Far-field Gain Research Articles

Evaluation of a double-lens dielectric radome using a microstrip patch antenna for electromagnetic applications

The advancement of increasingly powerful antennas has increased the complexity of radome electromagnetic (EM) design and analysis. The antenna systems are protected from environmental influences by radomes, which are dielectric and electromagnetically transparent structures. Because the presence of the radome affects the performance parameters of the antenna, such as the radiation pattern, reflected power, and side lobe level, its design should not be done independently of the antenna analysis. The great majority of ground-based hemispherical radomes are used for satellite communication antennas, commercial and military radars, telemetry systems, and other uses. Patch antennas, reflector antennas, phased array radars, and other antenna systems are used in these applications. The operational effectiveness of a radome architecture for housing multiple patch antenna systems is proposed and evaluated. The proposed line of work includes antenna-radome interaction analyses, electromagnetic designs for radome walls, and radiation patterns for reflector antennas. COMSOL Multiphysics was used to develop the EM radome and examine the antenna-radome interaction. The findings of a comprehensive analysis into the differences in radiation patterns produced by patch antennas with and without radomes are presented in this article. At a frequency of 1.62 GHz, a plot and investigation of the far-field gain of the microstrip patch antenna with and without radome were done. The radome is estimated to add 0.09 dBi to the gain boost experienced by the microstrip patch antenna.Abbreviations: EM, Electromagnetic; DSF, Dielectric space frame radome; IFR, Induced field ratio; RF, Radio frequency; VSWR, Voltage standing wave ratio; FEM, Finite element method; SRR, Split ring resonator; CATR, Compact antenna test range; DUT, Device being tested; LHM, Left-handed metamaterials; PML, Perfectly matched layer; PTFE, Polytetrafluoroethylene.

EXPERIMENTAL ANALYSIS OF A 2.4 GHZ ANTENNA FOR TYRE PRESSURE MONITORING SYSTEM

Antennas used for tyre pressure monitoring systems are usually enclosed by the tyre. On its own, the antenna may have excellent properties. However, the wheel and tyre may have an impact on the performance of the antenna. This paper investigated the performance of a simple 2.4 GHz whip antenna for a tyre pressure monitoring system. The antenna was modelled using HFSS, while the wheel and tyre were modelled using SolidWorks. The wheel and tyre can have an impact on the antenna performance. The reflection coefficients, VSWR, gain and radiation pattern were determined through simulations, using HFSS. The antenna operation was checked at different positions and configurations to the wheel to determine its’ optimum position for effective signal radiation. The four different configurations were: antenna grounded to the middle of the rim, antenna ungrounded to the wheel’s edge, antenna grounded to the wheel’s edge, and antenna grounded to the wheel’s edge enclosed by the tyre. The result shows that electrically grounding the antenna to the wheel by the edge improves its performance. Also, the tyre did not negatively impact the far-field gain of the antenna.

Electrically Small Antenna For RFID-Based Implantable Medical Sensor

We present a sub-GHz, low profile Electrically Small Antenna (ESA), designed for UHF RFID miniaturised battery free Implantable Wireless Medical Devices (IWMDs). The custom ESA is a linearly polarised dipole, and its topology leverages a meanderline structure to miniaturise its form factor. Furthermore, the ESA utilises a receded ground plane to improve its gain performance and achieve resonance, at the desired sub-GHz design frequency of 915 MHz. The ESA’s dipole characteristics provide an added benefit of 180∘ bi-directional RF signal propagation. The ESA’s design was optimised to integrate the footprint of a UHF RFID sensor chip (SL900A). By integrating the UHF RFID chip on the ESA, a complete wireless battery free sensory medical device, with an integrated antenna, can be realised. The antenna has a formfactor of 12.75×12.25×0.29 mm3. A prototype of the proposed ESA was fabricated and encapsulated in Polydimethylsiloxane (PDMS). Measurements of the prototyped ESA’s input reflection coefficient (S11) and farfield gain values, at 915 MHz, were -26.44 dB and -18.88 dBi, respectively and demonstrated significantly better gain and efficiency performance, when compared to peer reviewed work. The ESA can be used as an antenna for various battery-free subcutaneous implants with a connected sensor (e.g. temperature) or sactuator (e.g. neurostimulator).

A Switchable Filtering Antenna Integrated with U-Shaped Resonators for Bluetooth, WLAN & UWB Applications

In this paper, A Switchable Filtering Antenna Integrated With U-Shaped Resonators for Bluetooth, WLAN & UWB Applications is presented. To achieve the UWB operation, a rectangular defect on the ground plane and square slots are etched on the rectangular patch. The selectivity of frequency is achieved by integrating a Hairpin filter. Three switches are connected at the corners of the filter to achieve frequency re-configurability. A total of eight Boolean combinations are possible by controlling ON and OFF these switches. This filtering antenna acts as a band pass filter and picks distinct frequency bands within the UWB frequency. It can be used for wireless applications such as Long-Distance Radio Communication, Aviation Services, WLAN, C-band satellite communication, Wi-MAX, mobile satellite sub-band, radar communications, and space communications. In addition, two inverted U- shaped resonators of differing lengths are engraved on the rectangular microstrip patch to operate at Bluetooth frequency applications with frequencies ranging from 2.4 to 2.458GHz. The maximum gain obtained out of all operating frequencies is 4.82dBi at a frequency of 9.5GHz. The proposed antenna is simulated using the 3D-Simulation tool CST MWS. The performance of the designed antenna is estimated using the parameters like return loss, VSWR, and Far-field Gain characteristics.

Design of a Novel Compact MICS Band PIFA Antenna for Implantable Biotelemetry Applications

An implantable stacked planar inverted-F antenna (PIFA) for biotelemetric communication in the 402-405 MHz Medical Implant Communications Service (MICS) frequency band is designed and fabricated. With the proposed PIFA structure, a slot on each radiating patch was embedded, resulting in a size reduction of 0.013 λ and a compact size of 10 × 10 × 1.905 mm3. Both in vitro and in vivo experiments verified the simulation performance with characteristics of -10 dB bandwidth of 29 MHz, radiation efficiency of 0.9%, and a maximum far-field gain of -18.8 dB. We calculated the safety power delivered to the antenna using the specific absorption rate (SAR) limitation standard. Compared to other implantable antennas for biotelemetry, this antenna performs comparably and has a smaller size. This design would further develop implantable medical devices that communicate in the MICS band.

A Loop Antenna Array With an Enlarged Near-Field Interrogation Zone for UHF RFID Near-Field and Far-Field Applications

This letter presents a loop antenna array for ultrahigh frequency near-field and far-field radio frequency identification (RFID) reader applications. The antenna array consists of several microstrip collinear loop antennas, and each loop antenna is composed of several periodic radiating units. By deploying microstrip collinear radiating units, a novel loop antenna with in-phase radiating currents is realized, which generates a strong and uniform magnetic field over a large interrogation area and a horizontally polarized omnidirectional radiation. By configuring the array antenna, the magnetic fields distribute on the entire antenna array and create an enlarged near-field reading area. The far-field coverage is enlarged by the superposition of omnidirectional radiation. The antenna array is simulated and validated with a four-element prototype made on FR-4 substrates. The antenna array is measured to have a −10 dB impedance bandwidth from 802 to 963 MHz with an enlarged near-field reading volume of 280 × 280 × 540 mm and a far-field gain of 6.66 dBi at the UK RFID band.

Spatial Processing Using High-Fidelity Models of Dual-Polarization Antenna Elements

This paper generalizes a recent improvement to a traditional spatial-processing algorithm to optimally use body-mounted arrays of dual-polarization radio-frequency antenna elements rather than single-polarization antenna elements. The paper’s generalized algorithm exploits high-fidelity far-field gain and polarization data, generated most practically by a computational electromagnetic solver (CES), to characterize the antenna array’s individual dual-polarization elements. Using this characterization and that of the desired and undesired communication nodes’ antennas, the generalized algorithm determines the array’s optimal weights. The subsequent application of a CES to a practical scenario, in which an optimally weighted array of dual-polarization antenna elements is mounted on a representative body, demonstrates the generalized algorithm’s exceptional spatial-processing performance.

Design and Performance Measurement of Implantable Differential Integrated Antenna for Wireless Biomedical Instrumentation Applications

The growing demand of implantable medical devices is crucial for enabling real-time monitoring in biomedical and healthcare fields. This paper presents a differential integrated antenna for biomedical instrumentation applications in the Industrial, Scientific, and Medical (ISM) frequency bands (915 MHz and 2.45 GHz). The size of the proposed cubic flat differential system is (0.103λg × 0.103λg × 0.005λg), where λg is the guided wavelength at 915 MHz. The performance analysis of the differential antenna is carried out within homogeneous, heterogeneous, and realistic body models to design the proposed implantable integrated antenna. To validate the design method, a differential antenna is fabricated and assembled with different circuit components as per the simulation scenario and experimentally verified in the vicinity of skin mimicking phantom and minced pork. The measured -10 dB impedance bandwidth and far-field gain in the phantom are 16.4% and -30.3 dB, respectively, at 915 MHz, and 10.2% and -21.2 dB, respectively, at 2.45 GHz. Also, the communication link is calculated and evaluated based on the specific absorption rate (SAR) of the proposed differential integrated antenna at 1 W input power.

On-Demand Reconfigurable WiMAX/WLAN UWB-X Band High Isolation 2×2 MIMO Antenna for Imaging Applications

In this paper, on-demand rejection of interfering bands with operating band intended for UWB-X band applications utilizing a diversity antenna with a dimension of 24 × 48 mm2 has been reported. Two sharp rejecting bands, WiMAX and WLAN are obtained by using an anchor-shaped stub embedded within a slotted radiating patch and externally connected C-type stub. MIMO antenna configuration offers isolation of more the 30 db in both measured and simulation environments. The designed MIMO antenna offers good time-domain characteristics and is characterized utilizing various parameters including S-parameters, radiation efficiency, far-field gain, radiation pattern, ECC, DG, TARC, and CCL.

Triple-Band Uniform Circular Array Antenna for a Multi-Functional Radar System

A phased array radar has been developed toward an effective means for integrating multiple functionalities into one radar platform. The radar system necessitates the ability to operate at multiple frequencies simultaneously. In this paper, a triple-band uniform radial sub-array using a shared aperture antenna is proposed for a multi-functional radar system. An efficient placement of different radiating elements is realized based on the radial displacement of the circular array. In addition, multi-layer feed networks are used to reduce the intricacy of integrating several feed networks into one antenna. The reasonable matching characteristics and far-field gain are acquired at the S-band, C-band, and X-band. The measured results of the prototype are presented, and the results are compared to the simulation, which showed a good agreement.

A Novel Antenna for UHF RFID Near-Field Applications

This paper proposed a novel antenna for ultra-high frequency (UHF) radio frequency identification (RFID) near-field applications with uniform distribution of the electric field along the x-axis (Ex), and the y-axis (Ey). The proposed antenna adopted a spiral structure to achieve broadband and multi-polarization. The novel antenna achieved good impedance matching within 860–960 MHz. Using a ground plate, the proposed antenna achieved low far-field gain and a maximum gain of less than −11 dBi. The component of the excited electric field Ex and Ey parallel to the antenna surface was uniformly distributed, and there was no zero point. The proposed antenna achieved a 100% read rate of tags parallel to its surface in the reading area of 150 mm × 150 mm × 220 mm. Simulation results were consistent with the results of real-world measurements, and the proposed antenna was suitable as a reader antenna in near-field applications. The polarization mode of RFID tags is mostly linear polarization, and the placement of tags in practical applications is diversified. Compared with the traditional RFID reader antenna, the proposed antenna achieves uniform electric field distribution parallel to the antenna surface, but the single-direction electric field has zero-reading points, which is easy to cause the misread of tags. The RFID tags can be read more accurately. To verify the scalability of the reading area of the spiral antenna unit, it was used for array design, and simulations were conducted using 1 × 2, 2 × 2, 1 × 4, and 2 × 4 arrays. The component distribution of the electric field excited by the four array antennas in the x and y directions was uniform and the reading area was controllable. Therefore, the proposed spiral antenna has the expandability of the reading area and can meet the needs of different application scenarios by changing the number of array units. With the array extension, the matching network also extends, and the impedance characteristics of the array antenna are somewhat different, but they also meet the application requirements.

An Inset-Feed On-Chip Frequency Reconfigurable Patch Antenna Design with High Tuning Efficiency and Compatible Radome Structure for Broadband Wireless Applications

A novel, dual edge-shaped frequency reconfigurable antenna with a highly compact size is proposed, using microstrip line-based inset-feed mechanism. The presented antenna uses cost-effective ROGER substrate with a thickness of 0.787 mm and has been studied for its gain and radiation pattern in the radome structure presence. The antenna resonates within the range of 3 GHz to 9 GHz approximately, with maximum tuning efficiency of 43 % at 6.5 GHz, covering the major wireless applications of aviation service and wireless local area network (WLAN) in the upper segment of S-band along with worldwide interoperability for microwave access (WiMAX), long-distance radio telecommunications, and X-band satellite communication. The proposed antenna works resourcefully with a reasonable gain of 2.3 dBi at 5.04 GHz, significant bandwidth of 2800 MHz (maximum at 6.5 GHz), directivity, and reflection coefficient. The proposed multiband reconfigurable antenna along with radome structure using ABS material has been investigated under high-frequency simulation environment of HPEEsof of ADS (by Keysight Technologies) and 3d radiation pattern (far-field gain, directivity and power calculations) have been obtained using momentum and EMDS simulators of ADS. The final implementation size (without radome structure) for the patch design comes out to be 23 mm X 26 mm large.

Derivation of Far-field Gain Using a Gain Reduction Effect in the Fresnel Region

A handy method of calculating far-field gain based on the magnitude of the power transmission in a Fresnel region is presented, which can be applied to the phaseless near-field measurement. Due to the short range inside an anechoic chamber, the probe antenna is often placed in the Fresnel region of the antenna under test (AUT). It is well-known that far-field gain of an antenna gradually reduces when one antenna moves to the other one placed in a proximity distance. This fact can be advantageously applied to estimate the far-field gain in a far-field region. The proposed method offers rapid estimation of the far-field gain based on the simple input knowledge such as the probe antenna gain and the magnitude of the power transmission and the separation distance between AUT and probe antenna. The proposed method can be applicable to a wide range of microwave antennas. This feature makes it possible to offer preliminary measurement results and reference parameters of the measurement for the various types of microwave antennas.

Quadrilateral Spatial Diversity Circularly Polarized MIMO Cubic Implantable Antenna System for Biotelemetry

This article presents a first of its kind, coplanar waveguide (CPW)-fed 3-D multi-input-multi-output (MIMO) ground radiating cubic antenna (CA), implantable in the human upper arm for biotelemetry applications. The four antenna elements are circular in shape and loaded with a pair of slots to obtain circular polarization (CP). It excites diversified CP radiation in Industrial, Scientific, and Medical (ISM) band 2.45 and 5.8 GHz in orthogonal space to establish communication between the human body moving in random directions and base-station. The overall dimensions of the proposed antenna are 15 × 15 × 15 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . Monitoring circuit PCB is placed at the top, and the bottom side of the cube and central hollow space is filled with a dry solid phantom for impedance matching. The CA is simulated in the vicinity of the canonical arm tissue model in HFSS software and examined in a realistic human model. The far-field gain is -18.5 dB with -32 dB isolation between elements. The CA is fabricated, and measurements are carried out in skin-fat-muscle phantom and minced pork. Simulated results closely match with measured results. The results show that the proposed CA is polarization and 3-D orientation insensitive and provides good MIMO properties. The low SAR value of the CA allows maximum transmit power of 5.81 mW, makes it a suitable choice to transfer high data rate (200 Mb/s) to an external antenna of diverse polarization. These features make CA an attractive solution for real-time healthcare applications.

A Symmetrically Stacked Planar Antenna Concept Exhibiting Quasi-Isotropic Radiation Coverage

This letter presents a symmetrically stacked planar antenna (SSPA) featuring switchable quasi-omnidirectional and omnidirectional radiation patterns to accomplish a quasi-isotropic radiation coverage. The proposed antenna consists of two identical planar patch antenna elements. By separately controlling the phase of the two excitation ports, the comprised antenna collectively emulates either an electric dipole mode or a magnetic dipole mode. Collectively, these two complementary dipoles enable a full spherical coverage with a simulated far-field gain variation lower than 6.8 dB. In actual usage scenarios, the proposed antenna can encapsulate various RF circuits and components between the two antennas due to the ground planes functioning as electromagnetic shielding structures. Studies confirm that quasi-isotropic characteristics are preserved for highly integrated user scenarios.

Development of 60-GHz millimeter wave, electromagnetic bandgap ground planes for multiple-input multiple-output antenna applications

For 60-GHz band communications, both the mutual coupling and transmission distance restrict the performance of a multiple-input multiple-output (MIMO) antenna array. Several studies presented different types of meta-materials and electromagnetic bandgap (EBG) structures to improve the performance of a MIMO antenna array at the 60-GHz band. In this paper, we presented the four-element MIMO patch antenna with different types of EBG structures for the millimeter wave (mmW)communications at the 60-GHz unlicensed industrial, scientific, and medical band. The single element of the MIMO antenna array covered the mmW band from 57 GHz to 63 GHz having the dimensions of 1.3 mm × 1.8 mm × 0.1 mm. We developed a set of square-shaped, cross-shaped, and complex-slotted EBG ground planes between the antenna elements for the performance improvement. All the three EBG ground planes provided significant coupling reduction between the mmW MIMO antenna elements. The proposed EBG structures exhibited wide bandgap characteristics and improved scattering parameters in the desired frequency band. In contrast with the cross- and complex-slotted, the square-shaped EBG structure substantially improved the overall gain of MIMO antenna array. In addition, the square-shaped EBG reformed the maximum beam and enhanced the far-field gain pattern in the desired direction. Experimental results conducted with the fabricated prototypes showed a good agreement with the simulation results and adequately covered the 60-GHz band. The low-profile and salient features of the proposed MIMO antenna array shows the potential for on-chip applications at 60 GHz.

UHF pure near‐field RFID reader antenna based on CSRR

An ultra-high frequency (UHF) travelling wave antenna based on complementary split ring resonator (CSRR) element is investigated in this study for pure near-field radio frequency identification (RFID) system. The proposed antenna consists of a T-type power divider, 180 ° phase shifter, two microstrip transmission lines ended with two 50 Ω resistors and the metal ground loaded CSRR elements. The CSRR elements are loaded on the metal floor corresponding to the minimum current points and middle of the two transmission lines. The CSRR elements resonate at the centre frequency and introduce coupling to enhance the magnetic field. The measured − 10 dB impedance bandwidth of the proposed antenna is 46 MHz (889–935 MHz), which covers the standards of Chinese and American bands. The reading regions for near-field tag, far-field tag and anti-metal tag are 400 × 200 × 10 mm 3 , 400 × 200 × 70 mm 3 and 400 × 200 × 60 mm 3 , respectively. The far-field gain is less than − 22 dBi, which makes the antenna suitable for the pure near-field application.

MIMO handset antenna for 5G/WLAN applications

We propose a dual-module multiple-input multiple-output (MIMO) antenna for portable terminals. The operating bands of the handheld terminal antenna are 5G (3.4–3.8 GHz) and WLAN (5.150–5.925 GHz). Antenna elements of 5G and WLAN are spaced to reduce coupling between antenna elements in the same module. The return loss of all antenna elements is larger than 6 dB. The isolation between all elements is larger than 14 dB. The radiation efficiency of the high-frequency antenna is greater than 50%, and the radiation efficiency of the low-frequency antenna is greater than 40%. The far-field gain of all elements is greater than 2.2 dBi.

Multipolarized Reader Antenna With Periodic Units Based on Electric Field Coupling for UHF RFID Near-Field Applications

This paper presents a multipolarized reader antenna with periodic units based on electric field coupling for near-field applications of ultra-high frequency (UHF) radio frequency identification (RFID). The antenna units are composed of two branches that are mirror-symmetric with respect to the ${x}$ -axis and produce ±45° linear polarization. A 90° phase difference is produced between the upper and lower branches by introducing a phase shifter into the upper branch, so that the near-field electric fields excited in the horizontal plane exhibit a quasi-circular polarization distribution. The proposed design is validated by simulations and experiments using prototype 4-unit and 6-unit antennas. The proposed antennas can generate strong and uniform electric fields and provide reading volumes of 400 mm $\times \,\,320$ mm $\times \,\,300$ mm and 560 mm $\times \,\,320$ mm $\times \,\,300$ mm for the 4-unit and 6-unit antennas, respectively, regardless of the orientation of the tags in the horizontal plane. In addition, the far-field gain is low with a maximum of −6 dBi, thus the misreading of tags outside the reading region is avoided. The proposed antenna achieves impedance matching over the Chinese UHF RFID band (920–925 MHz) and therefore meets the application requirements of near-field RFID reader antennas.

Uncertainty Analysis of Far-Field Gain Measurement of DRGH Using the Single-Antenna Method and Amplitude Center Distance

The single-antenna gain calibration method was first proposed by Glimm et al. of Physikalisch-Technische Bundesanstalt in 1999. Their method requires the measurements of the reflection coefficient of an antenna under test (AUT) in free space and the reflection coefficient on a large metal plane using two different measurement setups. On the other hand, we proposed a new single-antenna gain calibration method that can measure these quantities using the same measurement setup. Our proposed method uses the average value of the reflection coefficients of the AUT for various distances from the large metal plane to the AUT. Furthermore, we established a measurement setup for our proposed single-antenna method for a double-ridged guide horn (DRGH) antenna in the frequency range from 1 to 6 GHz. To estimate the antenna gain, we applied the Friis transmission formula, which included the amplitude center distance of the antenna. By using our proposed method and the measurement setup, the expanded uncertainty ( $k = 2$ ) of the DRGH was estimated to be from 0.61 to 1.70 dB over a frequency range from 1 to 6 GHz.