Edip Niver

Fabry-Perot diaphragm fiber-optic sensor

The general theory of a diaphragm fiber-optic sensor (DFOS) is proposed. We use a critical test to determine if a DFOS is based on Fabry-Perot interference or intensity modulation. By use of the critical test, this is the first design, to the best of our knowledge, of a purely Fabry-Perot DFOS, fabricated with microelectromechanical system technology, and characterized as an audible microphone and ultrasonic hydrophone with orders of improvement in signal-to-noise ratio.

Microwave Bessel Beams Generation Using Guided Modes

A novel method is devised for Bessel beams generation in the microwave regime. The beam is decomposed in terms of a number of guided transverse electric modes of a metallic waveguide. Modal expansion coefficients are computed from the modal power orthogonality relation. Excitation is achieved by means of a number of inserted coaxial loop antennas, whose currents are calculated from the excitation coefficients of the guided modes. The efficiency of the method is evaluated and its feasibility is discussed. Obtained results can be utilized to practically realize microwave Bessel beam launchers.

A theoretical model for radio signal attenuation inside buildings

A theoretical model is proposed for predicting path loss inside buildings. The theory involves a waveguide model of the indoor environment which permits a rigorous modal solution similar to that developed by Mahmoud and Wait (1974) for propagation in tunnels. Comparisons of the theory with the measurements made by Arnold, Murray and Cox (1989) at the AT&T Laboratories building in Crawford Hill, NJ, show general agreement. >

Evaluation of the TRANSCOM's system for managing incidents and traffic (TRANSMIT)

TRANSCOMs system for managing incidents and traffic (TRANSMIT) is a traffic surveillance and incident detection system that is based on traffic probes equipped with the E-ZPass electronic toll collection tags. The evaluation has been carried out to assess its communication system performance, its incident detection capability, and the traffic-flow parameters estimation, and to identify its current and potential benefits. The TRANSMIT communication system exhibited excellent performance in terms of the transmission rates system wide. The TRANSMIT incident detection algorithm performed very favorably in comparison to the results of the best incident detection algorithms reported in the literature. The link travel time estimates were found to be within the 95% confidence interval. The system offers a unique opportunity for researchers to collect travel-time data in real time, and direct measurements of the space mean speed, as well as incident detection related data.

Transportation Operations Coordinating committee system for managing incidents and traffic : Evaluation of the incident detection System

The Transportation Operations Coordinating Committee’s System for Managing Incidents and Traffic (TRANSMIT) is an operational test that uses vehicles equipped with tags of the E-ZPass electronic toll collection system as traffic probes for traffic surveillance and incident detection. The TRANSMIT incident detection algorithm is based on statistical comparison of real-time estimates of travel times with continuously updated historical travel times for the same time period of the day and type of day (weekday, Saturday, Sunday, or holiday). The probability of detecting an incident and the false-alarm rates produced by TRANSMIT during a 4-month evaluation period (January to April 1996) may be considered excellent for the data collected on the New York State Thruway and satisfactory for the data collected on the Garden State Parkway. The mean time to detection of an incident was not estimated at this stage of the evaluation. The TRANSMIT communication system exhibited excellent performance in terms of the transmission rates systemwide, which were found to be near 100 percent. Only the radio link at Tappan Zee Bridge exhibited a lower transmission rate. A limited probe vehicle test was conducted to determine the detection rate at individual roadside terminals. The lower detection rates observed were site specific rather than systemwide. The performance of the TRANSMIT incident detection algorithm performed very favorably compared with the performances of the best incident detection algorithms reported in the literature.

Center embossed diaphragm design guidelines and Fabry-Perot diaphragm fiber optic sensor

This research established the design guidelines for center embossed diaphragms for micro-diaphragm fiber type sensors. Following the guidelines, a center embossed diaphragm fiber optic sensor (CE-DFOS) based on Fabry-Perot interference was designed and fabricated with micro-electro-mechanical system (MEMS) technology. The CE-DFOS was experimentally verified to have the designed intrinsic frequency, and demonstrated high sensitivity in parallel testing with a piezoelectric (PZT) sensor.

Morphological Operators for Polarimetric Anomaly Detection

We introduce an algorithm of morphological filters and propose its use to classic polarization metrics for applications requiring passive longwave-infrared, polarimetric remote sensing and real-time anomaly detection. The approach significantly augments the daytime and nighttime detectability of weak-signal manmade objects immersed in a predominant natural background scene. A tailored sequence of signal-enhancing filters is featured, consisting of basic and higher level morphological operators to achieve a desired goal. Qualitatively, the goal is to effectively squeeze the variance of pixel values representing the natural clutter background, while simultaneously spreading the pixel variance within the manmade object class and separating the pixel mean averages between the two classes of objects. Using real data, the approach persistently detected with a high confidence level three mobile military howitzer surrogates (targets) from natural clutter, during a 72-h coverage. Targets were posed at three aspect angles (range 557 m), yielding a negligible false alarm rate. Performance was invariant to diurnal cycle and mild atmospheric changes.

Broadband circularly polarized antennas for UHF SATCOM

Novel circularly polarized (CP) antenna configurations derived from Moxon type antenna (bent dipole element over a ground plane) for broadband UHF SATCOM applications. A sequence of topologies starting from a single vertical element to two vertical elements of the Moxon arms, then widened strip arm elements were studied. Further, arms were widened to bowtie structures with bents at 90°. for achieving broadband operation. Bowtie elements were further split and optimized at a certain angle to achieve wider bandwidth. The logic in this evolution was to obtain highest possible gain based on Fano-Chu limits, which suggests that higher gain can be achieved in an electrically small antenna with maximized metallization in the structure that fill the volume. Circular polarization is obtained by two Moxon based cross elements that are fed through a hybrid 90° quadrature coupler. For the antennas that are prototyped, return loss S11 measurements were performed, and gains are simulated using HFSS. For the band of 225–400 MHz, antenna gain varies between 8–12 dB, and S11 is measured to be below 10 dB. Fabricated antennas coupled to a hybrid coupler yielded excellent bandwidths, low cross-polarization and low back lobes on the finite ground planes.

Frequency characterization of a thin linear antenna using diakoptic antenna theory

A frequency-dependent analytical expression for the input impedance of a thin wire antenna is obtained using diakoptic theory. The linear antenna is diakopted into electrically short segments, where each is treated as a component with two terminals (except for end pieces, which have only one terminal). An impedance matrix is found which characterizes coupling between all segments. By expanding the free-space Greens function in a power series in wavenumber k, each entry in the resultant impedance matrix is obtained as an explicit function of frequency. The input admittance is found as a ratio of two polynomials in wavenumber k. A more systematic approach for the solution of the input admittance is achieved by expanding both the unknown current vector and the Greens function in power series in k. Equating coefficients of like powers in k leads to a numerically efficient algorithm which is used to determine the input admittance as a function of frequency. Numerical results compare well with the input impedance obtained from a conventional integral equation solution. >

A conceptual framework for intelligent monitoring systems

This paper discusses the conceptual development of a continuously monitored intelligent system for underground infrastructure. The proposed sensors are based on advanced coupling and refinement of several technologies: electrically conducting composite pipe (ECCP), electrochemical impedance spectroscopy (EIS) and time domain reflectometry (TDR). A significant benefit gleaned from the combination of these technologies is that the resulting system may be used on non-metallic, as well as, metallic pipes. In addition, the synergism of the technologies obtains the maximum information regarding defect location and characterization. The monitoring signal, waveguides, and damage sensor are also discussed, as well as, the data fusion, dynamic modeling and simulation requirements for the intelligent monitoring system.