Antenna Side Research Articles

Prediction of ground multipath parameters from range-gain measurements using Prony's technique

Prony's technique is used to estimate multipath parameters from range-gain patterns produced by ground multipath interference in line-of-sight radio links. The field distribution at the transmitting antenna side is obtained by digital reconstruction from the range-gain pattern that is recorded, at constant height, along ground surface. The technique is presented as a competitive alternative to the Fourier transform, where much shorter data windows are sufficient for the proposed technique. The technique is validated by calculated and measured range-gain patterns, and the predicted values are in good agreement with the actual ones. Prony's technique produced predictions with comparable errors to the Fourier technique from much smaller data windows.

A RHOMBIC PATCH MONOPOLE ANTENNA WITH MODIFIED MINKOWSKI FRACTAL GEOMETRY FOR UMTS, WLAN, AND MOBILE WIMAX APPLICATION

This paper presents a rhombic patch monopole antenna applied with a technique of fractal geometry. The antenna has multiband operation in which the generator model, which is an initial model to create a fractal rhombic patch monopole, is inserted at each center side of a rhombic patch monopole antenna. Especially, a modified ground plane has been employed to improve input impedance bandwidth and high frequency radiation performance. The proposed antenna is designed and implemented to effectively support personal communication system (PCS 1.85–1.99 GHz), universal mobile telecommunication system (UMTS 1.92–2.17GHz), wireless local area network (WLAN), which usually operate in the 2.4 GHz (2.4–2.484 GHz) and 5.2/5.8 GHz (5.15–5.35 GHz/5.725–5.825GHz) bands, mobile worldwide interoperability for microwave access (Mobile WiMAX), and WiMAX, which operate in the 2.3/2.5 GHz (2.305– 2.360 GHz/2.5–2.69 GHz) and 5.5 GHz (5.25–5.85 GHz) bands. The radiation patterns of the proposed antennas are similar to an omnidirectional radiation pattern. The properties of the antenna such as return losses, radiation patterns and gain are determined via numerical simulation and measurement. Corresponding author: C. Mahatthanajatuphat (cmp@kmutnb.ac.th). 58 Mahatthanajatuphat et al.

Novel MMIC protection technique in plasma etching process for mechanically movable RF mems antenna

AbstractIn this article, we proposed the novel monolithic microwave integrated circuit (MMIC) protection technique in plasma etching process for MMIC mounted mechanically movable RF MEMS antenna. We could eliminate the distortion of radiation pattern caused by RF feed line on antenna frame and torsional hinge as using MMIC direct mounting on antenna plate instead of using external RF power source. Silicon‐based mechanically movable RF MEMS antenna was released using DRIE process, which was performed on the backside of silicon substrate after MMIC mounting on RF MEMS antenna plate. An aluminum layer on the front side of RF MEMS antenna plays a role of etch stop layer for DRIE process. We measured the radiation pattern as rotating the moving plate along the vertical‐ and horizontal‐direction hinge mechanically. We could obtain the radiation pattern without gain reduction and distortion of radiation pattern. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3089–3093, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23870

WCDMA multi‐service uplink capacity of highways cross‐shaped microcells

AbstractThe multi‐service uplink capacity and the interference (intracellular and intercellular) statistics (mean and variance) of the sectors of the cross‐shaped wide‐band code‐division multiple access (WCDMA) microcell are studied using a model of nine highway microcells in rural zone. The two‐slope propagation loss model with lognormal shadowing is used in the analysis. The capacity and the interference statistics of the microcell are studied for different sector range, antenna side lobe levels and different standard deviation of the power control (PC) error. It is shown that, reducing the antenna side lobe level increases the sector capacity. Also, it is shown that the sector range to get the quasi‐maximum sector capacity is on the order of 600–1200 m. Copyright © 2008 John Wiley & Sons, Ltd.

WCDMA Uplink Capacity of a Long Tunnel Cigar-shaped Microcells for Underground Train Service

In this paper, the capacity and the interference statistics of the sectors of the cigar-shaped WCDMA microcells are studied using the hybrid model of propagation. A model of nine microcells in a metro tunnel is used to analyze the uplink capacity and the interference statistics. The capacity and the interference statistics of the microcells in metro tunnels are studied in this work for different propagation parameters, antenna side lobe levels, sector ranges and bends losses.

Design, fabrication and testing of UHV compatible high power RF devices for lower hybrid current drive system on SST-1 tokamak

Maintaining plasma current under steady state conditions is one of the most important pre-requisites for a tokamak-based reactor. Lower hybrid current drive (LHCD) system aims to drive tokamak plasma current by means of RF power. The LHCD system on SST-1 tokamak is based on two 500 kW, CW klystrons operating at 3.7 GHz. A waveguide transmission line transmits power from source to the antenna. A phased array waveguide antenna is used to couple power to the plasma. The antenna side of the transmission line is placed inside the tokamak vacuum vessel. The design and fabrication of this In-Vessel system has to satisfy the demands of high power RF as well as ultra high vacuum (UHV) compatibility. This paper describes some of the critical UHV compatible In-Vessel RF devices, their design, fabrication, and test results.

Compact Circularly Polarized Rectenna With Unbalanced Circular Slots

A novel rectifying antenna (rectenna) using a compact circularly polarized (CP) patch antenna with RF-to-DC power conversion part at 2.45 GHz is introduced, in which the unbalanced slots structure is adopted for size reduction and 2nd harmonic rejection. To contribute a rectenna for RF power conversion, the back side of the CP antenna is the doubler rectifier circuit with 3rd order harmonic rejection radial stub for efficiency optimization and harmonic power re-radiation elimination. The adopted CP antenna built on low cost FR-4 substrate has measured bandwidth of 137 MHz (10 dB return loss) as well as 30 MHz CP bandwidth (3 dB axial ratio). By up to 3rd order harmonic rejection, the RF-to-DC conversion efficiency would reach 53% and 75% with 1 K Omega resistor load under ANSI/IEEE uncontrolled and controlled RF human exposure limit respectively.

Reduced size small dual and multi‐frequency microstrip antennas

AbstractThis study presents theoretical and experimental investigations on novel, compact, single layer and single probe‐fed rectangular microstrip patch antennas for dual and multi frequency operation. The novel design is achieved by cutting two rectangular slots at one side of the patch antenna. Compared with the conventional rectangular patch antenna, our antenna can achieve reduction in patch size up to 85%. Dual frequency operation has also been achieved effectively by just adjusting the feed position of a conventional rectangular patch antenna. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 961–965, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23255

Digital real-time control for an ICRF fast ferrite tuning system on Alcator C-Mod

A double-stub fast ferrite tuning (FFT) system has been developed and installed on the Alcator C-Mod tokamak for real-time ion cyclotron range of frequencies (ICRF) antenna matching. The FFT uses a digital feedback control system consisting of a Linux server, a compact PCI digitizer and MDSplus interface. The software is written in IDL, and runs with interrupts disabled. During a plasma discharge, the computer records the forward RF power, reflected power, and phase data on both the antenna side and the transmitter side of the tuning system, calculates the required magnetic coil currents in the ferrite tuners to minimize the reflected power to the antenna, and sends out the current demands in each computation cycle. The FFT system has been demonstrated to achieve good matching to antenna loading in low confinement modes (L-mode), high confinement modes (H-mode), and plasmas with edge-localized modes (ELMs) in Alcator C-Mod.

Hexagonal Monopole Strip Antenna with Rectangular Slot for 100–1000 MHz SFCW GPR Applications

A printed ultra wideband (UWB) monopole antenna is proposed for applications on stepped frequency continuous wave (SFCW) ground penetrating radar (GPR) within a frequency range of 100–1000 MHz. The proposed antenna consists of a hexagonal strip line with resistive loading and a rectangular slot that is added to the ground plane side of the printed antenna implemented on FR4 epoxy materials. The resistive loading at the hexagonal monopole is effective to increase bandwidth in the higher frequency region, while the rectangular slot is used to improve bandwidth characteristic in the lower frequency region. This paper investigates the characteristic improvement in the lower frequency region by applying a parametric study on the rectangular slot that is added at the ground plane side of the UWB monopole antenna. Computer simulation was conducted and measurements were carried out to validate the result.

A Double Square Loop Antenna with Modified Minkowski Fractal Geometry for Multiband Operation

A double square loop antenna with fractal geometry that supports for multiband operation is proposed. The antenna has multiband operation in that the generator model, which is an initial model to create a fractal loop antenna to operate at the first and second resonant frequencies, is inserted at each center side of a big square loop antenna. It also has a small square loop to operate at the third resonant frequency. The proposed antenna is implemented and shown to effectively support the global system for mobile communication (880-960 MHz), digital communication system (1710-1880MHz), personal communication system (1850-1990 MHz), universal mobile telecommunication system (1920-2170 MHz), and wireless local area network (2400-2483 MHz) bands. The radiation patterns of the proposed antenna are still similar to a bidirectional radiation pattern. The properties of the antenna such as return losses, radiation patterns and gain are determined via numerical simulation and measurement.

WCDMA Multiservice Uplink Capacity of Highways Cigar-Shaped Microcells

The multiservice uplink capacity and the interference (intracellular and intercellular) statistics (mean and variance) of the sectors of cigar-shaped wideband code-division multiple access (WCDMA) microcell are studied using a model of 5 highway microcells in rural zone. The two-slope propagation loss model with lognormal shadowing is used in the analysis. The capacity and the interference statistics of the microcell are studied for different sector ranges, antenna side lobe levels, standard deviation of the power control error, breakpoint distance, and different intersites correlation coefficient. It is shown that reducing the antenna side lobe level increases the sector capacity. Also, it is shown that the sector range that gives the quasi the maximum sector capacity is in the order of 800 to 1200 m.

WCDMA uplink capacity and interference statistics of highways cigar-shaped microcells

The capacity and the interference statistics (mean value and variance) of the sectors of the cigar-shaped Wideband Code Division Multiple Access microcells are studied. The two-slope propagation model is used in the analysis. A model of five microcells is used to calculate the uplink capacity and interference statistics assuming highways cigar-shaped microcells. The capacity and the interference statistics of the microcell are studied for different sector range, propagation exponent, antenna side lobe levels and different standard deviation of the power control error. It is noticed that the quasi-maximum uplink sector capacity can be got when the sector range R is between 600 and 1,200 m and the sidelobe level of the directive antenna used in each sector is on the order of ?15 dB.

Study of Isosceles Trapezoidal Edge Tapered Phased Array Antenna for Solar Power Station/Satellite

Minimizing the Side Lobe Level (SLL) and attain highest achievable Beam Collection Efficiency (BCE) is a critical goal for Solar Power Station/Satellite (SPS). If all antennas are uniformly excited then the main beam will carry only a part of the total energy due to the higher SLL. SLL is decreased and BCE is increased by adopting edge tapering for SPS. But edge tapering is a complex technical problem for SPS. So an optimization is needed between uniform amplitude distribution and edge tapering system. We have derived a new method of edge tapering called Isosceles Trapezoidal Distribution (ITD) edge tapering. Only a small number of antennas from each side of the phased array antenna are tapered in this method. ITD edge tapering is almost uniform so it is technically better. We have compared different amplitude distribution systems; uniform, Gaussian, Dolph-Chebyshev and the newly derived ITD method. The SLL reduction in ITD is even lower than those of other kinds of edge tapering. Therefore the amount of losing power in the SLL in ITD is lower. As a result the interference level becomes lower and BCE becomes higher in this method. The higher BCE and better SLL performance than those with uniform distribution can be achieved in ITD with phase error and under unit failed condition.

ICRF long-pulse discharge and interaction with a chamber wall and antennas in LHD

During long-pulse discharges by minority ion cyclotron range of frequencies (ICRF) heating (majority: He++ and minority: H+) in the large helical device (LHD), phenomena of hot spots on antenna side protectors, localized divertor plate temperature increase and sparks from inner side of torus were observed. Plasma duration time was limited by the gradual or sudden density increase. The gradual density increase was due to outgassing from the graphite divertor plates or antenna side protectors with hot spots. The spark resulted in sudden density increase. It is thought that the localized divertor plate temperature increase and sparks are attributed to the high-energy ions accelerated in front of ICRF antennas. By suppressing these phenomena the world largest input energy was achieved.

WCDMA Uplink Capacity and Interference Statistics of Highways Shaped Microcells with Imperfect Power Control and Finite Transmitted Power

The capacity and the interference statistics (mean and variance) of the sectors of a Cigar-, Tee-, and Cross-shaped WCDMA microcells are studied. Models of 5, 7, and 9 microcells are used to analyze the uplink capacity of the cigar-, Tee-, and cross-shaped W-CDMA microcell, respectively. The capacity and the interference statistics of the microcell are studied for different sector range and antenna side lobe levels. It is shown that the highest sector capacity is obtained when the microcell is cigar-shaped. For a cross-shaped microcell, the sector capacity is the lowest. Also it is shown that the uplink sector capacity will be very high if synchronous WCDMA is used in the uplink. To get the quasi maximum capacity, the sector range should be (0.6 --- 1) km and the side lobe level of the directive antenna used in each sector should be --- 15 dBc or lower.

Exploring with damaged antennae: do crayfish compensate for injuries?

Appendages are important sources of sensory information for all animals that possess them but they are commonly damaged in nature. We describe how the tactile system of the crayfish Cherax destructor functioned when subjected to the kind of damage found in wild-caught or cultured animals. Touch information was methodically varied by the removal of antennae and chelae. The resulting behaviour was analysed in a T-maze. Crayfish with a single antenna ablated turned toward the intact appendage, however, those with only a partial ablation did not, suggesting that a tactile information threshold exists for normal behaviour. When exposed to the same environment after an antennal ablation but with no prior experience in that terrain, crayfish also turned toward the side of the intact antenna. By contrast, when animals with experience obtained in a previous trial with intact antennae were tested after ablation of one antenna, they did not turn into one arm of the maze more than the other. These two outcomes indicate that behaviour is affected by an interaction between the time at which an injury occurs and an animal's knowledge of the topography, and that an injury may affect learning. We also tested to see if other appendages could provide tactile information to compensate for antennal loss. Input from the chelae did not affect the turning behaviour of crayfish in the maze.

W-CDMA Uplink Practical Capacity and Interference Statistics of Rural Highways Cigar-Shaped Microcells with Imperfect Power Control and Finite Transmitted Power

The capacity and the interference statistics of the sectors of the cigar-shaped W-CDMA microcell are studied. A model of 5 microcells is used to analyze the uplink. The microcells are assumed to exist in rural zones. The capacity and the interference statistics of the microcell are studied for different sector range, different antenna side lobe levels, different values of the break point distance, different values of the propagation parameter s 2 and different standard deviation of the power control error.

Sensory asymmetries in the olfactory system underlie sexual pheromone communication in the cockroach Nauphoeta cinerea

In most insect species, males process female sex pheromone information in specific macroglomeruli in the olfactory lobes of their brains. The purpose of this report is to present a novel system of pheromone perception. In Nauphoeta cinerea cockroaches, males produce sex pheromones that induce mating behavior in females but neither sex has macroglomeruli. In this study, we show that female N. cinerea show asymmetry in the number of glomeruli whereas males do not. Females have more glomeruli on the right side and amputation of the right antenna reduced female ability to find a male and mate whereas amputation of the left antenna did not. We show that a key factor in female mating behavior is perception of the male sex pheromone seducin by the right antenna and the asymmetrically organized deutocerebral glomeruli associated with it. In the symmetrical olfactory system of males the detection of seducin may be involved in establishing dominance hierarchies.

Ground clutter cancellation in incoherent radars: solutions for EISCAT Svalbard radar

Abstract. Incoherent scatter radars measure ionosphere parameters using modified Thomson scatter from free electrons in the target (see e.g. Hagfors, 1997). The integrated cross section of the ionospheric scatterers is extremely small and the measurements can easily be disturbed by signals returned by unwanted targets. Ground clutter signals, entering via the antenna side lobes, can render measurements at the nearest target ranges totally impossible. The EISCAT Svalbard Radar (ESR), which started measurements in 1996, suffers from severe ground clutter and the ionosphere cannot be measured in any simple manner at ranges less than about 120–150 km, depending on the modulation employed. If the target and clutter signals have different, and clearly identifiable, properties then, in principle, there are always ways to eliminate the clutter. In incoherent scatter measurements, differences in the coherence times of the wanted and unwanted signals can be used for clutter cancellation. The clutter cancellation must be applied to all modulations, usually alternating codes in modern experiments, used for shorter ranges. Excellent results have been obtained at the ESR using a simple pulse-to-pulse clutter subtraction method, but there are also other possibilities.Key words: Radio science (ionospheric physics; signal processing; instruments and techniques)