Nazifa Tahir

Toward the Development of Millimeter Wave Harmonic Sensors for Tracking Small Insects

Entomologists need to observe and monitor insects in their natural habitats for various reasons. One of the most common techniques in use today is to attach low-cost harmonic sensor or transponder to insects and to track them using an associated harmonic radar. Existing harmonic transponders based on monopoles, loop-dipoles, and Minkowski loops have been successfully attached to small low-flying insects. However, they offer significant constraints from a mounting perspective, weight and size considerations, aerodynamic drag, and the elevation of the insect center of gravity. This paper addresses these issues by presenting novel design methodologies for millimeter wave harmonic sensors and radar. The sensors address the challenges of ease of design and fabrication, robustness, conversion efficiency, miniaturization, antenna entangling, and attachment problems that are generally encountered with other transponders.

A novel approach of feeding, impedance matching and frequency tuning of microstrip patch antenna by single microstrip line

Microstrip patch antennas with transmission line feed are widely being used in developing harmonic transponders. The paper presents a novel technique of using a single microstrip line for feeding, impedance matching and frequency tuning of patch antenna instead of using separate transmission line and stubs. The impedance matching and frequency tuning is carried out by varying the width and length of the feed respectively. The paper validates the technique both by simulation and experimentally developing 10.6 GHz circularly polarized patch antenna.

Millimeter wave band waveguide-to-probe transition for planar harmonic tag antennas

The paper presents a waveguide-to-probe transition for testing millimeter wave band planar harmonic tag antennas. It discusses in detail the design and the tuning approach for developing the waveguide transition. The transition limits the radiation leakage and is easy to fabricate. However, it is narrow band and could not be used for testing multiple antennas simultaneously. The working of the transition is validated by measuring the return losses of 77 GHz planar harmonic antenna which are in good agreement with the simulated results.

Investigation of effects of coax-to-microstrip transition on planar harmonic tag antennas

The paper investigates the effects of using coax-to-microstrip line transition with different mounting techniques and coaxial line terminals for measuring the characteristics of microstrip antenna. The investigations reveal that the antenna return losses and magnitude of characteristic impedance are least effected by vertically mounted tab terminal coaxial line. However, all the coaxial lines shift the phase of the characteristic impedance which requires phase correction.

Conservative data fusion for decentralized networks

The paper investigates a technique for computing conservative data fusion for gaussian mixture model (GMM) in decentralized networks with any topology. The main advantage of conservative solutions is that they do not deteriorate the performance of a sensor network in presence of any kind of correlations. The paper exploits normalize geometric mean for computing conservative data fusion. It computes normalized geometric mean by Newton generalized binomial theorem and Monte Carlo technique. It is shown that the solution by Newtons generalized binomial theorem exhibits divergence and numerical instability. On the other hand, Monte Carlo technique offers conservative solution. The tradeoffs are that it requires considerable computational time and is expensive as large numbers of samples are required to get statistical accuracy.