Antenna Impedance Research Articles

Closed-Loop Antenna Impedance Tuning via Transfer Function Learning for 5G Sub-6 GHz User Equipment

Closed-Loop Antenna Impedance Tuning (CL-AIT) is a technique to adaptively reduce the antenna impedance mismatch by monitoring changes in the antenna impedance and adjusting a tunable matching network (or tuner). This work presents a data-driven CL-AIT solution to find the optimal code for configuring the tuner in order to maximize the power transferred to the antenna; it also minimizes the need for extensive antenna characterization required normally for tuners. A key idea is to learn a transfer function representing the reflection coefficient from data by utilizing the tuner topology. Once the data-driven cost function becomes available, the optimal tuner code is efficiently found with the help of hill-climbing (HC) search. Experimental results demonstrate that the proposed solution sufficiently reduces the impedance mismatch under various antenna conditions and maximum power is delivered to antenna.

Согласование антенного устройства канала управления и приемо-передающего модуля беспилотного летательного аппарата в условиях обледенения

The results of experimental studies of the antenna impedance of the control channel, an unmanned aerial vehicle in icing conditions are presented. A mathematical model of the antenna of the control channel of an unmanned aerial vehicle in icing conditions and without them is presented. The method of synthesis of broadband matching devices adapting radio engineering systems to varying load impedance in a wide range of natural conditions of their operation is shown. A broadband matching circuit has been synthesized for the antenna device of the control channel of an unmanned aerial vehicle in icing conditions, which provides a gain in the potentially achievable radio line range of up to 25% relative to the antenna device without a matching circuit.

Triple Band Mime Antenna for Modern Commercial Applications

The article presents the analysis and design of MIMO monopoly Antenna along with split ring resonator to get frequency notch characteristic in the wide band. Frequency notch characteristics are achieved by keeping the split ring resonators on one side of the substrate and on the back of the substrate at deficient ground structure a complementary split Ring resonator with respect to microstrip feeding. Between 2.5-9.5GHz and 12.548-20GHz the dual notch band characteristics are acquired. The inspected conformal characteristics of the antenna hold eminent unceasing reflection coefficient characteristics at different angles in the overall band. Analyzed the unit cell of the SRR and also examined the antenna impedance and radiation characteristics of the model.

Improving power transfer in rectenna via impedance matching at GHz frequencies

A simple and elegant impedance-matching method for rectenna operating in a narrow frequency range is presented. The method used two coplanar strip lines emerging from the antenna feed-point, to correct for the reactive component of the antenna impedance on one side, and to connect the rectifier and transform its impedance on the other side. The experimental results were supported by numerical simulations, which suggest that the same impedance matching technique can be used for mm-waves and terahertz (THz) radiation applications. Microwave characterization of the fabricated devices (impedance-matched and non-matched) showed that the responsivity of the impedance-matched rectenna is approaching an order of magnitude higher at 20 GHz than that of a control device without a matching network.

Modeling, Analysis, and Reduction of Radiated EMI Due to the Voltage Across Input and Output Cables in an Automotive Non-Isolated Power Converter

This article investigates the radiated electromagnetic interference (EMI) due to the voltage between input and output cables in a non-isolated power converter. The radiated EMI model of a non-isolated power converter is first developed and quantified based on the circuit topologies, printed circuit board (PCB) parasitics, switching waveforms, and transfer functions. Second, an antenna model is developed for converter cables based on the antenna impedance and the antenna transfer function. Third, a complete radiated EMI model is developed based on the converter's EMI model and the cable's antenna model. Fourth, the radiated EMI is analyzed based on the developed model. Finally, two radiated EMI noise reduction techniques, optimizing PCB layout and adding a cross capacitor, are proposed. The developed radiated EMI model and the proposed radiated EMI reduction techniques are verified with both simulations and experiments. The techniques are also extended to other two non-isolated power converter topologies when the radiated EMI is caused by the voltage between the input and output cables.

Quantum Based Particle Swarm Optimization for Equivalent Circuit Design of Terminal Antenna Impedance

AbstractIn this paper, an improved quantum‐behaved particle swarm optimization (QPSO) approach for modeling antenna impedance is illustrated. In the proposed study, the enhanced weighted quantum particles swarm optimization (EWQPSO) is introduced with the aim to achieve local convergence acting on a reduced number of free parameters. To verify the performance of the proposed EWQPSO, several tests involving Ipersphere, Alpine, De Jong, Zakharov, Salomon functions were carried out. The obtained results demonstrated that the convergence is achieved more quickly by the EWPSO than other optimization algorithms based on QPSO. A lumped element equivalent circuit was designed to model the terminal impedance of a broadband planar sinuous antenna in the frequency range from 1 to 3 GHz. The developed EWQPSO algorithm is then used to recover all the parameters characterizing the equivalent circuit. The resulting circuit exhibited a good impedance fidelity over the whole frequency range.

Single-Ended Quadrature Coupler-Based VSWR Resilient Joint mm-Wave True Power Detector and Impedance Sensor

Intelligent reconfigurable RF/millimeter-wave (mm-Wave) front ends primarily rely on built-in-self-test (BiST) circuits for real-time performance monitoring, particularly in phased arrays, where antenna elements&#x2019; driving impedance varies substantially during beam steering due to the undesired element couplings. This severely degrades the power amplifier&#x2019;s (PA) performance. To address this problem, we propose a quadrature coupler-based voltage standing wave ratio (VSWR)-resilient mm-Wave joint impedance/true power detector integrated with a PA using the GlobalFoundries 45-nm CMOS silicon on insulator (SOI) process. A comprehensive theoretical comparison between the traditional and proposed coupler sensors is presented, including implementation details and design tradeoffs. Design guidelines for both the proposed coupler sensor and the integrated PA are presented to maximize sensing accuracy. The detailed data processing techniques are explained to accurately extract the sensor outputs and highlight hardware limitations. At 38 GHz, the proposed sensor measures the antenna impedance for VSWR <inline-formula> <tex-math notation="LaTeX">$=3$ </tex-math></inline-formula>:1 with a maximum <inline-formula> <tex-math notation="LaTeX">$\vert \Gamma \vert $ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$\angle \Gamma $ </tex-math></inline-formula> error of 0.238 and 28.9&#x00B0; respectively. The 90&#x00B0; coupler network demonstrates a 16-dB dynamic range with an error within &#x00B1;0.5 dB for 50-<inline-formula> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> power sensing, as well as sensing the real power delivered to a complex antenna load for VSWR <inline-formula> <tex-math notation="LaTeX">$=3$ </tex-math></inline-formula>:1 with less than &#x00B1;3.35-dB power sensing error. The chip die occupies an area of <inline-formula> <tex-math notation="LaTeX">$1.31\times1.36$ </tex-math></inline-formula> mm², while the sensor alone occupies an area of <inline-formula> <tex-math notation="LaTeX">$0.47\times0.971$ </tex-math></inline-formula> mm².

Negative input impedance of a dipole antenna printed on a grounded tellegen metamaterial substrate

Negative input impedance of a dipole antenna printed on a grounded tellegen metamaterial substrate

Frequency-Selective Surface Stopband Designed with a Genetic Algorithm for Gain Enhancement of a Broadband Monopole Antenna

This paper presents an unusual, high-performance, cost-efficient, wideband frequency-selective surface (FSS) designed with a genetic algorithm (GA) and its effect on the performance of a broadband M-shaped monopole antenna. Each FSS unit cell with the dimensions of 0.2λ&lt;sub&gt;0&lt;/sub&gt; × 0.2λ&lt;sub&gt;0&lt;/sub&gt; × 0.01λ&lt;sub&gt;0&lt;/sub&gt; acts as a stopband filter for a wide bandwidth of 5.5 GHz (105%, 2.6–8.1 GHz). The FSS properties and advantages to antennas were tested via numerical simulations and measurements, respectively. Using the 6×6 array of the designed FSS unit cell as a reflector, the antenna impedance bandwidth improved from 96.1% (3.1–8.1 GHz) to 98.07% (3.3–8.4 GHz), with a center frequency of 5.2 GHz. In addition, the antenna gain improved at the maximum of 7.8 dBi, which was sustained from 9 dBi to 10.1 dBi for the entire bandwidth.

Transient analysis of dynamically switched frequency shift keyed transmitters

A dynamically switched matching network for transmitting a wideband frequency shift keyed (FSK) signal from an electrically small monopole antenna is studied. The effects of switch synchronization, frequency deviation, the antenna's impedance, and Q-factor at the two carrier frequencies are studied. It is found that the average energy per bit of the transmitted FSK waveform is maximum when the loss of reactive energy between states transition is minimised by switching it at the instant of peak voltage across the antenna's terminals. However, a switching network topology that stores more energy is shown to be less sensitive to the synchronization condition. In addition, we show that this dynamically switched system transmits more bit energy when the carriers are closely spaced due to a smaller change in stored energy levels between states. Results are presented using a detailed analytical study and full wave simulation. Near field measurements from a monopole antenna circuit model show that under proper conditions, an FSK signal can be transmitted at a rate 7 times greater than the bandwidth of the transmit antenna with minimal signal quality degradation.

Novel CMOS-based multi-band terahertz detector for passive imaging

The existing terahertz detectors based on complementary metal oxide semiconductor cannot meet the design requirements of passive terahertz focal plane imaging chips owing to the problems of excessive noise or high-power consumption. To overcome this limitation, this study innovatively proposes using the gate of an N-type metal oxide semiconductor (NMOS) as a matching impedance of a multi-band terahertz on-chip antenna. In this way, the conversion of incident radiation into heat is achieved, and it is concentrated above the NMOS channel. The temperature characteristics of the equivalent impedance of the NMOS in the cutoff region are used to measure the incident radiated power without the DC bias current. The principle and simulation results of the proposed detector are given by system modeling, multi-band terahertz on-chip antenna design, and detector design. The experimental results show that the noise equivalent power of the proposed detector is very close to 1 under liquid nitrogen cooling, which can meet the design requirements of passive terahertz focal plane imaging chips.

A Novel Wideband and Multi-band Implantable Antenna Design for Biomedical Telemetry

In this work, a novel multi-tracks wideband and multi-band miniaturized antenna design for implanted medical devices biomedical telemetry is proposed. This antenna entirely covers seven frequency bands which are the bands (401−406) MHz of the Medical Device Radiocommunications Service (MedRadio), the three bands (433.1−434.8), (868.0−868.6), and (902.8−928.0) MHz of the Industrial, Scientific, and Medical (ISM), and the three bands (608−614) MHz, and (1.395−1.400) and (1.427−1.432) GHz of the Wireless Medical Telemetry Service (WMTS). The antenna possesses a compact full size of (19.5 × 12.9 × 0.456) mm3. The antenna miniaturization and impedance bandwidth enhancement are achieved using two techniques: the patch slotting and insertion of open-end slots in the ground plane, respectively. Prototype of proposed antenna with multi-tracks has been fabricated and tested in free space. The comparison between the simulated and measured reflection coefficient has been done and found in good agreement with each other. Furthermore, simulations of the proposed antenna implanted in the underneath the scalp in a realistic human model shows a wideband operation from 0.19 to 0.94 GHz, and from 1.38 to 1.54 GHz corresponding to return loss (S11 ≤ −10 dB). Link budget calculation is performed to specify the range of telemetry considering both Specific Absorption Rate (SAR) restrictions and effective isotropic radiated power (EIRP) limitations. The designed implantable antenna with full ground plane presents an appropriate reflection coefficient for muscle implantation. Furthermore, the designed implanted muscle antenna may be also suitable for skin implantation.

Impedance matching system using triple liquid stub tuners for high-power ion cyclotron resonance heating in EAST tokamak.

Ion cyclotron resonance heating (ICRH), one of the main auxiliary methods, for high-power and long-pulse plasma heating had been developed in Experimental Advanced Superconducting Tokamak (EAST). An impedance matching system, one important part of ICRH, had been developed for high-power injection and transmitter protection by reducing the reflected power from the antenna. The input impedance in the outlet of the stub tuner can be measured by voltage-current probes installed on the coaxial transmission line between the antenna and triple liquid stub tuners, and the optimum liquid levels in the stub tuners can be calculated based on the input impedance. The calculation and adjustment process of the optimum liquid levels are described comprehensively in this article. Finally, impedance matching had been achieved between two shots during EAST experiments. In the near future, a real-time impedance matching system will be developed to prevent large variations of the ICRH antenna impedance and achieve steady-state and long-pulse operation with the ICRH system.

Design of an Analog RFID-Based Tag Antenna with Opened Circuited L-Shaped Stubs for Applications in Localization

This paper presents a new analog design for a radio-frequency identification (RFID) tag antenna with a long-read range oriented to localization applications. The actual work focuses on the analog input characterization of antenna impedance by studying the capacitive effect, created by the gaps, and the effect of the introduced opened circuited L-shaped stubs, on the RFID tag characteristics. Numerical and measured results confirm that proposed tag antenna performances are significantly improved by introducing gaps and stub structures and after optimizing their dimensions, such as length and width. The introduced stubs with optimum dimensions provide good impedance matching, and improved return loss values. Furthermore, two operating frequency bands have been created when the antenna is excited by a 50 Ω port: a low-frequency band around 837 MHz and a higher one around 927 MHz. These results have been validated by measured ones. The proposed RFID antenna is mainly composed of three split rectangular resonators (SRR) where introduced structures concern only the larger SRR. The optimized antenna has an area of 76 × 24.6 mm2 and is printed on the Taconic RF-60A substrate with a dielectric constant of 6.12, a thickness of 1.6 mm, and a loss tangent of 0.025. Simulation results show interesting communication performances, of the proposed tag antenna, with a return loss of −22.3 dB around 916 MHz and a long-read range up to 25 m when it is fed by an industrial Mping M730 chip with a power sensitivity of −24 dB and an output impedance Zchip = 16 − j194 (Ω) at 916 MHz

Designing an E-shaped Microstrip Patch Antenna for Ultra-wide Band Application using Line Feeding

This paper presents the plan and reenactment ofthe super wideband working recurrence Eshape microbandrecieving wire for different remote applications. This recievingwire will give the vital broadband in different applicationslike remote detecting, biomedical applications, portable radiosatellites, remote correspondences, and then some. This recievingwire structure gives a usable recurrence scope of 3.14-10.6 GHz,making the radio wire appropriate for the super wideband. Theperformance of the designed antenna was analysed in termsof gain, return loss, VSWR, Axial Ratio, Conjugate MatchingFactor, Antenna Efficiency, Current Distribution, Impedance ofAntenna, Radiation Pattern. The proposed recieving wire isplanned utilizing a polyimide substrate with a substrate tallnessof 1.6 mm. Axial ratio is less than 0 dB. For the frequency zeroGHz the Conjugate Matching Factor is -forty-five dB, for thefrequency four.6 GHz the Conjugate Matching Factor is zero dBand for the frequency five GHz the Conjugate Matching Factoris -five Db. For the frequency of 4.6 GHz with a return loss of-24dB .The smith chart of E Patch Antenna is 5.253+j55Ω, Theradiation efficiency at the frequency 5.65GHz is 88 per cent. TheAntenna Efficiency for the frequency 4.5 GHz is 80 %.

The bow‐tie antenna: Performance limitations and improvements

The simple planar shape and wideband input impedance of the bow-tie antenna make it suitable to diverse wideband applications. However, the radiation pattern of this kind of antenna is not stable and the gain in the broadside direction deteriorates with increasing frequencies. In this article, the operation of both the triangular and the rounded-edge versions of the bow-tie antenna is thoroughly investigated and the performance thereof is compared. A technique to maximise such performance, which consists of inserting radially aligned grooves in the radiators' ends, is presented. The bandwidth, defined by a broadside gain of at least 2 dBi and a reflection coefficient magnitude of less than −10 dB, is improved from 85.7% to 97.9% in simulations. Such an improvement is validated through the measurement of two prototypes, in which the presented technique also increases the broadside gain in up to 1.5 dB, with no significant change in the shapes of the radiation patterns and in the reflection coefficient magnitude.

A Flexible and Low-Cost UHF RFID Tag Antenna for Blood Bag Traceability

A new low-profile flexible RFID tag antenna operating in the ultra-high frequency (UHF) European band (865 MHz–868 MHz) is proposed for blood bag traceability. Its structure combines inductive and capacitive parts with nested slots allowing for the achieving of conjugate impedance matching with the IC-chip. The whole electrical parameters of the environment (substrate, bag, and blood) were considered for the design of the tag antenna. A good agreement was obtained between the measurements and electromagnetic simulations for the input impedance of the tag antenna in the UHF band. A reading range close to 2.5 m was experimentally obtained. Therefore, this tag antenna could be effective and useful in future RFID systems for blood bag monitoring, thus improving patient safety in healthcare infrastructures.

Impedance Relations for Differential Antennas and Single-Ended Counterparts

The impedance parameters of a two-port network are employed to deduce the differential and common-mode as well as single-ended input impedances of a differential antenna. The relationships between these impedances are considered. It is shown that there exist simple quantitative relations, which may be used to determine one impedance from the other whose solution is already known. In addition, an important attempt is made to extend Booker’s relation for differential complementary dipoles and slots to single-ended counterparts.

On the effect of S-parameter stability of antenna and coupler on electrical balance duplexing

Electrical Balance Duplexers (EBDs) provide transmit-receive isolation to implement a form of self-interference cancellation to facilitate simultaneous transmission and reception from a single antenna in systems like In-Band Full-duplex (IBFD) transceivers. EBD works by coupling transmitter, receiver, antenna, and balancing impedance using a hybrid coupler. In recent pieces of literature, antenna impedance variations are considered the main factor limiting the EBD isolation bandwidth, while the EBD balancing impedance needs to be equal as much as possible to the antenna impedance to achieve high isolation. But hybrid couplers are also not ideal elements, and their S-parameters are not stable in the frequency domain. In this work, five broadband RF devices (two antennas, two couplers, and a 50-Ohm RF-load) are used to form four EBD set-ups. One of the antennas, designed by the authors, has more impedance stability in the frequency domain than the other one, which is a commercial antenna. Also, one of the couplers, designed by the authors, has more S-parameter stability in Ultra-Wideband (UWB) frequency domain than the other one, which is a commercial UWB coupler. The implemented EBDs show that when both antenna and coupler have strong S-parameter stabilities in the frequency domain, wider isolation bandwidth (UWB 1.5–3.5 GHz range) and higher EBD isolation are obtained.

Theory and Analysis of the Loop Antenna and Ω-Shaped Loop-Dipole Antenna

This paper first examines and corrects Storer’s theory of circular loop antennas, and then investigates theoretically the proposed Ω-shaped loop-dipole antenna. Special emphasis is given to the analysis of the effect of the higher-order terms of the Fourier series as a remainder on the current distribution, input impedance, and radiation patterns of the thin-wire circular loop antenna. It is found that the remainder must be included in the calculation of the current distribution and input impedance but can be neglected to simplify the calculation of far-field radiation. Then, a theoretical model is proposed to analyze the radiation fields, directivity, and input impedance of the proposed Ω-shaped loop-dipole antenna based on the loop and dipole antennas’ theories. Analytical expressions for the radiation fields, directivity, and input impedance of the Ω-shaped loop-dipole antenna are derived. The theoretical and numerical results are compared for the Ω-shaped loop-dipole antennas of practical interests. They are in good agreement.