Resonant Frequency Of Antenna Research Articles

Liquid metal antenna-based pressure sensor

In this paper, a centre-fed, finite-length, infinitesimally thin dipole antenna is presented as a pressure sensor to monitor pressure changes in geotechnical engineering. The antenna consists of a liquid metal (eutectic gallium–indium alloy) injected in microfluidic channels, which are enclosed in the elastic material polydimethylsiloxane (PDMS); therefore, the liquid antenna is stretchable and frequency reconfigurable and can thus be used as a pressure sensor when the length of the elastic material PDMS is changed under pressure. The effects of the geometrical parameters of the dipole antenna on its resonant frequency are investigated using the finite-element software HFSS. Based on the numerical results, the liquid-metal antenna is designed, fabricated and measured, and its resonant frequencies are recorded under different pressures. According to the experimental results, the relation between the resonant frequency of the liquid antenna and the applied pressure is defined, and it is consistent with the numerical and theoretical results. Moreover, the experimental results show that the relation between the displacement and the resonant frequency is in good agreement with the numerical and theoretical results. Thus, there is a linear relation between the resonant frequency of the antenna and the applied pressure as well as between the resonant frequency and the displacement. Therefore, this frequency-reconfigurable liquid-metal dipole antenna is suitable for use as a pressure sensor.

Control of magnetoelectric antenna by electric field

The results of researching on the microwave processes in the microstrip antenna in which the substrate is consist of composite structure: ferroelectric – ferromagnetic – dielectric was presented. The paper shows that unified wave can be present in this structure, which combines the properties of electromagnetic and spin types of waves – this is a hybrid electromagnetic-spin wave. The dispersion characteristic of this wave was obtained and its dependence on the applied electric field to the ferroelectric layer was established. This dependence is a consequence of two effects: magnetoelectric effect and dependence dielectric constant from applied electric field. The total effect is a change in the resonant frequency of antenna under study about 2 GHz with the applied electric field changed on 40 kV/cm. It was also found that, depending on the value of the applied electric field, the mode of standing waves can be achieved.

A Compact Hybrid-Fed Microstrip Antenna for Harmonics-Based Radar and Sensor Systems

In this letter, we propose and experimentally validate a compact hybrid-fed microstrip antenna for the harmonics-based radar and sensor systems, which receive the fundamental tone and retransmit the modulated second harmonic. The proposed microstrip antenna is based on a simple single-layered and dual-feed structure, consisting of an inner circular patch operating in the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">110</sub> mode (second harmonic; 6 GHz) and an outer split-ring patch operating in the higher order TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">210</sub> or TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">310</sub> mode (fundamental frequency; 3 GHz). By varying the feed position and the geometry of the split-ring patch, a specific higher order mode can be excited at the fundamental frequency. Moreover, analytical expressions were derived for calculating the antenna's resonant frequencies. Our measurement results show that the maximum realized gain is 1.17 dB at 3 GHz and is 3.33 dB at 6 GHz, with good impedance matching (|S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | <; -15 dB) and high isolation (<; -20 dB).

Active Compact Wearable Body Area Networks for Wireless Communication, Medical and IoT Applications

The development of compact wearable antennas and transceivers for communication, IoT (Internet of Things), and biomedical systems will be presented in this paper. Development of Compact efficient wearable antennas is one of the major challenges in development of wearable communication, IoT, and medical systems. The main goal of wireless body area networks (BANs), WBANs, is to provide continuously medical data to the physician. Body area network (BAN) antennas should be flexible, lightweight, compact, and have low production cost. However, low efficiency is the major disadvantage of small printed antennas. Microstrip antennas resonant frequency is altered, due to environment conditions, different antenna locations, and different system operation modes. These disadvantages may be solved by using compact active and tunable antennas. A new class of wideband active wearable antennas for medical applications is presented in this paper. Amplifiers may be connected to the wearable antenna feed line to increase the system dynamic range. Small lightweight batteries supply the bias voltage to the active components. An active dual polarized antenna is presented in this paper. The active dual polarized antenna gain is 14 ± 3 dB for frequencies ranging from 380 to 600 MHz. The active transmitting dual polarized antenna output power is around 18 dBm. A voltage-controlled diode, varactor, may be used to control the antenna electrical performance at different environments. For example, an antenna located in patient stomach area has VSWR (Voltage Standing Wave Ratio) better than 2:1 at 434 MHz. However, if the antenna will be placed on the patient back, it may resonate at 420 MHz. By varying the varactor bias voltage, the antenna resonant frequency may be shifted from 420 to 434 MHz. An ultra-wideband passive and active printed slot antenna may be employed in wideband wearable communication systems. The active slot antenna gain is 13 ± 2 dB for frequencies from 800 MHz to 3 GHz.

Mechanical Deformation Detection of Building Structures Using Microstrip Patch Antennas as Sensors

A miniaturized quarter-wavelength microstrip patch antenna is developed to monitor the mechanical deformation of building structures. In order to minimize the physical dimension as well as improve the sensitivity of resonant frequency of the patch antenna, via holes are added to the antenna and the operational resonant frequency of the antenna is designed to be 2.4 GHz. Practical measurement for the resonant frequency is implemented to figure out the relationship between mechanical deformation and resonant frequency. Additional tensile tests are employed by increasing strain increments per loading step so that a larger shift caused by a larger deformation can be reached. It is revealed that the transmission efficiency of mechanical deformation is about 70% and the proposed antenna can sensitively monitor the mechanical deformation of building structures. Furthermore, different substrates in the antenna are investigated and the measurement results show that the RT5870 substrate has much better transmission efficiency than FR4 substrate. The proposed different antennas are designed to meet the specific needs of practical applications.

Remote monitoring of cardiac activity using a flexible loop antenna

In this paper, a meandered loop antenna, useful for medical cardiac monitoring application, more specifically, for heart beating close scrutiny is designed and experimentally tested. The proposed antenna is operating at the MICS band displays a high flexibility which allowing it to be curved easily around the heart's wall. In both, Simulation and measured results the antenna shows a sensitive nature any change introduced in heart's model size and would certainly bring about a noticeable shift in the antenna's resonant frequency. Linking the frequency variations taking place in concord with the heart movement turns out to stand as an effective key that provides extremely valuable information about the heart's activities. A correspondence between the obtained frequency variation linking with the change in size of the heart. In addition to the frequency response evaluation, the antenna characteristically displays an omni-directional radiation pattern, which necessarily fits it for in-body operation.

Photoluminescence-Driven Broadband Transmitting Directional Optical Nanoantennas.

Optical nanoantennas mediate near and far optical fields. Operating a directional nanoantenna in transmitting mode is challenging because the antenna needs to be driven by a nanosized optical frequency generator, which must work at the antenna's resonance frequency and be precisely attached to the antenna's feed with correct polarization. Quantum emitters have been used as optical nanogenerators, but their precise positioning relative to the nanoantenna is technically challenging, setting up a barrier to the practical implementation. One unique source to drive nanoantenna is the photoluminescence from the material of the nanoantenna because the high operational frequency of the antenna reaches the regime for the electronic transitions in matter. Here, we exploit plasmon-modulated photoluminescence (PMPL) as an effective optical source to drive directional nanoantennas. We experimentally realize two technically challenging theoretical proposals, namely, an optical nanospectrometer based on Yagi-Uda nanoantennas and tunable broadband directional emission from log-periodic nanoantennas. Using photoluminescence from the nanoantenna as an optical source promotes practical implementation of transmitting optical nanoantennas.

Design and Comparative Analysis of Rectangular Slot Microstrip Patch Antennas for X-band Applications

Microstrip patch antenna is a compact antenna which suffers the limitations of poor gain and reduction in radiation pattern. To reduce the resonance frequency of microstrip antenna increases the length of surface current with help of cutting slots in the patch. In this paper, a comparison of four Microstrip antennas with unequal length of rectangular slots is proposed. The microstrip antennas having rectangular shaped ground plane and FR4-epoxy substrate with relative permittivity 4.4, relative permeability 1 and dielectric loss tangent 0.02 with an overall size of 100×100×5 mm3. The performance of antennas is compared with slots in the patch and the effects of rectangular slots using operating frequency of 8 to 12 GHz are presented. The design simulate and analyze on FEM based HFSSv11 and this helps to compute VSWR, return loss, gain, radiation efficiency and 3D polar plot of the proposed microstrip antenna. The proposed configuration gives broadside gain of more than 8 dBi and VSWR (&gt;2) over entire range in simulated results.

Microstrip patch antenna for simultaneous strain and temperature sensing

A patch antenna, consisting of a radiation patch, a dielectric substrate, and a ground plane, resonates at distinct fundamental frequencies that depend on the substrate dielectric constant and the dimensions of the radiation patch. Since these parameters change with the applied strain and temperature, this study investigates simultaneous strain and temperature sensing using a single antenna that has two fundamental resonant frequencies. The theoretical relationship between the antenna resonant frequency shifts, the temperature, and the applied strain was first established to guide the selection of the dielectric substrate, based on which an antenna sensor with a rectangular radiation patch was designed and fabricated. A tensile test specimen instrumented with the antenna sensor was subjected to thermo-mechanical tests. Experiment results validated the theoretical predictions that the normalized antenna resonant frequency shifts are linearly proportional to the applied strain and temperature changes. An inverse method was developed to determine the strain and temperature changes from the normalized antenna resonant frequency shifts, yielding measurement uncertainty of 0.4 °C and 17.22 μ for temperature and strain measurement, respectively.

Boundary Estimation of Imaged Object in Microwave Medical Imaging Using Antenna Resonant Frequency Shift

The performance of microwave imaging systems can be significantly improved by incorporating boundaries of the imaged object as a priori information. While it might be possible to manually measure that boundary in a controlled laboratory environment, this cannot be achieved in the clinical environment due to the impracticality of such a measurement in addition to the effect of the natural subject’s movement. In this paper, a method for boundary identification at the same time of imaging and using the same data captured for imaging is presented. The method is based on the relation between the imaging antennas’ resonant frequency and the location of the imaged object. The imaging antennas’ resonant frequency shifts when that antenna faces an imaging object, which is effectively a lossy dielectric in biomedical application, and that shift depends on the distance between the antenna and the object. The proposed technique is quite fast in scanning, computation, and image creation as it does not need additional devices for accurate boundary estimation. The method is tested via simulations and human trials using a torso imaging system. The collected data across the band 0.75–1.75 GHz using a 12-element antenna array, which is extended to 24 virtual elements, enclosing the human torso are processed to successfully estimate the torso boundary in a more accurate way than other methods. The included results in imaging a lung cancer case indicate that the accurate detection of the torso boundary improves microwave images.

Effect of heterogeneity in additively manufactured dielectric structures on RF response of microstrip patch antennas

Microstrip patch antennas with a tunable radiofrequency (RF) response are a great candidate for additive manufacturing (AM) process. First, three separate sets of ABS samples were created at three different machine preset fill densities using an extrusion based 3D printer. Once fabricated, actual solid volume fraction of each set of samples was measured using a 3D X-ray computed tomography microscope. It is observed that the factory preset fill-density values are only applied to the core region and actual solid volume fractions for each sample set are different from printer-preset values. Also, the printed materials appeared to exhibit anisotropy such that the thickness direction dielectric properties are different from the in-plane properties (planar isotropy). Microstrip patch antennas created on the AM fabricated ABS were tested for resonant frequencies using a vector network analyzer (VNA). The measured resonant frequencies combined with ANSYS-HFSS simulation were used to estimate bulk dielectric constant of ABS and equivalent dielectric properties in planar and thickness directions. It is observed that the antenna resonant frequency decreases with an increase in core solid volume fraction. Also, in-plane permittivity appeared to have minimal effect on antenna resonant frequency, while the thickness direction properties have substantial effects.

Perancangan Antena Mikrostrip Multiband Bentuk Segi Empat 2 Patch Menggunakan Gabungan Metode Array Dan Slot

Antenna is the most important thing in wireless technology. The technology of communication in this era does not only work on only one frequency, but it has many work frequency. In this research, the method that is used to create the antenna works in Multiband by using an array and slot method. Based on the result of this research, quadrilateral microstrip antenna by using 2 patches has a resonant frequency of 1,3 GHz, 1,8 GHz, 2,4 GHz, and 2,8 GHz. From the measurement results that is done, all antennas that resonate at that frequency has met the antenna standard which is the value of return loss less than -10 dB and VSWR less than 2, so that the antenna that has been made can work well in accordance with the function of the antenna. The slot method used in the design of microstrip antenna operates to add up the resonant frequency of the antenna and improve the value of return loss. Meanwhile, the array method that is used can add up the resonant frequency in microstrip antenna. By combining both methods in the design of quadrilateral microstrip antenna, it will generate a multiband antenna resonance frequency.

A Stacked Dual-Frequency Microstrip Patch Antenna for Simultaneous Shear and Pressure Displacement Sensing

This paper presents a simultaneous shear and pressure displacement sensor based on the microstrip patch antenna technology. The antenna sensor consists of a dual-frequency patch antenna, a superstrate, and a rectangular director. The two fundamental resonant frequencies of the patch antenna are influenced by the lateral and vertical positions of the director with respect to its radiation patch. Therefore, the shear and pressure displacements of the director can be determined simultaneously from two fundamental antenna resonant frequencies. The antenna sensor was designed, fabricated, and tested to characterize its sensing performance. An algorithm was developed to inversely determine the shear and pressure displacements from the measured antenna frequencies. We validated that the typical measurement uncertainties of the antenna sensor is ±0.3 mm for the shear displacement and ±0.15 mm for the pressure displacement. The presented shear/pressure displacement sensor is intended for monitoring the interaction between the human body and assistive medical devices (e.g., prosthetic liners, diabetic shoes, seat cushions, and so on).

Mesh parameters influence on transparent and active antennas performance at microwaves

Optically transparent and active square loop coplanar antennas operating in X-band are investigated in this letter. The frequency tunability is provided by a surface mounted beam-lead varactor with micrometric size, thereby no-visible to the naked eye. The influence of the metal mesh parameters on the sheet resistance (from 0.05 Ω/sq to 0.54 Ω/sq), the optical transparency (from 66% to 89%) and the microwave performance (return loss, resonance frequency, radiation pattern and gain) of such antennas is evaluated, compared with those of an opaque counterpart, and finally discussed. This study paves the way of their promising implementation on new surfaces, namely building and car windows for future wireless communications systems.

Design Parameters for Phase‐Change Materials for Nanostructure Resonance Tuning

Phase‐change materials (PCMs) are a promising platform for programmable metamaterials in the infrared (IR) spectral range. This is based on the large refractive index change between the amorphous and crystalline phases of PCMs accompanied by their low dielectric losses in the IR. These PCMs can exist in various stoichiometries, leading to distinct changes in dielectric properties which can be exploited for resonance tuning. To investigate these differences, nanoantennas with thin films of three (GeTe)x–(Sb2Te3)1−x compounds such as Ge2Sb2Te5 (GST‐225), Ge3Sb2Te6 (GST‐326), and Ge8Sb2Te11 (GST‐8211) are combined. Different PCM stoichiometries regarding their suitability for resonance tuning are systematically compared for the first time and the PCM GST‐8211 is introduced into the field of photonics. An increase of the antenna resonance frequency shift based on an increasing GeTe content in the compound is experimentally demonstrated. This leads to the largest figure of merit for antenna resonance tuning in the IR using PCMs reported so far. Based on the insights obtained, the changes in the real part of the permittivity Δε1, the band gap EG, and the charge carrier concentration N are identified as design parameters for resonance tuning with PCMs.

Antenna gain enhancement by using metamaterial radome at THz band with reconfigurable characteristics based on graphene load

The reconfigurable concept of a graphene loaded patch antenna with increasing gain is proposed in this paper. We have developed the patch antenna with inset feed for THz band application for which graphene load is used to obtain the reconfigurable characteristic. It has been shown that by increasing the graphene chemical potential, the antenna resonant frequency shifted and the gain increased drastically up to 4 dBi. Additionally, we have shown that antenna efficiency is improved up to 78% which shows more than 100% of enhancement in comparison to basic antenna by increasing the graphene chemical potential. Finally, considering the antenna gain improvement, we have implemented the metamaterial layer over the antenna. In this case, the gain is increased more than 5–6 dBi. In addition, when we put the metamaterial layer over the antenna, the graphene layer shows more linear characteristics. By using parametric studies, we have defined the best point for metamaterial layer around 0.58λ. The final antenna gain is more than 11 dBi, which is useful for THz communication and THz medical imaging systems.

Coaxial Feed Pyramidal Horn Antenna with High Efficiency

ABSTRACTIn this paper, a short pyramidal horn antenna with coaxial feed has been designed and fabricated with 52% bandwidth, which covers CDMA and GSM 900 bands. The total length of the antenna including coaxial feed is approximately 0.85λ at the lowest usable frequency. The effect of coaxial probe length, probe radius, and its location from the short wall of the waveguide on the resonance frequency, impedance matching, and bandwidth of the horn antenna have been analysed using CST Microwave studio software. Also, parametric analyses have been done by varying the horn length and aperture dimensions to study radiation characteristics of the horn antenna. The horn length has been optimized to obtain maximum efficiency for a fixed aperture. Simulation results show that as the frequency increases from 700 to 1130 MHz, the gain monotonically increases from 8.4 to 12.6 dBi with maximum efficiency of 80% at 850 MHz and it varies between 72% and 80% over this band. The pyramidal horn antenna has been fabricated and measured results are in good agreement with the simulated results.

A Frequency- and Polarization-Reconfigurable Circular Cavity Antenna

The principle and experimental validation of a frequency- and polarization-reconfigurable antenna using switching PIN diodes is presented in this letter. The antenna is based on a center-fed circular cavity with switchable shorting vias along its outer edge. Turning a set of shorting vias on on one side and off on the other side creates a radiating slot with controllable length and location along the side wall of the cavity that results in different antenna resonance frequencies and polarizations. As a proof of concept, a particular realization of the antenna is designed that can change the linear polarization in six different angles and at five discrete frequencies (spanning more than one octave). Based on the proposed concept, quasi-continuous frequency- and polarization-reconfiguration is feasible using individual control of a large number of switching devices.

Enhancement of Patch Antenna Gain Using Cylindrical Shell-Shaped Superstrate

A novel structure to enhance patch antenna gain based on phase compensation concept is presented. Putting a superstrate as flat artificial lens over normal patch antenna, phases of distributed electric field arrows will be same, leading to patch antenna gain enhancement. By introducing a novel criterion named phase pattern consideration for phase compensation method, a new shaped superstrate for this method is designed. Since design strategy for the superstrate is extracting from phase pattern of distributed electric field, antenna gain is increased 48% compared to the previous structure for patch antenna gain enhancement using phase compensation method. While resonance frequency and impedance bandwidth of normal patch antenna and patch antenna presented in the previous work are almost the same with proposed antenna, antenna gain is intensified from 6.9 to 10.2 dB. Moreover, a method for compacting antenna size based on 3 dB angular beamwidth is suggested. Finally, the proposed antenna is fabricated, and its measurement results verify gain enhancement.

The directivity of a compact antenna: an unforgettable figure of merit

When an electrically small antenna is conceived, designed, simulated, and tested, the main emphasis is usually placed immediately on its impedance bandwidth and radiation efficiency. All too often it is assumed that its directivity will only be that of a Hertzian dipole and, hence, its directivity becomes a minor consideration. This is particularly true if such a compact antenna radiates in the presence of a large ground plane. Attention is typically focused on the radiator and its size, while the ground plane is forgotten. This has become a too frequent occurrence when antennas, such as patch antennas that have been augmented with metamaterial structures, are explored. In this paper, it is demonstrated that while the ground plane has little impact on the resonance frequency and impedance bandwidth of patch antennas or metamaterial-inspired three-dimensional magnetic EZ antennas, it has a huge impact on their directivity performance. Moreover, it is demonstrated that with both a metamaterial-inspired two-element array and a related Huygens dipole antenna, one can achieve broadside-radiating electrically small systems that have high directivities. Several common and original designs are used to highlight these issues and to emphasize why a fundamental figure of merit such as directivity should never be overlooked.