Passive Antenna Research Articles

77-GHz Four-Element Phased-Array Radar Receiver Front End

A phased-array receiver module operating at 77 GHz is designed and manufactured to obtain beam-steering capability. The module has four patch antennas integrated with three active phase shifter (APS) chips on a single-layer Rogers 3003 printed circuit board PCB board. The W-band 1.65-mm2 novel APS chip is fabricated using 0.13- $\mu \text{m}$ SiGe Heterojunction Bipolar Transistor (HBT) technology. The APS consumes 100-mW dc power and achieves a peak gain of 9 dB at W-band and covers 360°. The phase shifter chips and PCB are packaged using low-cost wire-bond interconnections with insertion loss less than 7.5 dB. A novel method that exploits Klopfenstein tapering is also designed to connect coplanar waveguide to microstrip line with minimum insertion loss around 77 GHz. The measured gains of the phased-array receiver and passive four-element antenna array are compared. The module and passive array achieve the maximum gains of 9.7 and 10.4 dBi at 77 GHz. The simulated and measured results present well agreement at the W-band frequency. The beam can be steered to ±30°.

Passive Wireless Frequency Doubling Antenna Sensor for Strain and Crack Sensing

This paper presents the design, simulation, and validation experiments of a passive (battery-free) wireless frequency doubling antenna sensor for strain and crack sensing. Since the length of a patch antenna governs the antenna’s resonance frequency, a patch antenna bonded to a structural surface can be used to measure mechanical strain or crack propagation by interrogating resonance frequency shift due to antenna length change. In comparison with previous approaches such as radio frequency identification, the frequency doubling scheme is proposed as a new signal modulation approach for the antenna sensor. The proposed approach can easily distinguish backscattered passive sensor signal (at the doubled frequency $2{f}$ ) from environmental electromagnetic reflections (at original reader interrogation frequency $f$ ). To accurately estimate the performance of the frequency doubling antenna sensor, a multi-physics coupled simulation framework is proposed to aid the sensor design while considering both the mechanical and electromagnetic behaviors. Two commercial software packages, COMSOL and Advanced Design System (ADS), are combined to leverage the features from each other. The simulated performance of the frequency doubling antenna sensor is further validated by experiments. The results show that the sensor is capable of detecting small strain changes and the growth of a small crack.

A Simple Low-Cost Shared-Aperture Dual-Band Dual-Polarized High-Gain Antenna for Synthetic Aperture Radars

This paper presents a novel shared-aperture dual-band dual-polarized (DBDP) high-gain antenna for potential applications in synthetic aperture radars (SARs). To reduce the complexity of SAR antennae, a DBDP high-gain antenna based on the concept of Fabry–Perot resonant cavity is designed. This antenna operates in both $C$ - and $X$ -bands with a frequency ratio of 1:1.8. To form two separate resonant cavities, two frequency selective surface layers are employed, leading to high flexibility in choosing desired frequencies for each band. The beam-scanning capability of this proposed antenna is also investigated, where a beam-scanning angle range of ±15° is achieved in two orthogonal polarizations. To verify this design concept, three passive antenna prototypes were designed, fabricated, and measured. One prototype has broadside radiation patterns, while the other two prototypes have frozen beam scanned to +15°. The measured results agree well with the simulated ones, showing that the high gain, high port isolation, and low cross-polarization levels are obtained in both the bands. Compared with the conventional high-gain DBDP SAR antennae, the proposed antenna has achieved a significant reduction in the complexity, mass, size, loss, and cost of the feed network.

Review of Recent Developments in Filtering-Antennas

In recent years, different filtering antenna topologies have been studied and proposed to meet various objectives of innovative technologies used in modern radar and wireless communication applications. Filtering antenna design is a combination of microwave filter and antenna to achieve radiating and filtering functions within one design. This combination improves the performance and reduces the size. Furthermore, it provides frequency reconfiguration by using active components employed in the design. However, mismatch between the filter and antenna leads to increase the loss. Moreover, increase the number of the active components may influence the radiation characteristic and return loss. In this review, various design topologies have been summarized and divided into two design approaches: bandpass filter integrated with antenna and bandstop filter integrated with antenna. Active filtering antennas integrated with active tuning/switching devices and passive filtering antennas have been discussed. Examples of each design approach are discussed along with their advantages and challenges. Therefore, this review is useful to understand the current studies of the filtering-antenna design and introduce a suitable design that can be used in modern wireless communication technology.

Multidirectional Receiving System for RF to dc Conversion Signal: Application to home automation devices

In this article, we present an original solution for radio frequency (RF) to dc conversion with multiple antennas. The presented device operates at 2.45 GHz. It combines passive parasitic element antennas (PEAs) and RF to dc converters. The proposed device collects the RF energy with six independent antennas and realizes the conversion and summation of the dc voltages. The objective is to perform uniform coverage of a room with a gain superior to a single and omnidirectional antenna. The typical application can be energy harvesting or detection for the command unit in home automation. This last application is our goal, and interest in the solution has been demonstrated through an application that aims at reducing standby mode consumption of electronic devices. The article focuses on the critical points to realize an efficient summation. The whole system has been designed and manufactured to work in rooms from 3 m to 15 m wide. The measured performances have been validated.

Modified UTD-based UHF RFID tag antenna with two-pronged fork slot for coated metallic cylindrical surface

This research has proposed a modified uniform geometrical theory of diffraction (UTD) for radiation to investigate the radiation pattern on the coated metallic curved surface. The modified UTD, which accounts for the existence of the impedance surface (coating), is applied to the development of a compact UHF RFID passive tag antenna with a two-pronged fork slot to be mounted on the coated metallic cylindrical drum. In the calculation, the UHF RFID tag was initially represented by electric tangential (Ez-source) and equivalent magnetic tangential to the surface (Mz-source). The results indicated that the Mz-source could achieve a greater communication area, and thus the design of the tag antenna is of equivalent magnetic source. Simulations were then carried out to determine the optimal antenna parameters, and an antenna prototype was fabricated and tested. The simulation and measured results are in agreement. The research findings validate the effectiveness of the modified UTD-based UHF RFID tag for application on the coated metallic curved surface.

Design of an X‐band Vivaldi antenna with low radar cross section

In this study, a passive Vivaldi antenna design is proposed for radar cross section (RCS) reduction using object shaping method. The implementation of annular slot along with exponential curves in the radiator reduced the scattering along the surface of the radiator. This contributes reduction in structural mode RCS throughout the operational bandwidth without affecting the impedance performance of the antenna. Monostatic RCS of the antenna is discussed for two incident angles. A minimum RCS reduction of 13 dB is achieved when the incident angle is Θ = 60° and a maximum of 19 dB reduction is achieved at Θ = 75°. The proposed antenna offers symmetric radiation pattern in both azimuth and elevation planes and also maintains co-polarisation to cross-polarisation ratio of 19 dB throughout the X-band (8–12 GHz). Prototype antenna is fabricated and tested to validate the simulated results.

Innovative manufacturing approach for paper‐based substrate integrated waveguide components and antennas

This study presents a novel low-cost manufacturing technique for paper-based microwave components. In particular, this work is focused on the implementation of substrate integrated waveguide (SIW) passive circuits and antennas. The proposed manufacturing technique requires the preliminary preparation of the metallised paper substrate, obtained by stacking different layers of paper, and eventually gluing two aluminium foils on both faces of the paper substrate. Subsequently, the circuit pattern is obtained by milling machining. Finally, as the SIW structures require metal vias, cylindrical holes are obtained by drilling and then metallised by conductive paste, by adopting a particular technique. The different steps are detailed in this study, and the basic features of the proposed technique are compared with the traditional ink-jet-printing technology typically used for paper-based microwave circuits. Moreover, the fabrication and testing of several SIW components and antennas are presented in a comprehensive way, to demonstrate the potential of the proposed manufacturing technique and its applicability to the development of the next generation of eco-friendly wireless systems.

A zero power harmonic transponder sensor for ubiquitous wireless μL liquid-volume monitoring.

Autonomous liquid-volume monitoring is crucial in ubiquitous healthcare. However, conventional approach is based on either human visual observation or expensive detectors, which are costly for future pervasive monitoring. Here we introduce a novel approach based on passive harmonic transponder antenna sensor and frequency hopping spread spectrum (FHSS) pattern analysis, to provide a very low cost wireless μL-resolution liquid-volume monitoring without battery or digital circuits. In our conceptual demonstration, the harmonic transponder comprises of a passive nonlinear frequency multiplier connected to a metamaterial-inspired 3-D antenna designed to be highly sensitive to the liquid-volume within a confined region. The transponder first receives some FHSS signal from an interrogator, then converts such signal to its harmonic band and re-radiates through the antenna sensor. The harmonic signal is picked up by a sniffer receiver and decoded through pattern analysis of the high dimensional FHSS signal strength data. A robust, zero power, absolute accuracy wireless liquid-volume monitoring is realized in the presence of strong direct coupling, background scatters, distance variance as well as near-field human-body interference. The concepts of passive harmonic transponder sensor, metamaterial-inspired antenna sensor, and FHSS pattern analysis based sensor decoding may help establishing cost-effective, energy-efficient and intelligent wireless pervasive healthcare monitoring platforms.

High elastic polyurethane/carbon nanotube composite laminate for structure health monitoring by gain shifting of antenna sensing element

The composite of carbon nanotubes and polyurethane (PU) was prepared by simple filtration technique. The PU nonwoven filtration membrane was prepared by electrospinning. A layer of carbon nanotubes was prepared by vacuum filtration on the surface of PU membrane. The resulting composite was subsequently placed on highly elastic polyurethane substrate. The contribution shows an efficient method of preparing the sensing element for monitoring the state of strain of loaded structures by using highly elastic polyurethane / carbon nanotubes composite. This sensor has been involved as passive antenna with stable resonance frequency of 650 MHz. When it is get deformed in the range from 0 to 3.5% the sensor gain was changing from -39 dB to - 19.45 dB. But if it is get deformed by 15% and again measured strain from 0 to 3.5%, sensor gain was changing from -33 dB to -12.3 dB, which clearly indicates the damage of structure.

Experimental Study on Inkjet-Printed Passive UHF RFID Tags on Versatile Paper-Based Substrates

We present the possibilities and challenges of passive UHF RFID tag antennas manufactured by inkjet printing silver nanoparticle ink on versatile paper-based substrates. The most efficient manufacturing parameters, such as the pattern resolution, were determined and the optimal number of printed layers was evaluated for each substrate material. Next, inkjet-printed passive UHF RFID tags were fabricated on each substrate with the optimized parameters and number of layers. According to our measurements, the tags on different paper substrates showed peak read ranges of 4–6.5 meters and the tags on different cardboard substrates exhibited peak read ranges of 2–6 meters. Based on their wireless performance, these inkjet-printed paper-based passive UHF RFID tags are sufficient for many future wireless applications and comparable to tags fabricated on more traditional substrates, such as polyimide.

DESIGN OF FLEXIBLE PASSIVE ANTENNA ARRAY ON KAPTON SUBSTRATE

Recently, the RF/microwave electronic technology evolved with the consideration of plastic and organic substrates. Such a technology offers two-folded benefits: in one side for lowering the fabrication cost and in another side for the possibility to bend electronic devices. Such a technology is particularly interesting for the implementation of antenna system. This paper is dealing with the design of flexible microstrip antenna 1:2 array. Theoretical approach on the typically symmetrical antenna 1:2 array is proposed. The design methodology of microstrip antenna combined with 1:2 T-power divider (T-PWD) is described. Based on the transmission line theory, the S-parameter model of the antenna system with non-standard reference load is established. Then, the microstrip antenna passive system is theoretical analysed in function of the physical dimensions of the designed structure. The feasibility of the flexible antenna passive system is investigated with the proof-of-concept (POC) designed on Kapton substrate. The POC prototype consisted of microstrip antenna 1:2 array is designed to operate at about 5.8 GHz. Comparisons between the full wave simulated and measured return losses were performed. Then, simulated radiation pattern highlights the efficiency of the fabricated prototype of passive antenna array.

A 2.45 GHz Phased Array Antenna Unit Cell Fabricated Using 3-D Multi-Layer Direct Digital Manufacturing

This paper reports on the design, fabrication and characterization of a 3-D printed RF front end for a 2.45 GHz phased array unit cell. The printed unit cell, which includes a circularly-polarized dipole antenna, a miniaturized capacitive-loaded open-loop resonator filter and a 4-bit phase shifter, is fabricated using a direct digital manufacturing (DDM) approach that integrates fused deposition of thermoplastic substrates with micro-dispensing for deposition of conductive traces. The individual components are combined in a passive phased array antenna unit cell comprised of seven stacked substrate layers with seven conductor layers. The measured return loss of the unit cell is ${>}12$ dB across the 2.45 GHz ISM band and the measured gain is ${-}11$ dBi including all components. Experimental and simulation-based characterization is performed to investigate electrical properties of as-printed materials, in particular the inhomogeneity of printed thick-film conductors and substrate surface roughness. The results demonstrate the strong potential for fully-printed RF front ends for light weight, low cost, conformal and readily customized applications.

Multibeam Pillbox Antenna With Low Sidelobe Level and High-Beam Crossover in SIW Technology Using the Split Aperture Decoupling Method

A novel dual-layer multibeam pillbox antenna with a slotted waveguide radiating part in substrate-integrated waveguide (SIW) technology is proposed. In contrast to previous works, the design goal is to have a multibeam antenna with arbitrary low sidelobes and at the same time a high crossing level between adjacent radiated beams. These two constraints cannot be satisfied simultaneously for any passive and lossless multibeam antenna systems with a single radiating aperture due to beam orthogonality. Here, this limitation is overcome using the “split aperture decoupling” method which consists in using two radiating apertures. Each aperture is associated with a pillbox quasi-optical system with several integrated feed horns in its focal plane so as to steer the main beam in the azimuthal plane. The antenna operates at 24.15 GHz and presents very good scanning performance over an angular sector of $\pm 40^\circ $ , with a good agreement between full-wave simulations and measurements. The crossover level between adjacent beams is about $- 3\;{\text {dB}}$ with a sidelobe level lower than $- 24\;{\text{dB}}$ for the central beam and better than $- 11\;{\text{dB}}$ for the extreme beam positions. The isolation between feed horns in the same pillbox system is better than 20 dB.

A new B-dot probe-based diagnostic for amplitude, polarization, and wavenumber measurements of ion cyclotron range-of frequency fields on ASDEX Upgrade

A new B-dot probe-based diagnostic has been installed on an ASDEX Upgrade tokamak to characterize ion cyclotron range-of frequency (ICRF) wave generation and interaction with magnetized plasma. The diagnostic consists of a field-aligned array of B-dot probes, oriented to measure fast and slow ICRF wave fields and their field-aligned wavenumber (k(//)) spectrum on the low field side of ASDEX Upgrade. A thorough description of the diagnostic and the supporting electronics is provided. In order to compare the measured dominant wavenumber of the local ICRF fields with the expected spectrum of the launched ICRF waves, in-air near-field measurements were performed on the newly installed 3-strap ICRF antenna to reconstruct the dominant launched toroidal wavenumbers (k(tor)). Measurements during a strap current phasing scan in tokamak discharges reveal an upshift in k(//) as strap phasing is moved away from the dipole configuration. This result is the opposite of the k(tor) trend expected from in-air near-field measurements; however, the near-field based reconstruction routine does not account for the effect of induced radiofrequency (RF) currents in the passive antenna structures. The measured exponential increase in the local ICRF wave field amplitude is in agreement with the upshifted k(//), as strap phasing moves away from the dipole configuration. An examination of discharges heated with two ICRF antennas simultaneously reveals the existence of beat waves at 1 kHz, as expected from the difference of the two antennas' operating frequencies. Beats are observed on both the fast and the slow wave probes suggesting that the two waves are coupled outside the active antennas. Although the new diagnostic shows consistent trends between the amplitude and the phase measurements in response to changes applied by the ICRF antennas, the disagreement with the in-air near-field measurements remains. An electromagnetic model is currently under development to address this issue.

Recent advances in theory and applications of substrate-integrated waveguides: A review

The use of substrate integrated waveguides (SIW) for microwave and millimeter wave integrated components has increased dramatically over the last decade. They mimic the performance of conventional metallic waveguides and they are fabricated using printed circuit boards using the top and bottom metallisation with two rows of vias forming the side walls. This creates a low profile, compact, and light weight alternative to conventional metallic waveguides, and they allow a direct interconnection with printed circuit boards and active components. This paper reviews the fundamental theory, documents the research that has been performed over the past decade, and summarises progress up to the recent state-of-the-art including novel SIW structures for passive circuits and antennas as well as new applications for reconfigurable and printed circuits using SIW technology.

Terahertz Magnetic Mirror Realized with Dielectric Resonator Antennas.

Single-crystal silicon is bonded to a metal-coated substrate and etched in order to form an array of microcylinder passive terahertz dielectric resonator antennas (DRAs). The DRAs exhibit a magnetic response, and hence the array behaves as an efficient artificial magnetic conductor (AMC), with potential for terahertz antenna and sensing applications.

SAR Study of Mobile Phones as a function of Antenna Q

High-Q tunable antennas are good alternatives to low-Q passive antennas because the antenna size can be smaller while covering the required long-term evolution (LTE) frequency bands. However, among other things, specific absorption rate (SAR) can become a challenge due to the relative high current density associated with high-Q antennas. The higher energy stored in the electric and magnetic near-field components can result in higher SAR. Hence, SAR study of high-Q antennas is necessary which, if not addressed, might not comply with the SAR safety guidelines. In this paper, SAR as a function of antenna Q is investigated numerically as well as experimentally at two distinct frequencies (720 and 1700 MHz). It is found that SAR increases as a function of antenna Q when no losses are considered. But when losses are included, there is no more a clear trend between SAR and antenna Q. Thus, the final SAR values depend on total losses of the mock-up (MU).

Complex Reflection Coefficient Synthesis Applied to Dual-Polarized Reflectarrays With Cross-Polar Requirements

An extended formulation of the intersection approach (IA) algorithm is presented to synthesize matrices of complex reflection coefficients for dual-polarized reflectarrays. The synthesis of complex reflection coefficients allows to impose copolar as well as cross-polar specifications, since these coefficients fully characterize the behavior of the unit cell. The implementation of the algorithm is based on the use of the fast Fourier transform (FFT) in both the forward and backward projectors of the IA, allowing for a highly efficient and fast synthesis process of dual-polarized reflectarrays. Although arbitrary restrictions can be enforced in the reflection coefficients, they might not be feasible for passive antennas. Hence, the unit cell is analyzed as a lossless and lossy passive two-port network and the restriction equations are derived for both cases involving amplitudes and phases of the reflection coefficients. The lossless constraints proved to be too restrictive so lossy restrictions should be applied to achieve feasible reflection coefficients for passive array design. Test cases are provided, which confirm that the algorithm is able to synthesize with success radiation patterns with copolar and cross-polar requirements with restrictions applied to the reflection coefficients.

Design of the ESPAR antenna with improved DC bias

ABSTRACTIn this article, an electrically steerable passive array radiator antenna was designed, consisting of a cylindrical dipole active element and four flat dipole parasitic elements. Using a varactor diode, which is a variable capacitor, reactance was applied to the parasitic elements and beam steering to a preferred direction can be achieved through the reactance change. A common ground was used for negative voltage applied lines, which were DC bias lines to control varactor diode voltage, with the active element ground. Using this structure, the number of DC bias lines could be reduced, resulting in the advantage of constructing a simple control circuit. In addition, using a quarter‐wave meander strip line in the negative voltage applied lines, a voltage standing wave ratio characteristic was improved and an antenna gain was increased. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2281–2286, 2015