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2015-06-19 PIER Letters Vol. 53, 127-135, 2015. doi:10.2528/PIERL15030307

Compact Differential Bandpass Filters Based on Coupled-Line Resonators with Improved Performance and Miniaturized Size

Hui Wang, Yi Yang, Zhi-Hong Ren, and Cheng Feng

Two compact differential bandpass filters (BPFs) based on coupled-line resonators and loaded capacitors are proposed in this work. By properly designing the coupled resonator and the loaded capacitance of original filter model, differential-mode (DM) passband responses and common-mode (CM) rejection can be obtained .For validation, two differential BPFs named Filter I and Filter II are discussed and experimentally characterized. One more DM transmission zero generated by out-of-phase cross-coupling is employed to control the DM bandwidth and sharpen the selectivity in Filter I while lumped capacitors are loaded in Filter II to replace capacitive coupled resonators for miniaturized size. Both filters are centered at 4.5 GHz with about 9% DM fractional bandwidth (FBW), less than 1.5 dB insertion loss, more than 15 dB return loss, and wideband CM suppression with more than 18 dB rejection. Furthermore, the size of Filter II is substantially smaller than Filter I and previously reported differential BPFs.

2015-06-16 PIER Letters Vol. 53, 121-126, 2015. doi:10.2528/PIERL15042006

A Novel Dumbbell-Shaped Defected Ground Structure with Embedded Capacitor and its Application in Low-Pass Filter Design

Zhi-Yong Chen, Lin Li, and Si-Si Chen

A novel dumb-bell-shaped defected ground structure (DB-DGS) with embedded capacitor is presented in this paper. Compared with conventional DB-DB-DGS structure, the proposed DB-DGS exhibits many attractive characteristics including double resonance, high Q value and compact size. The equivalent lumped circuit model for the novel DGS is developed, and its parameters are extracted. Based on this new DB-DGS, a low-pass filter (LPF) using the novel DB-DGS has been constructed, which provides a more steep rejection property, a wider stopband and compact size. The proposed structure is experimentally verified through the demonstration of a low-pass filter design.

2015-06-02 PIER Letters Vol. 53, 115-119, 2015. doi:10.2528/PIERL15040701

Wideband Balun Bandpass Filter Based on Substrate Integrated Waveguide and CSRRs

Wenjie Feng, Shunyu Yao, Jialiang Shen, and Rui Cao

A high selectivity wideband balun bandpass filter based on substrate integrated waveguide (SIW) and complementary split rings resonators (CSRRs) is proposed. 180° reverse phase characteristic between the two output ports can be easily realized by the multi-layer SIW power divider. Eight complementary split rings resonators are used to achieve the sharp rejection upper stopband. The proposed wideband balun filter exhibits a fractional bandwidth of 37% centered at 9.45 GHz and amplitude and phase imbalance less than 0.5 dB and 1°.

2015-05-31 PIER Letters Vol. 53, 107-113, 2015. doi:10.2528/PIERL15033005

An Efficient Algorithm for the Novel Weakly Conditionally Stable FDTD Method

Qi Liu, Xi-Kui Ma, and Feng Chen

In this paper, we present an efficient formulation of the novel weakly conditionally stable finite-difference time-domain (NWCS-FDTD) method for the electromagnetic problems with very fine structures in one or two directions. The formulation is obtained by using only algebraic manipulation of the original method, and therefore the numerical stability and dispersion properties can be preserved. Moreover, due to its simpler right-hand sides of the updating equations, the proposed algorithm is more efficient than the existing WCS-FDTD methods, allowing a significant reduction in the cost of CPU time. Numerical experiments are finally given to verify the accuracy and efficiency of the proposed method.

2015-05-31 PIER Letters Vol. 53, 101-106, 2015. doi:10.2528/PIERL15042704

A Low-Complexity Dual-Band Model for Dual-Band Power Amplifiers Based on Volterra Series

Tianjing Zhang, Cuiping Yu, Yuan'an Liu, Shulan Li, and Bihua Tang

A novel low-complexity dual-band digital predistortion (2D-LCMP) model for linearization of dual-band power amplifiers (PAs) is proposed in this paper. The in-band intermodulation (IM) and cross-band modulation (CM) distortion terms in the prior two-dimensional models have different impacts on the model performance. Therefore, they are considered respectively in the proposed model. Some redundant distortion terms are removed away to decrease the model complexity. In addition, the nonlinearity order and memory depth are frequency dependent for each band. Experimental measurements were performed on two types of wideband PAs. The results prove the superiority of the 2D-LCMP model.

2015-05-28 PIER Letters Vol. 53, 95-100, 2015. doi:10.2528/PIERL15030401

Microstrip Monopolar Patch Antenna for Bandwidth Enhancement

Qiao Zhang, Tongbin Yu, and Jundong Ye

A microstrip monopolar patch antenna with shorting vias in the circular patch and coupled ring for bandwidth enhancement is proposed. The bandwidth of the proposed antenna with shorting vias in the annular coupled ring is over 40% wider than that of the antenna without shorting vias in the annular ring. The proposed antenna provides a wide bandwidth because of four resonant modes, including the TM01 mode of the circular patch, TM01 mode of the coupled annular ring, TM02 mode of the circular patch, TM02 mode of the coupled annular ring. These modes can generate a omnidirectional pattern in the azimuth plane like a monopole antenna. A prototype was fabricated to confirm the simulation verdictions. Measured results show that 10-dB return loss bandwidth of 38.4% from 4.42 to 6.52 and average gain of 5 dBi acrossing the operating band are achieved for the proposed antenna with a low profile of 0.027 wavelength.

2015-05-22 PIER Letters Vol. 53, 89-94, 2015. doi:10.2528/PIERL15040702

High Selectivity Differential Bandpass Filter Using Dual-Behavior Resonators

Xin Gao, Wenjie Feng, and Wenquan Che

A high selectivity differential bandpass filter (BPF) using two pairs of dual-behavior resonators (DBRs) is proposed in this letter. A high selectivity passband for the differential mode with second harmonic suppression is achieved, by utilizing shorted coupled lines with two short stubs. For the common-mode (CM) circuit, the CM responses can be suppressed over a wide frequency band by the loaded open/shorted stubs. To validate the feasibility of the proposed filter, a planar differential BPF (3-dB fractional bandwidth 4.9%) with good CM suppression is designed and fabricated. The theoretical and measured results agree well and show good in-band filtering performances and out-of-band harmonic suppression performances.

2015-05-22 PIER Letters Vol. 53, 83-88, 2015. doi:10.2528/PIERL15032403

A Compact Antenna Design for UHF RFID Applications

Bing Wang

This paper presents a new compact end-fire antenna for ultra-high frequency (UHF) radio frequency identification (RFID) applications. The antenna has two meandered dipole drivers. A folded reflector and a rectangular reflector are demonstrated. The advantage of the end-fire antenna with meander dipole drivers compared to the conventional quasi-Yagi antenna is a reduction in the length of the driver, which allows closer space for RFID reader. The end-fire antenna is fabricated on a FR4 printed circuit board (PCB), the dimension of the antenna is 81×58 mm2. The measured bandwidth is around 25 MHz (905-930 MHz) under the condition of VSWR less than 2. The maximum gain of the end-fire antenna is 3.2 dB. The advantages of the new antenna element are that it is more compact than conventional design and it is suitable for fabrication on low-cost, low dielectric constant materials. The antenna configuration, design, simulated and measured results have been well discussed. A good agreement is obtained between the simulated and experimental results. This new compact end-fire antenna is desirable for RFID reader applications.

2015-05-22 PIER Letters Vol. 53, 77-82, 2015. doi:10.2528/PIERL15030107

An Ultra-Wideband Twin-Patch Monopole Antenna with Band-Rejection Characteristic

Chao-Ming Wu and Yi-Hong Liu

To suppress electromagnetic interference at 5.5-GHz WLAN (5.15-5.825 GHz) band operation, a novel ultra-wideband (UWB) design of a slotted twin-patch monopole antenna with a band-rejection characteristic is presented. The proposed antenna with a simple structure has a large impedance bandwidth, defined by 10-dB return loss, covering the range from 2.95 to 10.85 GHz, and a tunable cutoff band from 5.18 to 6 GHz for band-operation suppression. Measured monopole-like radiation pattern and in-band average gain of about 2.3 dBi have also been obtained, simultaneously, with good agreement to the simulated results.

2015-05-19 PIER Letters Vol. 53, 71-76, 2015. doi:10.2528/PIERL15031703

Electromagnetically-Coupled Millimeter-Wave Antenna Array with Non-Uniform Distribution for 60 GHz ISM Applications

Osama Mohamed Haraz Ahmed

In this article, the design of an electromagnetically-coupled millimeter-wave elliptical patch array antenna prepared to work in the 56-65 GHz (14.8%) frequency band is presented. The introduced antenna array is designed for low-loss, high-gain and low cross-polarization levels. The proposed antenna exhibits a measured gain of 8 dBi and good linear polarization across the desired frequency range. It has a good side lobe suppression better than 17 dB in both E- and H-planes. Measured and simulated results confirm that this antenna is a good candidate for short-range wireless communication applications at millimeter-wave frequencies.

2015-05-15 PIER Letters Vol. 53, 65-70, 2015. doi:10.2528/PIERL15041601

A Dual-Band Bandpass Filter for 2.4 GHz Bluetooth and 5.2 GHz WLAN Applications

Lakhindar Murmu and Sushrut Das

In this paper a dual-band bandpass filter using loaded stub in the ring resonator and etched nested C-shape defected ground structure (DGS) on ground plane is reported. The operating frequencies of the bandpass filter are selected for applications in Bluetooth (2.4 GHz-2.484 GHz) and WLAN (5.15 GHz-5.35 GHz) systems. Due to its applications in WLAN and Bluetooth system the filter will be subjected to high EM radiation from the antenna and nearby sources. Therefore, susceptibility study of such filter is very important. The susceptibility study of the filter has been carried out by subjecting the structure to an interference source. Experimental results are presented and analyzed.

2015-05-15 PIER Letters Vol. 53, 57-63, 2015. doi:10.2528/PIERL15020204

A Simple Dual-Band Circularly Polarized Rectangular Dielectric Resonator Antenna

Meng Zou and Jin Pan

A simple slot coupled dual-band circularly polarized (CP) rectangular dielectric resonator antenna (DRA) is presented. The TE111 and TE113 modes of the rectangular DRA are excited by a modified annular slot. Working principle of the proposed antenna is explained in this paper. Design guideline of the proposed antenna is also devised based on the parameter study. The simple feeding and radiating structures of the proposed antenna make it easy to be designed and fabricated. A prototype antenna was designed, fabricated and measured. The simulated and measured results confirm the dual-band CP performance of the proposed antenna.

2015-05-01 PIER Letters Vol. 53, 51-55, 2015. doi:10.2528/PIERL15032702

A Novel Printed Helical Antenna for a Circularly Polarized Tilted Beam

Xiao-Qiang Yang, Ze-Hong Yan, Tian-Ling Zhang, and Binbin Fan

A new printed helical antenna (PHA) for a circularly polarized (CP) titled beam is proposed. With the introduction of a multiple sections technique into the PHA's helical arm, the antenna radiates a CP titled beam. To feed the antenna, a matching network composed of a 50 Ω microstrip transmission line and two symmetrical λ0/8 open stubs is designed. The simulated and measured results show that the PHA radiates a CP tilted beam with a maximum radiation direction of (θmax, φmax) = (32°, 135°) at f0 = 2.11 GHz. The measured bandwidth with a reflection coefficient lower than −10 dB is 11.8% (1.99-2.24 GHz), and the experimental results for the radiation pattern, gain, and axial ratio (AR) are also presented.

2015-04-27 PIER Letters Vol. 53, 45-50, 2015. doi:10.2528/PIERL15030902

A New Omnidirectional Circular Polarization Microstip Antenna

Kun Wei, Jian-Ying Li, Ling Wang, and Zijian Xing

The configuration of a new circularly polarized microstrip antenna with omnidirectional radiation pattern for GPS-L1 application is proposed in this paper. The designed antenna has a back-to-back rectangular-patch structure, and two patches are fed by coaxial cable connected with a Wilkinson power divider. The horizontal omnidirectional radiation pattern was achieved by both simulation and measurement. Axial ratio in the peak gain plane was around 3 dB ranging from 1.5 dB to 3.6 dB. The variation of RHCP gain in the horizontal omnidirectional circular polarization plane was smaller than ±1 dBic. And peak RHCP gain of the designed antenna was about 2.3 dBic.

2015-04-24 PIER Letters Vol. 53, 37-44, 2015. doi:10.2528/PIERL15031003

Miniaturized Microstrip Patch Antenna with Spiral Defected Microstrip Structure

Hanae Elftouh, Naima Amar Touhami, and Mohamed Aghoutane

Use of discontinuities in microstrip lines is currently employed to improve the performance of different passive circuits, including reduction of amplifiers, enhancement of filter characteristics and applications to suppress harmonics in patch antennas. This paper presents an improved method of size reduction of a microstrip antenna using Defected Microstrip Structure (DMS) that it is used to perform serious LC resonance property in certain frequency. The DMS is integrated in antenna structure, and therefore this method keeps the antenna size unchanged and makes a resonance frequency. This resonance is due to the abrupt change of current path of antenna that resonates at 5.8 GHz which is shifted to 2.69 GHz thanks to spiral DMS. A prototype of the antenna was fabricated with an FR4 substrate and tested.

2015-04-16 PIER Letters Vol. 53, 29-35, 2015. doi:10.2528/PIERL15020601

Planar Dual-Band Power Divider with Short-Circuited Stub

Xin Huai Wang, Yangbing Xu, Le Kang, Xiao Shuang Li, Wei Jian He, and Xiao-Wei Shi

A novel planar dual-band microstrip power divider is proposed in this paper. The circuit is composed of two sections of transmission line, short-circuited stub line and planar resistor, which can provide high isolation and good amplitude balance simultaneously at two frequencies. The closed-form equations are derived,and the design procedures of dual-band power divider are given. To Certify the validity, a proposed power divider was fabricated and measured at 950 MHz and 2200 MHz which might be applied to M and CDMA systems. Both theoretical and simulated results are given, which are in good agreement with the measured results.

2015-04-13 PIER Letters Vol. 53, 21-27, 2015. doi:10.2528/PIERL15013104

Novel Dual-Band Bandpass Filter Based on Shorted Rectangular Patch Resonator

Kuan Deng, Caiyue Wen, Fei Li, and Wenquan Che

A novel dual-band bandpass filter based on shorted rectangular patch resonator is proposed and experimentally studied. The resonant modes and frequencies of the shorted rectangular patch resonator are analyzed. Based on miniature structure of the new resonator, a novel dual-band bandpass filter with good out-of-band performance is designed for demonstration. The experimental results agree well with numerical simulations.

2015-04-10 PIER Letters Vol. 53, 13-19, 2015. doi:10.2528/PIERL15012006

Complex Impedance-Transformation Out-of-Phase Power Divider with High Power-Handling Capability

Lulu Bei, Shen Zhang, and Kai Huang

A novel 180˚ out-of-phase power divider with complex-source to complex-load impedance transformation and high power-handling capability is proposed in this paper. It is composed of three double-sided parallel-strip lines (DSPSLs), a conduct plane in the middle as common ground, and two resistors for heat sinking and high isolation. Based on the rigorous odd- and even-mode analytical methods, closed-form design equations about electrical parameters are obtained. To demonstrate our design theory, a practical three-layer out-of-phase power divider is designed, simulated and measured. The measured results show that the return losses |Sii| (i=1, 2, and 3) are all larger than 17 dB. The insertion loss |S21| (|S31|) is 3.6 dB (3.7 dB). The isolation |S23| is -24 dB, and the output phase difference is -177˚ at the operating frequency. Good agreements between the simulated and measured results verify our design theory.

2015-04-10 PIER Letters Vol. 53, 7-12, 2015. doi:10.2528/PIERL15020201

A Compact Wideband Bandpass Filter Using a Coupled-Line Quad-Mode Resonator

Lixia Nan, Yongle Wu, Weimin Wang, Shulan Li, and Yuan'an Liu

A novel, compact wideband bandpass filter based on an improved quad-mode resonator is proposed in this paper. Due to the usage of a coupled-line section, the resonator has a quad-mode behavior. The resonant frequencies can be tuned by regulating not only the electrical lengths, but also the characteristic impedances. Owing to the symmetry of the construction, even- and odd-mode analysis is utilized to analyze the proposed resonator. Finally, a wideband bandpass filter with 88% (2.1 to 5.4 GHz) relative bandwidth is designed, fabricated, and measured. The measured results are in good agreement with the simulated ones, which demonstrates the feasibility of the design approach.

2015-04-09 PIER Letters Vol. 53, 1-6, 2015. doi:10.2528/PIERL15022503

Dual-Band Slotted Patch Antenna with Defective Ground for WLAN/WiMAX Applications

Chao-Ming Wu, Jia-Wun Syu, and Wen-Chung Liu

A novel printed antenna with a slotted patch and a defected ground structure (DGS) for dual-band operation is presented. By inserting an I-shaped slot into the patch and defecting the ground plane, triple-mode resonance for achieving dual operation bands, especially an extremely wide bandwidth for the higher band, can be excited. The measured bandwidths are 100 MHz (2.38-2.49 GHz) and 2.94 GHz (3.4-6.34 GHz) for the lower and upper bands, respectively, which agree well with the simulation. The experimental average gains across the two operating bands are 1.0 and 3.9 dBi, respectively, with typical radiation patterns for a patch antenna having a defective ground. The proposed antenna with a compact size of only 22×25 mm2 sufficiently covers performance requirement of the 2.4/5.2/5.8 GHz WLAN and the 3.5/5.5 GHz WiMAX operation systems.