jiao Li, Chen Ding, Feng Wei, and Xiao-Wei Shi

A compact balanced UWB bandpass filter (BPF) is proposed in this paper, which is based on the half-mode substrate integrated waveguide (HMSIW) and the differential defected ground structure (D-DGS). Using the HMSIW, the filter can achieve compact size, wide passband and good compatibility. Two D-DGS cells are employed to provide good suppression for the common-mode (CM) noise, while they have small effect on the performance of differential-mode (DM) signals. To validate the design theory, a microstrip balanced UWB BPF is designed, fabricated and measured to meet compact size, low insertion loss, good return loss as well as proper bandwidth. The predicted results are compared with measured data and show reasonable agreement.

2014-12-30 PIER Letters Vol. 51, 27-31, 2015. doi:10.2528/PIERL14112004

Dual-Band Dual-Polarized Circular Microstrip Patch Antenna with the Curved Slots on the Ground

Dan Yu, Shu-Xi Gong, Yunxue Xu, and Yang-Tao Wan

A center-feed dual-band dual-polarized circular microstrip antenna employing the curved slots on the ground is proposed. The proposed antenna radiates φ-polarization by introducing 10 units of curved slots symmetrically on the ground and θ-polarization by the coaxial probe at the center. The measured results show that the proposed antenna provides two resonant bands, TM01 and TM02 modes, covering the frequency bands of the WLAN (2.4-2.484 GHz) with an omnidirectional right-handed circular polarized (RHCP) radiation pattern and the WiMAX (3.3-3.6 GHz) with an omnidirectional horizontal polarized radiation pattern, respectively. In addition, the effects of the unit number of the curved slots and the width of the slots on the frequency ratio of these two resonant frequencies are studied. Furthermore, for the low profile of 0.056 λ0 and good omnidirectional characteristic, the antenna is suitable for the modern multi-band wireless communication systems.

2014-12-30 PIER Letters Vol. 51, 21-26, 2015. doi:10.2528/PIERL14101304

Focusing Properties of Hypergeometric Gaussian Beam through a High Numerical-Aperture Objective

Ji Peng, Zhengye Shan, Yangsheng Yuan, Zhifeng Cui, Wei Huang, and Jun Qu

The focusing properties of radially polarized hypergeometric Gaussian beam are studied using the Richards-Wolf vectorial diffraction model. Such a polarized beam is decomposed into radial and longitudinal polarization. With a proper combination of the beam order, beam size and imaginary parameter variables, the adjustably confined flat-topped focus and focal hole can be obtained in the focal region. Moreover, we got originality characteristic for the axial intensity distribution of two shaped symmetric light spots. The tight focusing of a hypergeometric Gaussian beam may find applications in data storage, laser drilling, optical trapping, etc.

2014-12-26 PIER Letters Vol. 51, 15-20, 2015. doi:10.2528/PIERL14112104

A Dual-Polarized MIMO Antenna with EBG for 5.8 GHz WLAN Application

Xiao-Yan Zhang, Xinxing Zhong, Bincheng Li, and Yiqiang Yu

A dual-polarized multiple-input-multiple-output (MIMO) antenna integrated with electromagnetic band-gap (EBG) is proposed. The MIMO antenna consists of two dual-polarized (0°and 90° polarizations) antenna elements. Each element includes four symmetrical arc-shaped slots. A mushroom-shaped EBG structure with four slots at its fringe is designed to enhance the gain of MIMO antenna. The bandwidth (return loss > 10 dB) of the proposed antenna is from 5.70 to 5.93 GHz, and the peak gain is 5.45 dBi. The isolation between the ports of adjacent antenna elements can be as small as less than -20 dB. The dual-polarized MIMO antenna with EBG has a compact volume of 44.5×77.5×1.6 mm3 and canbe suitable for 5.8 GHz WLAN application.

2014-12-26 PIER Letters Vol. 51, 7-14, 2015. doi:10.2528/PIERL14100901

Dual-Helix Monopole Antenna with Circular Polarization Operation for Minimally Invasive Surgery System

Jui-Han Lu, Yuan-Chih Lin, and Hao-Shiang Huang

A novel dual-helix monopole antenna with circular polarization (CP) operation is proposed. By utilizing a pair of asymmetrical strip-sleeves shorted at the ground plane, the proposed CP design at 2.45 GHz ISM band can easily be achieved and provides the impedance bandwidth (RL≧10 dB) about 240 MHz and the 6 dB axial-ratio (AR) bandwidth about 126 MHz. The measured peak gain and radiation efficiency are about 9.1 dBic and 81% across the operating bands, respectively.

2014-12-26 PIER Letters Vol. 51, 1-6, 2015. doi:10.2528/PIERL14102804

Compact Multilayer Hybrid Coupler Based on Size Reduction Methods

Young Kim and Youngchul Yoon

This paper presents a compact multilayer hybrid coupler based on a microstrip viatransition and short transmission line with a capacitor on each side to reduce circuit size. The microstrip via-transition is connected to two microstrip lines in different layers to configure a sandwich structure. To reduce the passive component circuit size, the design method uses a microstrip via-transition and a short transmission line with capacitors on each side. To validate the microstrip via- transition and short transmission line with capacitor, a multilayer hybrid coupler is implemented at a center frequency of 2 GHz. The measured characteristics agreed well with the simulation results, and above 90% circuit-size reduction compared with conventional couplers was realized.