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2021-04-17 PIER Letters Vol. 97, 115-120, 2021. doi:10.2528/PIERL21031203

Frequency Reconfigurable Antenna with Dual-Band and Dual-Mode Operation

Ting-Yan Liu, Jun-Yan Chen, and Jeen-Sheen Row

A frequency reconfigurable antenna with dual-band operation is presented. The antenna has a circular radiating patch loaded with an annular slot, and the slotted patch is shorted to the ground plane with four conducting posts. The antenna has three feed ports. Two of the ports are used to excite the slot mode resonant at a lower frequency, and broadside radiation with dual orthogonal linear polarizations can be obtained. The other port is used to excite the monopolar-patch mode resonant at a higher frequency, and conical radiation with vertical polarization can be yielded. To reconfigure the operation frequencies, four varactors are symmetrically placed across the annular slot. The simulated results indicate that the resonant frequency of the slot mode can be tuned from 1.62 to 1.17 GHz when the capacitance of the varactors is varied from 0.6 to 1.8 pF; besides, for each capacitance value, the impedance bandwidth of the antenna operating in the monopolar-patch mode can cover the frequencies from 2.4 to 2.5 GHz. Experiments are also carried out to validate the simulated data.

2021-04-16 PIER Letters Vol. 97, 105-113, 2021. doi:10.2528/PIERL21022104

A Method for Thinning Useless Elements in the Planar Antenna Arrays

Jafar Ramadhan Mohammed

In this paper, the thinning space is constrained to only outer sub-planar array elements instead of fully filled planar array. Since the amplitude weights of the outer elements have small amplitude excitations, they can be optimized to find the least useful elements and remove them without affecting the desired radiation characteristics. The binary genetic algorithm is used to perform such thinning optimization. Simulation results show that roughly the same performance can be achieved when the number of removed elements in the outer sub-array relative to the total number of the planar array elements does not exceed 19%. In addition, to keep the size of the thinned array equal to that of the original filled array, the perimeter elements were excluded from the thinning process. Also, some constraints on the thinned array pattern are imposed to control the null directions toward interfering signals.

2021-04-12 PIER Letters Vol. 97, 95-103, 2021. doi:10.2528/PIERL21020604

Quad-Port Miniaturized Ultra-Wideband MIMO Antenna with Metal Vias

Qingzhi Yang, Kang Wang, and Yufa Sun

A miniaturized four-port multiple-input multiple-output (MIMO) antenna for ultra-wideband (UWB) applications is presented. The proposed UWB MIMO antenna has a compact size of 34 × 34 mm2. Four antenna elements are placed orthogonally, and the element is connected to the feed line through metal vias in the substrate. These metal vias increase the bandwidth of the high frequency part of the antenna. A T-shaped slit, a rectangular slit, and a triangular chamfer are etched on the ground between two adjacent antenna elements. The working bandwidth of the antenna is 2.5-11.6 GHz, covering the entire UWB application band. The isolation between antenna elements is more than 18 dB within the operating bandwidth. Details of the design methodology and results are presented and discussed. Envelope correlation coefficient is computed, and it is within the acceptable limit, which validates the design concept for building a compact MIMO antenna system with good performance.

2021-04-08 PIER Letters Vol. 97, 87-94, 2021. doi:10.2528/PIERL21030702

Highly Sensitive Polymer Based Fabry-Perot Interferometer for Temperature Sensing

Lashari Ghulam Abbas, Farhan Mumtaz, Yutang Dai, Ai Zhou, Wenbin Hu, and Muhammad Aqueel Ashraf

A highly sensitive temperature sensor based on a polymer cavity of a Fabry-Perot interferometer (FPI) is experimentally demonstrated. The interferometer gives ease in fabrication, and it can be formed by the induction of a thermos-sensitive polymer layer in between two single mode fibers (SMFs). The polymer is used as an FPI cavity for temperature sensing. Due to high thermal expansion coefficient (TEC) and thermos-optic coefficient (TOC) of polymer make the interferometer highly sensitive to ambient temperature. The maximum temperature sensitivity of 2.2209 nm/°C for the polymer FPI cavity of 40.61 µm in the ambient temperature range of 28°C to 34°C is obtained. The proposed sensor shows the advantages of high sensitivity, compactness, simple fabrication, and low cost. Thus, it may become a part of various practical applications in the field of environmental science and engineering sciences.

2021-04-08 PIER Letters Vol. 97, 77-85, 2021. doi:10.2528/PIERL21021003

A Novel Miniaturized Bandpass Filter Basing on Stepped-Impedance Resonator

Man Zhang, Minquan Li, Ping-Juan Zhang, Kaiyue Duan, Baokun Jin, Lichang Huang, and Yawen Song

This paper proposes a novel miniaturized bandpass filter by loading a stepped-impedance resonator (SIR). Owing to the intrinsic characteristic of SIR, a third-order bandpass filter with SIR is presented, which has a size reduction of 38% compared with the conventional hairpin-line filter. On account of the electrical tape gap effect of a defected ground structure (DGS), further miniaturization is realized by introducing a pair of complementary split-ring resonator (CSRR) DGSs. Besides, frequency selectivity and out-of-band rejection can be improved by adding CSRR DGS and source-load (S-L) coupling structures, which produce two transmission zeros at two side band of passband respectively. The results show that the passband range is 3.4-3.6 GHz, and the final size is reduced by 50.3%.

2021-04-07 PIER Letters Vol. 97, 69-76, 2021. doi:10.2528/PIERL21031501

Comparative Analysis of Electromagnetic Performance of Magnetic Gear

Xiaocun Huang, Yuxiu Guo, and Libing Jing

In order to investigate the influence of different magnetization modes on the electromagnetic performance of magnetic gear, four models of magnetic gear with different magnetization modes are established. The finite element method is used to simulate the four models and compare their performances. The distribution of magnetic flux lines, air gap magnetic field, harmonic distribution, static torque and dynamic torque are calculated, respectively. The simulation results show that the coaxial magnet gear with Halbach array has larger air gap flux density amplitude, smaller air gap harmonic content and higher output torque than the other three kinds of magnetic gears.

2021-04-06 PIER Letters Vol. 97, 61-68, 2021. doi:10.2528/PIERL21022601

Design of Low Profile Multiband Reflective Polarization Converter for Both Linear and Circular Polarized Waves

Surya Durga Padmaja Bikkuri and Alapati Sudhakar

This paper presents a multifunctional metasurface based reflective polarization converter, to convert the polarization of incident electromagnetic wave in three adjacent frequency bands. In the first band linear to circular polarization conversion and in the remaining two bands linear to orthogonal polarization conversion is achieved. The designed metasurface consists of two circular split rings and a star-shaped split resonator which is fabricated on a metal-backed dielectric substrate. From the simulation results, it is evident that the orthogonal linear polarization conversion band is observed at 9.2 GHz and 12.8 GHz with a polarization conversion ratio of more than 92%. Similarly, it is identified that the same metasurface converts the incident linear polarized wave to circularly polarized wave at 7.3 GHz. Furthermore, the proposed metasurface maintains the handedness of the circularly polarized incident wave at 9.2 & 12.8 GHz frequency upon reflection. The proposed multifunctional polarization converter has a simple planar geometry and low profile which can be used in many applications, such as reflector antennas, imaging systems, remote sensors, and radiometers.

2021-03-29 PIER Letters Vol. 97, 51-59, 2021. doi:10.2528/PIERL21012201

Compact Quarter Mode and Eighth Mode Substrate Integrated Waveguide Bandpass Filters with Frequency-Dependent Coupling

Zhiwei Shi, Guohui Li, Yulu Song, and Binbin Cheng

This paper presents two size-miniaturized quarter mode (QM) and eighth mode (EM) substrate integrated waveguide (SIW) bandpass filters (BPFs), which are embedded with a novel frequency-dependent coupling (FDC) structure. The proposed FDC is implemented as a composition of balanced folding lines and inductive iris. One additional transmission zero (TZ) introduced by FDC between two cavities leads to higher frequency selectivity and better out-of-band rejection. Higher order modes suppression appears by combining the loaded paired open stubs on feeder lines with FDC technique, achieving a wide stopband. Meanwhile, the circuit dimension is further reduced by symmetrically cutting SIW. To validate the novel approach, the frequency-dependent coupling matrix (CM) is implemented to determine characteristics of the proposed structure in theory, QM- and EM-SIW BPFs loaded with FDC have been designed, fabricated and measured. Experimental results illustrate the characteristics of miniaturization and good performance. All results are in good agreement.

2021-03-25 PIER Letters Vol. 97, 45-50, 2021. doi:10.2528/PIERL21030404

Matrix Splitting Technique for Solving Electromagnetic Scattering Problems Over a Wide Angle by Compressive Sensing

Qi Qi, Xin-Yuan Cao, Ming Sheng Chen, Zhi-Xiang Huang, and Xian-Liang Wu

By combining the method of moments and the compressive sensing theory, a rapid scheme for analyzing the electromagnetic scattering problems over a wide incident angle has been developed, by which the calculation times of traditional method of moments can be decreased efficiently. To further reduce the calculation times, the matrix splitting technique is proposed to establish a new scheme in this paper. The basic principle is elaborated in detail, and the effectiveness of the new scheme is verified by numerical results.

2021-03-23 PIER Letters Vol. 97, 35-43, 2021. doi:10.2528/PIERL20122601

An Online Extraction Method of Noise Source Impedance Based on Network Analyzer

Ming-Xing Du, Yang Li, Qiqi Dai, and Ziwei Ouyang

This paper presents an online noise source impedance extraction method based on network analyzer. Firstly, the composition scheme of the measurement method is given, the equivalent circuit model of the measurement system established, and the port structure of the equivalent circuit analyzed. Secondly, two known standard resistances are used to calibrate the measuring system and connecting wires. Finally, the passive device and DC/DC converter are used as the equipment to be tested, and the measurement results are compared with those of other methods and impedance analyzer. The comparison results show that the measurement method has high measurement accuracy and good temperature sensitivity.

2021-03-22 PIER Letters Vol. 97, 27-34, 2021. doi:10.2528/PIERL20112403

Fast Estimate of Plane Wave Attenuation of Conductive Powders for Rapid Deployment of Customized Cement Based Microwave Absorbing Solutions

Narayanan Sabarish and Madaswamy Jayakumar

Enhancing the electromagnetic absorption properties of pozzolanic cement provides scope for low cost realisation of frequency screened buildings. Electromagnetic wave attenuation attribute of conductive filler inclusions determines the absorption properties of filler loaded cement mortar. A transmission line based rapid measurement technique for the speedy estimate of microwave attenuation of conductive fillers is presented, providing quick approximates of cement mortar thickness for realizing customized absorption loss. Ash from three units of steel plant including EAF, AoD, and ARS units is investigated. Coaxial transmission line supports TEM propagation, hence is well suited for estimating plane wave characteristics. Ash filled coaxial transmission structures are subjected to scattering matrix measurements in the frequency range 800 MHz-4 GHz. Plane wave attenuation is estimated from the scattering matrix transfer coefficient (S21). Ashes guarantee minimum 10 dB/m attenuation in the specified frequency range with ash from ARS unit providing loss over 50 dB/m. The database of customized cement mortar (composite) thickness for realizing varied absorption losses, incorporating ARS ash, is projected. The presented technique reduces the requirement of anechoic chambers, broad band horns, and liability of prototyping large mortar samples (all frequency dependent), for estimating shielding properties of conductive filler loaded cement mortar composites, over wide band. Cement panels with customized absorption loss provide scope as low cost solution for managing device co-location issues encountered in evaluating EMI/EMC concerns is future IoT based systems.

2021-03-15 PIER Letters Vol. 97, 21-26, 2021. doi:10.2528/PIERL21012701

Design of a Compact Lowpass-Bandpass Diplexer with High Isolation

Seda Elden and Ali Kursad Gorur

In this paper, a novel compact lowpass-bandpass microstrip diplexer with high isolation is proposed. The proposed structure consists of a lowpass filter section and a bandpass filter section. The lowpass filter section is designed at a cut-off frequency of 2 GHz with sixth order elliptic filtering characteristics. The bandpass filter section is designed at 3.5 GHz by using a meandered dual-mode loop resonator (MDMLR). The MDMLR is coupled to input port by open circuited feeding lines. The lowpass-bandpass diplexer is formed by combining lowpass and bandpass filter sections without using an additional matching circuit. The designed lowpass-bandpass diplexer has been fabricated and measured in a very good agreement with the simulated results. Isolation between the output ports has been measured as better than 40 dB.

2021-03-15 PIER Letters Vol. 97, 13-19, 2021. doi:10.2528/PIERL21011902

A Terahertz Demultiplexer Based on Metamaterials Applied to Terahertz Communication Systems

Wu Pan, Xuewen Zhang, Yong Ma, Zhen Zhang, Xi Wang, Tao Shen, Yi Li, and Lihao Yang

This paper proposes a novel terahertz demultiplexer based on metamaterials. Its surface metal structure comprises double U-shaped structures and a rectangular wire. The demultiplexer can separate terahertz of 0.225 THz and 0.410 THz, with high isolations of 41 dB and 38 dB, low insertion losses of 0.07 dB and 0.11 dB, and stable group delays of 3.5 ps and 3.8 ps at the center frequency, respectively. The equivalent parameters of metamaterials are simulated, and the electric field, current, and power distribution characteristics at operating frequency points are analyzed. This metamaterial is easy to process and is expected to be applied in future 6G wavelength division multiplexing systems.

2021-03-10 PIER Letters Vol. 97, 7-12, 2021. doi:10.2528/PIERL21011303

Frequency Reconfigurable High Power GaN /AlGaN HEMT Based Self Oscillating Active Integrated Antenna

Rakhi Kumari, Ananjan Basu, and Shiban Kishen Koul

This paper presents two circuits for a high power GaN/AlGaN HEMT based self oscillating Active Integrated Antenna (AIA) using feedback topology. The first circuit, a fixed frequency high power source, is designed using a two-port T-coupled patch antenna in parallel feedback of a device. This circuit radiates 41 dBm power at 2.34 GHz frequency when being biased at Vgs = -2.1 V and Vds = 25 V. The second circuit, a frequency reconfigurable high power source, is designed using a frequency reconfigurable T-coupled two-port patch antenna in parallel feedback of a device. Frequency reconfigurability is achieved in the second circuit by adding one more strip and two pin diodes at both sides of centre patch of the two-port patch antenna. Change of biasing voltage of pin diodes changes the frequency of oscillation of the circuit. This circuit radiates 32.4 dBm power at 2.1 GHz when pin diodes are off and radiates 32 dBm power at 2.7 GHz when pin diode is on. To the best of our knowledge, the first circuit implemented radiates the highest power using single device whereas the second circuit is the first implementation of reconfigurable oscillating AIA in GaN and also delivers the same power in both states. Each circuit measures 80 mm x 80 mm.

2021-03-01 PIER Letters Vol. 97, 1-6, 2021. doi:10.2528/PIERL21010605

Microstrip Crossover on FR-4 Substrate

Takeru Inaba and Hitoshi Hayashi

This letter shows a compact planar microstrip crossover. The crossover design employs a microstrip to coplanar waveguide transition. The crossover is fabricated on a low cost and readily available FR-4 substrate, and simulation and measurement responses in the low frequency band have been shown. The number of GND vias forming a quasi-coaxial section that confined the electric field around the signal via was increased to improve impedance matching. The core size of the circuit is as compact as 20 mm × 10 mm even in the low frequency band. The crossover operates in the low frequency band with insertion loss of less than 1 dB, return loss of more than 10 dB, and isolation of more than 15 dB.