Passive Antenna Research Articles

A Review of Microstrip Patch Antenna-Based Passive Sensors.

This paper briefly overviews and discusses the existing techniques using antennas for passive sensing, starting from the antenna operating principle and antenna structural design to different antenna-based sensing mechanisms. The effects of different electrical properties of the material used to design an antenna, such as conductivity, loss tangent, and resistivity, are discussed to illustrate the fundamental sensing mechanisms. Furthermore, the key parameters, such as operating frequency and antenna impedance, along with the factors affecting the sensing performance, are discussed. Overall, passive sensing using an antenna is mainly achieved by altering the reflected wave characteristics in terms of center frequency, return loss, phase, and received/reflected signal strength. The advantages and drawbacks of each technique are also discussed briefly. Given the increasing relevance, millimeter-wave antenna sensors and resonator sensors are also discussed with their applications and recent advancements. This paper primarily focuses on microstrip-based radiating structures and insights for further sensing performance improvement using passive antennas, which are outlined in this study. In addition, suggestions are made for the current scientific and technical challenges, and future directions are discussed.

Wideband circularly polarized high accuracy survey active antenna for global navigation satellite systems applications

AbstractThis letter presents a new circularly polarized (CP) active antenna for global navigation satellite systems (GNSS) operating in the L1‐band (1.164–1.28 GHz) and L2‐band (1.525–1.615 GHz). The active antenna consists of a passive antenna and a two‐channel low‐noise amplifier (LNA) circuit. To achieve wideband coverage of the L1/L2 bands while maintaining a low profile, a new electroplating process is utilized in fabricating the passive antenna. Additionally, to realize CP performance, the passive antenna is sequentially fed by four ports with a wideband feeding network. To minimize phase variations, a 90° phase shifter loaded with open‐short‐stub is integrated into the feeding network. Furthermore, to improve noise immunity, out‐of‐band rejection, and amplify GNSS signals, the LNA circuit cascades two‐stage dielectric bandpass filters and three‐stage LNAs. Consequently, the circuit features a low noise figure of below 1.65 dB, a maximum out‐of‐band rejection level of 60 dB, and a stable active gain of 30 dB. The performance of the active antenna is evaluated in an outdoor open field using a GNSS receiver.

Active–Passive Reconfigurable Antenna Covering 70–7200 MHz Bandwidth

Active–Passive Reconfigurable Antenna Covering 70–7200 MHz Bandwidth

Overcoming limitations of passive invisible antennas through bianisotropic nonreciprocal mantle cloaks

Overcoming limitations of passive invisible antennas through bianisotropic nonreciprocal mantle cloaks

A patch-antenna-based smart aggregate for passive strain sensing in concrete

This paper presents an innovative smart aggregate based on passive patch antenna. The designed unstressed patch antenna components which can move relatively serves as a sensing unit, and the sensing unit can be embedded in concrete to form smart aggregates for strain sensing after encapsulation. The study investigates the influence of different encapsulation materials and external environments on the electromagnetic parameters of the patch antenna sensing unit within the smart aggregate. Furthermore, it establishes the theoretical relationship between the resonant frequency of the sensing unit and the deformation of concrete. When using shielding material to encapsulate the patch antenna, it can avoid the influence of external dielectric environment variation; when using non-shielding materials to encapsulate the patch antenna, external environmental sensing can be achieved. Simulations and experimental tests were used to study the characteristics of two different encapsulation methods. Two patch-antenna-based smart aggregates with different dielectric substrates, Rogers RT5880 and Rogers RO3010, were fabricated, which can be embedded inside the concrete and realize the passive sensing of the internal strain of the concrete. The fabricated smart aggregates no longer require continuous power supply, thus having better applicability. Experimental tests were undertaken to demonstrate the viability of the proposed patch-antenna-based smart aggregate. The sensing sensitivities of the proposed smart aggregates based on patch antennas with dielectric substrates Rogers RO3010 and Rogers RT5880 were 1.219 MHz/100 με and 0.598 MHz/100 με, respectively.

The main directions of enhancement of digital antenna arrays

The development of modern radio electronic systems causes an increase in the requirements for the parameters of antenna devices (AU) and causes the transition from previously used mirror antennas and passive phased array antennas (FAA) to active FAA (AFAA), the considerable advantage of which is a significant reduction in energy losses of transmitted and received signals by reducing the distance of the low-noise amplifier input and output of power amplifier to the antenna element. Further development of the AU is the transition from AFAA with analog beamforming to digital antenna arrays (DAR) with digital beamforming, the advantages of which are due to the possibility of forming multibeam receiving and transmitting radiation patterns with independent control of the direction and shape of the beams, as well as the possibility of flexible change of operating modes. The use of a DAR with two-dimensional electronic scanning provides a significant increase in the efficiency of radio-electronic systems. Thus, their use in radar provides a gain in the efficiency of using the time, energy, frequency and spatial resources of radar with CAR up to 13 times compared with radar with passive FAA and AFAA with one-dimensional scanning. The disadvantages of the DAR are the high cost and increased energy consumption due to the installation of active elements in each transceiver channel, as well as the long time required to create new products, associated with a large amount of software and a complex structure for building a CAR. To overcome these disadvantages, manufacturers of antenna arrays and developers of the radio-electronic element base are creating new technical solutions. The main directions of development of technologies for the production of DAR functional devices that reduce the cost and reduce the time needed to create new products are shown: the development of common modules that allow you to create scalable DAR, increasing the integration of microwave monolithic integrated circuits with the placement of the maximum number of transceiver channels on one chip, increasing the integration of ASIC, including ADCs, DACs and digital signal processing devices, increasing the clock frequencies of digital functional nodes, as well as the development of circuit solutions for building nodes with low energy consumption.

Radio frequency electric field-enhanced sensing based on the Rydberg atom-based superheterodyne receiver.

We present enhanced sensing of a radio frequency (RF) electric field (E-field) by the combined polarizability of Rydberg atoms and the optimized local oscillator (LO) field of a superheterodyne receiver. Our modified theoretical model reveals the dependencies of the sensitivity of E-field amplitude measurement on the polarizability of Rydberg states and the strength of the LO field. The enhanced sensitivities of the megahertz (MHz) E-field are demonstrated at the optimal LO field for three different Rydberg states ${\rm 43D}_{5/2}$, ${\rm 60S}_{1/2}$, and ${\rm 90S}_{1/2}$. The sensitivity of 63 MHz for the ${\rm 90S}_{1/2}$ state reaches 9.6 $\times 10^{-5}\rm \,V/m/\sqrt {Hz}$, which is approximately an order of magnitude higher than those already published. This result closely approaches the sensitivity limit of a 1 cm passive dipole antenna without using an impedance matching network. This atomic sensor based on the Rydberg Stark effect with heterodyne technique is expected to boost an alternative solution to electric dipole antennas.

Introduction of the orthogonal mode via the polarization conversion parasitic structure for the isolation enhancement of MIMO patch antennas

Abstract In this study, a high-isolation multiple-input multiple-output (MIMO) microstrip patch antenna (MPA), which utilizes an orthogonal mode cancellation method is proposed. This method employs TM10 and TM01 modes, which are simultaneously excited in the rectangular passive MPA. Initially, a rectangular decoupling structure featuring polarization rotation characteristics is designed. Further studies show that by loading the polarization conversion parasitic structure (PCPS), the electric field of the spatial coupling wave can be transformed from the x-polarized TM10 mode to the y-polarized TM01 mode. Therefore, TM10 and TM01 modes from the excited antenna and decoupling structure are concurrently coupled to the passive antenna, forming an evident weak-field region on the passive antenna. Placing the feeding probe of the passive MPA within the weak-field region prevents signal reception at the port. Consequently, this results in an extremely low mutual coupling of −49 dB at a resonant frequency of 5.8 GHz. Finally, a prototype of the proposed antenna is fabricated and tested, and the measured results closely match the simulated results. Additionally, it is observed that PCPS slightly influences the performance of the MIMO antenna.

A Phase Shift-Based and Quadrant-Distinguishable Passive Microstrip Antenna Sensor for Metal Crack Detection

A Phase Shift-Based and Quadrant-Distinguishable Passive Microstrip Antenna Sensor for Metal Crack Detection

Novel printed passive ultra high frequency radio frequency identification antenna using meander technique

<p>In this paper, a novel radio frequency identification (RFID) antenna using a meander technique associated with a slotted patch is studied for RFID applications in the ultra high frequency (UHF) band [867.5-868 MHz]. The proposed RFID antenna is designed on a Kapton substrate with dielectric constant 3.5 and loss of 0.0027. It consists of two opposite meander line antennas of 8 turns each one and interconnected to ALIEH H3 microchip associated to two slotted patch’s with a global size 105×25×0.1 mm<sup>3</sup>. The proposed RFID antenna is designed and simulated using CST MWS as an electromagnetic solver. The results of the simulation show a return loss of -22.64 dB at 868 MHz, a reading distance of around 5 m, and a simulated input impedance of the antenna are 31.72+j109.68 Ω at the operating frequency 868 MHz.</p>

A Novel Antenna Design of Compact HF and UHF Passive RFID Tags with Interconnected Structure for Energy Harvesting and Tracking Systems

We propose a new dual-band passive RFID tag antenna design by combining a rectangular spiral coil and patch-meander-line dipole with an interconnected structure. This design enables operation in high-frequency (HF) and ultra-high-frequency (UHF) RFID systems, suitable for energy harvesting and tracking applications. The simulations by the CST full-wave software demonstrate conjugate impedance matching between the tag antenna and two RFID tag chips. At 13.56 MHz (HF), the tag antenna exhibits an inductive reactance of 422.79 Ω, while at 922.5 MHz (UHF), it presents an impedance of 9.41+j174.96 Ω. The antenna generates a maximum magnetic field intensity of 0.5 A/m and omnidirectional electromagnetic fields with an antenna realized gain of -4.26 dBi at 922.5 MHz. We also analyze the impact of the tag antenna combination using numerical software. Furthermore, we fabricate a prototype tag antenna and validate its performance with RFID readers. The proposed tag antenna achieves the maximum read ranges of 11 cm and 6.9 m for the HF (13.56 MHz) and UHF (920-925 MHz) bands, respectively, accompanied by the energy harvesting of 1.48 volts at the HF band by the coupling magnetic field received by the HF antenna to the chip ST25DV04K at the output voltage pin.

Movement of an imperiled esocid fish in an agricultural drain

Animal movement is increasingly affected by human alterations to habitat and climate change. In wetland systems, widespread hydrologic alterations from agriculture have changed the shape, function, and stability of shallow streams and wetland habitats. These changes in habitat quality and quantity may be especially consequential for freshwater fishes such as Grass Pickerel (Esox americanus vermiculatus), a small predatory fish found in disjunct populations across southern Ontario and listed as Special Concern under Canada’s Species at Risk Act. To characterize Grass Pickerel movement response to stream-channel alterations, Fisheries and Oceans Canada implemented a tracking study to monitor the movements of a Grass Pickerel population in an agricultural drain on the Niagara Peninsula (Ontario, Canada). From 2009 to 2013, 2007 Grass Pickerel were tagged and tracked in the 37.3 km2 Beaver Creek watershed using a combination of mark-recapture surveys and eight fully automated passive integrated transponder tag antennas. Most individuals moved within 500 m (i.e., stationary fish) while 16% of the fish moved > 500 m (i.e., mobile fish), with a maximum median movement distance of 1.89 km and a maximum movement distance of 13.5 km (a long-tail distribution). Most movements occurred near the largest confluence where only a few were long-distance upstream or downstream movements. Mobile fish were larger than their stationary counterparts. Grass Pickerel in sites with higher abundance had more mobile fish, implying potential density dependence. Our results highlight that, while a long-distance dispersal ability exists in extant Grass Pickerel populations, the current conditions of riverscapes may prevent these dispersals from occurring. For declining Grass Pickerel populations, limitations to their movement ecology may substantially increase the likelihood of local extirpations.

Computer Vision-Aided Reconfigurable Intelligent Surface-Based Beam Tracking: Prototyping and Experimental Results

In this paper, we propose a novel computer vision-based approach to aid reconfigurable intelligent surface (RIS) for dynamic beam tracking and implement the corresponding prototype verification system. A camera is attached at the RIS to obtain the visual information about the surroundings, with which RIS identifies the incident beam direction and the desired reflected beam direction, and then adjusts the reflection coefficients according to the pre-designed codebooks. We build a 20-by-20 RIS running at 5.4 GHz and develop a high-speed control board to ensure the real-time refresh of the reflection coefficients. Meanwhile we implement an independent peer-to-peer communications system to simulate the physical link between the base station and the user equipment. The vision-aided RIS prototype system is tested in two mobile scenarios: RIS works in near-field conditions as a passive array antenna of the base station; RIS works in far-field conditions to assist the communication between the base station and the user equipment. The experimental results show that RIS can quickly adjust the reflection coefficients for dynamic beam tracking with the help of visual information.

Error Vector Magnitude as a Performance Standard for Antennas in the Millimeter-Wave Era: Part 2: Modeling, simulation, and measurement methods

The error vector magnitude (EVM) is a comprehensive measure of the amplitude and phase distortion of digitally modulated signals and a potential tool for characterizing the performance of active beamforming arrays, especially at millimeter-wave frequencies, because of the high level of integration and limited spacing between the radiating elements. A review of the EVM measurement process and fundamental principles for time-domain demodulation with a vector signal analyzer (VSA) and spectral correlation with a vector network analyzer (VNA) was presented in [1]. This article demonstrates how researchers have modeled and measured impairments from antenna and phased array signal transmission to characterize their influence on the EVM of single and multicarrier digital signals. It presents examples of simulation models and measurements of the distortion from ultrawideband (UWB) passive antenna transmission, power amplifier (PA) nonlinearities, and phased array beam squint and beam scan intersymbol interference (ISI). A brief survey of over-the-air (OTA) test ranges for EVM analysis is also provided. This overview of state-of-the-art EVM simulation and measurement methods is intended to help interested readers understand and enhance the EVM performance analysis methods applied to antennas and phased arrays in this new era of millimeter-wave communications.

INEMI MAESTRO: Glass Substrates for mmWave/sub-THz Applications

This paper will explore the use of glass substrates for wireless components at frequencies ranging from 30 GHz - 240 GHz. Applications include both communications and radar/sensing. Examples of devices that can benefit from glass substrates include individual passive devices, filters, diplexers, and antenna arrays. We will discuss the properties of glass and how they translate into improved performance with lower power and size.

Optimized Precoding for MU-MIMO With Fronthaul Quantization

One of the first widespread uses of multi-user multiple-input multiple-output (MU-MIMO) is in 5G networks, where each base station has an advanced antenna system (AAS) that is connected to the baseband unit (BBU) with a capacity-constrained fronthaul. In the AAS configuration, multiple passive antenna elements and radio units are integrated into a single box. This paper considers precoded downlink transmission over a single-cell MU-MIMO system. We study optimized linear precoding for AAS with a limited-capacity fronthaul, which requires the precoding matrix to be quantized. We propose a new precoding design that is aware of the fronthaul quantization and minimizes the mean-squared error at the receiver side. We compute the precoding matrix using a sphere decoding (SD) approach. We also propose a heuristic low-complexity approach to quantized precoding. This heuristic is computationally efficient enough for massive MIMO systems. The numerical results show that our proposed precoding significantly outperforms quantization-unaware precoding and other previous approaches in terms of the sum rate. The performance loss for our heuristic method compared to quantization-aware precoding is insignificant considering the complexity reduction, which makes the heuristic method feasible for real-time applications. We consider both perfect and imperfect channel state information (CSI).

What we can do with sounds

Auditory perception can be dynamic when sound sources are in motion or changing, when the listener is moving relative to the source of sound, or both. Moreover, our engagement with the acoustic environment is often active rather than passive. That is, sounds can be brought into use to support and guide perceptual-motor behaviour. This presentation will review examples of recent empirical work on the role of auditory perception in the control of motor behaviour: what we can do with sounds. Data from experiments on intercepting moving objects without vision, acoustic navigation and orientation in people with visual impairments, exploration and learning of novel digital musical instruments, and rhythmic sounds in gait rehabilitation, all demonstrate different ways that sounds can convey action-relevant information for skilful listeners. Furthermore, they point to a need to consider the auditory system not merely as a passive antenna for inert distal stimuli, but as integrated within an active meaning-seeking organism interacting with a dynamic environment.

2-D Localization System for Mobile IoT Devices Using a Single Wi-Fi Access Point With a Passive Frequency-Scanned Antenna

A novel two-dimensional indoor location system for IoT devices employing a single Wi-Fi Access Point is presented. The x, y position is estimated with a combination of Directionof-Arrival (DoA) and Time-of-Flight (ToF) algorithms. The azimuthal DoA is estimated using a modified MUSIC technique, which requires the acquisition of the Received Signal Strength Indicator (RSSI) using different Wi-Fi frequency channels in the 2.4 GHz band, together with a dual-port frequency-scanning antenna (FSA). This allows a wide Field-of-View (FoV) of 180: for the DoA. To estimate the ranging distance, an algorithm based in the 802.11mc Fine Time Measurement (FTM) protocol is employed to consider the effects of the channel hopping. Therefore, the proposed system does not rely on Channel State Information (CSI) or complex IQ information, which is not available in commercial Wi-Fi APs. The proposed system has been fully implemented with a commercial Wi-Fi AP and tested in a practical scenario, proving a root-mean-square error (RMSE) when estimating the localization of mobile devices of only 1.43m, in a wide area of 12 m x 12 m.

Integrated factor of efficiency of antenna system using in the radar

Integrated efficiency factors are used not only at the design stage, but also in the case of choosing a ready-made system. In this case, the purpose of the research is to get an answer to the question of the expediency of its purchase (deployment), or monitoring the effectiveness of the system during its operation and developing proposals for optimizing the ways of its use and modernization. Since any system has limited resources when solving assignment tasks, it is necessary to develop a generalized efficiency factor from the standpoint of analyzing the effective allocation of radar resources when using antenna systems of various types in its composition. The aim of the article is to increase the efficiency of the use of radar resources in the antenna system. Achieving this goal includes solving the following tasks: substantiation of an integrated efficiency factor of the use of the antenna system in the radar, the use of an integrated efficiency factor to compare different types of antenna systems in the radar. А comparison of the efficiency of using a digital antenna array (DAA) with two-dimensional electronic scanning of the radiation pattern and parallel space surveillance, a reflector antenna, a passive phased antenna array with one-dimensional scanning, as well as an active phased antenna array with one-dimensional scanning and parallel space surveillance has been performed. It has been shown that the efficiency of using a DAR with two-dimensional electronic scanning is 2.3...15.6 times higher than the efficiency of other types of antenna systems. The proposed efficiency factor makes it possible to compare the efficiency of the use of radar resources when using different types of antenna systems, taking into account the features of their construction and the requirements for the purpose of the radar.

Dark band artifact in transcranial MR-guided focused ultrasound: Mechanism and mitigation with passive crossed wire antennas

Current FDA-approved transcranial MR-guided focused ultrasound (tcMRgFUS) transducers cause a curved dark band in 3 T brain images that runs through midbrain targets of ablative treatments for essential tremor and other applications, and signal is reduced by at least 25% elsewhere in the brain. This limits the set of scans that can be performed to guide and assess the effects of treatment. An electromagnetic simulation study was performed to elucidate the mechanisms causing the dark band. Based on the results, a pair of passive antennas in a “propeller-beanie” configuration were designed to manipulate the reflected waves to avoid signal cancellation within the brain. The antennas were optimized and validated with in-vivo experiments and hydrophone measurements. The simulation study revealed that the dark band is caused by RF waves reflected from the transducer's ground plane, which cancel with incoming waves from the scanner's body coil. The passive antennas shifted the dark band out of the brain and increased transmit efficiency in the center of brain 2.3 times while improving field homogeneity by 50%. They also increased receive sensitivity and SNR in anatomic and temperature imaging. They caused no detectable distortion in hydrophone-measured focal pressure profiles. The conductive ground planes and coupling media used in tcMRgFUS and other piezoelectric FUS transducers interact with a 3 T scanner's RF fields to reduce transmit efficiency and SNR. For tcMRgFUS scenario, “propeller beanie” passive reflecting antennas alleviated these effects. This could make a broader set of imaging sequences available to guide tcMRgFUS treatment.