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2021-06-15 PIER Letters Vol. 98, 61-68, 2021. doi:10.2528/PIERL21042901

Bandpass Filters Based SIW Square Cavity with Novel Feeding and Coupling Schemes

Bo Yin, Qianqian Huang, and Xiangyu Shi

This paper presents two novel different feeding and coupling schemes to solve the problem of generating transmission zeros (TZ) in lower stopband and their applications to design single-band filters. The designed two filters are based on substrate integrated waveguide (SIW) square cavity with orthogonal ports. In the design of Filter A, two L-shaped stubs are introduced to form an addition coupling path between two ports, which cause the generation of one TZ. Other two TZs are formed due to the resonance characteristics of L-shaped stubs and ports offset. Two metal vias are used to adjust center frequency slightly. In the design of Filter B, other two stubs are designed to form two additional coupling paths, thus forming a total of three coupling paths with the original path. Two TZs are obtained by utilizing the phase difference between different paths, and one TZ is generated for the resonance characteristics of the proposed stub 3. Simultaneously, an L-shaped slot is used to adjust center frequency. Both designed filters use the coplanar waveguide (CPW) structure to control bandwidth. Two filters are set to operate at 14.4 GHz with bandwidth of 800 MHz. Both filters are fabricated and measured. The simulation results of two filters are in good agreement with the measured ones.

2021-06-07 PIER Letters Vol. 98, 55-60, 2021. doi:10.2528/PIERL21050203

Surface-Mount PIFA Using Ball Grid Array Packaging for 5G mmWave

Xi Wang, Xiubo Liu, Wei Zhang, Dongning Hao, and Yanyan Liu

In this letter, a surface-mount planar inverted-F antenna (PIFA) is proposed for the 5G mmWave system using ball grid array packaging (BGA). To meet the requirement of cost-effectiveness, the proposed antenna element is designed on a single FR4 layer to achieve low cost. To achieve a compact size, the BGA packaging is used on the proposed antenna element. Finally, the size of the antenna prototype is only 4.5 mm × 4.5 mm × 1.3 mm. Besides, the surface-mount feature allows the proposed antenna to be integrated with other devices in the same system package. The simulation and measurement results are discussed in detail. The measurement results show that the impedance bandwidth of - 10 dB is 15.3 % (24.7-29.6 GHz), and the peak gain is 5.85 dBi at 28 GHz. The proposed PIFA can be used in the 5G NR bands N257 (26.5-29.5 GHz), N258 (24.25-27.5 GHz), and N261 (27.5-28.35 GHz).

2021-06-02 PIER Letters Vol. 98, 49-54, 2021. doi:10.2528/PIERL21031303

Synthesis of in-Line Fully Canonical Response Filters with Frequency-Variant Couplings

Angel Triano and Pedro de Paco

A direct synthesis approach is presented to realize in-line topology filters with adjacent frequency-variant couplings implementing a transmission response with the same number of finite transmission zeros as poles. The proposed method starts with an N-order fully canonical filter response definition. A non-resonant node (NRN) is incorporated into the transversal network to make room for an extra coupling, and as a consequence of the extended similarity transformation applied, the NRN is transformed into a resonant node. The result is a network with N poles and N transmission zeros implemented with N+1 resonant nodes and N FVC, being able to describe a fully canonical response with an inline network without cross couplings.

2021-05-30 PIER Letters Vol. 98, 41-48, 2021. doi:10.2528/PIERL21031108

Gain Enhancement Using Modified Circular Loop FSS Loaded with Slot Antenna for Sub-6 GHz 5G Application

Anubhav Kumar, Asok De, and Rakesh Kumar Jain

In this paper, a modified circular loop FSS with a slot antenna is proposed for sub-6 GHz 5G applications. The proposed FSS reduces the resonant frequency to towards lower bands of conventional circular FSS without change in its size. The operating bandwidth (-10 dB) of proposed antenna loaded with polarization insensitive single-layer FSS varies from 3.6 GHz to 6.1 GHz with an average gain of 7-7.5 dB and a maximum realized gain of 7.87 dB. An FSS superstrate is loaded onto a slot antenna to increase the realized gain of 4 dB, where the FSS shows desirable electromagnetic wave reflection characteristics over operating bandwidth and can be used in 5G sub-6 GHz band applications.

2021-05-29 PIER Letters Vol. 98, 33-40, 2021. doi:10.2528/PIERL21041701

A Low-Loss Dual-Band Negative Group Delay Circuit with Flexible Design

Yuwei Meng, Zhongbao Wang, Yu Bai, Shao-Jun Fang, and Hongmei Liu

A low-loss dual-band negative group delay circuit (NGDC) with a flexible design is proposed. The proposed NGDC consists of a transmission line coupled asymmetrically with two step-impedance open-loop resonators. The negative group delay (NGD) times and center frequencies of the lower and upper bands can be tuned independently. To verify the design concept, two dual-band NGDC prototypes I and II are fabricated and measured. The measured NGD times of prototype I are -4.9 ns and -4.8 ns at the center frequencies of 1.949 GHz and 2.054 GHz, respectively. The insertion loss is lower than 2.7 dB and the return loss larger than 11.2 dB in both NGD bands. For prototype II, the NGD times at 1.949 GHz and 2.086 GHz are -4.7 ns and -3.3 ns, respectively. The measured insertion loss is better than 2.4 dB with the return loss larger than 11.9 dB.

2021-05-19 PIER Letters Vol. 98, 25-31, 2021. doi:10.2528/PIERL21040207

Optimization of the Wheeler Cap Technique for Efficiency Measurement of RFID Antennas Matched to Complex Loads

Nadeen Rishani, Jean-Marc Laheurte, Stephane Protat, and Raed Shubair

This paper proposes an improved mathematical formulation of Johnston's approach to measure the radiation efficiency of an antenna, based on the Wheeler Cap (WC) technique. The proposed modifications allow the measurement of the radiation efficiency of small antennas matched to complex loads implemented on Radio Frequency IDentification (RFID) tags. The studied structure is a low-cost, silver-printed, differentially-fed RFID dipole antenna. The antenna is printed on a flexible PET (polyethylene terephthalate) paper that is conformable on various objects. Link budget measurements validate the accuracy of the formulation, which can be applied to any dipole antenna matched to an RFID chip with a complex input impedance.

2021-05-17 PIER Letters Vol. 98, 17-24, 2021. doi:10.2528/PIERL21022501

Orbital Angular Momentum Orthogonality Based Crosstalk Reduction

Unaiza Tariq, Hiva Shahoei, Guang Yang, and Duncan L. MacFarlane

We report a reduction in crosstalk between a transmitting antenna and an adjacent receiving antenna due to the use of radiation patterns with different orbital angular momentum (OAM). This crosstalk reduction is based on the orthogonality between different OAM modes. To generate OAM beams, patch array antennas are designed using High frequency simulation software (HFSS). The designed antennas are fabricated and characterized. An experiment is carried out to determine the amount of crosstalk reduction achieved due to the OAM nature of the signals transmitted. The variation of this crosstalk reduction with the distance between the transmitting and receiving antennas is also studied. The results obtained are verified through theoretical analysis using simulations in HFSS. A maximum theoretical crosstalk reduction of 3.6 dB has been obtained, and a crosstalk reduction of 2.6 dB has been realized experimentally. The results may benefit full-duplex communication links.

2021-04-29 PIER Letters Vol. 98, 9-16, 2021. doi:10.2528/PIERL21022603

Mechanisms and Influence Factors of Dynamic Behavior of Water Droplets on the Composite Insulator Surface Under AC Electric Field

Wen Cao, Hua Feng, Hao Xue, Wei Shen, Long Zhao, and Hao Yang

The deformation behaviors of a droplet on surface of composite insulator can strengthen local electric field, which could finally lead to flashover. Both experiments and numerical simulations for dynamic behaviors of a droplet on the surface of a composite insulator under applied AC voltage are investigated in this paper. Experiments are performed to study the influences of water droplet's volume and conductivity on the dynamic behaviors. Two critical parameters are proposed to describe the morphological change process of water droplet, and it is shown that the process can be divided into three stages. Moreover, these motion laws are explained by establishing theoretical factors and physical influence models. In addition, we perform computer simulation to study the dynamic behaviors of a water droplet under AC field, and the findings are in good consistency with our experimental results, proving the rationality of the theoretical physical model. It is found that the vibration frequency of droplet changes regularly with at different stages under the AC electric field.

2021-04-21 PIER Letters Vol. 98, 1-8, 2021. doi:10.2528/PIERL21032401

A Dual-Band 8-Element 4/5G Printed MIMO Antenna Using Open Slot Radiators

Mohamed Morsy

This paper presents a dual-band eight-element multiple-input multiple-output (MIMO) antenna for 5G applications. The 8-element antenna is formed into two 4×4 MIMO systems that operate at 2500-2600 MHz and 1800-2200 MHz bands. The antenna elements are mounted along the perimeter of a rectangular ground plane with a total size of 110 × 80 mm2 and are printed on both sides of a low-profile PCB material. Elements radiate through open rectangular slots etched on the antenna's ground conductor. The open slots are excited by T-shaped microstrip lines fed by 50-Ω coaxial connectors. The size of the ground plane's slots, and the T-shaped radiators control the resonance of the antenna's elements. The proposed design employs orthogonal elements to mitigate mutual coupling. The isolation between ports is less than -10 dB. The radiation efficiency ranges from 40% to 65% across operating frequency bands.