Triangular Slot Research Articles

Design of triangular slot antenna for triple‐band (2.4/5.2/5.8 GHz) antenna with fork‐like tuning stub

AbstractA novel design for a triangular slot antenna with fork‐like tuning stub for 2.4/5.2/5.8 GHz triple‐band applications is presented in this article. The prototype consists of a triangular slot and a fork‐like tuning stub. The triangular slot is fed by a 50‐Ω microstrip line with a fork‐like tuning stub, which is printed on the opposite side of the microwave substrate. As seen in the experimental results, the impedance bandwidth (VSWR 1:2) of the proposed bandwidth is about 550 MHz for the 2.4‐GHz band and 1.736 GHz for the 5‐GHz band. This is a microstrip antenna for IEEE 802.11a/b wireless local area networks applications. Simulated and experimental results for the return loss, radiation patterns, and gains are presented and discussed.© 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1561–1565, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22499

Compact dual-polarised square microstrip antenna with triangular slots for wireless communication

Design of a dual linearly-polarised microstrip patch antenna, excited by two orthogonal microstrip feed lines, is presented. A reduction in patch size of 35% is obtained when compared to a square patch operating at the same frequency. The polarisations are oriented at +45 and −45° with an isolation of more than 36 dB between the ports. Unlike earlier designs, the proposed structure provides better gain.

2.4/5-GHz dual-band triangular slot antenna with compact operation

A novel compact dual-band equilateral-triangular slot antenna (ETSA) for 2.4/5-GHz wireless local area networks (WLANs) is presented. A pair of F-shaped strips are centrally inset at the side edge of the ETSA to extend the surface-current path of dual operating bands in order to lower both operating frequencies simultaneously. And, the obtained impedance bandwidths cover the required bandwidths of IEEE 802.11b/g (2400–2484 MHz) and IEEE 802.11a (5150–5950 MHz). The measured antenna radiation patterns are approximately bidirectional at the two resonant frequencies. Peak antenna gains for the operating frequencies across dual WLAN bands are measured to be, respectively, 2.8 and 5 dBi with gain variations within 1.0 dBi. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 81–84, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20730

Planar‐fed compact circular‐polarised microstrip antenna with triangular‐slot loading

AbstractA planar‐fed circular‐polarised (CP) microstrip patch antenna is presented and discussed. It is demonstrated that embedding four right‐angle triangular slots in a nearly square patch antenna and exciting with an offset inset feed, size reduction of up to 43% can be achieved while still maintaining planar impedance matching. The proposed design shows no significant reduction in the axial‐ratio bandwidth and has relaxed manufacturing tolerances. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 226–228, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20100

Gain enhancement of a circularly polarized equilateral-triangular microstrip antenna with a slotted ground plane

A novel circular polarization (CP) design of a single-feed equilateral-triangular microstrip antenna with enhanced antenna gain is presented. This CP design is obtained by placing three triangular slots at properly locations below the equilateral-triangular radiating patch in the ground plane. By adjusting one of the triangular slot's side lengths slightly longer than that of the others, two orthogonal near-degenerate resonant modes for CP radiation can be excited. Measured antenna gain in this study can easily be increased by 3.3 dBi (5.1 dBi versus 1.8 dBi), as compared to the same height, substrate material, operating frequency and radiating patch shape of a regular equilateral-triangular microstrip antenna without triangular slots in the ground plane. Prototype antenna is fabricated for experimental evaluation. Simulated and measured results are presented.

Single‐feed circularly polarized triangular microstrip antenna with triangular slot for compact operation

AbstractNovel compact circular polarization (CP) designs of a single‐feed triangular microstrip antenna with a triangular slot or an inverted triangular slot are proposed and experimentally studied. For the design with a triangular slot, CP operation can easily be achieved by inserting a slit with a length about 24% of the slot's side length at the center of the inner bottom edge of the patch. As for the design with an inverted triangular slot, the insertion of a slit with a length about 12% of the slot's side length can result in CP radiation. Results also indicate that with the triangular slot embedded in the patch, the proposed CP design can have an antenna size reduction of about 30% as compared to the regular‐size CP design using a simple triangular patch. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 263–266, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10433

Mean flow and turbulence measurements in a triangular turbulent free jet

Detailed mean flow and turbulence measurements were made, using hot-wire anemometry, in the near flow field of a turbulent, incompressible air jet issuing from a sharp-edged equilateral triangular slot into stagnant air surroundings. The measured quantities included the three components of the mean velocity vector, the three turbulence intensities, and two of the Reynolds shear stresses. The results indicate that the jet spreads faster on its base side than at its apex. This difference in spreading leads to an inversion of the jet shape at about five equivalent slot diameters downstream from the slot exit plane. The Reynolds shear stress levels, compared to those found in round turbulent free jets at the same downstream locations, are higher in the triangular jet, implying improved mixing.

A NONDESTRUCTIVE TEST FOR DETERMINATION OF OPTIMUM MATURITY OF FRENCH (GREEN) BEANS (Phaseolus vulgaris)1

ABSTRACTOptimal maturity stage of Burpee Stringless Variety of French (green) beans was determined by a trained sensory panel using beans harvested at definite intervals of growth till over‐maturity. Of the changes in ten physico‐chemical characteristics studied during growth, weight to length (W/L) ratio is closely related to the sensory characteristics and can be used as a simple non‐destructive test for determining the optimal maturity. The beans are very tender up to a W/L ratio of 0.4 g/cm, tender from 0.41 to 0.5 g/cm which is optimal mature stage, mature from 0.51 to 0.6 g/cm, and over‐mature thereafter.The maximum force required to cut the bean by placing on its edge or flat in the triangular slot of the Warner‐Bratzler shear press was 9.0 kg in tender beans and could be made use of as an instrumental method for determining the maturity. The force required to cut the beans edgewise was more than in the flat position at or before the optimal maturity and the values reversed thereafter.Changes in total solids, alcohol insoluble solids and fibrous matter contents between tender and mature ones are too sudden and large during the short transition period for being used as objective method(s) but yielded meaningful data when considered along with W/L ratio or shear force.

The correlation of slot‐opening with flow rate for air bubbling into water

AbstractWhen air flows through a slot in a vertical diaphragm into a tank full of water, the level on the air‐inlet side is depressed below the apex of the slot. This depression, defined as the slot‐opening, has been correlated with the air rate. Some 300 determinations have been made at air rates between 0·01 and 800 cu. ft. per min. for one rectangular and one triangular slot. A few further measurements have been made with slots of varied dimensions.All these measurements are shown to fit with the simple hydrodynamic theory (Rogers & Thiele, 1934) when this is modified to take account of surface tension effects. The new theory requires that below a critical air rate the slot opening should be determined by surface tension effects alone, whereas above this rate the original hydrodynamic equations would apply. The values now found for the constants of these equations are significantly different from those proposed by the previous workers. In particular, the exponent of h (the slot opening) now corresponds with the theoretical values to within the limits of experimental accuracy. The larger values obtained in the earlier work (Roger & Thiele, 1934: Spells & Bakowski, 1950) were probably due to the inclusion of measurements below the critical rate.

Research Items

A Cypriote Threshing Sledge.—In Man for August, Mr. J. Hornell describes a very ancient type of implement known as a dukani or ‘threshing sledge’ used by the Cypriote farmer for threshing grain. This is a broad board about six and a half feet long, of which a length of nearly five feet is straight, the remaining portion at the forward end being inclined upward at an angle of 18°–20°. The breadth varies in different dukani from 24 in. to 27 in. The board is made up of two planks joined lengthwise edge to edge. Except for a margin of eight inches at either end the bottom surface is studded with many rows of sharp-edged flints inserted by their bases in long and narrow triangular slots. In one example there were twenty-two rows in one plank and twenty-three in the other. Each row consisted of ten flints in each plank, each row being set alternately to the one in front and the one behind. The total for the two planks was 450 flints. The thickness of the two boards is 2½ inches, but the thickness is cut down slightly from the fore-end and the size of the flints for a short distance anteriorly is smaller. They range from 13/4 in. to 2¼ in. in length and from 1½ in. to 13/4 in. in height. The shape of the flints is roughly triangular with two long knife-edged sides and a thick and massive butt. The projecting edge is arched and one face is always convex, the other keeled. The slots into which the flints are inserted are made by a chisel of peculiar form. When all the flints have been inserted in the slots, hot pitch is poured along the rows just as the ancient Egyptians fastened the flints in their sickles with a plaster setting. The sledges are drawn by two oxen flint side downward over the threshing floor, which is thickly strewn with sheaves. The driver sits on a chair placed midway between the transverse battens. This form of threshing appliance is a survival of the Roman tribuhim which persists in Syria, Asia Minor, Georgia, and Greece. In some parts of Spain and the Canary Islands it is in use without the flints as the straw is required whole.