PIER Letters | PIER Journals

2024-01-18

PIER Letters

Vol. 116, 105-111, 2024

download: 144

Dual-Feed Orthogonally Polarized Compact 8-Element MIMO Antenna Using Metallic Stub and Decoupling Unit for Isolation Enhancement of Sub-6 GHz 5G Application

Munusami Cholavendan and Venkatesan Rajeshkumar

A compact dual-feed multiple-input multiple-output (MIMO) antenna is designed for sub-6 GHz 5G applications with isolation enhancement. The proposed dual-polarized MIMO antenna formed by each patch uses two inset-feed lines placed orthogonal to each other with symmetric conditions, which excite each port to resonate at the same frequency (3.65 GHz). The stub is identified diagonally based on plated through-hole technology between orthogonal ports. The structure employs a half mode and maintains minimum inter-port isolation (≤-12 dB) of each patch, followed by another patch to form an 8-element miniaturized MIMO antenna. High isolation (≤-15 dB) is achieved with the help of a decoupling structure placed between the antennas in the ground plane. Measurements of a fabricated prototype validate the simulation results. The diversity performances of MIMO antenna parameters like envelope correlatio coefficient (ECC), diversity gain (DG), and Mean Effective Gain (MEG) are also found within acceptable ranges.

Dual-feed Orthogonally Polarized Compact 8-element MIMO Antenna Using Metallic Stub and Decoupling Unit for Isolation Enhancement of Sub-6 GHz 5G Application

2024-01-18

PIER Letters

Vol. 116, 101-104, 2024

doi:10.2528/PIERL23121901

download: 69

A High Performance Duplexer Based on Dual-Mode E-Type Resonator

Mingxin Liu , Mingfu Li , Hui Li and Yan Chen

A novel compact planar duplexer is proposed. It consists of three dual-mode E-shaped microstrip resonators and works well on the WCDMA system with uplink band of 1940 MHz-1955 MHz and downlink band of 2130 MHz-2145 MHz. The high rectangular coefficient of the duplexer makes its frequency selectivity high, and its small size is convenient for further miniaturization. In the product test, the duplexer is found to meet the band requirements very well with high isolation levels of -44 dB and -48 dB at the first and second frequency centers, respectively, which are better than those with similar frequency bands in the references.

A High Performance Duplexer Based on Dual-mode E-type Resonator

2024-01-18

PIER Letters

Vol. 116, 95-100, 2024

doi:10.2528/PIERL23101302

download: 89

A Novel Microwave Equalizer Based on SIR Loading with Internal Coupled-Lines

Xiaolei Yang , Honglin Zhang , Wencheng Ren , Chunlei Yuan , Lijie Xu and Dong Chen

This paper proposes the design of a microwave equalizer based on SIR loading with internal coupled-line. By loading a ring-type stepped impedance resonator (SIR) with internal coupled-lines, a microwave equalizer with positive slope transmission characteristics is presented. The frequency response is synthesized using a second-order SIR, and a detailed theoretical derivation of the equalizer is presented. A prototype of the equalizer is fabricated and measured to validate its expected performance, with the measurements showing good agreement with the predictions. The microwave amplitude equalizer demonstrates the necessary gain slope across its entire operational frequency range. Finally, a potential design scheme for a microwave amplitude equalizer is proposed.

A Novel Microwave Equalizer Based on SIR Loading with Internal Coupled-lines

2024-01-15

PIER Letters

Vol. 116, 87-94, 2024

doi:10.2528/PIERL23112202

download: 116

Realization of a Second-Order Wide-Stopband Substrate-Integrated Waveguide Filter Using the Weakest Electric Field Method and DGS Structure

Yuxin Fang , Xiaohei Yan , Yixian Wang and Shengbing Zhang

To increase the stopband width of the filter, a second-order wide-stopband substrate-integrated waveguide filter is suggested. This filter is designed by utilizing a DGS structure and the weakest electric field approach. To suppress the modes, the filter sets the inner and outer coupling windows at the modes' weakest electric fields (TE₁₂₀/TE₂₁₀, TE₂₂₀). Additionally, a new nested U-shaped DGS structure is implemented to suppress the TE₁₃₀ mode, hence expanding the stopband width of the filter. The filter has been processed and measured, and the findings indicate a 4.5 GHz center frequency, a -3 dB bandwidth of 240 MHz, a relative bandwidth of 5.3%, an insertion loss of -1.2 dB in the passband, and a -22 dB stopband, which can be extended up to 9.4 GHz (i.e., 2.1 times the center frequency). The simulated and measured results demonstrate good alignment. Compared to other SIW filters, the current filter achieves a wider stopband while using fewer orders and implementing a straightforward design method, providing potential value for applications.

Realization of a Second-order Wide-stopband Substrate-integrated Waveguide Filter Using the Weakest Electric Field Method and DGS Structure

2024-01-13

PIER Letters

Vol. 116, 79-85, 2024

doi:10.2528/PIERL23120301

download: 186

Bandpass Filter for 5G Sub-6 GHz Bands

Jiajia Wang , Shuo Yu , Xiaofan Yang and Xiaoming Liu

The performance requirements for filters in the microwave frequency band are particularly stringent, particularly in terms of high bandwidth and out-of-band rejection. However, meeting these requirements within the constraints of a compact size presents a significant challenge. A coupled step-impedance resonator bandpass filter is proposed. The filter combines U-shaped branches and L-shaped branches to create multiple resonance points while expanding the bandwidth, and the in-band ripple is also improved by this folded structure that greatly reduces the filter size. The microstrip filter measures only 9.6 mm × 8.8 mm × 1.1 mm, has a center frequency of 4.65 GHz, and achieves a relative bandwidth of 60.2%. The filter can be used in 5G n77 (3300~4200 MHz), n78 (3300~3800 MHz), n79 (4800~4960 MHz), and WLAN (5150~5850 MHz) bands. In addition, the filter has a left-side rectangular coefficient of 1.12, insertion loss <0.4 dB, and return loss better than 17 dB.

2024-01-09

PIER Letters

Vol. 116, 71-78, 2024

doi:10.2528/PIERL23101303

download: 123

Compact and Broadband CPW-to-RWG Transition Using Resonator with Impedance-Matching Element

Ir-Ving Tseng , Ming-Feng Zheng , Ting-Tzu Cho and Chun-Long Wang

This paper proposes a compact and broadband coplanar waveguide (CPW)-to-rectangular waveguide (RWG) transition using a resonator with an impedance-matching element. The transition size is as small as 7.66 mm, and the frequency range for which the reflection coefficient is smaller than -15 dB covers from 8.05 GHz to 12.18 GHz (FBW = 40.83%), almost encompassing the full X-band (8.2-12.4 GHz). To reduce the size of the transition, a short-circuited stub phase shifter is used to replace the half-wavelength phase shifter, resulting in a miniaturized CPW-to-RWG transition using the resonator with the impedance-matching element. The transition size is further reduced from 7.7 mm to 5.9 mm. Besides, the frequency range for which the reflection coefficient is smaller than -15 dB covers from 8.05 GHz to 12.38 GHz (FBW = 42.38%), nearly encompassing the full X-band (8.2-12.4 GHz) as usual. To verify the simulation results, both CPW-to-RWG transitions using the resonator with the impedance-matching element are fabricated and measured. The simulation and measurement results are in reasonable agreement.

Compact and Broadband CPW-to-RWG Transition Using Resonator with Impedance-matching Element

2024-01-09

PIER Letters

Vol. 116, 63-70, 2024

doi:10.2528/PIERL23113005

download: 135

A High Efficiency and Low Mutual Coupling Four-Element Antenna Array for GNSS Applications

Abdullah Madni and Wasif Tanveer Khan

In this manuscript, a compact four-element antenna array is introduced for global navigation satellite system (GNSS) upper L-band applications. The proposed design is modelled using a higher epsilon substrate to obtain a smaller patch footprint. The array consists of four rectangular right hand circularly polarized (RHCP) patches etched on a circular substrate having a compact diameter of only 125 mm. The patch elements cover the BeiDou B1 (1561.098 MHz), GPS L1 (1575.42 MHz), Galileo E1 (1575.42 MHz) and GLONASS G1 (1602 MHz) bands with an axial ratio below 3 dB. A defected ground structure (DGS) has been integrated in the ground plane of the proposed array along with a novel meta-isolator on the top side between the antennas to achieve a high isolation level of more than 24 dB in the complete band of interest. The proposed antenna array has a high gain of more than 6.9 dBi and a radiation efficiency greater than 93%. A prototype of the proposed array is fabricated, and measured results are presented to validate the design.

A High Efficiency and Low Mutual Coupling Four-element Antenna Array for GNSS Applications

2024-01-08

PIER Letters

Vol. 116, 55-62, 2024

doi:10.2528/PIERL23110801

download: 175

Low Loss Anisotropic Circular Near-Zero Flexible Metasurface for Gain Enhancement

Arun Shaji B K , Muhammed Hunize C V , Anju Pradeep and Murali K P

This paper proposes a new low loss high dielectric substrate made of CaTiO₃ incorporated butyl rubber (CBR). The synthesized material has a dielectric loss of 0.0048 and dielectric constant of 11.7. A novel circular anisotropic structure is used in the design of metamaterial unit cell. This metamaterial structure exhibits near-zero refractive index at 2.4 GHz. The extraction of refractive index is done from the scattering parameters using generalised sheet transition condition. An array of 3 × 3 unit cell is the metasurface superstrate, which is proposed for the gain enhancement. It is kept above the microstrip patch antenna working at 2.4 GHz. The proposed superstrate provides a gain enhancement of 4.6 dB. The height between the antenna and the superstrate is optimized to 0.088λ. The enhancement of gain on metasurface substrate with different loss tangents is analyzed. The simulation and measurement results of antenna with superstrate show good agreement with a peak gain of 7.6 dBi. The radiation efficiency of the antenna is increased by 42%.

Low Loss Anisotropic Circular Near-zero Flexible Metasurface for Gain Enhancement

2024-01-06

PIER Letters

Vol. 116, 47-53, 2024

doi:10.2528/PIERL23111306

download: 145

Wideband Multifunctional Bessel Beams by High Efficiency Spin-Decoupled Metasurface for Near Field Applications

Hui-Fen Huang and Chu-Xin Zheng

This paper develops a wideband spin-decoupled unit cell to form high efficiency wideband spin-decoupled metasurface (MTS), which can achieve more versatile Bessel beams with independent control of the beam direction, polarization and Orbital angular momentum (OAM) mode for near field applications. The MTS is designed for wideband dual Bessel beams: Beam-I (RHCP, θ₁=30˚, φ₁=180˚, l=1), Beam-II (LHCP, θ₂=30˚, φ₂=0˚, l=0), where φ and θ are the azimuth and elevation angles, respectively; l is the OAM mode; and RHCP(LHCP) represents the right (left) hand circular polarization. Compared with conventional phase gradient MTSs, the proposed MTS achieves more versatile functionalities and better performance: wideband (35.3%), dual Bessel beams, circular polarization (CP), high aperture efficiency (AE) 40%, carrying OAM modes, high ratio of non-diffraction distance/aperture size (6.41), high conversion efficiency for Bessel beams (33%), and high OAM purity (78%-99%). Simulated and measured results agree well, and validate the design method. The proposed unit cell can be used to design other high performance multifunctional Bessel beams. The designed Bessel beams have potential applications in dense channel high capacity communication, efficient wireless power transfer, high-resolution imaging, medical treatment.

Wideband Multifunctional Bessel Beams by High Efficiency Spin-decoupled Metasurface for Near Field Applications

2024-01-05

PIER Letters

Vol. 116, 39-45, 2024

doi:10.2528/PIERL23101301

download: 439

An Active Flux Model-Based Sensorless Flux Weakening Control Algorithm for Permanent Magnet Synchronous Motors

Kun Li , Lin Wang and Yilin Zhu

In order to improve the stability of sensorless high-speed operation of permanent magnet synchronous motors and effectively expand the speed range, a voltage closed-loop flux weakening sensorless algorithm based on the active flux model is proposed. Firstly, the mathematical model of sensorless control of the PMSM is designed based on the active flux model, and the state of the PMSM flux weakening operation is analyzed. Then, based on the voltage closed-loop flux weakening control method, the corresponding flux weakening control algorithm is analyzed and designed. Meanwhile, based on the active flux model, the speed and rotor position of the motor are observed by sliding mode observer and phase-locked loop method. After that, the flux weakening control method and the sensorless control method are combined to realize the sensorless flux weakening control method to improve the stability of the control system. Finally, the proposed algorithm is validated on the experimental platform. The experimental results show that the proposed method can prevent the system from losing control during flux weakening processes, effectively improve system stability, and have smaller angle errors. The speed convergence time is shortened by 80% compared to the non flux weakening control.

An Active Flux Model-based Sensorless Flux Weakening Control Algorithm for Permanent Magnet Synchronous Motors

2024-01-01

PIER Letters

Vol. 116, 31-38, 2024

doi:10.2528/PIERL23110301

download: 177

Hexa-Slot Wheel Shaped Fractal Orthogonal MIMO Antenna with Polarization Diversity for UWB Applications

Ramesh Deshpande and Yalavarthi Usha Devi

In this paper, a hexa-slot wheel shaped fractal antenna is proposed for UWB applications. Fractal structure (wheel shaped hexa slots) is developed by inscribing hexagons and circles inside a circular patch monopole antenna. Then orthogonal MIMO antenna with polarization diversity is proposed that operates from 1.39-15.18 GHz with an impedance bandwidth of 13.79 GHz. Its performance is analyzed at three resonant frequencies 5.8 GHz, 8.3 GHz and 10 GHz. It exhibits good diversity performance with ECC < 0.035, DG very close to 10, isolation > 35 dB, CCL < 0.35 bits/s/Hz values. The proposed MIMO fractal antenna achieved an average radiation efficiency of 83.11% with 3.26 dB maximum peak gain. TARC characteristics and time domain behavior using group delay are also examined. Simulated and measured results are in good agreement and hence the proposed MIMO antenna with polarization diversity is well suitable for UWB applications.

Hexa-slot Wheel Shaped Fractal Orthogonal MIMO Antenna with Polarization Diversity for UWB Applications

2023-12-30

PIER Letters

Vol. 116, 23-30, 2024

doi:10.2528/PIERL23102706

download: 156

Novel Sparse Linear Array Based on a New Suboptimal Number Sequence with a Hole-Free Difference Co-Array

Ashish Patwari and Pradyumna Kunchala

In this paper, we propose a new sparse linear array (SLA) that enjoys a hole-free difference co-array (DCA) and closed-form expressions for its sensor positions. The proposed configuration is valid for arrays containing seven or more sensors (N≥7). Exact expressions for the array aperture and achievable degrees of freedom (DOFs) have been derived. Numerical simulations were performed using MATLAB to reinforce the theoretical understanding. The main aim of this study is not to claim superiority over any existing SLA design, but to report that we have found a new number sequence that can act as an SLA. Except for being highly susceptible to mutual coupling, the proposed array has all the desirable features of a good SLA. We observed that the proposed array is on par with other SLAs for N<20. However, for 20 or more sensors, the array aperture does not scale rapidly in proportion to the added sensors and fails to match the resolution and/or DOFs offered by other sparse arrays. Nevertheless, the proposed sparse array is based on a unique and previously unknown number sequence.

Novel Sparse Linear Array Based on a New Suboptimal Number Sequence with a Hole-free Difference Co-array

2023-12-27

PIER Letters

Vol. 116, 17-22, 2024

doi:10.2528/PIERL23100701

download: 175

Mechanism of Microwave Effect on the Extraction Process of Tea Polyphenols

Dan Li , Tao He , Boyu Li , Ziqin Wang and Zhengming Tang

Microwave-assisted extraction (MAE) is an effective method for extracting tea polyphenols. However, research on MAE mainly focuses on experimental methods, which not only leads to a large amount of experimental work but also generates a lot of material waste. In addition, due to the lack of mechanism research, it is difficult to find a more effective method. In this study, based on electromagnetic field theory, the heat and mass transfer model of tea polyphenol extraction is established based on measuring the dielectric properties of the extract. The distribution of temperature, diffusion coefficient, and flow rate of microwave-assisted extraction of tea polyphenols are all analyzed in detail. The results show that the temperature distribution in the extraction system is uneven. The middle temperature of the extraction solution is high and the edge is low. Moreover, with the increase of microwave power and extraction temperature, the diffusion coefficient is gradually increased, and the flow rate increases, which is more conducive to the extraction process as time goes by. This study provides a theoretical basis for the microwave-assisted extraction of tea polyphenols, reducing experimental workload and material waste.

Mechanism of Microwave Effect on the Extraction Process of Tea Polyphenols

2023-12-26

PIER Letters

Vol. 116, 9-16, 2024

doi:10.2528/PIERL23101101

download: 206

Circularly Polarized Antenna Array Using Filtering Phase Shifting Theory

Xin Guo , Meiyu Du , Wen Wu , Zhihong Feng and Zhiping Wan

A new circularly polarized (CP) array using the filtering phase shifting theory is designed. First, it is displayed that a phase designable filter can be obtained by controlling the position of the transmission zero (TZ) of the doublet topology. Next, by mapping the topology into a stub-loaded resonator (SLR) and using the patch as the last resonating mode, a phase designable 3rd-order filtering antenna element is designed. Then, two filtering antenna elements with 90° phase difference are obtained. Finally, by using the slot-coupled feed structure, four elements with phases of 0°, 90°, 180°, 270° are rotated sequentially to form a circularly polarized array. The measured results show that the impedance bandwidth is 8.1% (5.07-5.5 GHz); the axial ratio (AR) bandwidth is 6.7% (5.05-5.4 GHz); the maximum CP realized gain is 10.5 dBic; and the good filtering function is implanted.

Circularly Polarized Antenna Array Using Filtering Phase Shifting Theory

2023-12-26

PIER Letters

Vol. 116, 1-7, 2024

doi:10.2528/PIERL23103102

download: 175

Design of a Microstrip Filtering Antenna Without Extra Circuits and Its Application in Orbital Angular Momentum (OAM) Filtering Antenna

Jia Liang , Dan Wang , Zisen Qi , Yun Gao and Qingmei Wei

In this paper, a microstrip filtering antenna is proposed with gain-filtering response. The antenna consists of an E-shaped radiator and a slotted U-shaped coupling structure. Three radiation nulls are obtained by the radiator, the U-shaped coupling structure and the two slots. The filtering antenna has no extra circuits, which indicates that it is easy to design. A 4-element filtering OAM antenna array is also designed to validate its applicability in OAM antennas. Measured results show excellent performance of the array, which also make it a potential candidate for 5G wireless communication devices.