Antenna Displacement Research Articles

Beam-steering of dielectric flat lens nanoantenna with elliptical patch based on antenna displacement for optical wireless applications

In this paper, the switched-beam nanoantenna (NA) concept is introduced with a theoretical design of an inhomogeneous dielectric flat lens modelled with different materials to steer and enhance the radiation in a particular direction based on shifting the illuminator element. Firstly, the design of hybrid plasmonic NA is introduced and analyzed considering different silicon patch shapes such as rectangular, circular, hexagonal, and elliptical shapes. The elliptical patch NA achieves a gain of up to 10.7 dBi and a return loss of − 14.41 dB. Then the design of a gradient-index dielectric flat lens with the NA is introduced to improve the antenna performance by increasing the directivity and consequently decreasing the beam-width. Furthermore, the beam-steering capabilities by displacement of the NA according to different feeding points along the X and Y-direction. By using the gradient-index dielectric flat lens, the gain is increased to 18.4 dBi with an improvement in the return loss reach to − 19.15 dB compared with traditional NA. In addition, the beam-steering capabilities were achieved with a range ± 60° × ± 55° with acceptable average antenna gain, side-lobe levels, and half power beam-width of 16.5 dBi, − 12.3 dB and 13.6° respectively.

Vivaldi Antennas for Contactless Sensing of Implant Deflections and Stiffness for Orthopaedic Applications.

The implementation of novel coaxial dipole antennas has been shown to be a satisfactory diagnostic platform for the prediction of orthopaedic bone fracture healing outcomes. These techniques require mechanical deflection of implanted metallic hardware (i.e., rods and plates), which, when loaded, produce measurable changes in the resonant frequency of the adjacent antenna. Despite promising initial results, the coiled coaxial antenna design is limited by large antenna sizes and nonlinearity in the resonant frequency data. The purpose of this study was to develop two Vivaldi antennas (a.k.a., “standard” and “miniaturized”) to address these challenges. Antenna behaviors were first computationally modeled prior to prototype fabrication. In subsequent benchtop tests, metallic plate segments were displaced from the prototype antennas via precision linear actuator while measuring resultant change in resonant frequency. Close agreement was observed between computational and benchtop results, where antennas were highly sensitive to small displacements of the metallic hardware, with sensitivity decreasing nonlinearly with increasing distance. Greater sensitivity was observed for the miniaturized design for both stainless steel and titanium implants. Additionally, these data demonstrated that by taking resonant frequency data during implant displacement and then again during antenna displacement from the same sample, via linear actuators, that “antenna calibration procedures” could be used to enable a clinically relevant quantification of fracture stiffness from the raw resonant frequency data. These improvements mitigate diagnostic challenges associated with nonlinear resonant frequency response seen in previous antenna designs.

Transverse Kerker Scattering for Angstrom Localization of Nanoparticles.

Angstrom precision localization of a single nanoantenna is a crucial step towards advanced nanometrology, medicine, and biophysics. Here, we show that single nanoantenna displacements down to few angstroms can be resolved with sub-angstrom precision using an all-optical method. We utilize the tranverse Kerker scattering scheme where a carefully structured light beam excites a combination of multipolar modes inside a dielectric nanoantenna, which then, upon interference, scatters directionally into the far field. We spectrally tune our scheme such that it is most sensitive to the change in directional scattering per nanoantenna displacement. Finally, we experimentally show that antenna displacement down to 3Å is resolvable with a localization precision of 0.6Å.

Mitigation of Antenna Displacement with Array Antenna for Data Transmission in Wireless Power Transfer System

Magnetic resonance wireless power transfer is expected to be one of the prevalent schemes because of its high efficiency and long transmission range. However, in this scheme, there is a problem that the characteristics of a transmission channel changes in according with the distance between coil antennas. This paper investigates the performance of data transmission with an array antenna in a wireless power transfer system. In the assumed system, the same antennas for wireless power transfer are used for data transmission. The assumed system uses multiple transmit antennas and beamforming is realized by shifting the phases of signals in a transmitter. Numerical results obtained through computer simulation show that the proposed scheme can mitigate the dependently of a bit error rate (BER) to the distance between the antenna coils. The variation of the performance is suppressed within 1–3 dB at the BER of $$10^{-5}$$ in the case of two transmit antennas. In addition, the system with two transmit antennas achieves 2 dB or more improvement in term of the BER performance than that with a single antenna at specific antenna distances.

Challenges in Assessing PPP Performance

AbstractThe Precise Point Positioning (PPP) GPS data processing technique has developed over the past 15 years to become a standard method for growing categories of positioning and navigation applications. The technique relies on single receiver point positioning combined with precise satellite orbit and clock information, pseudorange and carrier-phase observable filtering, and additional error modelling. Uniquely addressed is the current accuracy of the technique, and explains the limits of performance, which will be used to define paths for future improvements of the technology.PPP processing of over 300 International GNSS Service (IGS) stations over one week results in few millimetre positioning rms error in the north and east components and centimetre-level in the vertical (all one sigma values). These results are categorised into quality classes in order to analyse the root causes of the resultant errors: "best", "worst", multipath, antenna displacement effects, satellite availability and geometry, etc. Also of interest in PPP performance is solution convergence period. Static, conventional solutions are slow to converge, with approximately 20 minutes required for 95% of solutions to reach a horizontal accuracy of 20 cm or better.From the above analysis, the limitations of PPP and the source of these limitations are isolated, including site displacement modelling, geometric measurement strength, pseudorange multipath and noise, etc. It is argued that new ambiguity resolution and multi-GNSS PPP processing will only partially address these limitations. Improved modelling is required for: site displacement effects, pseudorange noise and multipath, and pseudorange and carrier-phase biases. As well, more robust undifferenced carrier phase ambiguity validation and improved stochastic modelling is required for the pseudorange and carrier-phase observables to allow for more realistic position uncertainties.

Frequency Structures Vibration Identified by an Adaptative Filtering Techiques Applied on GPS L1 Signal

This paper is part of a research under enhancement since 2001, in which the main objective is to measure small dynamic displacements by analysis of L1 GPS carrier frequency with 1575.42 MHz—wavelength 19.05 cm, under an adaptive method for collecting data and filtering techniques. This method, named Phase Residual Method (PRM) is based on the frequency domain analysis of the phase residuals resulted from the L1 double difference static data processing of two satellites in almost orthogonal elevation angle. In this work it is proposed to obtain the phase residuals directly from the raw phase observable collected in a short baseline during a limited time span, in lieu of obtaining the residual data file from regular GPS processing programs. In order to improve the ability to detect millimetric displacements, two filtering techniques are introduced. The first one is the autocorrelation that reduces the phase noise with random time behavior. The other one is the running mean to separate low frequency from the high frequency phase sources. Two trials are presented to verify the proposed method and filtering techniques applied. One simulates a 2.5 millimeter vertical GPS antenna displacement and the second using the data collected during a bridge dynamic load test. The results show a good consistency to detect millimetric oscillations from L1 frequency and filtering techniques.

Simulations Of Air Flow Over A Parabolic Antenna

Abstract In this paper it is present the influence of the wind on a parabolic antenna, in order to study this influence it was made simulations of air flow over a parabolic antenna. The simulations are made with antenna positioned at 90°, 135°. A three – dimensional finite element is simulated for determination of the antenna displacement.

Remote Sensing of Vital Signs Using a Doppler Radar and Diversity to Overcome Null Detection

Vital signs detection by means of several topologies based on Doppler radar are proposed in this paper with the aim of overcoming the problem of null detection. They are based on phase and frequency diversity. The proposed topologies are an alternative to I/Q demodulation and double-sideband transmission. Four topologies are proposed, three of them based on phase diversity and one based on frequency diversity. The first topology is based on using two phase-shifted receivers. The second one is based on a physical antenna displacement between two receivers. A third system with a dynamic phase variation is also presented, which permits to work with only one receiver. The last topology is a radar with frequency diversity within the 2.4 GHz ISM band, which permits a dynamic change of the frequency dynamically in order to place the receiver always in a maximum. A system to empirically characterize nulls is also developed to validate the proposed topologies.

Spatial Characterization of GNSS Multipath Channels

There is a growing interest in detecting and processing Global Navigation Satellite System (GNSS) signals in indoors and urban canyons by handheld devices. To overcome the signal attenuation problem in such adverse fading environments, long coherent integration is normally used. Moving the antenna arbitrarily while collecting signals is generally avoided as it temporally decorrelates the signals and limits the coherent integration gain. This decorrelation is a function of the antenna displacement and geometry of reflectors and angle of arrival of the received signal. Hence, to have an optimum receiver processing strategy it is crucial to characterize the multipath fading channel parameters. Herein, Angle of Arrival (AoA) and Angle Spread (AS) along with signal spatial correlation coefficient and fading intensity in GNSS multipath indoor channels are defined and quantified theoretically and practically. A synthetic uniform circular array utilizing a right-hand circular polarized (RHCP) antenna has been used to measure the spatial characteristics of indoor GNSS fading channels. Furthermore, rotating effect of a circular polarized antenna on the synthetic array processing and AoA estimation has been characterized. The performance of the beamforming technique via array gain is also assessed to explore the advantages and limitations of beamforming in fading conditions.

Use of a Single L1 GPS Receiver for Monitoring Structures: First Results of the Detection of Millimetric Dynamic Oscillations

AbstractThis paper presents preliminary results to determine small displacements of a global positioning system (GPS) antenna fastened to a structure using only one L1 GPS receiver. Vibrations, periodic or not, are common in large structures, such as bridges, footbridges, tall buildings, and towers under dynamic loads. The behavior in time and frequency leads to structural analysis studies. The hypothesis of this article is that any large structure that presents vibrations in the centimeter-to-millimeter range can be monitored by phase measurements of a single L1 receiver with a high data rate, as long as the direction of the displacement is pointing to a particular satellite. Within this scenario, the carrier phase will be modulated by antenna displacement. During a period of a few dozen seconds, the relative displacement to the satellite, the satellite clock, and the atmospheric phase delays can be assumed as a polynomial time function. The residuals from a polynomial adjustment contain the phase modula...

FILTERING TECHNIQUES APPLIED ON RAW CARRIER PHASE FOR GPS DETECTING SMALL DYNAMIC DISPLACEMENTS

This work is part of a research under construction since 2000, in which the main objective is to measure small dynamic displacements by using L1 GPS receivers. A very sensible way to detect millimetric periodic displacements is based on the Phase Residual Method (PRM). This method is based on the frequency domain analysis of the phase residuals resulted from the L1 double difference static data processing of two satellites in almost orthogonal elevation angle. In this article, it is proposed to obtain the phase residuals directly from the raw phase observable collected in a short baseline during a limited time span, in lieu of obtaining the residual data file from regular GPS processing programs which not always allow the choice of the aimed satellites. In order to improve the ability to detect millimetric oscillations, two filtering techniques are introduced. One is auto-correlation which reduces the phase noise with random time behavior. The other is the running mean to separate low frequency from the high frequency phase sources. Two trials have been carried out to verify the proposed method and filtering techniques. One simulates a 2.5 millimeter vertical antenna displacement and the second uses the GPS data collected during a bridge load test. The results have shown a good consistency to detect millimetric oscillations.

The Experimental Characterization of UWB Antennas via Frequency-Domain Measurements

Experimental characterization of UWB antennas can in many cases be performed using traditional frequency-domain antenna measurements, combined with careful application of well-known integral-transform and linear time-invariant (LTI) system techniques. In this paper, UWB antenna descriptors, including impulse response, energy gain, correlated energy gain, and correlation coefficient, are determined from frequency-domain measurements of transfer functions. Results are presented for two representative UWB antennas: a double-ridged (DR) horn, and a 120deg biconical antenna (Figure 1). The fundamental quantity is taken as the antenna transfer function, which is measured using a modified three-antenna method. One critical step is to extract the free-space component of the port-to-port transfer function, which, in turn, requires careful attention to definition and measurement of the distance. After the transfer function is obtained, standard linear system techniques can be freely applied. The transfer-function measurement technique involves redundant information due to (a) the use of the three-antenna method with identical antennas, and (b) the use of complex data from a vector network analyzer. This redundancy can be exploited to check consistency and repeatability, by comparing the measured phase with Hilbert-transformed data, as well as by comparing the three estimates with each other. The extracted linear phase is a highly sensitive indicator of antenna displacement, and defines a unique distance for any given pair of antennas in a given orientation. In the three-antenna case with identical antennas, the result is a unique reference plane for the antenna that is not tied to a particular frequency.

Source Stirring Mode for Reverberation Chambers

The paper investigates the possibility of reverberating a shielded room by means of source mode stirring. The transmitting antenna position and orientation are randomly changed inside a sub-volume of the chamber. In general, antenna displacement can be achieved by a proper design of an array of antennas, where one or more antennas are activated at different time instants. This technique eliminates mechanical rotating paddles inside the chamber, and offers the advantage of a continuous wave (CW) operation with respect to the frequency stirring method. The preliminary experimental and simulated results encourage further investigation of the proposed technique.

Basic design and construction of the Vienna FES implants: existing solutions and prospects for new generations of implants

We can distinguish 3 generations of FES implants for activation of neural structures: 1. RF-powered implants with antenna displacement dependent stimulation amplitude; 2. RF-powered implants with stabilised stimulation amplitude; and 3. battery powered implants. In Vienna an 8-channel version of the second generation type has been applied clinically to mobilisation of paraplegics and phrenic pacing. A 20-channel implant of the second generation type for mobilisation of paraplegics and an 8-channel implant of the third generation type for cardiac assist have been tested in animal studies. A device of completely new design for direct stimulation of denervated muscles is being tested in animal studies. There is a limited choice of technologically suitable biocompatible and bioresistant materials for implants. The physical design has to be anatomically shaped without corners or edges. Electrical conductors carrying direct current (D.C.) have to be placed inside a hermetic metal case. The established sealing materials, silicone rubber and epoxy resin, do not provide hermeticity and should only embed DC-free components. For electrical connections outside the hermetic metal case welding is preferable to soldering; conductive adhesives should be avoided. It is advisable to use a hydrophobic oxide ceramic core for telemetry antenna coils embedded in sealing polymer. Cleaning of all components before sealing in resin is of the utmost importance as well as avoidance of rapid temperature changes during the curing process.

Power focusing characteristics of ellipsoidal reflector

Power focusing characteristics of a prolate spheroidal reflector, the aperture of which is parallel to the line connecting the two focuses, are numerically studied. As a transmitting and a receiving antenna, linear wires with finite length are placed at or near the focuses of the reflector. Reflected near fields from the reflector are calculated by the physical optics technique, and transmitting and receiving antenna characteristics are obtained by the method of moments. Calculated results are given for the power focusing characteristics as a function of the eccentricity, the aperture size of the reflector, antenna directions, antenna lengths, and the receiving antenna displacement. Better power focusing characteristics are obtained when the transmitting antenna becomes less directive, or the size of the aperture becomes larger. Measured and calculated results agree very well.