Rectangular Radiator Research Articles

Radiation Impedance of Rectangular CMUTs.

Recently, capacitive micromachined ultrasound transducers (CMUTs) with long rectangular membranes have demonstrated performance advantages over conventional piezoelectric transducers; however, modeling these CMUT geometries has been limited to computationally burdensome numerical methods. Improved fast modeling methods, such as equivalent circuit models, could help achieve designs with even better performance. The primary obstacle in developing such methods is the lack of tractable methods for computing the radiation impedance of clamped rectangular radiators. This paper presents a method that approximates the velocity profile using a polynomial shape model to rapidly and accurately estimate radiation impedance. The validity of the approximate velocity profile and corresponding radiation impedance calculation was assessed using finite element simulations for a variety of membrane aspect ratios and bias voltages. Our method was evaluated for rectangular radiators with width:length ratios from 1:1 up to 1:25. At all aspect ratios, the radiation resistance was closely modeled. However, when calculating the radiation reactance, our initial approach was only accurate for low aspect ratios. This motivated us to consider an alternative shape model for high aspect ratios, which was more accurate when compared with FEM. To facilitate the development of future rectangular CMUTs, we provide a MATLAB script that quickly calculates radiation impedance using both methods.

A method for calculating radiation resistance of the simply supported rectangular radiator

Abstract Radiation resistance in general is a key parameter to measure the radiation efficiency of a vibrating radiator. The traditional calculation method of self-radiation resistance of simply supported rectangular radiator needs to be calculated by numerical integration. In this study, a calculation method for the radiation resistance is proposed based on ANSYS. To verify the correctness of the method provided in this paper, several examples are provided. The calculation results show that the radiation resistance of the simply supported rectangular radiator tends to be stable after reaching its peak value, and this is consistent with the results obtained by the traditional calculation method.

Resolution limits for radiation-induced acoustic imaging for in vivo radiation dosimetry

Objective. Radiation-induced acoustic (RA) computed tomographic (RACT) imaging is being thoroughly explored for radiation dosimetry. It is essential to understand how key machine parameters like beam pulse, size, and energy deposition affect image quality in RACT. We investigate the intricate interplay of these parameters and how these factors influence dose map resolution in RACT. Approach. We first conduct an analytical assessment of time-domain RA signals and their corresponding frequency spectra for certain testcases, and computationally validate these analyses. Subsequently, we simulated a series of x-ray-based RACT (XACT) experiments and compared the simulations with experimental measurements. In-silico reconstruction studies have also been conducted to demonstrate the resolution limits imposed by the temporal pulse profiles on RACT. XACT experiments were performed using clinical machines and the reconstructions were analyzed for resolution capabilities. Main results. Our paper establishes the theory for predicting the time- and frequency-domain behavior of RA signals. We illustrate that the frequency content of RA signal is not solely dependent on the spatial energy deposition characteristics but also on the temporal features of radiation. The same spatial energy deposition through a Gaussian pulse and a rectangular pulse of equal pulsewidths results in different frequency spectra of the RA signals. RA signals corresponding to the rectangular pulse exhibit more high-frequency content than their Gaussian pulse counterparts and hence provide better resolution in the reconstructions. XACT experiments with ∼3.2 us and ∼4 us rectangular radiation pulses were performed, and the reconstruction results were found to correlate well with the in-silico results. Significance. Here, we discuss the inherent resolution limits for RACT-based radiation dosimetric systems. While our study is relevant to the broader community engaged in research on photoacoustics, x-ray-acoustics, and proto/ionoacoustics, it holds particular significance for medical physics researchers aiming to set up RACT for dosimetry and radiography using clinical radiation machines.

A Novel Dual-Band Circularly Polarized Wearable Antenna.

A circularly polarized wearable antenna operating in the 2.45/5.8 GHz ISM dual bands is proposed, which consists of a coplanar waveguide-fed rectangular monopole antenna and two parasitic branches. The monopole rectangular radiation patch can generate 2.45 and 7 GHz frequency bands and has linear polarization characteristics. By adding L-shaped parasitic branches and L-like grounded branches on both sides of the monopole, the 7 GHz operating frequency band can be moved to the 5.8 GHz frequency band, and circular polarization characteristics can be achieved in both the 2.45 and 5.8 GHz frequency bands. The size of the antenna is 48.7 mm × 42.1 mm × 1.016 mm. The simulated -10 dB impedance bandwidths of the antenna are 1.8-2.66 GHz and 5.48-6.98 GHz, respectively. The 3 dB axial ratio bandwidths are 2.34-2.67 GHz and 5.58-6.39 GHz, respectively, and it has dual-band circular polarization characteristics. In addition, the radiation characteristics of the antenna and its safety performance near the human body were analyzed. The antenna prototype has been constructed, and the measurement and simulation results have good consistency. The proposed antenna is suitable for application in wearable devices.

Efficient broadband fractal antenna for WiMAX and WLAN

This article presents a new design of a compact fractal antenna that operates across various wireless communication applications with wideband functionality. With a peak gain of 6.8 dB and a radiation efficiency ranging from 91% to 94%, the designed antenna operates in the frequency range of 3.2–7.5 GHz. The antenna consists of a rectangular radiator with integrated rectangular slots on one side of an FR4 substrate, while a partial ground plane is etched on the other side. The fabricated prototype was tested and measured. The results present a good agreement with the simulated results. The results presented by this antenna demonstrate high competitiveness for wireless communication applications such as Wi-Fi and WLAN and presents a promising solution to meet the increasing demand for compact and high-performance wireless communication devices. Additionally, the antenna has a small size of only 34 × 30 × 1.6 mm3, making it suitable for applications where space is limited. Overall, this paper provides an innovative and efficient design that offers excellent performance and is suitable for various wireless communication applications.

A dual-band wideband high-gain slot loaded microstrip patch antenna

This paper presents a dual-band, wideband, high-gain microstrip patch antenna applied to 5G band. The antenna consists of two rectangular radiation patches of different sizes, connected by a microstrip line and fed by a coaxial line. The dual-band is achieved by both rectangular radiation patches producing dual target resonant frequency points. This antenna provides the freedom for adjusting both resonant frequencies independently. To increase the antenna bandwidth, long slots are loaded at specific positions on each rectangular patch, allowing for dual-mode resonance radiation in each frequency band. This antenna operates in a shorted-edge resonant mode, where metal grounding holes added on the patch act as shorting walls. The size of a radiation patch is only half that of a standard resonant mode patch, making this antenna compact in size. Measurement results show that the antenna has an impedance bandwidth of 4.98–5.56 GHz (11.0%) and 5.74–6.62 GHz (14.2%), which completely cover the 5G band of China (5.18–5.52 GHz and 5.74–5.82 GHz). The maximum measured realized gain is 8.1 dB in the low-frequency band and 10.2 dB in the high-frequency band. This antenna offers advantages of dual-band operation, broadband, low-profile, high-gain, which is suitable for 5G band applications with targeted coverage requirements.

COMPACT TWO-PORT ANTENNA WITH PARASITIC NOTCH AND DEFECTive GROUND FOR WIRELESS COMMUNICATION

This paper presents a compact multiple input multiple output antenna (MIMO) with a wireless local area network (WLAN) notch characteristic for ultra-wideband (UWB) applications. The two modified rectangular radiators share a common ground that provides UWB response. The design is modeled over FR4 material and has an overall compact size of 0.34 λ0 × 0.24 λ0 × 0.015 λ0 mm3 at the frequency of 2.9 GHz. A tree-shaped decoupling structure with multiple slots in the ground is introduced between the ports to establish good isolation. The open-ended slots in the ground perturb diminish the surface current between two ports and ensure the isolation larger than 20 dB in the entire UWB from 2.9 GHz to 10.2 GHz. An S-shaped parasitic stub is utilized at the backside of the radiating element to implement a band notch characteristic from 5.03 GHz to 5.90 GHz. The proposed antenna is also investigated for wearable applications with a human tissue model showing a small SAR value (less than 1.6 W/kg). The simulated and measured result shows that the designed antenna suits MIMO performance and wearable devices.

A Dual-CP Quad-Port MIMO Antenna With Reduced Mutual Coupling for X-Band Application

A compact quad-port MIMO antenna with dual-polarization is proposed. Each of the four antenna elements features a modified rectangular radiator (MRR) backed by a partial ground plane and fed by a T-shaped microstrip line. The four antenna elements are interconnected by an X-shaped strip and isolated by a modified plus-shaped (MPS) structure, resulting in over -18 dB of isolation. With a small footprint of only 36 mm × 27 mm, the antenna exhibits a 10-dB impedance bandwidth with a completely overlapping 3-dB axial-ratio bandwidth (ARBW) of 19.32% (7.90–9.59 GHz). Additionally, it can provide a gain of over 3.5 dBi, an efficiency of over 70%, and an envelope correlation coefficient (ECC) of less than 0.01 in both isotropic and real propagation scenarios.

Circularly polarized printed dual port MIMO antenna with polarization diversity optimized by machine learning approach for 5G NR n77/n78 frequency band applications

In this communication, a planar dual port multiple input multiple output antenna of size 1.2λ0 × 0.6λ0 × 0.008λ0 with LHCP/RHCP features is reported for the fifth-generation new radio n77/n78 sub-6 GHz wireless applications band. The single unit of the proposed design consists of a modified L-shape rectangular radiator with Z-shape slot loaded DGS. The defected ground structure is optimized through machine learning algorithms to achieve the maximum ARBW (output) by Right Shifting (RS) and left shifting (LS) the DGS and obtaining input features. The performance metric for ANN with ADAM optimizer was found to be optimal with MSE and R2 of 0.99 and 0.82, respectively. ANNs can leverage gradient information to guide the optimization process. This enables faster convergence towards optimal solutions compared to popular GAs and PSO, which are often gradient-free optimization methods. The MIMO configuration is achieved by creating a mirror image of the single unit about the x-axis. The salient features of the proposed design are (a) Impedance bandwidth (IBW) of 3.0–4.2 GHz covering the n77/n78 band, (b) 3-dB axial ratio bandwidth (ARBW) of the 2.6–3.9 GHz (c) Port-1 is generating RHCP while Port-2 is generating LHCP, results in polarization diversity. Different diversity performance parameters (ECC < 0.005, DG ~ 9.99 dB, and MEG < 3 dB) are in the optimum range confirming the proposed configuration as a suitable design for a MIMO radiator.

A METAMATERIAL INSPIRED SPLIT RING RESONATOR ACCOMPLISHED MULTIBAND ANTENNA FOR 5G AND OTHER WIRELESS APPLICATIONS

A multiband antenna is proposed in this paper, accomplished with a split ring resonator (SRR) in the ground plane for portable and wireless applications. The rectangular radiator is unified with a semi-circular stub improving the impedance matching in the antenna. Further, the radiator creates an optimized rectangular slot to obtain the multiband operation. The SRR in the ground plane demonstrates the metamaterial (MTM) characteristics that significantly improve the 10 dB impedance bandwidths (IBW) and enhance realized gain in the multi-band antenna. The proposed antenna is procuring the five 10 dB IBW, which can be prominent for RADAR (2.96 GHz - 3.06 GHz), 5G (3.92 GHz - 4.32 GHz and 4.64 GHz - 5.04 GHz), WLAN (5.32 GHz - 5.64 GHz) and ISM band (5.7 GHz - 6 GHz) applications. The gain enhancement is obtained in all operating bands of the antenna, and a maximum 5.24 dB gain is achieved at a 4.14 GHz frequency.

Reconstruction of thermoacoustic emission sources induced by proton irradiation using numerical time reversal

Objective. Mapping of dose delivery in proton beam therapy can potentially be performed by analyzing thermoacoustic emissions measured by ultrasound arrays. Here, a method is derived and demonstrated for spatial mapping of thermoacoustic sources using numerical time reversal, simulating re-transmission of measured emissions into the medium. Approach. Spatial distributions of thermoacoustic emission sources are shown to be approximated by the analytic-signal form of the time-reversed acoustic field, evaluated at the time of the initial proton pulse. Given calibration of the array sensitivity and knowledge of tissue properties, this approach approximately reconstructs the acoustic source amplitude, equal to the product of the time derivative of the radiation dose rate, mass density, and Grüneisen parameter. This approach was implemented using two models for acoustic fields of the array elements, one modeling elements as line sources and the other as rectangular radiators. Thermoacoustic source reconstructions employed previously reported measurements of emissions from proton energy deposition in tissue-mimicking phantoms. For a phantom incorporating a bone layer, reconstructions accounted for the higher sound speed in bone. Dependence of reconstruction quality on array aperture size and signal-to-noise ratio was consistent with previous acoustic simulation studies. Main results. Thermoacoustic source distributions were successfully reconstructed from acoustic emissions measured by a linear ultrasound array. Spatial resolution of reconstructions was significantly improved in the azimuthal (array) direction by incorporation of array element diffraction. Source localization agreed well with Monte Carlo simulations of energy deposition, and was improved by incorporating effects of inhomogeneous sound speed. Significance. The presented numerical time reversal approach reconstructs thermoacoustic sources from proton beam radiation, based on straightforward processing of acoustic emissions measured by ultrasound arrays. This approach may be useful for ranging and dosimetry of clinical proton beams, if acoustic emissions of sufficient amplitude and bandwidth can be generated by therapeutic proton sources.

Close-Packed Quad-Element Triple-Band-Notched UWB MIMO Antenna With Upgrading Capability

A close-packed 4-port multiple-input multiple-output (MIMO) antenna with three notched bands (NBs) is designed for ultra-wideband (UWB) applications. The presented antenna contains four monopole antenna elements (AEs) with rectangular radiators, each fed by an L-shaped microstrip line. The compact size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$35.9\times 35.9\times0.8$ </tex-math></inline-formula> mm is attained by cropping the lower axis of the antenna and optimization. The isolation greater than 19 dB is accomplished by the orthogonal direction of AEs and cross-shaped decoupling structure (CSDS). The designed antenna can realize wireless local area network (WLAN) and X-band NBs by etching two C-shaped slits from each radiator and Worldwide Interoperability for Microwave Access (WiMAX) NB by introducing an L-shaped slit in the ground. By placing these NBs in appropriate positions, their efficiencies are decreased for their better rejection. The value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert \text{S}_{\mathrm {ii}}\vert &lt; -10$ </tex-math></inline-formula> dB is from 3.2 to 10.8 GHz (except for three NBs). Also, the 4-port MIMO antenna is upgraded to a 16-port MIMO antenna by arranging the four identical 4-port MIMO antennas side by side with a small gap of 8 mm. The upgraded antenna gives bandwidths from 3.38 to 10.56 GHz with three NBs, isolation >20.9 dB, and size <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$79.8\times79.8$ </tex-math></inline-formula> mm2, which is appropriate for future wireless communications.

Super Ultra-Wideband Planar Antenna with Parasitic Notch and Frequency Selective Surface for Gain Enhancement

A compact Super ultra-wideband (SUW) antenna is discussed in this work. A rectangular radiator is modified into a tree-shaped structure with the defected partial ground to enhance the operating bandwidth. The novel rectangular parasitic with the circular slot is used as a notch in the ground plane which prevents the WLAN frequency. The proposed SUW antenna is achieving the 10 dB impedance bandwidth (IBW) from 3.5 GHz to 66.5 GHz frequency with a notched band varying from 5.0 GHz to 5.4 GHz. The bandwidth ratio (BDR) of the proposed SUW antenna is 1773.4 whereas the obtained bandwidth percentage (BW %) is 180. A modified SRR frequency selective surface (FSS) is designed for UWB application to improve the gain of the antenna. The compact unit cell of FSS is having electrical dimensions of 0.16λ0x 0.16λ0 The antenna achieves the maximum realized gain 9.46 dB when FSS is loaded as a superstrate and up to 5.2 dB gain enhancement is observed in the UWB frequency.

Miniaturized tri‐wideband antenna loaded with metamaterial meander lines

AbstractHere presents a new miniaturized tri‐wideband antenna loaded with metamaterial meander lines. The antenna consists of a rectangular radiation patch loaded with two compact metamaterial components. The three frequency bands are the results of resonances of a rectangular patch at 5.5 GHz, interdigital meander slit at 3.6 GHz, and virtual grounded thin meander stub at 7.5 GHz. More size miniaturization is accomplished by a compact virtual ground structure and cutting the upper and left edges of the substrate. Furthermore, matching at all bands is improved by taking advantage of stepped microstrip feed line and truncated rectangular ground plane. Measured results shows the frequency ranges of 3.32–4.06 GHz (20%), 5.17–6.06 GHz (16%), and 7.17–10.32 (36%). The antenna is analyzed with an equivalent circuit model. In comparison to previous works, this antenna has a simple design, very compact size of 10 mm × 15 mm × 0.8 mm, three wide working bands, and matching levels better than −20 dB at all resonant frequencies.

Reconstruction of thermoacoustic emission sources from proton irradiation using numerical time reversal

Dose delivery in proton beam therapy for cancer treatment can be mapped by analyzing thermoacoustic emissions measured by ultrasound arrays. Here, a method is presented for spatial mapping of thermoacoustic sources using numerical time reversal, simulating physical re-transmission of measured emissions into the medium. The spatial distribution of acoustic sources is shown to be approximated by the amplitude envelope of the time-reversed field, evaluated at the time of emission. Given calibration of the array sensitivity and knowledge of tissue properties, this approach approximately reconstructs the induced acoustic pressure, equal to the product of radiation dose, density, and Grueneisen parameter. Numerical time reversal is implemented using two models for array elements, as either ideal line sources or diffracting rectangular radiators. Demonstrated reconstructions employ previously reported measurements of thermoacoustic emissions from proton energy deposition in tissue-mimicking phantoms. For a phantom incorporating a bone layer, reconstructions account for the higher sound speed in bone. Spatial resolution of reconstructions, assessed by widths of reconstructed Bragg peaks, is improved in the array direction by incorporation of diffraction effects. In comparisons with corresponding Monte Carlo simulations, source distributions correspond well with simulated proton dose, while source localization with respect to room coordinates is improved by incorporating sound speed inhomogeneities.

UWB MIMO antenna with 4-element, compact size, high isolation and single band rejection for high-speed wireless networks

In this paper, a miniaturized size UWB 4-element MIMO antenna with a band rejection feature is introduced. The four elements have a rectangular radiator with curved edges and a partial ground plane with an etched slot to enlarge the bandwidth of the suggested structure to operate from 3 up to 12 GHz with S11 ≤ − 10 dB. The high isolation between elements was achieved by forming the antennas orthogonally without adding decoupling elements to simplify the design. The suggested design has a size of 47 × 47 mm2 placed on low price FR4 substrate. A simple slot is etched into the radiator to achieve the desired band rejection. The simulated and tested outcomes achieved operated band extended from 3 up to 12 GHz with band rejection feature within 3.3 GHz up to 4.3 GHz to eliminate interference with WIMAX applications and high isolation of more than 22 dB between ports. Also, the antenna fulfills peak gain of 3.5 dBi, envelope correlation coefficient(ECC) < 0.005, diversity gain (DG) 9.98 dB and channel capacity loss (CCL) < 0.4 bit/s/Hz within the operating bands. The outcomes have good consistency which made the suggested antenna to be used in UWB MIMO systems.

Investigation on Thermal Analysis of Spacecraft Radiators

In this research, the main objective is to compare the thermal properties of the rectangular and honeycomb structured space radiators used in spacecraft. The comparison of radiators was done by conducting steady state thermal analysis on these radiators by applying varying heat loads over it to analyse the thermal properties acting over them. The selection of appropriate material for the radiators was based on tensile strength, resistance to high temperature, and the type of working fluid considered. From the simulation results, the honeycomb structures of spacecraft radiator could withstand to a higher temperature gradient, and the rate of heat dissipation was much higher in comparison with rectangular fin type radiator, and hence it can be considered as a great replacement in near future.

Broadband Coplanar Waveguide to Air-Filled Rectangular Waveguide Transition

This article introduces a novel transition between coplanar waveguide (CPW) and air-filled rectangular waveguide (RWG). A rectangular radiator etched with a semi-elliptic slot is connected to the center conductor of CPW to realize the transition, which broadens the bandwidth. This direct transition does not require intermediate transition or air-bridges. Moreover, the planar circuit of the transition can be designed with high- and low-permittivity materials (εr = 10.2 and 2.22), which offer more benefits in both PCB and MMIC design. Two back-to-back transition prototypes at X-band are designed, fabricated and measured. The 15 dB fractional bandwidths are expanded to 44.7% and 47.6% respectively, which have been demonstrated in both of the transitions (εr = 10.2 and 2.22). The measurement results agree well with simulation results, which validate the feasibility of this design.

8-Port MIMO Antenna Having Two Notched Bands for Chipless UWB-RFID Tags

An 8-element Multiple Input Multiple Output (MIMO) antenna is implemented for Chipless-RFID Tags (CRT) that function in the Ultra-Wideband (UWB) frequency range. The single UWB antenna contains a rectangular radiator in which two ellipses are cut from the two lower corners. Also, two circles are etched from the upper corners of the ground. This antenna is designed by placing eight antenna elements at 45&#x2218; direction (clockwise and anticlockwise) and a thin line-shaped decoupling structure is used to enhance isolation at lower frequencies. Also, a T-shaped structure is used to enhance the notched band characteristics. The working frequency of the antenna is from 3.5 GHz to 10.5 GHz with WiMAX and WLAN notched bands using U-slot and Split Ring Resonator (SSR) metamaterial, respectively. The antenna obtains a peak gain of 5 dB (single element). This antenna has radiation efficiency from 76.4% to 92.7%. This antenna design will inspire the designers of chipless RFID (CRFID) to produce low-cost tags.

Inset-fed microstrip patch antenna for ubiquitous wireless communication applications

This paper presents an inset-fed microstrip patch antenna for ubiquitous wireless communication applications. The studied design is comprised of an inset-fed rectangular radiator and a partial ground plane and is printed on an FR4 microwave substrate. The measured results reveal that the fabricated prototype achieved a good impedance bandwidth of 1.78 GHz (2.02 GHz-3.8 GHz) and is able to cover well-established narrow-bands including ISM, IMT, Wi-Fi, Bluetooth, WiMAX, WLAN and 3.5 GHz for sub-6 GHz 5G communication system. Moreover, it achieved a maximum gain of 5.14 dBi, a maximum efficiency of 94.16% and exhibits stable radiation patterns which make it a suitable candidate to be used in narrow-band wireless communication services.