Bow-tie Slot Research Articles

Design and Performance of a 30/40 GHz Diplexed Focal Plane for the BICEP Array

We demonstrate a wideband diplexed focal plane suitable for observing low-frequency foregrounds that are important for cosmic microwave background polarimetry. The antenna elements are composed of slotted bowtie antennas with 60% bandwidth that can be partitioned into two bands. Each pixel is composed of two interleaved 12 × 12 pairs of linearly polarized antenna elements forming a phased array, designed to synthesize a symmetric beam with no need for focusing optics. The signal from each antenna element is captured in-phase and uniformly weighted by a microstrip summing tree. The antenna signal is diplexed into two bands through the use of two complementary, six-pole Butterworth filters. This filter architecture ensures a contiguous impedance match at all frequencies, and thereby achieves minimal reflection loss between both bands. Subsequently, out-of-band rejection is increased with a bandpass filter and the signal is then deposited on a transition-edge sensor bolometer island. We demonstrate the performance of this focal plane with two distinct bands, 30 and 40 GHz, each with a bandwidth of ∼20 and 15 GHz, respectively. The unequal bandwidths between the two bands are caused by an unintentional shift in diplexer frequency from its design values. The end-to-end optical efficiency of these detectors is relatively modest, at 20%–30%, with an efficiency loss due to an unknown impedance mismatch in the summing tree. Far-field beam maps show good optical characteristics, with edge pixels having no more than ∼5% ellipticity and ∼10%–15% peak-to-peak differences for A–B polarization pairs.

Compact conformal metasurface antenna for hyperthermia applications

In this paper, the design, analysis and evaluation of a new compact conformal metasurface (MTS)-based bow-tie slot antenna is presented for hyperthermia treatment of cancer. A bow-tie slot antenna in close proximity with tissue designed at 2.45 GHz was used to excite the MTS layer, which is made of a 4 × 4 uniform array of square unit cells. The proposed MTS-based antenna is compact and provides enhanced penetration depth in the tissue medium as compared to the bow-tie antenna only. To verify the design concept, both the proposed MTS-based antenna and bow-tie antenna were fabricated, and the measured results are well anticipated. Finally, the MTS applicator is terminated with water bolus and tissue to characterize its hyperthermia performance in a real scenario. The key features of the proposed MTS applicator include wide impedance bandwidth (stable hyperthermia performance), enhanced penetration depth and effective field size, single-layer structure and ease of fabrication.

Multiple slot modules for high field magnetic resonance imaging array coils.

Mitigating coupling effects between coil elements represents a continuing challenge. Here, we present a 16-bowtie slot volume coil arranged in eight independent dual-slot modules without the use of any decoupling circuits. Two electrically short "bowtie" slot antennas were used to form a "module." A bowtie configuration was chosen because electromagnetic modeling results show that bowtie slots exhibit improved efficiency when compared to thin rectangular slots. An eight-module volume coil was evaluated through electromagnetic modeling, bench tests, and MRI experiments at 4.7T. Bench tests indicate that worst-case coupling between modules did not exceed -14.5dB. MR images demonstrate well-localized patterns about single excited modules confirming the low coupling between modules. Homogeneous MR images were acquired from a synthesized quadrature birdcage transmit mode. MRI experiments show that the RF power requirements for the proposed coil are 9.2 times more than a birdcage coil. Whereas from simulations performed to assess the proposed coil losses, the total power dissipated in the phantom was 1.1 times more for the birdcage. Simulation results at 7T reveal an equivalent B1 + homogeneity when compared with an eight-dipole coil. Although exhibiting higher RF power requirements, as a transmit coil when the power availability is not a restriction, the inherently low coupling between electrically short slots should enable the use of many slot elements around the imaging volume. The slot module described in this paper should be useful in the design of multi-channel transmit coils.

Anisotropic Complementary Metantenna for Low Sidelobe Radiation and Low In-Band Co-Polarized Scattering Using Characteristic Mode Analysis

An anisotropic complementary metantenna (ACMA) is proposed for the integration of low sidelobe radiation and low in-band co-polarized (IBCP) scattering with the aid of characteristic mode analysis (CMA). With the guidance of CMA, the proposed ACMA evolving from a conventional metantenna (MTA) not only generates a coding phase distribution for low scattering but also restores broadside radiation modes like a uniform MTA. With the IBCP conditions set to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$x$ </tex-math></inline-formula> -polarization and the band around 9 GHz, the ACMA is constructed by mixing two types of double-layer anisotropic complementary metasurface (MTS) unit cells. Two desired characteristic modes of ACMA are simultaneously excited by a substrate integrated waveguide (SIW) cavity through dual bow-tie slots. Both the simulation and experiments demonstrate that the proposed ACMA achieves both the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$x$ </tex-math></inline-formula> -polarized broadside radiation with sidelobe level below −18.9 dB and IBCP scattering levels below −17.8 dB over the frequency range from 8.87 to 9.78 GHz.

Low-Profile and Wideband Unidirectional Antenna With Ferrite Loading for UHF Applications

A low-profile and wideband unidirectional antenna with ferrite loading is presented for ultrahigh-frequency (UHF) applications. This design comprises a slotted bowtie antenna with parasitic elements placed 50 mm over a ground plane. A small amount of ferrite loaded on the center of the ground plane plays a crucial role in improving the performance of the low-profile antenna. The ferrite used here is a new type of magnetodielectric material with relatively high permeability and permittivity, as well as low magnetic and dielectric loss. The loaded ferrite introduces an additional phase change of the electromagnetic field reflected by the ground to improve the impedance matching, bandwidth, efficiency, and gain of the low-profile antenna. The evolution process and mechanism of the proposed antenna are elaborated. For validation, an optimized antenna prototype was fabricated and measured. The measured results are consistent well with their simulations, which shows the realized gain of 7.2–9 dBi over <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert \text{S}_{11}\vert \le -10$ </tex-math></inline-formula> dB impedance bandwidth of 38% (480–705 MHz). The overall profile of this antenna is only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.08\lambda _{0}$ </tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is the free-space wavelength at the lowest frequency of operation.

A Miniaturized Wideband Planar Bow-Tie Slot Antenna with Asymmetric CPW

In this paper, a novel miniaturized wideband planar bow-tie slot antenna is proposed. For the purpose of miniaturization and wide bandwidth, the effects of the dimension and shape of the bow-tie slot and feed structure are analyzed. This antenna adopts a water droplet slot, fed by an optimized asymmetric coplanar waveguide (CPW). By adjusting the feeding line, the impedance characteristic of the antenna is greatly improved that leads to a broader bandwidth. The proposed antenna operates from 2.8 GHz to 5.25 GHz with a gain of 3.8 dB. Compared with the traditional triangle bow-tie antenna, the relative bandwidth of the proposed antenna is broadened to more than 61%, while the size is reduced by about 36%, which indicates the proposed antenna is suitable for a variety of wireless applications.

Semi-Annular-Ring slots loading for broadband circularly polarized DR-Rectenna for RF energy harvesting in smart city environment

This article describes a circularly polarized (CP) broadband rectenna enabling sensing nodes connected in the smart cities to harvest radio frequency (RF) energy from the surrounding atmosphere. The proposed antenna efficiently operates at the 5.8 GHz Wi-Fi band (5.725–5.875 GHz) and the Wi-Fi 6E band (5.925–7.125). The antenna is a semi-cylindrical dielectric resonator antenna (S-CDRA) energized by a microstrip feed. Semi-annular slots are introduced around a Bow-tie slot from the ground plane side, enhancing the bandwidth, gain, and CP characteristics. The antenna provides an impedance bandwidth (BW) of 2.89 GHz (5.45–8.34 GHz) and offers CP characteristics with an axial ratio (AR) bandwidth of 680 MHz (5.67–6.35 GHz). The antenna maintains a minimum gain of 4.8 dBic. A series-pair configuration is proposed for an extended operating range and better conversion efficiency. The maximum simulated and measured conversion efficiencies are 66.6% and 65.2% at 11 dBm input power, respectively.

High-Isolation MIMO Antenna for 5G Millimeter-Wave Communication Systems

The work in this article presents the design and realization of a low-profile, four-port MIMO antenna supporting fifth-generation (5G) wireless applications operating at a millimeter-Wave (mm-Wave) band. Each MIMO antenna is a 2-element array fed with a corporate feeding network, whereas the single antenna is a patch with a bow-tie slot at the center and slits at the edges. The vertical and horizontal slots are incorporated as a Defected Ground Structure (DGS) to optimize the antenna performance. In addition, a slotted zig-zag decoupling structure is etched from edge to edge on the top side to enhance the isolation. Significant isolation (&gt;−40 dB) is achieved between antenna elements by employing spatial and polarization diversity techniques. The proposed antenna covers the 5G mm-Wave band with a −10 dB bandwidth ranging from 27.6–28.6 GHz, whereas the maximum gain attained for the proposed structure is 12.02 dBi. Moreover, the lower correlation values, higher diversity gain, and lower channel capacity loss make it a suitable contender for 5G MIMO applications at the mm-Wave range.

A Study on Gain Enhanced Leaf-Shaped Bow-Tie Slot Array Antenna within Quasi-Millimeter Wave Band

In this paper, a linear array of 4 leaf-shaped bowtie slot antennas is proposed for use in quasi-millimeter wave band. The slot antennas array is designed to operate at 28 GHz frequency band. The leaf-shaped bowtie slot antenna is a type of self-complementary antenna with low profile and low cost of fabrication. The proposed antenna structure offers improvement in radiation pattern, gain, and -10 dB impedance bandwidth. Through out of this paper radiation pattern, actual gain, and -10 dB impedance bandwidth are evaluated by Finite Different Time Domain (FDTD) simulation. Antenna characteristics are analyzed in the frequency range of 27 GHz to 29 GHz. To improve antenna characteristics such as actual gain and -10 dB impedance bandwidth, a dielectric superstrate layer with relative permittivity of 10.2 is placed on top of ground plane of the slot antennas array. Three antenna structures are introduced and compared. With two layers of dielectric superstrate on top of the antennas ground plane, analysis results show that -10 dB impedance bandwidth occupies the frequency range of 27.17 GHz to 28.39 GHz. Therefore, the operational impedance bandwidth is 1.22 GHz. Maximum actual gain of the slot antennas array with two dielectric superstrate layers is 20.49dBi and —3 dB gain bandwidth occupies the frequency range of 27.02 GHz to 28.57 GHz. To validate the analysis results, prototype of the designed slot antennas array is fabricated. Characteristics of the slot antennas array are measured and compared with the analysis results.

A Modified Bow-Tie Slot Loaded Cavity Backed Antenna Based on SIW

A Modified Bow-Tie Slot Loaded Cavity Backed Antenna Based on SIW

Vertically Polarized Loop-Fed Slot Antenna With Top-Loading Metasurface for Omnidirectional LTE Base Station Application

A novel wideband vertically polarized (VP) omnidirectional antenna is proposed in this letter. Two crossed bowtie slots are fed by a loop which is arranged above the ground vertically. The loop works in the one wavelength mode together with its image with respect to the ground, and accordingly the quasi-omnidirectional radiation can be achieved. The bowtie slots are introduced to expand the working bandwidth. Afterwards, a top-loading patch is utilized to improve the impedance matching. Furthermore, the complete patch is replaced by the metasurface to suppress the lateral current so that the stable omnidirectional radiation can be maintained in the operating band. A prototype is fabricated and measured. The -10 dB impedance bandwidth covers the LTE band of 1.7-2.7 GHz. The proposed antenna is well tailored for indoor ceiling base station applications.

A Compact High Gain Multiband Bowtie Slot Antenna with Miniaturized Triangular Shaped Metallic Ground Plane

This paper presents a new compact, high gain and multiband planar bowtie slot antenna. The antenna structure comprises of dielectric substrate, copper conducting sheet, fillet triangular-shaped slots, and a chamfered metallic ground plane. The proposed antenna model is fed with the 50 Ω standard grounded coplanar waveguide (GCPW) feedline. The designed antenna is low profile with compact dimensions of 0.379λ×0.186λ×0.012λ at 2.39 GHz frequency. Stable multi-resonant behavior of frequencies is obtained with the material selection, slots dimensions and position. Moreover, the parametric study has been carried out in order to validate the frequency tuning mechanism and impedance matching control. The novelty of designed antenna lies in high performance features which have been achieved with ultra-compact (0.039λ×0.022λ) modified triangular shaped metallic ground plane. The proposed antenna is fabricated and experimentally verified. The antenna key features in terms of return loss, surface current distribution, peak gain, radiation efficiency and radiation patterns have been analyzed and discussed. The designed radiator exhibits the excellent performance including strong current density, peak realized gain of 6.3 dBi, 95% radiation efficiency, wide fractional bandwidth of 39.5% and good radiation characteristics at in-band frequencies. The simulation and measured results are in good agreement and hence make the proposed antenna a favorable candidate for the advanced heterogeneous wireless communication applications.

Design and Optimization of CPW-Fed Bow-Tie Slot Patch Antenna

In this article, a mirror edged bow tie slot antenna is modelled and fed by a CPW fed with a finite ground plane. This design is calculated and its material properties such as its substrate FR4 is utilized which is easily available and less cost of fabrication. The height of the substrate is 2.96mm, with sr=2.The operating frequency is set at 2.45GHz which is ISM frequency band of operation. The antenna was simulated using CST Microwave suite and its results are inferred. The resonating frequency is at 2.581 GHz. This antenna is used for Wi-Fi applications.

Investigation of Microwave Ablation Process in Sweet Potatoes as Substitute Liver.

The microwave ablation technique to destroy cancer tissues in liver is practiced clinically and is the subject of ongoing research, e.g., ablation monitoring. For studies, liver tissue from cattle or pigs is often used as a substitute material. In this work, sweet potato is presented as an alternative material for microwave ablation experiments in liver due to similar material properties. Sweet potatoes as a substitute for liver have the advantages of better handling, easy procurement and stable material properties over time for microwave ablation experiments. The dielectric constant and electrical conductivity of sweet potato are characterized for temperature variation with the help of high-temperature dielectric probe. Furthermore, a test setup is presented for microwave ablation experiments in which a bowtie slot antenna matched to sweet potato is placed on its surface to directly receive the microwave power from a self-developed microwave applicator inserted into a sweet potato 4 cm below the surface antenna. A high-power source was used to excite the microwave powers up to 80 W and a spectrum analyzer was used to measure the signal received by the surface antenna. The experiments were performed in an anechoic chamber for safety reasons. Power at 50 W and 80 W was stimulated for a maximum of 600 s at the 2.45 GHz ISM band in different sweet potato experiments. A correlation is found between the power received by the surface antenna and rise of temperature inside sweet potato; relative received power drops from 1 at 76 C to 0.6 at 88 C (max. temperature) represents a 40% relative change in a 50 W microwave ablation experiment. The received power envelope at the surface antenna is between 10 mW and 32 mW during 50 W microwave ablation. Other important results for 10 min, 80 W microwave ablation include: a maximum ablation zone short axis diameter of 4.5 cm and a maximum ablation temperature reached at 99 C, 3 mm away from the applicator’s slot. The results are compared with the state of the art in microwave ablation in animal liver. The dielectric constant and electrical conductivity evolution of sweet potato with rising temperature is comparable to animal liver in 50–60 C range. The reflection loss of self-developed applicator in sweet potato is below 15 dB which is equal to reflection loss in liver experiments for 600 s. The temperature rise for the first 90 s in sweet potato is 76 C as compared to 73 C in liver with 50 W microwave ablation. Similarly, with 80–75 W microwave ablation, for the first 60 s, the temperature is 98 C in sweet potato as compared to 100 C in liver. The ablation zone short-axis diameter after 600 s is 3.3 cm for 50 W microwave ablation in sweet potato as compared to 3.5 cm for 30 W microwave ablation in liver. The reasons for difference in microwave ablation results in sweet potato and animal liver are discussed. This is the first study to directly receive a signal from microwave applicator during a microwave ablation process with the help of a surface antenna. The work can be extended to multiple array antennas for microwave ablation monitoring.

A Single Layer Dual-Polarization Printed Bow-Tie Slot Broadband Antenna with C-Band Stop

In this letter, a single layer dual-polarization printed bow-tie slot broadband antenna with C-band stop is presented. The proposed antenna consists of two pairs of mirror-symmetric and mutually perpendicular bow-tie slots with two coplanar waveguide (CPW)-fed. The proposed antenna has a very simple structure and the measured results demonstrate the antenna performance can be achieved a wide impedance bandwidth 79.1% for | S11 | and | S22 | ≦ -10dB from 1.3 ~ 3 GHz and 62.3% from 5.25 ~ 10 GHz, which has been implemented the operating band for GPS (1575MHz), WLAN band (2.4GHz and 5.8GHz), and 6 GHz unlicensed spectrum (5.925 ~ 7.125 GHz), UWB band (3.1 ~ 10.6 GHz), LTE Upper band (LTE, 1710 ~ 2690 MHz) applications. The measured in-band isolation performance between the two ports | S21 | ≦ -15.5dB from 1.4 ~ 3 GHz, and | S21 | ≦ -21dB from 5 ~ 10 GHz is significantly achieved and the radiation pattern, peak gain, and efficiency of the proposed antenna are measured as well. In the end, the simulated and measured radiation patterns are compared.

Compact wideband circularly polarized bowtie slot antenna for WBAN applications

A printed compact wideband circularly polarized bowtie slot antenna (WCPBSA) is proposed and presented for wireless body area network (WBAN) applications. The proposed FR4 dielectric based compact antenna has been designed by etching a wide bowtie shaped slot in the ground plane along with a pair of thin slits inserted in the ground plane. The proposed slot antenna is excited by a 50 Ω feedline with dual horizontal stepped stubs, protruding in opposite directions in the slot, which excites dual orthogonal modes to achieve a wide simulated 3-dB axial ratio bandwidth (ARBW) of 48.14% in 4.1 – 6.7 GHz frequency band with approximately identical 10 dB return loss (RL) bandwidth. The proposed WCPBSA is also experimentally verified on human body and observed to be of low specific absorption rate (SAR) value of 0.975 W/kg over 10 g of human tissues and a measured gain of 4.1 dBi at frequency 5.8 GHz. Then proposed WCPBSA of size 20 × 20 × 0.8 mm3 is designed, fabricated and the measured results are verified and validated with simulated results.

MTM- and SIW-Inspired Bowtie Antenna Loaded with AMC for 5G mm-Wave Applications

This paper investigates a feasible configuration of slotted bowtie antenna based on MTM and SIW properties for 5G millimeter-wave applications. To realize the proposed slotted bowtie antenna in a compact dimension with high performances, the MTM and SIW concepts are implemented by applying the trapezoidal slots on the top surface of the antenna and metallic via holes through the substrate layer connecting the top surface to the ground plane. The antenna has been fed with a simple microstip-line which is connected to a waveguide-port. It is shown that the slotted bowtie antenna with a small dimension of 30 × 16 × 0.8 mm3 operates over a measured wideband of 32–34.6 GHz with the fractional bandwidth, average gain, and radiation efficiency of 7.8%, 3.2 dBi, and 50%, respectively. To improve the antenna's performance, the artificial magnetic conductor (AMC) properties have been employed on the ground plane by loading vertical and linear slots with various lengths. The AMC slots are aligned under the trapezoidal slots on the top surface to transfer the maximum electromagnetic signals to them for optimum radiation. The proposed method enlarges the antenna’s effective aperture area, keeping constant its physical dimensions. The proposed AMC-loaded antenna covers wider frequency range of 30–37 GHz in measurement, which corresponds to 21% fractional bandwidth. The average experimental gain and radiation efficiency have been increased to 5.5 dBi and 66.5%, respectively, which illustrate the effectiveness of the proposed AMC-loaded antenna. The results confirm that the proposed slotted bowtie antenna with advantages of compact dimension, wide bandwidth, high gain and efficiency, low profile, being cost-effective, simple design, and easy fabrication process, which makes it applicable for mass production, can be a good candidate for 5G millimeter-wave applications.

Low-Profile Wideband Unidirectional Circularly Polarized Metasurface-Based Bowtie Slot Antenna

In this paper, the design of a wideband circularly polarized (CP) bowtie slot antenna that uses metasurfaces is presented. The antenna consists of a single-layer substrate with 4 × 4 periodic corner-truncated metasurface patches printed at the top side of the substrate and a bowtie-shaped slot etched on the ground plane. The corner-truncated metasurface patches are utilized to convert the linearly polarized wave into a CP wave. The antenna is fed by a 50-Ω coplanar waveguide. The antenna, with an overall size of 42 mm × 42 mm × 2.3 mm (0.71 λo × 0.71 λo × 0.038 λo at 5.1 GHz), was fabricated and measured. The measured reflection coefficient for |S11| < -10 dB yielded an impedance bandwidth of 3.75–6.67 GHz (55.7%), an axial ratio (AR) bandwidth of 4.38–5.98 GHz (31.37%), a 3-dB gain bandwidth of 3.75–6.0 GHz (46.88%), a peak gain of 7 dBic, and a high radiation efficiency of more than 93% within the AR bandwidth.

Low profile broadband substrate‐integrated waveguide to rectangular waveguide transition for W‐band automotive radar

Low profile broadband substrate-integrated waveguide to rectangular waveguide (RWG) transitions have been proposed for RF verification of W-band automotive radar. The transition is designed on a PCB, which is assembled between the radar board and instrument waveguide port. In the design of the transition, a magnetoelectric (ME) dipole is introduced to excite the basic mode of RWG, and a bowtie slot is designed to excite the ME dipole with a broadband performance. The measured frequency band of back-to-back transitions is 68.4–85.3 GHz for a 5 mil RO3003 covered multilayer radar board and 68.6–89.3 GHz for a 10 mil RO3003 covered board, respectively. The calibrated single transition loss is 0.58 and 0.33 dB, respectively. The proposed low profile transitions are robust to assembly errors and convenient for fast RF verification of automotive front-end in the design stage.

Effects of an FSS Reflector on a Microstrip Line Fed Bow-Tie Slot Antenna

Abstract This paper describes the analysis of the effects of a frequency selective surface (FSS) on the characteristics of a microstrip line fed antenna with a bow-tie slot in the ground plane for operation in the frequency range 1 to 10 GHz. The use of the FSS is proposed to miniaturize the antenna structure and increase the number of resonance frequencies and the gain. Air gaps can be inserted between the antenna and the FSS to allow for the adjustment of the resonance frequencies and increase the bandwidth. To prove the concept, antenna prototypes printed on a 30×30 mm2 FR4 low-cost substrate are designed, fabricated and tested. Good agreement is obtained between numerical simulations and experimental results, thus validating the proposed design procedure. The obtained miniaturization and multiband effects can be most convenient for multiservice wireless system applications such as WLAN, WiMAX, 4G, and 5G mobile communication systems.