Semicircular Slot Research Articles

Broadband Semielliptical Patch Antenna with Semicircular Ring Slot for WiMax Application

This paper reports the design and analysis of a semielliptical patch antenna modified by cutting semicircular ring slot in patch geometry and obtained results are discussed. The reported antenna is designed on a multilayered substrate material having two glass epoxy FR-4 substrates separated by a thin foam substrate having thickness 1.0 mm. The size of ground plane is 75 mm×75 mm, whereas the patch dimension along major and minor axes is 23.0 mm and 14.0 mm, respectively. The two modes corresponding to resonance frequencies 3.39 GHz and 3.73 GHz are excited to provide wide impedance bandwidth 21.1% with respect to central frequency with stable radiation patterns. The antenna shows circular polarization with axial ratio bandwidth 5.5% and minimum axial ratio value 1.65 dBi. The radiation patterns of proposed antenna are normal to the surface of patch and are almost identical in shape as required for practical applications. The proposed antenna covers entire median band of WiMax communication systems ranges from 3.40 GHz to 3.6 GHz.

Semicircular Slot-Tuned Planar Half-Ellipse Antenna With a Shallow Vee-Cavity in Vital Sign Detection

Ultrawideband (UWB) antenna is one critical part of the impulse radar system. In this paper, a shallow Vee-cavity shielded planar dipole antenna working at the center frequency of 400 MHz for UWB vital sign detection radar is investigated numerically and experimentally. It consists of two half-ellipse-shape arms tuned with four semicircular slots and a shallow Vee-cavity. The voltage standing wave ratio (VSWR), input impedance, and radiation waveforms are all analyzed. The resistive and slot loading techniques for improving impulse radiation and reducing late-time ringing are adopted. Several important parameters of the designed antenna have been studied. The influence of a shallow rectangular cavity and the proposed Vee-cavity on the antenna characteristics is also under consideration. Finally, one prototype antenna is fabricated and applied to UWB vital sign detection radar system. The experimental results indicate that the proposed half-ellipse antenna with a Vee-cavity works satisfactorily in the radar system.

Three‐dimensional folded antenna with ultra‐wideband performance, directional radiation and compact size

A compact ultra-wideband (UWB) antenna with directional radiation is presented. The antenna has a low profile and does not need a large ground for its performance. The antenna is based on using a three-dimensional folded structure that is modified using semi-circular slots on bowtie-shaped elements. The antenna's mechanism, its design guidelines and its optimisation are described thoroughly. A prototype of the antenna is fabricated andmeasured for performance verification. The prototype shows 77% fractional bandwidth (centred at 2 GHz) based on 10 dB return loss reference. The equivalent overall size of the prototype is (λeff/3) × (λeff/4) × 0.07λeff (λeff = effective wavelength at the lowest resonant frequency), which proves the compactness of the antenna. The antenna shows unidirectional radiation pattern with around 15 dB front-to-back ratio, -20 dB cross-polarisation in the two principle planes and around 5 dBi gain. The antenna is prescribed for compact UWB applications that use the low 1-3 GHz frequency band.

A Compact UWB Diversity Antenna

A compact printed ultrawideband (UWB) diversity antenna with a size of 30 mm × 36 mm operating at a frequency range of 3.1–10.6 GHz is proposed. The antenna is composed of two semielliptical monopoles fed by two microstrip lines. Two semicircular slots, two rectangular slots, and one stub are introduced in the ground plane to adjust the impedance bandwidth of the antenna and improve the isolation between two feeding ports. The simulated and measured results show that impedance bandwidth of the proposed antenna can cover the whole UWB band with a good isolation of < −15 dB. The radiation patterns, peak antenna gain, and envelope correlation coefficient are also measured and discussed. The measured results show that the proposed antenna can be a good candidate for some portable MIMO/diversity UWB applications.

Compact printed monopole antenna for ultra‐wideband application with dual band‐notched characteristic

ABSTRACTIn this article, a compact ultrawideband (UWB) microstrip‐fed printed monopole antenna with dual band‐notched characteristics is proposed. The proposed design consists of a radiating patch with semielliptical shape and the modified ground plane with two bevels on the upper edge of the ground plane to cause the wideband from 3.1 to 10.6 GHz for UWB application. In addition, cutting two semicircular slots on the bottom edge of the ground plane, operating band is further extended above 10.6 GHz. The band notch at the two bands 3.4–3.6 GHz and 5.6–5.8 GHz is achieved using a pair of concentric annular slots with splits in them in opposite side. Fine tuning is possible with adjusting the length and radius of those slots. The antenna size is 24 × 34.6 mm and designed using FR4 substrate having εr = 4.4 and thickness of 0.8 mm. Design and optimizations have been carried out using HFSS v13.0 and there is good agreement with measured results. The proposed antenna exhibits a nearly omnidirectional radiation pattern in the H‐plane, and a dipole‐like radiation pattern in the E‐plane for the entire pass band. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2595–2600, 2013

Design and analysis of compact printed dual band-notched ultrawideband (UWB) antenna

A compact printed ultrawideband (UWB) antenna with dual band-notched characteristics is proposed for UWB integration communication system. The presented design, having a total size of 30 × 25 mm, consists of a folded fork-shaped radiator fed by a microstrip line and a modified ground plane with trapezoid-shaped slots on its top edge, which can effectively increase the bandwidth of the proposed antenna. To avoid potential interferences, a straight, open-ended quarter-wavelength slot and a semicircular half-wavelength slot are etched in the radiating patch to generate dual notched bands in 3.3–3.6 GHz for WiMAX and 5.15–5.825 GHz for WLAN. Lumped-element equivalent circuit model is carried out to comprehend and predict the dual band-notched properties. Good agreement is achieved between the simulation and measurement, which shows that the proposed antenna provides an impedance bandwidth of more than 145% between 2.7 and 17 GHz, two independently controllable notched bands and good omnidirectional radiation patterns.

A Slot Loaded Circularly Polarized Patch Antenna for UHF RFID Reader

The design of a simple UHF (ultrahigh frequency) RFID (radio frequency identification) reader antenna that operates within the 900 MHz band (902-928 MHz) is studied. To generate circular polarization (CP) radiation, a novel method of loading a semicircular slot into the main circular radiating patch is proposed. To allow optimum impedance matching with enhanced CP bandwidth, the L-shaped probe-feed technique is employed in this design. From the experimental results, besides achieving a gain level of more than 7 dBic, the proposed antenna can also yield an impedance bandwidth (10-dB return loss) from 880 to 1100 MHz, while good CP performances between 901 to 930 MHz are exhibited. To further validate the experimental results, parametric studies are also carried out via simulation.

A planar circular ring ultra-wideband antenna with dual band-notched characteristics

A compact planar monopole ultra-wideband (UWB) antenna with dual band-notched characteristics is proposed in order to minimize the interference between UWB systems and existing world interoperability for microwave access and wireless local area network operating bands. The antenna has a microstrip line-fed circular ring radiator with one etched partial concentric annular slot and one semi-circular slot. Two rectangular slots are also etched to connect the slots to the outer and inner periphery of the circular ring radiator. The desired dual band-notched UWB operation can be obtained by choosing the size and location of the etched slots. Experimental results show that with a compact size of 24 mm × 26 mm the proposed antenna achieves a wide impedance bandwidth from 2.79 to more than 11 GHz with two frequency notched bands of 3.3–3.8 and 5.1–6 GHz for WiMAX and WLAN, respectively. Moreover, the antenna exhibits stable radiation characteristics and a good time domain behavior which makes it suitable for being used in the future UWB applications.

Compact Band-Notched UWB Printed Planar Inverted Cone Antennas

A tapered microstrip-fed printed inverted cone antenna with band-notched characteristics suitable for Ultra-Wideband (UWB) wireless systems is proposed. The antenna design consists of a semicircular slot embedded in a planar inverted cone as the radiating patch and a partial tapered ground plane. The proposed antennas are printed on a substrate of permittivity 4.4 and operate over a wide impedance bandwidth from 2.71 GHz to 16 GHz for VSWR 2:1. A semicircular slot is embedded in a planar inverted cone for rejecting the 5 - 6 GHz WLAN band. Prototypes are fabricated according to the optimized parameter values, and the antenna characteristics are measured. The results show that the proposed antennas are of the UWB characteristics and exhibit band rejection of 5 - 6GHz. The radiation patterns are stable and omnidirectional.

Compact ultra-wideband CPW-FED printed semicircular slot antenna

A new compact configuration of a printed CPW-fed semicircular slot antenna with a CPW-to-CPW step transition is presented. Its bandwidth is enhanced for ultra-wideband (UWB) operation by combining linear and stepped CPW-to-CPW transitions along the feed line. Its measured 10 dB return loss bandwidth is 3.1–13.8 GHz (126%). This, together with its nearly constant measured gain of 3.5 dBi ± 1 dB from 3 to 10 GHz, makes it suitable for UWB applications. Details of the proposed antenna are described, and both theoretical and experimental results are presented. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2367–2372, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25481

Compact printed CPW-fed monopole ultra-wideband antenna with triple subband notched characteristics

A coplanar waveguide fed monopole ultra-wideband antenna with triple subband notched characteristics and small volume (23×29×0.8 mm3) is presented. The proposed antenna yields impedance bandwidth of 3.1–10.6 GHz with return loss S11<−10 dB, except for the three subbands of 3.3–3.7 GHz for WiMAX, 5.15–5.825 GHz for WLAN and 7.25–7.75 GHz for the downlink of X-band satellite communication systems. These notched subbands are obtained by etching two simple types of slots on the radiating patch, which are L-shaped and semicircular slots. The antenna was successfully fabricated and measured, showing broadband matched impedance and nearly omnidirectional radiation pattern.

ANALYSIS OF AN INCLINED SEMI-CIRCULAR SLOT IN THE NARROW WALL OF A RECTANGULAR WAVEGUIDE

An inclined semi-circular slot cut in the narrow wall of a rectangular waveguide has been analyzed. By enforcing the boundary condition of continuity of the tangential magnetic field at the slot aperture, an integral equation with the aperture electric field as the unknown has been obtained and solved by the method of moments (MoM). The equivalent slot admittance is then determined. Different slot parameters, such as scattering coefficients, normalized resonant conductance, resonant length versus tilt angle, and radiation patterns, have been studied. The results obtained by the MoM have been verified by comparing them against those results obtained with HFSS.

Novel dual‐broadband design of semicircular slot antenna for wireless communication

AbstractA novel design of semicircular slot antenna with dual‐broadband operation for 2.4/5 GHz wireless local network area (WLAN) is proposed. With the use of an arc‐shaped strip inset along the circle edge of the semicircular slot antenna, a new resonant mode close to the second operating mode of the regular semicircular slot antenna is excited to enhance the operating bandwidth of the high band, and the obtained impedance bandwidths for two operating bands can reach about 14.8% for 2.4 GHz band and 22.0% for 5 GHz band, which cover the required bandwidths of IEEE 802.11b/g (2.4–2.484 GHz) and IEEE 802.11a (5.150–5.950 GHz). The measured peak antenna gains for the operating frequencies across dual WLAN bands are measured to be, respectively, 4.7 and 4.9 dBi with the gain variations within 0.5 dBi. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2165–2169, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22670

Broadband coplanar waveguide‐fed slot antenna for wireless local area networks and microwave imaging applications

AbstractA broadband CPW‐fed semicircular slot antenna is proposed for 2–6 GHz WLAN (wireless local area networks) and microwave imaging applications. The total dimension of the bidirectional slot antenna is 80 mm by 50 mm and is designed on a 0.5‐mm‐thick Duroid 5880 substrate (dielectric constant = 2.2). The antenna operates from 2 to 6 GHz within VSWR of 2.5:1. The same antenna on a combination rectangular cylindrical cavity with cavity depth of 10 mm provides a directional beam, 11 dB front‐to‐back (F/B) ratio and a bandwidth of 63% (2.8–5.4 GHz). © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 846–852, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22276

A broadband folded‐slot antenna with a semi‐circular extension

AbstractA coplanar waveguide (CPW)‐fed broadband folded‐slot antenna is proposed. Broadband operation is achieved by designing an adjacent semicircular slot to a folded‐slot antenna. A prototype antenna was fabricated on RO4003 (εr = 3.38, substrate thickness = 1.5 mm) and measured for VSWR characteristics. The antenna can operate in the 4–6‐GHz frequency range and has a bandwidth of 42.8% within 2:1 VSWR. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 32–37, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20037

Propagation of short fatigue cracks from notches in a Ni base superalloy: experiments and modelling

A notched specimen containing a semicircular slot (0.1 mm deep) was designed to simulate the growth of three‐dimensional short cracks under a stress concentration. Fatigue tests were performed on N18 superalloy at 650 °C with trapezoidal loading cycles. A high‐resolution optical measurement technique proved to be capable of detecting half‐surface crack increments as small as 10 μm, and the potential drop method was found to be inappropriate for very small crack lengths. The stress intensity factor, ΔK, was calculated using a weight functions method. Non‐uniform stress fields were determined by FEM modelling using elasto‐viscoplastic constitutive equations. The plasticity‐induced crack closure effect was calculated within the specimen using viscoplastic FEM modelling. The prediction of crack aspect ratio was used to investigate differences of closure along the crack front. The role of notch plasticity on these differences is discussed. Using these calculations, it is shown that the apparent differences between the growth behaviour of short and long cracks can be largely accounted for.

A novel microstrip-line-fed printed semicircular slot antenna for broadband operation

A novel design of a microstrip-line-fed printed semicircular slot antenna is proposed. A prototype of the proposed antenna is also constructed and experimentally studied. Results show that, by protruding a small rectangular slot of proper dimensions along the direction of the microstrip feed line, good impedance matching over a wide operating bandwidth for the proposed antenna can be obtained. The constructed prototype shows an operating bandwidth, determined by the 10 dB return loss, of about 46%, which is about three times that of a corresponding conventional printed wide rectangular slot antenna. Details of the proposed antenna and obtained experimental results are presented. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 237–239, 2000.

Experiments on 3-D crack growth in uniaxial compression

A study of spatial crack propagation under uniaxial compression was undertaken in a brittle transparent plastic with artificially induced internal cracks. The specific issue addressed was whether there was a qualitative difference between 2-D and 3-D crack propagation. Fracture of heterogeneous materials (e.g., rocks) under uniaxial compression is produced by propagation of internal cracks towards the load, some of which propagate so extensively that they eventually split the material into columns. Experimental and theoretical studies of this phenomenon based on 2-D models (plates with through cracks.) showed that the extensive crack growth towards compression emerged from pre-existing (initial) defects such as through cracks in plates inclined to the compression axis, or cylindrical pores (e.g., [1-10]). The main point of these studies is that a single 2-D microdefect is capable of producing extensive crack growth sufficient to cause fracture. In reality however, pre-existing cracks are three-dimensional, which can result in a more complicated mechanism of their growth. A limited number of experiments: Adams and Sines [4] and Cannoo et al. [11], have been reported on studies of the growth of inclined disk-like cracks in uniaxially compressed transparent samples (from PMMA polimethilmethacrylate plastic). However, the dimensions of the PMMA samples used in these experiments were not sufficient to investigate the extensive crack growth. In order to study mechanisms of fracture in uniaxial compression, further experiments are required using sufficiently large samples which would provide enough room for extensive crack growth. In addition, the spatial interaction of several growing cracks has to be investigated. This paper reports the results of such experiments. 1. Sample preparation and experimental technique. In the experiments, parallelepiped samples made from transparent casting polyester resin "Polylite 61-209" with cross-section dimensions of 55 mm x 55 mm, and a height of 120 mm were used. When frozen to -17°C, this material is perfectly brittle, deforms without barrelling and has linear stress-strain behaviour up to its burst-like fracture. The mechanical properties evaluated during the tests are: Young's modulus _=_4GPa; uniaxial compressive strength _=_ 140MPa; fracture toughness _=_0.6MPa-m 1/2. Two methods of modelling the internal initial disk-like cracks were adopted: (1) embedding a thin disk-like inclusion into the resin block during casting. The inclusion consisted of two aluminium foil disks greased and put together and held within the sample by two cotton threads; (2) cutting two semi-circular slots of 0.3 mm thickness in two halves of the sample and then gluing the halves together (this method was used in [4]). In order to ensure the contact between the opposite faces of the crack, teflon or greased foil disks were inserted into the slots (According to the 2-D analysis [9], the initial cracks, i.e. voids with contacted lips are the strongest drivers of the extensive crack growth).