Nuri W. Emanetoglu

Electrically conductive nano graphite-filled bacterial cellulose composites

A unique three dimensional (3D) porous structured bacterial cellulose (BC) can act as a supporting material to deposit the nanofillers in order to create advanced BC-based functional nanomaterials for various technological applications. In this study, novel nanocomposites comprised of BC with exfoliated graphite nanoplatelets (xGnP) incorporated into the BC matrix were prepared using a simple particle impregnation strategy to enhance the thermal properties and electrical conductivity of the BC. The flake-shaped xGnP particles were well dispersed and formed a continuous network throughout the BC matrix. The temperature at 10% weight loss, thermal stability and residual ash content of the nanocomposites increased at higher xGnP loadings. The electrical conductivity of the composites increased with increasing xGnP loading (attaining values 0.75 S/cm with the addition of 2 wt.% of xGnP). The enhanced conductive and thermal properties of the BC-xGnP nanocomposites will broaden applications (biosensors, tissue engineering, etc.) of BC and xGnP.

A low-cost harmonic radar for tracking very small tagged amphibians

A low-cost, hand-held harmonic radar is described for tracking tagged amphibians weighting less than a gram during a cryptic period of their life history. The radar is based on inexpensive, commercial 5.8 GHz wireless communications and 11.6 GHz satellite television technology. The performance of the system was accurately predicted from laboratory measurements by defining an appropriate harmonic tag conversion efficiency. The harmonic radar has a demonstrated maximum tag detection range of 20 ft. The best performance was achieved with an asymmetric, dielectric sleeved dipole with a 1:2 arm length ratio.

A wideband harmonic radar for tracking small wood frogs

A wideband harmonic radar for tracking very small wood frogs in a high clutter environment is described. The one watt peak power radar transmitted in the 5.8 GHz ISM band and received in the 12 GHz satellite TV band. By transmitting a 150 MHz bandwidth linear frequency modulated waveform and exploiting the frequency doubling property of the harmonic tag to increase the bandwidth to 300 MHz, a range resolution of 1.6 feet was demonstrated. Furthermore, by resolving transmitter leakage and multipath, and by coherently integrating the tag return, the wideband harmonic radar sensitivity was improved by 20 dB over a comparable CW harmonic radar.

An asymmetrical dipole tag with optimum harmonic conversion efficiency

Extremely small passive dipole tags have been used for tracking insects with a harmonic radar. It will be shown that by adjusting the dipole feed point location, the conversion efficiency, and hence the maximum detection range, can be optimized. Analysis, simulations and measurements on X-band tags confirm that the best tag efficiency is achieved with a half-wavelength dipole and asymmetric 1:2 dipole arm lengths.

A 5.8 GHz harmonic RF tag for tracking amphibians

The proposed printed circuit harmonic RF dipole tag on a ground plane with an appropriate impedance matching technique offer better sensitivity at low excitation levels when compared to a more conventional wire harmonic dipole tag. By exploiting existing Wi-Fi and satellite TV technology, it should be possible to build a capable, low cost harmonic radar.

A 250-Mb/s Data Rate IR-UWB Transmitter Using Current-Reused Technique

This paper describes the design, simulation, implementation and testing of an impulse-radio ultra-wideband bi-phase shift keying (IR-UWB BPSK) transmitter, working in the frequency range between 3.5 and 6.5 GHz. The transmitter has been optimized to achieve the maximum distance of transmission while working within the power limits specified by the Federal Communications Commission (FCC). In this transmitter, the IR-UWB signal is generated by differentiating a Gaussian signal and then amplifying the differentiated signal. This is accomplished using a current-reused power amplifier circuit as both the differentiator and amplifier. A theoretical analysis is performed to obtain the relationship between the output amplitude and the data rate of the transmitted signal. The simulations and experimental results of the IR-UWB BPSK transmitter, implemented in a 180-nm CMOS process, are then presented. The transmitter was found to function at data rates up to 250 Mb/s with a maximum peak amplitude of 0.5 V. The dc energy consumption of the transmitter is 86 pJ/pulse. The energy efficiency is 26.2% for the pulsewidth of 1 ns. The experimental results show that power spectral density of the transmitter agrees with the simulated results and is within the FCC limits. The total core area of the chip is 0.22 mm2.

The radar microphone: A new way of monitoring honey bee sounds

This paper describes a radar microphone for studying incidental and deliberate insect sounds. It was specifically designed to record the sounds coming from honey bees inside a beehive. The sensor is based on a Doppler radar measuring the vibrations of a high dielectric object, such as a bee. It is shown that if the vibrational amplitude is much less that the radar wavelength, the frequency of the mechanical vibration and the frequency of the phase modulation in the reflected radar signal are the same. The instrument was implemented safely and inexpensively with readily available 5.8 GHz wireless components. The output of the radar microphone is a signal no different from the signal that might be recorded with an acoustic microphone. As such the same data collection and processing techniques can be applied. Examples are given of vibrations and airborne sounds from bees inside an observation hive.

A constant beamwidth reflector antenna for a harmonic radar operating in the near-field

A dual-frequency constant beamwidth reflector antenna for use with a harmonic radar in the focused near-field is proposed. The technique matches reflector defocusing effects to the frequency dependent phase center displacement of a log-period dipole antenna feed by specifying the LPDA apex angle. The technique was verified by simulations and measurements.

Effect of axial rotation on mutual coupling between helical antennas in a doppler radar

Some amount of mutual coupling between the transmit and receive antennas is required for proper operation of a logarithmic square-law detector in a Doppler radar. The radar performance is shown to be optimized when the mutual coupling magnitude is reduced to equal the magnitude of the target return. If the transmit and receive antennas are same-sense axial mode helical antennas, the mutual coupling reduction can be accomplished by a mechanical rotation of one of the antennas about its axis. This result is verified by electromagnetic simulations and by measurements with a 5.8 GHz Doppler radar and a mechanical honeybee radar cross-section simulator.

Comparison of a small parabolic reflector for use with an acoustic and a radar microphone

The gain, beamwidth and frequency response of a small, portable parabolic reflector used in an acoustic microphone and in a radar microphone are compared. These microphones are intended for remotely monitoring the 170-250 Hz buzz of honey bees. The RF microphone is based on a Doppler radar operating in the 5.8 GHz ISM band. It detects mechanical vibrations rather than sound. The gain and beamwidth of a reflector with an audio microphone is very good at high audio frequencies, however it is very poor at low frequencies. By contrast, when properly tuned, the performance of the same parabolic reflector with a radar microphone excels at a 200 Hz audio frequency.