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Microwave Passive Components
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Microwave Passive Components

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "E：Engineering and Technology".

Deadline for manuscript submissions: closed (30 June 2023) | Viewed by 39740

Special Issue Editor

Prof. Dr. Guo Liu

E-Mail Website
Guest Editor
School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
Interests: vacuum electronic devices; passive pulse compressor; microwave biosensor; dielectric microwave measurement
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Nowadays, devices and systems based on micro-, millimeter and terahertz waves are widely used in all aspects of life, such as 5G/6G communication, vehicle imaging radar, medical, bioscience, security, etc. As we know, microwave passive components play an important role in the design and applications of these devices and systems. The development of advanced machining technologies such as the Micro-Electro-Mechanical System (MEMS), 3D-printing, and micro-/nanomachining, machining accuracy and ability of passive components, especially, have been improved greatly. In addition, in the last two decades, novel concepts and mechanisms have been continually introduced or proposed from other fields, including meta-material, vortex electromagnetic wave and spoof surface plasmon. As a result, microwave passive devices/components have entered a new stage controlled by information coding. This means that the performance of microwave passive devices still has great potential in the future, and may contribute to the miniaturization and integration of RF circuits and devices. Therefore, this Special Issue, named “Microwave Passive Components”, was born. This Special Issue will accept research papers and review articles focusing on the theory, modeling, simulation, measurement and applications of passive components, circuits, devices and systems in the microwave, millimeter-wave and terahertz-wave bands.

I am looking forward to receiving your submissions and contributions to this Special Issue!

Dr. Guo Liu
Guest Editor

Manuscript Submission Information

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Keywords

  • theory, modeling, fabrication, measurement and applications
  • microwave, millimeter and terahertz wave passive component/devices applied in the communication, radar and some other systems
  • passive component/devices in antenna, filters, biosensors, vacuum electronic devices, pulse compressor, particle accelerator, etc.
  • other work related to microwave devices

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Related Special Issue

Published Papers (19 papers)

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Research

14 pages, 4880 KiB  
Article
Dual-Band and Wideband Bandpass Filters Using Coupled Lines and Tri-Stepped Impedance Stubs
by Abdullah J. Alazemi
Micromachines 2023, 14(6), 1254; https://doi.org/10.3390/mi14061254 - 14 Jun 2023
Cited by 5 | Viewed by 1910
Abstract
In this paper, two bandpass filters—one with a dual-band response and the other with a wideband response—were designed, implemented, and experimented with. The filters are based on the novel combination of series coupled lines and tri-stepped impedance stubs. However, coupled lines along with [...] Read more.
In this paper, two bandpass filters—one with a dual-band response and the other with a wideband response—were designed, implemented, and experimented with. The filters are based on the novel combination of series coupled lines and tri-stepped impedance stubs. However, coupled lines along with tri-stepped impedance open stubs (TSIOSs) give a third-order dual passband response. The advantage of dual-band filters using coupled lines and TSIOSs is that they have wide passbands that are close together and separated by a single transmission zero. In contrast, the inclusion of tri-stepped impedance short-circuited stubs (TSISSs) instead of TSIOSs provides a fifth-order wide passband response. The advantage of wideband bandpass filters using coupled lines and TSISSs is that they have a very good selectivity factor. Theoretical analysis was carried out to validate both filter configurations. The tested bandpass filter using coupled lines and TSIOS units had two close wide passbands operating at 0.92 and 1.52 GHz center frequencies, respectively. The dual-band bandpass filter was implemented to operate in GSM and GPS applications. The first passband had a 3 dB fractional bandwidth (FBW) of 38.04%, while the second passband had a 3 dB FBW of 22.36%. The experimental result of the wideband bandpass filter (with coupled lines and TSISS units) had a center frequency of 1.51 GHz with a 3 dB fractional bandwidth of 62.91% and a selectivity factor of 0.90. A good congruence was demonstrated between the full-wave simulated and tested results for both filters. Full article
(This article belongs to the Special Issue Microwave Passive Components)
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11 pages, 2802 KiB  
Article
Design of a Switchable Filter for Reflectionless-Bandpass-to-Reflectionless-Bandstop Responses
by Gangxiong Wu, Hao Wu, Wei Qin, Jin Shi, Wei Zhang, Longlong Lin and Qian Li
Micromachines 2023, 14(2), 424; https://doi.org/10.3390/mi14020424 - 10 Feb 2023
Cited by 2 | Viewed by 1802
Abstract
In this paper, a switchable filter based on the microstrip line (ML) with reflectionless-bandpass-to-reflectionless-bandstop responses is designed, theoretically validated, and fabricated. This single-port reflectionless bandpass filter (R-BPF) consists of a BPF and a shunt-connected bandstop section with terminated absorption resistors. The single-port reflectionless [...] Read more.
In this paper, a switchable filter based on the microstrip line (ML) with reflectionless-bandpass-to-reflectionless-bandstop responses is designed, theoretically validated, and fabricated. This single-port reflectionless bandpass filter (R-BPF) consists of a BPF and a shunt-connected bandstop section with terminated absorption resistors. The single-port reflectionless bandstop filter (R-BSF) is made of a BSF and a parallel bandpass circuit with terminated absorption resistors. These two reflectionless operational modes, namely R-BPF and R-BSF, are allowed to reconfigure the multifunctional filtering device using PIN diodes. In addition, a theoretical analysis of terminal impedance is performed to illustrate the working mechanism of the reflectionless response. To demonstrate the application of the proposed designs, a prototype of the switchable filter for R-BPF to R-BSF responses is fabricated and measured. For the R-BPF mode, the 3-dB fractional bandwidth (FBW) is 36.75% (1.67–2.42 GHz) with a 10-dB reflectionless bandwidth (RBW) of 1.36–2.58 GHz (i.e., FBW of 61.9%). For the R-BSF mode, the 10-dB bandwidth is 13% (1.85–2.11 GHz) with a 10.7-dB RBW of 1–3 GHz (i.e., FBW of 100%). An acceptable agreement between the measured and simulated results has been achieved. Full article
(This article belongs to the Special Issue Microwave Passive Components)
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9 pages, 2770 KiB  
Article
Miniaturized Quad-Band Filter Design Using Substrate Integrated Coaxial Cavity
by Chung-I G. Hsu, Wanchu Hong, Mingchih Chen, Wei-Chun Tu, Gwan-Wei Su and Min-Hua Ho
Micromachines 2023, 14(2), 347; https://doi.org/10.3390/mi14020347 - 30 Jan 2023
Cited by 1 | Viewed by 1420
Abstract
We propose a miniaturized quad-band filter (QBF), designed using substrate-integrated coaxial cavities (SICCs). The employed SICC structure consists of two vertically stacked substrates with a large circular patch embedded in between. The embedded patch is segmented unevenly into four pieces, which are shorted [...] Read more.
We propose a miniaturized quad-band filter (QBF), designed using substrate-integrated coaxial cavities (SICCs). The employed SICC structure consists of two vertically stacked substrates with a large circular patch embedded in between. The embedded patch is segmented unevenly into four pieces, which are shorted to the cavity’s bottom wall through one or two blind vias. This SICC structure exhibits four independently controlled resonances with frequencies much lower than the frequency of its conventional SIW cavity counterpart, thus achieving size reduction. A sample quad-band filter is designed and fabricated for experimental measurement. Reasonably good agreement between measured and simulated data is observed. Full article
(This article belongs to the Special Issue Microwave Passive Components)
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14 pages, 5026 KiB  
Article
Fabrication of Substrate-Integrated Waveguide Using Micromachining of Photoetchable Glass Substrate for 5G Millimeter-Wave Applications
by Seung-Han Chung, Jae-Hyun Shin, Yong-Kweon Kim and Chang-Wook Baek
Micromachines 2023, 14(2), 288; https://doi.org/10.3390/mi14020288 - 22 Jan 2023
Cited by 2 | Viewed by 3051
Abstract
A millimeter-wave substrate-integrated waveguide (SIW) was firstly demonstrated using the micromachining of photoetchable glass (PEG) for 5G applications. A PEG substrate was used as a dielectric material of the SIW, and its photoetchable properties were used to fabricate through glass via (TGV) holes. [...] Read more.
A millimeter-wave substrate-integrated waveguide (SIW) was firstly demonstrated using the micromachining of photoetchable glass (PEG) for 5G applications. A PEG substrate was used as a dielectric material of the SIW, and its photoetchable properties were used to fabricate through glass via (TGV) holes. Instead of the conventional metallic through glass via (TGV) array structures that are typically used for the SIW, two continuous empty TGV holes with metallized sidewalls connecting the top metal layer to the bottom ground plane were used as waveguide walls. The proposed TGV walls were fabricated by using optical exposure, heat development and anisotropic HF (hydrofluoric acid) etching of the PEG substrate, followed by a metal sputtering technique. The SIW was fed by microstrip lines connected to the waveguide through tapered microstrip-to-waveguide transitions. The top metal layer, including these feedlines and transitions, was fabricated by selective metal sputtering through a silicon shadow mask, which was prefabricated by a silicon deep-reactive ion-etching (DRIE) technique. The developed PEG-based process provides a relatively simple, wafer-level manufacturing method to fabricate the SIW in a low-cost glass dielectric substrate, without the formation of individual of TGV holes, complex time-consuming TGV filling processes and repeated photolithographic steps. The fabricated SIW had a dimension of 6 × 10 × 0.42 mm3 and showed an average insertion loss of 2.53 ± 0.55 dB in the Ka-band frequency range from 26.5 GHz to 40 GHz, with a return loss better than 13.86 dB. The proposed process could be used not only for SIW-based devices, but also for various millimeter-wave applications where a glass substrate with TGV structures is required. Full article
(This article belongs to the Special Issue Microwave Passive Components)
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12 pages, 2943 KiB  
Article
A Balanced Substrate Integrated Waveguide Phase Shifter with Wideband Common-Mode Suppression
by Wei Zhang, Jin Shi, Gangxiong Wu, Longlong Lin and Kai Xu
Micromachines 2023, 14(2), 285; https://doi.org/10.3390/mi14020285 - 22 Jan 2023
Cited by 1 | Viewed by 1648
Abstract
In this paper, a slotted substrate integrated waveguide (SIW) is used to create a balanced phase shifter with wideband common-mode (CM) suppression. Differential-mode (DM) impedance matching and CM suppression are achieved by utilizing the fact that TE20 mode and TE10 (TE [...] Read more.
In this paper, a slotted substrate integrated waveguide (SIW) is used to create a balanced phase shifter with wideband common-mode (CM) suppression. Differential-mode (DM) impedance matching and CM suppression are achieved by utilizing the fact that TE20 mode and TE10 (TE30) mode can only transmit DM signals and CM signals, respectively, and by increasing the bandwidth for CM suppression via slots. Furthermore, a wideband phase shift with low phase deviation can be obtained due to the phase slop counteract between the slot and the delay line. Compared with the state-of-the-art, the proposed one has the advantages of wideband CM suppression, wide phase shift range, and a simple and easy-to-make structure. Five prototypes covering the frequency of 3.5 GHz are designed with the relative operating bandwidth for 45° ± 2° (90° ± 4.5°, 135° ± 6°, and 180° ± 8°) phase shifter of 20% (20%, 20%, and 20%), with the minimum insertion loss of 0.41 dB (0.5 dB, 0.58 dB, and 0.59 dB), with the minimum return loss greater than 15 dB, and with the relative bandwidth for 15-dB CM suppression of 59% (59%, 58%, and 57%). Full article
(This article belongs to the Special Issue Microwave Passive Components)
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19 pages, 5861 KiB  
Article
Design and Implementation of a Ku-Band High-Precision Blackbody Calibration Target
by Jie Liu, Zhenlin Sun, Guangmin Sun, Yu Li, Tong Cao and Wenjie Tang
Micromachines 2023, 14(1), 18; https://doi.org/10.3390/mi14010018 - 21 Dec 2022
Cited by 3 | Viewed by 1760
Abstract
Microwave radiometers can be used in human tissue temperature measurement scenarios due to the advantages of non-destructive and non-contact temperature measurement. However, their accuracy often cannot meet the needs of practical applications. In this paper, a Ku-Band high-precision blackbody calibration target is designed [...] Read more.
Microwave radiometers can be used in human tissue temperature measurement scenarios due to the advantages of non-destructive and non-contact temperature measurement. However, their accuracy often cannot meet the needs of practical applications. In this paper, a Ku-Band high-precision blackbody calibration target is designed to provide calibration for microwave radiometers and meet the requirements of a high temperature-measurement accuracy and high temperature-measurement resolution. From a practical application point of view, the blackbody calibration target needs to have the characteristics of high emissivity and high temperature uniformity. However, previous studies on blackbody calibration targets often focused on the scattering characteristics or temperature uniformity of the calibration target separately, and thus lack a comprehensive consideration of the two characteristics. In this paper, the electromagnetic scattering model and the temperature-distribution model of the calibration target are established through the multi-physical simulation combined with the Finite Element Method. Then, according to the simulation results of the two characteristic models, the structural parameters and composition of the coated cone array are continuously optimized. In addition, to achieve high-precision temperature control of the blackbody calibration target, this paper studies three PID controller parameter self-tuning algorithms, namely, BP-PID, PSO-PID and Fuzzy-PID for the optimal parameter tuning problem of traditional PID algorithms and determines the optimal temperature-control algorithm by comparing the performance of heating and cooling processes. Then, the blackbody calibration target is processed and manufactured. The arch test system is used to validate the reflectance of the calibration target, the emissivity is calculated indirectly, and the temperature-distribution uniformity of the temperature-control panel of the calibration target is tested by a multi-point distribution method. Finally, the uncertainty of the brightness temperature of the blackbody calibration target is analyzed. Full article
(This article belongs to the Special Issue Microwave Passive Components)
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10 pages, 6619 KiB  
Article
Flexible Low-Loss Thin Flimsy Stripline for High-Speed Connections
by Jau-Jr Lin and Yi-Da Tsai
Micromachines 2022, 13(12), 2218; https://doi.org/10.3390/mi13122218 - 14 Dec 2022
Cited by 1 | Viewed by 1639
Abstract
Increasing numbers of antennas are being placed inside laptop screen bezels. Connections between antennas and laptop bases have become challenging owing to space limitations. Thus, this paper proposes a flexible low-loss thin flimsy stripline structure for high-speed applications. The cable should be sufficiently [...] Read more.
Increasing numbers of antennas are being placed inside laptop screen bezels. Connections between antennas and laptop bases have become challenging owing to space limitations. Thus, this paper proposes a flexible low-loss thin flimsy stripline structure for high-speed applications. The cable should be sufficiently thin to avoid causing a water ripple effect while under the screen panel. Furthermore, the cable should be sufficiently flexible to traverse the hinges between the laptop screen and base. This study aims to design a cable with a total thickness of less than 0.6 mm and an insertion loss of less than 10 dB/m at a frequency of 6 GHz. Polytetrafluoroethylene (PTFE), a flexible material, can be used to meet these requirements. We simulate the characteristics of various PTFE layer thicknesses. The trend shows a thicker PTFE layer and lower insertion loss. Finally, we fabricate and test two structures with different thicknesses. Both thicknesses are less than 0.6 mm, and the insertion losses are less than 10 dB/m at 6 GHz. We demonstrate the feasibility of the proposed design and fabrication process for these applications through simulations and measurements. Full article
(This article belongs to the Special Issue Microwave Passive Components)
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12 pages, 4014 KiB  
Article
Enhancement of the Optical and Dielectric Properties at Low Frequency of (Sr1−xCax)5Ti4O13, (0 ≤ x ≤ 0.06) Structure Ceramics
by Sara J. Ahmed, Asad Ali, Abid Zaman, Aiyeshah Alhodaib, Abdulaziz H. Alghtani, Imen Bejaoui, Vineet Tirth, Ali Algahtani, Mohsin Khan, Abdullah and Mohammed Aljohani
Micromachines 2022, 13(11), 1824; https://doi.org/10.3390/mi13111824 - 26 Oct 2022
Cited by 1 | Viewed by 1658
Abstract
Low loss Ruddlesden–Popper (RP) series, i.e., (Sr1−xCax)5Ti4O13, 0.0 ≤ x ≤ 0.06, has been synthesized by a mixed oxide route. In this work, the substitution of Ca2+ cation in Sr5Ti [...] Read more.
Low loss Ruddlesden–Popper (RP) series, i.e., (Sr1−xCax)5Ti4O13, 0.0 ≤ x ≤ 0.06, has been synthesized by a mixed oxide route. In this work, the substitution of Ca2+ cation in Sr5Ti4O13 sintered ceramics was chosen to enhance the structural, optical, and dielectric properties of the product. It was found that the Ca2+ content has significant effects on enhancing the dielectric properties as compared to Mn and glass additions. It was observed that the relative density, band gap energy, and dielectric loss (tangent loss) increase while relative permittivity decreases along with Ca2+ content. High relative density (96.7%), low porosity, and high band gap energy (2.241 eV) values were obtained in (Sr1−xCax)5Ti4O13, 0.0 ≤ x ≤ 0.06 sintered ceramics. These results will play a key role in the application of dielectric resonators. Full article
(This article belongs to the Special Issue Microwave Passive Components)
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12 pages, 2608 KiB  
Article
Study of the Role of Titanium and Iron Cathodic Cages on Plasma-Nitrided AISI 430 Ferritic Stainless Steel
by Mirza Z. Babur, Aiyah S. Noori, Zafar Iqbal, Muhammad Shafiq, Muhammad Asghar, Abdulaziz H. Alghtani, Vineet Tirth, Ali Algahtani and Abid Zaman
Micromachines 2022, 13(10), 1739; https://doi.org/10.3390/mi13101739 - 14 Oct 2022
Cited by 2 | Viewed by 1811
Abstract
In contrast to austenitic and martensitic stainless steels, ferritic stainless steels have a lower hardness and wear resistance but exhibit excellent corrosion resistance. Due to this fact, their use in the aerospace, automobile, and house construction industries is restricted. Several methods have been [...] Read more.
In contrast to austenitic and martensitic stainless steels, ferritic stainless steels have a lower hardness and wear resistance but exhibit excellent corrosion resistance. Due to this fact, their use in the aerospace, automobile, and house construction industries is restricted. Several methods have been utilized to enhance the tribological characteristics of ferritic stainless steels. In this work, titanium nitride coating has been carried out by using a cathodic cage of titanium material, and later on, the titanium cathodic cage is replaced by an AISI-304 cathodic cage in a CCPN chamber to form iron nitride coating on AISI-430 ferritic stainless steel coupons through a plasma nitriding process for 4 h at a fixed temperature of 400 °C. The microstructures and mechanical traits of all processed and control coupons were analyzed using scanning electron microscopy, X-ray diffraction, ball-on-disc wear tester, and microhardness tester techniques. The results showed that hardness increased up to 1489 HV with the titanium cage, which is much higher than the hardness of the base material (270 HV). The titanium cage-treated coupons have high layer thickness, smooth surface morphology, and a minimum crystallite size of 2.2 nm. The wear rate was reduced up to 50% over the base material after the titanium cage plasma treatment. The base coupon exhibited severe abrasive wear, whereas nitrided coupons exhibited dominant adhesive wear. In the iron nitride coatings, this effect is also important, owing to the more influential cleaning process in a glow discharge, and the better adhesion with enhanced interlayer thickness is attributed to the fact that the compliance of the interlayer minimizes shear stresses at the coating–substrate interface. The use of a graded interface improves adhesion compared with the case where no interlayer is used but a titanium interlayer of comparable thickness provides a significant increase in measured adhesion. For both titanium and iron nitride films, there is a reduction in wear volume which is a function of interlayer thickness; this will have a substantial effect on wear lifetime. Thus by careful control of the interlayer thickness and composition, it should be possible to improve coating performance in tribological applications. Full article
(This article belongs to the Special Issue Microwave Passive Components)
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23 pages, 12083 KiB  
Article
Characteristic Mode Analysis-Based Compact Dual Band-Notched UWB MIMO Antenna Loaded with Neutralization Line
by Praveen Kumar, Tanweer Ali and Manohara Pai MM
Micromachines 2022, 13(10), 1599; https://doi.org/10.3390/mi13101599 - 26 Sep 2022
Cited by 30 | Viewed by 2462
Abstract
The advancement of electronic gadgets makes it possible for a device to be multipurpose, which calls for attributes such as compactness and larger bandwidth, with improved data transfer rate. This paper introduces the compact, closely placed two-port dual band-notched UWB antenna using a [...] Read more.
The advancement of electronic gadgets makes it possible for a device to be multipurpose, which calls for attributes such as compactness and larger bandwidth, with improved data transfer rate. This paper introduces the compact, closely placed two-port dual band-notched UWB antenna using a neutralization line as a decoupling structure. The projected antenna design comprised a circle and rectangle embedded monopole radiator with the defected ground structure to attain the UWB spectrum. Further dual notches are attained by carving the U-shape and inverted U-shape slots on the feedline and radiator. The dual band-notched UWB antennas are placed with the separation of 3.8 mm (0.04 λ; λ is computed using 3.4 GHz frequency). The coupling effect between the close proximity elements is decoupled using the neutralization line. The presented antenna has overall dimensions of 21.5 × 28 × 1.6 mm3 (0.24 × 0.31 × 0.01 λ3) and exhibits S11 below −10 dB from 3.4–11.9 GHz, with isolation better than 16 dB throughout the impedance bandwidth. The antenna also provides frequency band rejection of 4.5–5.3 GHz and 7.2–9 GHz covering the WLAN and entire X-band satellite communication. The projected antenna is explored through characteristic mode analysis, time-domain characteristics, and MIMO diversity features to analyze the effectiveness and usefulness of the antenna. The group delay is less than 1 ns except for the frequency rejection band and fidelity factor greater than 0.96. The projected antenna exhibits MIMO diversity metrics ECC < 0.3, DG > 9.6 dB, MEG < −3 dB, TARC < −10 dB, CCL < 0.3 bps/Hz, and ME < −2 dB across the operational frequency, except for the notched bands. The designed two-port antenna is validated by printing on an FR4 substrate. The simulated and measured findings are in line with and appropriate for MIMO wireless applications. Full article
(This article belongs to the Special Issue Microwave Passive Components)
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10 pages, 3325 KiB  
Article
120 GHz Frequency-Doubler Module Based on GaN Schottky Barrier Diode
by Honghui Liu, Zhiwen Liang, Jin Meng, Yuebo Liu, Hongyue Wang, Chaokun Yan, Zhisheng Wu, Yang Liu, Dehai Zhang, Xinqiang Wang and Baijun Zhang
Micromachines 2022, 13(8), 1172; https://doi.org/10.3390/mi13081172 - 25 Jul 2022
Cited by 9 | Viewed by 2419
Abstract
Traditional GaAs-based frequency multipliers still exhibit great challenges to meet the demand for solid-state high-power THz sources due to low breakdown voltage and heat dissipation of the Schottky barrier diode (SBD). In this study, a GaN SBD chain was fabricated with n− [...] Read more.
Traditional GaAs-based frequency multipliers still exhibit great challenges to meet the demand for solid-state high-power THz sources due to low breakdown voltage and heat dissipation of the Schottky barrier diode (SBD). In this study, a GaN SBD chain was fabricated with n−/n+-GaN structure. As a consequence, the breakdown voltage of 54.9 V at 1 μA and cut-off frequency of 587.5 GHz at zero bias were obtained. A 120 GHz frequency-doubler module based on the GaN SBD chain was designed and fabricated. When driven with 500 mW input power in a continuous wave, the output power of the frequency-doubler module was 15.1 mW at 120 GHz. Moreover, the experiments show that the frequency-doubler module can endure an input power of 2 W. In addition, it is worth noting that the SBD chain works well at an anode temperature of 337.2 °C. Full article
(This article belongs to the Special Issue Microwave Passive Components)
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11 pages, 3931 KiB  
Article
Frequency Scanning Dual-Mode Asymmetric Dual-OAM-Wave Generation Base on Broadband PB Metasurface
by Jiayu Yu, Qiurong Zheng, Xueqin Tang, Jie He, Jie Liu, Bin Zhang and Kun Zou
Micromachines 2022, 13(7), 1117; https://doi.org/10.3390/mi13071117 - 15 Jul 2022
Cited by 5 | Viewed by 1989
Abstract
Increasing information capacity is significant for high-speed communication systems in a congested radio frequency sequence. Vortex waves carrying mode orthogonal orbital angular momentum (OAM) have gained considerable attention in recent years, owing to their multiplexing quality. In this study, a broadband Pancharatnam–Berry (PB) [...] Read more.
Increasing information capacity is significant for high-speed communication systems in a congested radio frequency sequence. Vortex waves carrying mode orthogonal orbital angular momentum (OAM) have gained considerable attention in recent years, owing to their multiplexing quality. In this study, a broadband Pancharatnam–Berry (PB) metasurface element with a simple structure is proposed, which exhibits an efficient reflection of the co-polarized component and a full 2π phase variation in 10.5–21.5 GHz under circularly polarized wave incidence. By convolution and addition operations, the elaborate phase distribution is arranged and the corresponding metasurface-reflecting dual-mode asymmetric dual-OAM waves is constructed. Under continuous control of the working frequency, the OAM vortex beams with the topological charges 1 and −1 are steered to scan within the angle range of 11.9°–24.9° and 17.9°–39.1° at φ = 315° and 135° planes, respectively. The simulation and measurement results verified the feasibility of generating frequency-controlled asymmetric dual beams and the validity of dual-mode OAM characteristics, both in the near and far fields. This design approach has considerable potential in OAM wave multiplexing and wireless communication system transmission. Full article
(This article belongs to the Special Issue Microwave Passive Components)
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12 pages, 2932 KiB  
Article
A General FEM Model for Analysis of Third-Order Nonlinearity in RF Surface Acoustic Wave Devices Based on Perturbation Theory
by Baichuan Li, Qiaozhen Zhang, Xiangyong Zhao, Shaotao Zhi, Luyan Qiu, Sulei Fu and Weibiao Wang
Micromachines 2022, 13(7), 1116; https://doi.org/10.3390/mi13071116 - 15 Jul 2022
Cited by 7 | Viewed by 2092
Abstract
This article presents a general-purpose model that enables efficient and accurate calculation of third-order nonlinear signals in surface acoustic wave (SAW) devices. This model is based on piezoelectric constitutive equations combined with perturbation theory, which can be analyzed by full finite element method [...] Read more.
This article presents a general-purpose model that enables efficient and accurate calculation of third-order nonlinear signals in surface acoustic wave (SAW) devices. This model is based on piezoelectric constitutive equations combined with perturbation theory, which can be analyzed by full finite element method (FEM). For validation, third-order harmonic (H3) responses and intermodulation distortions (IMD3) in SAW resonators are simulated, and their calculation results fit well to experimental data in the literature. Then, the generation mechanisms of the third-order nonlinearity in SAW resonators are discussed. The dominant generation mechanisms for different nonlinear signals and the relation between electrode materials and H3 peak magnitude are revealed, which provides an important guideline for further nonlinear suppression. Full article
(This article belongs to the Special Issue Microwave Passive Components)
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9 pages, 2594 KiB  
Article
Design and Measurement of a Novel Overmoded TE01 Mode Converter for a Rectangular Gyro-TWT
by Chaoxuan Lu, Wei Jiang, Zewei Wu, Guo Liu, Jianxun Wang, Youlei Pu and Yong Luo
Micromachines 2022, 13(7), 1111; https://doi.org/10.3390/mi13071111 - 15 Jul 2022
Viewed by 1498
Abstract
The rectangular gyrotron traveling wave tube (gyro-TWT) with a large aspect ratio (α) has the potential to achieve megawatt-class output power. As an essential component of gyro-TWT, a novel overmoded Ka-band mode converter with an α of 6.19 is designed, analyzed, [...] Read more.
The rectangular gyrotron traveling wave tube (gyro-TWT) with a large aspect ratio (α) has the potential to achieve megawatt-class output power. As an essential component of gyro-TWT, a novel overmoded Ka-band mode converter with an α of 6.19 is designed, analyzed, and cold tested in this paper. Based on the magnetic dipole moment theory, the rectangular overmoded TE01 mode is excited via the rectangular fundamental TE10 mode. The cutoff waveguide is applied to prevent electromagnetic wave transport to the magnetron injection gun (MIG) region and also guarantee higher power electron beam transportation. Simulations predict an operation bandwidth higher than 4 GHz and greater than 99.8% mode purity between 33–37 GHz. To verify this design, the mode converter is manufactured and cold tested. The back-to-back measurement results exhibit a good agreement with the simulation. With similar topologies, the rectangular overmoded TE01 mode can be excited in a different α. Full article
(This article belongs to the Special Issue Microwave Passive Components)
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15 pages, 13080 KiB  
Article
Miniaturized MIMO Antenna Array with High Isolation for 5G Metal-Frame Smartphone Application
by Yuehui Gao, Junlin Wang, Xin Wang and Rui Shao
Micromachines 2022, 13(7), 1064; https://doi.org/10.3390/mi13071064 - 1 Jul 2022
Cited by 13 | Viewed by 2443
Abstract
In this paper, a highly isolated multiple-input multiple-output (MIMO) antenna array is proposed for fifth-generation (5G) metal frame smartphones. The eight identical small-sized inverted F-shaped folded slots are etched on the metal frame as a MIMO antenna. The bandwidth of the antenna can [...] Read more.
In this paper, a highly isolated multiple-input multiple-output (MIMO) antenna array is proposed for fifth-generation (5G) metal frame smartphones. The eight identical small-sized inverted F-shaped folded slots are etched on the metal frame as a MIMO antenna. The bandwidth of the antenna can be adjusted by changing one of the short branches of the antenna. The bandwidth of the antenna can reach the N79 band (4.4~5.0 GHz). By carefully arranging the positions of the eight antenna elements, ideal spatial diversity can be successfully achieved to mitigate the coupling between the antenna elements effectively. What is more, a small combination slot of C-shape (0.0078 × 0.047λ2) and vertical I-shape (0.12 × 0.004λ2) between each antenna element is introduced to improve the element isolation of the MIMO antenna system. The proposed MIMO array has been simulated, fabricated, and measured. The results show good impedance matching (return loss > 6 dB) and high isolation (>22 dB). Due to the decent element isolation, the envelope correlation coefficient (ECC) between each antenna element is below 0.049. It can provide a reliable anti-interference performance for the MIMO antenna system. In addition, the measured radiation efficiencies of the MIMO antenna system are higher than 50%. The interaction of the hand model with the MIMO antenna system is also investigated, including the specific absorption rate (SAR). Full article
(This article belongs to the Special Issue Microwave Passive Components)
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9 pages, 3026 KiB  
Article
Design and Characterization of Wideband Terahertz Metamaterial Stop-Band Filter
by Hao Li, Junlin Wang, Xin Wang, Yao Feng and Zhanshuo Sun
Micromachines 2022, 13(7), 1034; https://doi.org/10.3390/mi13071034 - 29 Jun 2022
Cited by 7 | Viewed by 1882
Abstract
We propose and design a metamaterial broadband stop-band filter with a steep cut-off in the terahertz region. The filter is based on the flexible structure of metal-dielectric-metal-dielectric-metal (MDMDM). Simulation results show that the filter has a center frequency of 1.08 THz, the square [...] Read more.
We propose and design a metamaterial broadband stop-band filter with a steep cut-off in the terahertz region. The filter is based on the flexible structure of metal-dielectric-metal-dielectric-metal (MDMDM). Simulation results show that the filter has a center frequency of 1.08 THz, the square ratio reaches 0.95, and the −20 dB bandwidth reaches 1.07 THz. In addition, it has excellent flat-top characteristics with an average transmission rate in the resistive band of no more than 5%. The relative bandwidth has been up to 99%, and stopband absorption rate has reached more than 98%. The effects of the main structural parameters on the transmission characteristics are discussed. The role of each layer of metal in the filter is explored by studying the effect of the variation of the number of metal layers on the filter. The symmetry of the structure ensures the polarization insensitivity of the filter at normal incidence. The correctness of the simulation results was verified by analyzing the effective permittivity and magnetic permeability. To investigate the transmission characteristics of the metamaterial filter in-depth, we analyzed the electric field strength and surface current distribution at the center frequency of the filter. The designed terahertz filter may have potential applications in terahertz communications, sensors, and emerging terahertz technologies. Full article
(This article belongs to the Special Issue Microwave Passive Components)
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13 pages, 4635 KiB  
Article
Switchable Multifunctional Terahertz Metamaterials Based on the Phase-Transition Properties of Vanadium Dioxide
by Zhanshuo Sun, Xin Wang, Junlin Wang, Hao Li, Yuhang Lu and Yu Zhang
Micromachines 2022, 13(7), 1013; https://doi.org/10.3390/mi13071013 - 27 Jun 2022
Cited by 12 | Viewed by 2126
Abstract
Currently, terahertz metamaterials are studied in many fields, but it is a major challenge for a metamaterial structure to perform multiple functions. This paper proposes and studies a switchable multifunctional multilayer terahertz metamaterial. Using the phase-transition properties of vanadium dioxide (VO2), [...] Read more.
Currently, terahertz metamaterials are studied in many fields, but it is a major challenge for a metamaterial structure to perform multiple functions. This paper proposes and studies a switchable multifunctional multilayer terahertz metamaterial. Using the phase-transition properties of vanadium dioxide (VO2), metamaterials can be controlled to switch transmission and reflection. Transmissive metamaterials can produce an electromagnetically induced transparency-like (EIT-like) effect that can be turned on or off according to different polarization angles. The reflective metamaterial is divided into I-side and II-side by the middle continuous VO2 layer. The I-side metamaterials can realize linear-to-circular polarization conversion from 0.444 to 0.751 THz when the incident angle of the y-polarized wave is less than 30°. The II-side metamaterials can realize linear-to-linear polarization conversion from 0.668 to 0.942 THz when the incident angle of the y-polarized wave is less than 25°. Various functions can be switched freely by changing the conductivity of VO2 and the incident surface. This enables metamaterials to be used as highly sensitive sensors, optical switches, and polarization converters, which provides a new strategy for the design of composite functional metamaterials. Full article
(This article belongs to the Special Issue Microwave Passive Components)
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8 pages, 6351 KiB  
Article
A Substrate Integrated Waveguide-Based W-Band Antenna for Microwave Power Transmission
by Liang Liu, Yu Yang, Chuan Yu, Shifeng Li, Hao Wu, Limin Sun and Fanbao Meng
Micromachines 2022, 13(7), 986; https://doi.org/10.3390/mi13070986 - 24 Jun 2022
Cited by 6 | Viewed by 1847
Abstract
A W-band slot array antenna based on a substrate integrated waveguide (SIW) for microwave power transmission (MPT) is proposed in this paper. By size optimization, the transition from the rectifier element to the antenna is limited to a small size. It realizes a [...] Read more.
A W-band slot array antenna based on a substrate integrated waveguide (SIW) for microwave power transmission (MPT) is proposed in this paper. By size optimization, the transition from the rectifier element to the antenna is limited to a small size. It realizes a compact arrangement of the radiating slots, which not only improves the aperture efficiency of the antenna but also makes it easy to integrate into a large-scale array. For antenna testing, a coplanar waveguide–SIW–rectangular waveguide transition structure is added at the end of the antenna, and an antenna with this transition structure is processed by PCB printing technology and measured. The measured reflection coefficient is less than −10 dB at 90–96 GHz, the aperture efficiency is greater than 60% at 93.5–94.5 GHz, the maximum gain is 13.2 dB at 93.5 GHz, and the aperture efficiency is 79%. The test results of the antenna show that the antenna has a good performance and can be applied to the MPT system as a rectenna. Full article
(This article belongs to the Special Issue Microwave Passive Components)
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10 pages, 3915 KiB  
Article
High-Property Refractive Index and Bio-Sensing Dual-Purpose Sensor Based on SPPs
by Shubin Yan, Pengwei Liu, Zhanbo Chen, Jilai Liu, Lifang Shen, Xiaoyu Zhang, Jiaming Cui, Tingsong Li, Yang Cui and Yifeng Ren
Micromachines 2022, 13(6), 846; https://doi.org/10.3390/mi13060846 - 29 May 2022
Cited by 6 | Viewed by 1943
Abstract
A high-property plasma resonance-sensor structure consisting of two metal-insulator-metal (MIM) waveguides coupled with a transverse ladder-shaped nano-cavity (TLSNC) is designed based on surface plasmon polaritons. Its transmission characteristics are analyzed using multimode interference coupling mode theory (MICMT), and are simulated using finite element [...] Read more.
A high-property plasma resonance-sensor structure consisting of two metal-insulator-metal (MIM) waveguides coupled with a transverse ladder-shaped nano-cavity (TLSNC) is designed based on surface plasmon polaritons. Its transmission characteristics are analyzed using multimode interference coupling mode theory (MICMT), and are simulated using finite element analysis (FEA). Meanwhile, the influence of different structural arguments on the performance of the structure is investigated. This study shows that the system presents four high-quality formants in the transmission spectrum. The highest sensitivity is 3000 nm/RIU with a high FOM* of 9.7 × 105. In addition, the proposed structure could act as a biosensor to detect the concentrations of sodium ions (Na+), potassium ions (K+), and the glucose solution with maximum sensitivities of 0.45, 0.625 and 5.5 nm/mgdL−1, respectively. Compared with other structures, the designed system has the advantages of a simple construction, a wide working band range, high reliability and easy nano-scale integration, providing a high-performance cavity choice for refractive index sensing and biosensing devices based on surface plasmons. Full article
(This article belongs to the Special Issue Microwave Passive Components)
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