Hooked loop antenna concept for Bluetooth headset applications

A small radiating element, designed to work simultaneously in GSM‐DCS‐PCS‐UMTS‐frequency bands, totally made up of metallic square parts on an air substrate is described. The total size of the supporting ground plane is smaller than λ/2 for the lower working frequency. By stacking two square wire‐patches, it is well‐known that both compactness, large bandwidth, and monopolar wire radiation pattern can be achieved. However, multiband behavior is always difficult to obtain using only stacked elements. The antenna proposed in this article uses two U slots in the upper plate to obtain the two desired frequency bandwidths. This new structure allows an easy realization and can be protected by a dielectric radome that could be taken into account during the optimization of the structure. Owing to its low profile, low cost and radioelectric properties such as large bandwidth and dipolar type radiation pattern, this antenna is very suitable for automobile or indoor ceiling applications needing a very small ground plane. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1247–1250, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24327

In this paper, a novel technique is proposed that is applicable to cases in which two-layered ground planes exist to achieve high radiation performance. The proposed ground radiation antenna is composed of a radiating loop and a feeding loop, which are built into separate two-layered ground planes. The feeding loop and radiating loop are located on the small top-layer ground plane and the large bottom-layer ground plane, respectively, so that two loops are magnetically coupled to each other, and the large bottom-layer ground plane is then excited as a radiator. The reference antenna is built with a radiating loop and a feeding loop only on the top-layer ground plane. High performances are achieved both in simulation and measurement.

Released in 2018, China’s Standards of English Language Ability (CSE) set a benchmark for language education and assessment in China, integrating with international standards. This study investigates whether CSE assessment literacy (understanding and applying CSE standards in assessment practice) enhances Language Assessment Literacy (LAL) among 233 university EFL teachers in China. Using a self-designed questionnaire assessing current LAL and CSE assessment literacy, the findings indicate that the teachers’ self-assessed LAL, classified into high, moderate, and low LAL profiles, was generally unsatisfactory. Awareness of the principles was highest in teachers with a moderate LAL profile and was minimal in teachers with a low profile. Proficiency in “CSE Background,” “Competence Classification,” and “Table Scales” was closely linked to elevated LAL profiles. Specifically, “CSE Background” improved LAL across low and moderate profiles, while “Competence Classification” and “Table Scales” mainly benefited the moderate profile, informing effective LAL and CSE training strategies.

This paper discusses the importance of developing cooling solutions for low profile devices. This is addressed with an experimental and theoretical study on forced convection cooling solution designs that could be implemented into such devices. Conventional finned and corresponding finless designs of equal exterior dimensions are considered for three different heat sink profiles ranging from 1 mm to 4 mm in combination with a commercially available radial blower. The results show that forced convection heat transfer rates can be enhanced by up to 55% using finless designs at low profiles with relatively small footprint areas. Overall, this paper provides optimization and geometry selection criteria, which are relevant to designers of low profile cooling solutions.

This paper is focused on the design of printed antennas based on electrically small resonators for microwave applications. Nowadays, low cost radiofrequency devices usually incorporate common planar microstrip antennas, consisting of a rectangular metal patch placed on top of a dielectric substrate mounted over a large ground plane. This type of antennas is supposed to provide a radiation diagram located in the half-space due to the presence of the ground plane. Nevertheless, since this kind of antennas can be viewed as an open circuited transmission line, the electric field at the edges of the conductor patch will spread into the surrounding substrate. This results in the extension of currents over a significant area of the ground plane. For this reason, the ground plane should be maintained electrically large, in order to preserve the radiation diagram and hence minimizing the radiation to the back side of the antenna. However, in some applications, the size of the antenna is a critical issue and should be minimized. To overcome this drawback, the use of an electrically small resonator is proposed, which concentrates the currents around its geometry, as a radiator. Considering that the particle is relatively close to the ground plane (and also its image, located on the opposite side of the ground plane), the induced currents in the ground plane are expected to be concentrated in a relative small region around the resonator. This fact leads to a reduction of the currents at the edges of the ground plane, resulting in the optimization of the FBR when its dimensions are decreased.

Magnetic and electric loop antennas were examined under a small or a large ground plane. For each ground plane setting, the loops were placed in five environments created by the presence of human body parts. They were free space, head only, hand only, head and hand, and simulated head. The results showed that the antenna was sensitive to the size of the ground plane. It also showed that the antenna patterns were severely distorted by the presence of a person except in the hand only cases. The change of the antenna pattern was far more dramatic when a real human head was placed near the antenna instead of the simulated head.

A printed antenna is a type of low-profile antenna that is commonly employed in wireless communication systems. It has sparked increased interest among communication engineers in recent years. The number of wireless standards has expanded over the previous decade because of downsizing, innovation and cost reduction. The development of low-profile and affordable antennas for a variety of applications has played a significant part in the current wireless communication systems and has also prompted researchers to do more study and inquiry. Antennas have become a necessary component of the front end of wireless communication networks. The printed antenna basically contains a radiating patch on the top surface of the dielectric substrate (ε r ≤ 10), while it has a ground plane on the bottom side. The feed line and radiating patch are fabricated on the same dielectric substrate by using photo-etching techniques. In general, various conducting materials such as copper, silver and gold are used for the fabrication of the patch and ground plane. The microstrip antenna is also called patch antenna or printed antenna. The main advantages of printed antennas are being lightweight and having smaller volume, compact size, low profile, low cost, planar configuration and conformal.

This paper presents the analysis, design and measurement of novel, low-profile, small-footprint folded monopoles employing planar metamaterial phase-shifting lines. These lines are composed of fully-printed spiral elements, that are inductively coupled and hence exhibit an effective high- mu property. An equivalent circuit for the proposed structure is presented, validating the operating principles of the antenna and the metamaterial line. The impact of the antenna profile and the ground plane size on the antenna performance is investigated using accurate full-wave simulations. A lambda/9 antenna prototype, designed to operate at 2.36 GHz, is fabricated and tested on both electrically large and small ground planes, achieving on average 80% radiation efficiency, 5% (110 MHz) and 2.5% (55 MHz) -10 dB measured bandwidths, respectively, and fully omnidirectional, vertically polarized, monopole-type radiation patterns.

Recent demands for miniaturized, lightweight, high data rate, and reliable wireless devices motivated researches and designers of wireless systems to adopt the use of multiple input-multiple output MIMO antenna arrays with close proximity of each other. One of the difficulties is to overcome the problems associated with the low isolation between any two closely spaced antennas. The low profile, small size, ease of fabrication, and simplicity of design encourage the use of the IFA/PIFA antennas. In this paper, two vertical IFA antennas with close separation of λ o /15 ( o /2) fed by coaxial lines are combined in an array operating at the frequency of 2.5 GHz. The two antennas are deployed on a ground backed substrate of 50 mm × 50 mm in length and width respectively and a thickness of 1.524 mm with a relative permittivity, e r of 10.2. Each IFA consists of a monopole as the main radiator with a length of 38 mm and a diameter of 1.22 mm placed 11 mm above the ground plane. The separation between the feeding point and the grounded end of the radiating element is 10 mm. The consequence of positioning the antenna in the proximity of each other is the high mutual coupling. To decrease the resulted effects, a new Defected Ground Structure (DGS) has been proposed. A rectangular slot of 32 mm and width of 1.5 mm with a strip line of 29 mm in length and a width of 1 mm have been introduced to the ground plane. The final proposed array with the DGS is shown in the attached figure. The Defected Ground Structure (DGS) has the effect of reducing the interaction between the antennas, main radiators, by restricting the current flow in the ground plane. A parametric study has been carried out to obtain the optimum dimensions of the structure using Ansys High Frequency Structure Simulator (HFSS). The S-Parameters of the design are shown in the enclosed figure. The antenna has an operating frequency of 2.5 GHz. A total isolation level of -22 dB has been achieved by the proposed structure at the operating frequency. The array with the proposed ground structure provides a gain of 3.9 dB at 2.5 GHz when the two ports are excited. This structure is a good candidate for reducing the mutual coupling between two vertical IFA for application utilizing MIMO techniques.

Multipath mitigating ground planes for dual band (L1/L2) global navigation satellite system (GNSS) antennas are proposed. Two novel ground planes; dual band electromagnetic band gap (EBG) ground plane and cross plate reflector ground plane (CPRGP) are presented. The ground planes are designed to improve the antenna backlobe and cross polarization performance at both L1 (1.575 GHz) and L2 (1.227 GHz) bands by suppressing the surface wave propagation. In contrast to the conventional corrugated type choke ring ground plane, the proposed ground planes have smaller thickness. The dual band EBG consumes larger space but still have the advantage of maintaining a low profile and low mass. The CPRGP however has the combined advantage of compact size and performance. The CPRGP ground plane also has low mass, low manufacturing cost and does not require any periodicity. Multipath mitigation performance of both ground planes is compared against the conventional choke ring type corrugated ground plane. Simulation results and multipath rejection ratio (MPR) of the proposed ground planes show that the CPRGP, EBG and choke ring ground planes give similar multipath mitigating performance with CPRGP having an added advantage of compact size.

In this paper, we propose a planar folded dipole antenna (PFDA). The PFDA consists of a folded loop element placed horizontally on the top of the ground plane (GP) so that the antenna has a lower profile. In the analysis, an electromagnetic simulator based on the model of moments is used. The design parameters, which are useful in practical operation, are obtained. An example of a low profile antenna is designed, based on these parameters, and antenna characteristics such as VSWR, the current distributions and the radiation patterns are shown. Furthermore, we study the miniaturization of the antenna including a GP by reducing the GP length.

Patch antennas usually involve a ground plane much larger than the radiating element. To make a patch antenna compact, it is significant to reduce the size of the large ground plane. In this paper, a compact multi-folded patch antenna with a substantially small ground plane for UWB (ultra wideband) application at the UHF (ultrahigh frequency) band is presented. The proposed antenna is derived from an ordinary L-shaped monopole antenna, and with the dimension of only 0.22λL× 0.092λL× 0.091λL (λL is the longest wavelength in the operating bandwidth) after folding the L-shaped radiating patch over the small ground plane. The characteristics such as impedance bandwidth, gain and pattern stability are analyzed and measured. According to the measured results, the antenna has an impedance bandwidth up to 61.5% for VSWR≤2, ranging from 450 MHz to 850 MHz, covering the band of DVB-T (Digital Video Broadcasting-Terrestrial) (470 MHz-862 MHz) and DTV (Digital TV) (470 MHz-806 MHz). Details of the fabricated antenna are described, and a prototype of the design example is constructed and studied.

In this paper, a novel planar active artificial magnetic conductor (AAMC) frequency-reconfigurable antenna printed on an FR4 substrate is proposed. Its AAMC metal pattern in a unit cell consists of a compound-five-ring nesting (CFRN) structure. It is loaded with only one varactor diode connected to the ground plane by a metallic via. In comparison to the conventional single-circle-ring AMC, the dimension of the CFRN-AMC has been reduced by about 44% along with a lower reflection loss. The frequency-reconfigurable antenna is constructed by placing a triangle-shaped dipole antenna operating at 1.8 GHz over the proposed active CFRN-AMC ground plane consisted with 5×5 periodic unit cells. The prototype of the CFRN-AMC-backed antenna was fabricated and measured. The measured results agree well with the simulated data. It is found that by tuning the capacitance applied on the CFRN-AMC from 2.2 to 0.5 pF, the frequency band of the AMC-based antenna has been varied in the range of 1.51 through 2.12 GHz along with the highest radiation gain of 5.37 dBi at 1.74 GHz. This gain is about 3.16 dB higher than that of the antenna without using the AMC. In addition, the presented CFRN-AMC-based antenna remains a very low profile, since the separation distance between the antenna and the AMC plane is only 2 mm or 0.012λ, where the λ denotes the wavelength at 1.8 GHz in free space.

Floating, i.e. not locally grounded, printed circuit boards (PCBs) at the end of a long harness and above a large ground plane are common in automotive applications. A problem in modeling such setups is the missing ground reference at the PCB side. In this work, two equivalent circuit models are extracted from PCB design data, one based on a broadband SPICE (BBSPICE) netlist generated from S-parameter simulation and the other obtained by partial element equivalent circuit (PEEC) method. They are compared against measurements results of a demonstrator PCB in above described setup. Investigations include the verification of both modeling approaches with respect to low frequency behavior, broadbandness, sensitivity to PCB circuitry modifications and grounding scheme, as well as model generation effort and simulation times.

5G communication systems are emerging due to the need for faster data rates and larger bandwidths. 5G require systems that of low profile, light weight and capable of achieving high bandwidths to ensure high efficiency. The 28GHz frequency band was selected for the study due to the low atmospheric absorption around this frequency and cost-effectiveness. The study presented a single element low profile microstrip antenna operating in the 28GHz frequency band. The proposed antenna was printed on a Rogers RT5880 substrate with dielectric constant of 2.2 and a loss tangent of 0.0009. The antenna consists of a rectangular radiating patch fed by a 50Ω microstrip line. In other to increase the gain of this antenna while maintaining a low compact profile, four rectangular-shaped slots were introduced on the patch. The positions of these slots were optimized using Computer simulation technology (CST) software. The antenna provided a gain of 7.67 dB with return loss of above −30dB. The antenna showed good radiation characteristics with radiation efficiency of 98% and achieved high bandwidth up to 2GHz.