Artykuły w czasopismach: „Tunable RF MEMS impedance matching”

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Guo, X. L., J. Huang, Z. L. Wang, H. H. Yin, Z. J. Zhang, M. Shi i H. Jiang. "Tunable Matching Network Using MEMS Switches". Advanced Materials Research 765-767 (wrzesień 2013): 2575–78. http://dx.doi.org/10.4028/www.scientific.net/amr.765-767.2575.

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This paper presents a novel approach in order to construct low-loss reconfigurable impedance matching networks and tuners using MEMS series-contact switches and periodic defected-ground-structures (DGSs) implemented on coplanar waveguide (CPW) transmission lines. The application of DGSs results in an improved insertion loss and power handling capability compared to the conventional RF MEMS impedance tuning networks. The proposed structure consists of 12 DGSs and RF MEMS series-contact switches. The tunable matching network was fabricated on a silicon substrate and is only 1.4×̃˾̈˰̽̽˰̹̾˰̵̹̓͊˾˰̸̵̤˰̵̵̴̱̽̓͂ͅ˰̼̿̓̓˰̶̿˰̸̵̈́˰̵͇̻̾̈́̿͂˰̸̵͇̾˰̵̴̓ͅ˰̈́̿˰̸̱̳̽̈́˰̱˰́̀˰Ω˰̴̼̱̿˰̈́̿˰̅̀˰Ω˰̶͂̿m 5GHz up to 40 GHz is only 0.8 dB. The results show that the tuner can achieve a broadband impedance match for a wide variety of loads that are either purely resistive or that have a large reactance as well.

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Iannacci, Jacopo, Giuseppe Resta, Paola Farinelli i Roberto Sorrentino. "RF-MEMS Components and Networks for High-Performance Reconfigurable Telecommunication and Wireless Systems". Advances in Science and Technology 81 (wrzesień 2012): 65–74. http://dx.doi.org/10.4028/www.scientific.net/ast.81.65.

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MEMS (MicroElectroMechanical-Systems) technology applied to the field of Radio Frequency systems (i.e. RF-MEMS) has emerged in the last 10-15 years as a valuable and viable solution to manufacture low-cost and very high-performance passive components, like variable capacitors, inductors and micro-relays, as well as complex networks, like tunable filters, reconfigurable impedance matching networks and phase shifters, and so on. The availability of such components and their integration within RF systems (e.g. radio transceivers, radars, satellites, etc.) enables boosting the characteristics and performance of telecommunication systems, addressing for instance a significant increase of their reconfigurability. The benefits resulting from the employment of RF-MEMS technology are paramount, being some of them the reduction of hardware redundancy and power consumption, along with the operability of the same RF system according to multiple standards. After framing more in detail the whole context of RF MEMS technology, this paper will provide a brief introduction on a typical RF-MEMS technology platform. Subsequently, some relevant examples of lumped RF MEMS passive elements and complex reconfigurable networks will be reported along with their measured RF performance and characteristics.

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Figur, Sascha A., Friedbert van Raay, Rüdiger Quay, Peter Lohmiller, Larissa Vietzorreck i Volker Ziegler. "RF-MEMS variable matching networks and switches for multi-band and multi-mode GaN power amplifiers". International Journal of Microwave and Wireless Technologies 6, nr 3-4 (12.03.2014): 265–76. http://dx.doi.org/10.1017/s175907871400021x.

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This work presents radio-frequency-microelectromechanical-system (RF-MEMS)-based tunable matching networks for a multi-band gallium nitride (GaN) power amplifer (PA) application. In the frequency range from 3.5–8.5 GHz return losses of 5–10 dB were measured for the input network, matching impedances close to the border of the Smith chart. For the output matching network return losses of 10–20 dB and insertion losses of 1.3–2 dB were measured. The matching networks can tune the PA to four different operating frequencies, as well as changing the transistor's mode of operation from maximum delivered-output-power to maximum power-added-efficiency (PAE), while keeping the operating frequency constant. Furthermore, different single pole double throw (SPDT)-switches are designed and characterized, to be used in frequency-agile transmit/receive-modules (T/R modules).

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Bhatia, Vinay, Sukhdeep Kaur, Kuldeep Sharma, Punam Rattan, Vishal Jagota i Mohammed Abdella Kemal. "Design and Simulation of Capacitive MEMS Switch for Ka Band Application". Wireless Communications and Mobile Computing 2021 (12.07.2021): 1–8. http://dx.doi.org/10.1155/2021/2021513.

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In this paper, RF MEMS switch with capacitive contact is designed and analyzed for Ka band application. A fixed-fixed beam/meander configuration has been used to design the switch for frequency band 10 GHz to 40 GHz. Electromagnetic and electromechanical analysis of three-dimensional (3D) structure/design has been analyzed in multiple finite element method (FEM) based full-wave simulator (Coventorware and high-frequency structure simulator). A comparative study has also been carried out in this work. The high resistivity silicon substrate ( tan δ = 0.010 , ρ > 8 k Ω − cm , ε r = 11.8 ) with a thickness of 675 ± 25 μ m has been taken for switch realization. The designed structure shows an actuation voltage of around 9.2 V. Impedance matching for the switch structure is well below 20 dB, loss in upstate, i.e., insertion loss >0.5 dB, and isolation of >25 dB throughout the frequency band is observed for the aforesaid structure. Furthermore, to increase the RF parameters, AIN dielectric material has been used instead of SiO2 resulting in capacitance in downstate that increases hence improved the isolation. The proposed switch can be utilized in various potential applications such as any switching/tunable networks phased-array radar, reconfigurable antenna, RF phase shifter, mixer, biomedical, filter, and any transmitter/receiver (T/R) modules.

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Sorrentino, Roberto, Paola Farinelli, Alessandro Cazzorla i Luca Pelliccia. "RF-MEMS Application to RF Tuneable Circuits". Advances in Science and Technology 100 (październik 2016): 100–108. http://dx.doi.org/10.4028/www.scientific.net/ast.100.100.

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The bursting wireless communication market, including 5G, advanced satellite communication systems and COTM (Communication On The Move) terminals, require ever more sophisticated functions, from multi-band and multi-function operations to electronically steerable and reconfigurable antennas, pushing technological developments towards the use of tunable microwave components and circuits. Reconfigurability allows indeed for reduced complexity and cost of the apparatuses. In this context, RF MEMS (Micro-Electro-Mechanical-Systems) technology has emerged as a very attractive solution to realize both tunable devices (e.g. variable capacitors, inductors and micro-relays), as well as complex circuits (e.g. tunable filters, reconfigurable matching networks and reconfigurable beam forming networks for phased array antennas). High linearity, low loss and high miniaturization are the typical advantages of RF MEMS over conventional technologies. Micromechanical components fabricated via IC-compatible MEMS technologies and capable of low-loss filtering, switching and frequency generation allow for miniaturized wireless front-ends via higher levels of integration. In addition, the inherent high linearity of the MEMS switches enables carrier aggregations without introducing intermodulation distortions. This paper will review the recent advances in the development of the RF MEMS to RF tunable circuits and systems.

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Qin Shen i N. S. Bar. "Distributed MEMS tunable matching network using minimal-contact RF-MEMS varactors". IEEE Transactions on Microwave Theory and Techniques 54, nr 6 (czerwiec 2006): 2646–58. http://dx.doi.org/10.1109/tmtt.2006.872943.

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Saha, Shimul C., Ulrik Hanke, Håkon Sagberg, Tor A. Fjeldly i Trond Sæther. "Tunable Lowpass Filter with RF MEMS Capacitance and Transmission Line". Active and Passive Electronic Components 2012 (2012): 1–5. http://dx.doi.org/10.1155/2012/502465.

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We have presented an RF MEMS tuneable lowpass filter. Both distributed transmission lines and RF MEMS capacitances were used to replace the lumped elements. The use of RF MEMS capacitances gives the flexibility of tuning the cutoff frequency of the lowpass filter. We have designed a low-pass filter at 9–12 GHz cutoff frequency using the theory of stepped impedance transmission lines. A prototype of the filter has been fabricated using parallel plate capacitances. The variable shunt capacitances are formed by a combination of a number of parallel plate RF MEMS capacitances. The cutoff frequency is tuned from C to X band by actuating different combinations of parallel capacitive bridges. The measurement results agree well with the simulation result.

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Palson, C. L., D. D. Krishna, B. R. Jose, J. Mathew i M. Ottavi. "Memristor Based Planar Tunable RF Circuits". Journal of Circuits, Systems and Computers 28, nr 13 (11.02.2019): 1950225. http://dx.doi.org/10.1142/s0218126619502256.

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Memristors have been recently proposed as an alternative to incorporate switching along with traditional CMOS circuits. Adaptive impedance and frequency tuning are an essential and challenging aspect in communication system design. To enable both, a matching network based on switchable capacitors with fixed inductors is proposed in this paper where the switching is done by memristive switches. This paper analyzes the operation of memristors as a switch and a matching network based on memristors which adaptively tunes with impedance and frequency. With three capacitor banks of each 0.5 pF resolution and two fixed inductors, matching for antenna impedance ranging from 20 to 200[Formula: see text]Ohms and for frequencies ranging from 0.9 to 3.2[Formula: see text]GHz is reported. Thereafter, an adaptive planar band-pass filter is implemented on CMOS technology with two metal layers. This adaptive frequency tunable band-pass filter uses a [Formula: see text] network with resonator tanks in both arms that operates at 2.45 GHz. It is tunable from 2.8[Formula: see text]GHz to 7.625[Formula: see text]GHz range. This tunability is achieved using tunable spiral inductor based on memristive switches. The proposed filter layout is implemented and simulated in ANSYS Designer. The initialization and the programming circuitry to enable adaptive switching of the memristive devices has to be addressed. Since RF memristive devices are not commercially available, circuit level simulations are done as a proof of concept to validate the expected results.

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Iannacci, J. "Reconfigurable RF-MEMS-based impedance matching networks for a hybrid RF-MEMS/CMOS class-E power amplifier". Microsystem Technologies 25, nr 12 (8.06.2019): 4709–19. http://dx.doi.org/10.1007/s00542-019-04510-3.

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Gholamian, Sholeh, i Ebrahim Abbaspour-Sani. "Design and Simulation of RF MEMS Tunable Spiral Inductor". Advanced Materials Research 403-408 (listopad 2011): 4148–51. http://dx.doi.org/10.4028/www.scientific.net/amr.403-408.4148.

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This paper presents a tunable inductor using MEMS technology .This tunable spiral inductor is designed in order to be used in RF circuits such as : controlled oscillators with voltage (VCO) , matching networks ,amplifiers etc . The electrostatic method is employed for tuning the inductor by the movement of cantilever beam downward and changing the value of magnetic flux. Value of inductance varies fram 1.15nh to 0.561 nh .therefore ,tunablity of 66.21% was achieved .Maximum quality factor in the above inductor was achieved az 13.88 in the frequency 0f 12 GHz and the value of resonance frequency was achieved as 19.5 GHz

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Figur, Sascha A., Friedbert van Raay, Rüdiger Quay, Larissa Vietzorreck i Volker Ziegler. "RF-MEMS multi-mode-matching networks for GaN power transistors". International Journal of Microwave and Wireless Technologies 6, nr 5 (1.04.2014): 447–58. http://dx.doi.org/10.1017/s1759078714000427.

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This work presents radio-frequency-microelectromechanical-system (RF-MEMS)-based tunable input- and output-matching networks for a multi-band gallium nitride (GaN) power-amplifier applications. In the first part, circuit designs are shown and characterized for a fixed operation mode of the transistor, i.e. either a maximum-output-power- or a maximum-power-added-efficiency (PAE)-mode, which are finally combined into a multi-mode-matching network (M3N); the M3N allows to tune the operation mode of the transistor independently of its operational frequency. The matching networks are designed to provide optimum matching for the power amplifier at three to six different operating frequencies for maximum-output-power- and maximum-PAE-mode. In the frequency range from 3.5 to 8.5 GHz, return losses of 10 dB and higher were measured and insertion losses of 0.5–1.9 dB were demonstrated for the output-matching networks. Further characterizations were performed to test the dependency on the RF-input power, and no changes were observed up to power levels of 34 dBm when cold-switched.

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Wong, Yan Chiew, Ranjit Singh Sarban Singh, Syafeeza Binti Ahmad Radzi i Norihan Binti Abdul Hamid. "Tunable impedance matching network with wide impedance coverage for multi frequency standards RF front-end". AEU - International Journal of Electronics and Communications 82 (grudzień 2017): 74–82. http://dx.doi.org/10.1016/j.aeue.2017.08.004.

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Hoarau, C., N. Corrao, J. D. Arnould, P. Ferrari i P. Xavier. "Complete Design and Measurement Methodology for a Tunable RF Impedance-Matching Network". IEEE Transactions on Microwave Theory and Techniques 56, nr 11 (listopad 2008): 2620–27. http://dx.doi.org/10.1109/tmtt.2008.2006105.

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Saberkari, Alireza, Saman Ziabakhsh, Herminio Martinez i Eduard Alarcón. "Active inductor-based tunable impedance matching network for RF power amplifier application". Integration 52 (styczeń 2016): 301–8. http://dx.doi.org/10.1016/j.vlsi.2015.07.013.

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Dal Fabbro, P. A., i M. Kayal. "RF power amplifier employing a frequency-tunable impedance matching network based on coupled inductors". Electronics Letters 44, nr 19 (2008): 1131. http://dx.doi.org/10.1049/el:20089196.

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Sahar, N. M., M. T. Islam, N. Misran i M. R. Zaman. "Development of Reconfigurable Antenna for Advanced Tracking Technology". Indonesian Journal of Electrical Engineering and Computer Science 10, nr 2 (1.05.2018): 672. http://dx.doi.org/10.11591/ijeecs.v10.i2.pp672-679.

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<p>This paper focuses on the design and fabrication of reconfigurable multiband antenna for RFID and GPS as an advance tracking technology for various applications that achieve a physically compact, planar profile and sufficient bandwidth. The antenna can be reconfigured as single band at 1.275 GHz for GPS applications when the switches are OFF state and dual-band frequencies at 0.915 GHz and 2.4 GHz required in RFID applications when the switches are ON state. The performance of the antenna involves changing the switches to ON or OFF mode by controlling RF switches. RF MEMs RMSW101, Single Pole Single Throw (SPST) switches have been chosen due to the satisfactory RF properties includes low insertion loss, good impedance matching and high isolation. The gain for single and dual band is greater than 2dBi. The design methodology and antenna measurement results are both presented and discussed in this letter.</p>

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Jmai, Bassem, Hugo Dinis, Pedro Anacleto, Adnen Rajhi, Paulo M. Mendes i Ali Gharsallah. "Modelling, design and fabrication of a novel reconfigurable ultra‐wide‐band impedance matching based on RF MEMS technology". IET Circuits, Devices & Systems 13, nr 8 (listopad 2019): 1299–304. http://dx.doi.org/10.1049/iet-cds.2019.0116.

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Lee, Dong-gu, Duehee Lee i Kuduck Kwon. "A CMOS Wideband RF Energy Harvester Employing Tunable Impedance Matching Network for Video Surveillance Disposable IoT Applications". Transactions of The Korean Institute of Electrical Engineers 68, nr 2 (28.02.2019): 304–9. http://dx.doi.org/10.5370/kiee.2019.68.2.304.

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Fouladi, Siamak, Frederic Domingue, Nino Zahirovic i Raafat R. Mansour. "Distributed MEMS Tunable Impedance-Matching Network Based on Suspended Slow-Wave Structure Fabricated in a Standard CMOS Technology". IEEE Transactions on Microwave Theory and Techniques 58, nr 4 (kwiecień 2010): 1056–64. http://dx.doi.org/10.1109/tmtt.2010.2042511.

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Chung, Myungjin, Heijun Jeong, Yong-Kweon Kim, Sungjoon Lim i Chang-Wook Baek. "Design and Fabrication of Millimeter-Wave Frequency-Tunable Metamaterial Absorber Using MEMS Cantilever Actuators". Micromachines 13, nr 8 (20.08.2022): 1354. http://dx.doi.org/10.3390/mi13081354.

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In this paper, a MEMS (Micro Electro Mechanical Systems)-based frequency-tunable metamaterial absorber for millimeter-wave application was demonstrated. To achieve the resonant-frequency tunability of the absorber, the unit cell of the proposed metamaterial was designed to be a symmetric split-ring resonator with a stress-induced MEMS cantilever array having initial out-of-plane deflections, and the cantilevers were electrostatically actuated to generate a capacitance change. The dimensional parameters of the absorber were determined via impedance matching using a full electromagnetic simulation. The designed absorber was fabricated on a glass wafer with surface micromachining processes using a photoresist sacrificial layer and the oxygen-plasma-ashing process to release the cantilevers. The performance of the fabricated absorber was experimentally validated using a waveguide measurement setup. The absorption frequency shifted down according to the applied DC (direct current) bias voltage from 28 GHz in the initial off state to 25.5 GHz in the pull-down state with the applied voltage of 15 V. The measured reflection coefficients at those frequencies were −5.68 dB and −33.60 dB, corresponding to the peak absorptivity rates of 72.9 and 99.9%, respectively.

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Sampe, Jahariah, Noor Hidayah Mohd Yunus, Jumril Yunas i Ahmad G. Ismail. "Performance Analysis of Low Power Radio Frequency Micro Energy Harvester using MEMS Antenna for Wireless Sensor Networks". Jurnal Kejuruteraan 35, nr 1 (30.01.2023): 133–40. http://dx.doi.org/10.17576/jkukm-2023-35(1)-13.

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Recently, there has been a growing tendency of interest from researchers to use ambient energy to power electronic equipment using various energy harvesting techniques. Micro energy harvesting is a potential technique to convert ambient energy from the environment to electrical energy. The wireless sensor network requires a constant source of electrical energy to activate it and the radio frequency (RF) ambient energy source that always exists in the environment is very suitable for use. Therefore, the designed and developed RF micro energy harvester consisting of an impedance matching circuit, a voltage multiplier and a rectifier circuit does not require an external energy source to activate it. This RF micro energy harvester circuit is constructed and simulated using PSPICE software by connecting a 1 MΩ load resistor. At an input power of -20 dBm or 10 μW captured by the MEMS antenna, the values of the output voltage and current produced in this energy harvester circuit are 2.36 V and 1.7 mA, respectively. Meanwhile, the maximum efficiency percentage of the entire RF micro energy harvester circuit is 55.7%. The output power value of 40.12 mW is higher than the input power value of 10 μW. This RF micro energy harvester is capable of activating a wireless sensor network with a minimum input current requirement of 1 mA. An integrated circuit layout using 180 nm CMOS technology for a multiplier circuit has been successfully developed with a very small size of 22.48 x 56.96 μm2 as proof that the circuit can be fabricated as an integrated circuit chip.

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Janardhanan, Shankaran, Joan Z. Delalic, Jeffrey Catchmark i Dharanipal Saini. "Development of Biocompatible MEMS Wireless Capacitive Pressure Sensor". Journal of Microelectronics and Electronic Packaging 2, nr 4 (1.10.2005): 287–96. http://dx.doi.org/10.4071/1551-4897-2.4.287.

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The objective of this research was to develop a wireless pressure sensor useful for monitoring bladder pressure. The wireless sensor consists of an active capacitive element and an inductor coil. The changes in pressure are related to the changes in the resonant frequency of the internal sensor. The existing pressure sensors have inductors formed on both sides of the substrate. The changes in internal capacitance of these sensors are related to the changes in pressure by impedance matching of the internal LC circuit. The deviation in bladder pressure is an important variable in evaluating the diseased state of the bladder. The inductor designed for this application is a spirally wound inductor fabricated adjacent to the capacitor. The external sensing uses equivalent changes in internal LC. The resonant frequency of the internal sensor is defined by the deformation of the plate, causing the plate to touch the dielectric on the fixed capacitive plate, which is reflected as changes in capacitance(C). The deformation of the plate has been modeled using Finite Element Analysis. The finite element analysis optimizes the dimensions of the design. Remote sensing is achieved through inductive coupling and the changes in pressure are determined. The device is tested for pressures ranging from 0–150 mmHg, bladder pressure. The RF Telemetry system has been modeled using Sonnet. The frequency range is between 100–670 MHz which is in compliance to that specified by Federal Communications Commission (FCC) regulations.

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Cho, Kwang Hwan, Jong Yoon Ha, Chong Yun Kang, Ji Won Choi, Young Pak Lee i Seok Jin Yoon. "Structural Features and Microwave Properties of Ba_0.5Sr_0.5TiO₃ Films Grown on Sapphire Substrates". Solid State Phenomena 124-126 (czerwiec 2007): 1829–32. http://dx.doi.org/10.4028/www.scientific.net/ssp.124-126.1829.

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The change in dielectric constant of ferroelectric materials as a function of electric field is the key to wide range of microwave application such as tunable filter, impedance matching network, and phase shifter. In this study, ferroelectric Ba0.5Sr0.5TiO3 (BST) films were grown on r-cut sapphire and polycrystalline sapphire (poly-sapphire) substrates by RF sputtering. The results of comprehensive structural diagnostics of the films are correlated with the dielectric constant and dielectric loss of a co-planar BST varactor, measured at a frequency range of 1~3 GHz. Textured BST films approximately 500 nm thick, grown on r-cut sapphire substrates, are characterized by high dielectric constant ≥ 650. However, polycrystalline BST films, grown on poly-sapphire substrates, are less strained, having dielectric constant range of 430 ~ 640.

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Gaur, Tushar, Pragya Mishra, Gopalkrishna Hegde i Talabattula Srinivas. "Modeling and Analysis of Device Orientation, Analog and Digital Performance of Electrode Design for High Speed Electro-Optic Modulator". Photonics 10, nr 3 (12.03.2023): 301. http://dx.doi.org/10.3390/photonics10030301.

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Electro-optic modulators (EOMs) are crucial devices for modern communication enabling high bandwidth optical communication links. Traveling wave electrodes are used to obtain high-speed modulation in these EOMs. We present the electrode design and analysis along with the study of effects of changing orientation on device performance for a thin-film lithium niobate tunable Mach–Zehnder interferometer (MZI) that offers sub-THz bandwidth operations. High velocity and impedance matching with low RF attenuation, high third-order SFDR (∼121 dB/Hz2/3) and a low half-wave voltage length product (1.74 V.cm) have been achieved for a bandwidth of 136 GHz. High-speed digital modulation using multi-level signal formats (PAM-2, QAM-4 and QAM-16) with low BER for 400 Gbps data has been demonstrated to assess the digital performance of the device.

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Park, Yong-Hee, Jae-Hyoung Park, Yong-Dae Kim, Hee-Chul Lee, Hong-Teuk Kim, Jonguk Bu i Hyo-Jin Nam. "A tunable planar inverted-F antenna with an RF MEMS switch for the correction of impedance mismatch due to human hand effects". Journal of Micromechanics and Microengineering 19, nr 1 (10.12.2008): 015026. http://dx.doi.org/10.1088/0960-1317/19/1/015026.

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Xia, Hong, Jin Min Song i Chang Jie Su. "Design and Implementation of Long Range UHF RFID Reader". Applied Mechanics and Materials 241-244 (grudzień 2012): 3229–37. http://dx.doi.org/10.4028/www.scientific.net/amm.241-244.3229.

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Aiming at the problems how to realize long range, high speed identification and how to integrate web with the management system in the UHF RFID applications, a UHF RFID reader system based on S3C2440 microprocessor and AS3992 UHF Reader chip is designed and implemented in this paper. By designing the RF front-end power amplifier and signal isolation circuit, the transmit power detection circuit and the antenna impedance tunable matching circuit, the transmit power reaches up to 32 dBm and the receiver SNR is improved at the same time, resulting in the stable read range reaching up to 12 meters. In order to integrate web control into the RFID management system, the reader system is transplanted into the embedded Linux OS and a web management system that is based on web server and CGI is constructed. Device drivers are developed and RFID APIs are packaged, greatly facilitating the software development and maintenance. By using the Random-Slotted anti-collision algorithm, high speed identification of ISO18000-6C RFID tags has been achieved.

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Ketata, Ilef, Sarah Ouerghemmi, Ahmed Fakhfakh i Faouzi Derbel. "Design and Implementation of Low Noise Amplifier Operating at 868 MHz for Duty Cycled Wake-Up Receiver Front-End". Electronics 11, nr 19 (8.10.2022): 3235. http://dx.doi.org/10.3390/electronics11193235.

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The integration of wireless communication, e.g., in real- or quasi-real-time applications, is related to many challenges such as energy consumption, communication range, quality of service, and reliability. The improvement of wireless sensor networks (WSN) performance starts by enhancing the capabilities of each sensor node. To minimize latencies without increasing energy consumption, wake-up receiver (WuRx) nodes have been introduced in recent works since they can be always-on or power-gated with short latencies by a power consumption in the range of some microwatts. Compared to standard receiver technologies, they are usually characterized by drawbacks in terms of sensitivity. To overcome the limitation of the sensitivity of WuRxs, a design of a low noise amplifier (LNA) with several design specifications is required. The challenging task of the LNA design is to provide equitable trade-off performances such as gain, power consumption, the noise figure, stability, linearity, and impedance matching. The design of fast settling LNA for a duty-cycled WuRx front-end operating at a 868 MHz frequency band is investigated in this work. The paper details the trade-offs between design challenges and illustrates practical considerations for the simulation and implementation of a radio frequency (RF) circuit. The implemented LNA competes with many commercialized designs where it reaches single-stage 12 dB gain at a 1.8 V voltage supply and consumes only a 1.6 mA current. The obtained results could be made tunable by working with off-the-shelf components for different wake-up based application exigencies.

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Kandala, Sri Kirthi, i Sung-Min Sohn. "Design of standalone wireless impedance matching (SWIM) system for RF coils in MRI". Scientific Reports 12, nr 1 (14.12.2022). http://dx.doi.org/10.1038/s41598-022-26143-9.

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AbstractThe radio frequency (RF) power transfer efficiency of transmit coils and the signal-to-noise ratio (SNR) at the receive signal chain are directly dependent on the impedance matching condition presented by a loaded coil, tuned to the Larmor frequency. Sub-optimal impedance condition of receive coils significantly reduces coil sensitivity and image quality. In this study we propose a Standalone Wireless Impedance Matching (SWIM) system for RF coils to automatically compensate for the impedance mismatch caused by the loading effect at the target frequency. SWIM uses a built-in RF generator to produce a calibration signal, measure reflected power as feedback for loading change, and determine an optimal impedance. The matching network consists of a capacitor array with micro-electromechanical system (MEMS) RF switches to electronically cycle through different input impedance conditions. Along with automatic calibration, SWIM can also perform software detuning of RF receive coils. An Android mobile application was developed for real-time reflected power monitoring and controlling the SWIM system via Bluetooth. The SWIM system can automatically calibrate an RF coil in 3 s and the saline sample SNR was improved by 24% when compared to a loaded coil without retuning. Four different tomatoes were imaged to validate the performance of SWIM.

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van Beek, Joost T. M., Marc H. W. M. van Delden, Auke van Dijken, Patrick van Eerd, Andre B. M. Jansman, Anton L. A. M. Kemmeren, Theo G. S. M. Rijks i in. "High-Q integrated RF passives and RF-MEMS on silicon". MRS Proceedings 783 (2003). http://dx.doi.org/10.1557/proc-783-b3.1.

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ABSTRACTA technology platform is described for the integration of low-loss inductors, capacitors, and MEMS capacitors on a high-resistivity Si substrate. Using this platform the board space area taken up by e.g. a DCS PA output impedance matching circuit can be reduced by 50%. The losses of passive components that are induced by the semi-conducting Si substrate can effectively be suppressed using a combination of surface amorphisation and the use of poly crystalline Si substrates. A MEM switchable capacitor with a capacitance switching factor of 40 and an actuation voltage of 5V is demonstrated. A continuous tuneable dual-gap capacitor is demonstrated with a tuning ratio of 9 using actuation voltages below 15V.

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Mohan, Arun, Ankit Kumar Sahoo i Saroj Mondal. "A tunable impedance matching strategy for RF energy harvesting systems". Analog Integrated Circuits and Signal Processing, 9.10.2022. http://dx.doi.org/10.1007/s10470-022-02105-z.

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Li, Liang, Taijun Liu, Yan Ye, Xiaojun Luo, Gang Cao, Xiaofeng Guo i Ming Hui. "Electronically Tunable Impedance-Matching Networks for Intelligent RF Power Amplifiers". TELKOMNIKA Indonesian Journal of Electrical Engineering 11, nr 11 (1.11.2013). http://dx.doi.org/10.11591/telkomnika.v11i11.3514.

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Takahashi, Kazunori, Ryoji Imai i Kengo Hanaoka. "Automatically Controlled Frequency-Tunable rf Plasma Thruster: Ion Beam and Thrust Measurements". Frontiers in Physics 9 (31.03.2021). http://dx.doi.org/10.3389/fphy.2021.639010.

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A fast and automatically controlled frequency-tunable radiofrequency (rf) system is installed in an rf plasma thruster consisting of a stepped-diameter insulator source tube wound by a single-turn loop antenna and a solenoid providing a magnetic nozzle, and immersed in vacuum. The frequency and the output power are controlled so as to minimize the reflection coefficient and to maintain the net power corresponding to the forward minus reflected powers at a constant level. The reproducibility of the impedance matching and the stability of the net rf power are assessed, showing the fast impedance matching within about 10 msec and the long and stable delivery of the rf power to the thruster. When increasing the rf power up to 500 W, discontinuous changes in the source plasma density, the imparted thrust, and the signal intensity of the ion beam downstream of the thruster are observed, indicating effects of the discharge mode on the thruster performance and the ion energy distribution.

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Wang, Qipeng, Zhiguo Su, Shunli Li, Hongxin Zhao i Xiaoxing Yin. "Electrically Tunable Liquid Crystal Phase Shifter With Excellent Phase Shift Capability Per Wavelength Based on Opposed Coplanar Waveguide". Journal of Physics D: Applied Physics, 14.07.2022. http://dx.doi.org/10.1088/1361-6463/ac8127.

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Abstract A tunable liquid crystal (LC) phase shifter based on opposed coplanar waveguide (OCPW) with excellent phase shift capability per wavelength is proposed. The proposed OCPW not only has good transmission characteristics and a quasi-TEM operating mode similar to the CPW, but also avoids the metalized via and complicated bias circuit in designing the phase shifter. Consequently, the phase shifter is easy to fabricate and miniaturize. The main structure of the phase shifter includes two functional components. One is the transition section, in which the flaring grounds and gradient stubs are utilized to realize the impedance and wave-number matching to the OCPW phase shift part; the other is a tunable phase shift section, which is composed of the OCPW centerline and ground with staggered periodic stubs stretching out. To realize tunable phase shifting by applying different DC bias voltages, a DC bias network capable of blocking RF signal is elaborately designed. An equivalent circuit model of the phase shift part is established and represented using the ABCD matrix, so that the relation between the related parameters and the phase shift per wavelength can be easily obtained to guide the design. The measurement results demonstrate that the proposed phase shifter achieves a total of 300° phase shifting, as high as 289°/λ0 phase shift per wavelength, and a good figure-of-merit (FoM) of 59°/dB at 14.5 GHz. The phase shifter features the reflection coefficient less than -10 dB and the transmission coefficient bigger than -6 dB from 9.3 GHz to 15 GHz.

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