Development of 2400-2450 MHz Frequency Band RF Energy Harvesting System for Low-Power Device Operation.

Recently, there has been an increasing fascination for employing radio frequency (RF) energy harvesting techniques to energize various low-power devices by harnessing the ambient RF energy in the surroundings. This work outlines a novel advancement in RF energy harvesting (RFEH) technology, intending to power portable gadgets with minimal operating power demands. A high-gain receiver microstrip patch antenna was designed and tested to capture ambient RF residue, operating at 2450 MHz. Similarly, a two-stage Dickson voltage booster was developed and employed with the RFEH to transform the received RF signals into useful DC voltage signals. Additionally, an LC series circuit was utilized to ensure impedance matching between the antenna and rectifier, facilitating the extraction of maximum power from the developed prototype. The findings indicate that the developed rectifier attained a peak power conversion efficiency (PCE) of 64% when operating at an input power level of 0 dBm. During experimentation, the voltage booster demonstrated its capability to rectify a minimum input AC signal of only 50 mV, yielding a corresponding 180 mV output DC signal. Moreover, the maximum power of 4.60 µW was achieved when subjected to an input AC signal of 1500 mV with a load resistance of 470 kΩ. Finally, the devised RFEH was also tested in an open environment, receiving signals from Wi-Fi modems positioned at varying distances for evaluation.

RF energy harvesters for wireless sensors, state of the art, future prospects and challenges: a review.

The power consumption of portable gadgets, implantable medical devices (IMDs) and wireless sensor nodes (WSNs) has reduced significantly with the ongoing progression in low-power electronics and the swift advancement in nano and microfabrication. Energy harvesting techniques that extract and convert ambient energy into electrical power have been favored to operate such low-power devices as an alternative to batteries. Due to the expanded availability of radio frequency (RF) energy residue in the surroundings, radio frequency energy harvesters (RFEHs) for low-power devices have garnered notable attention in recent times. This work establishes a review study of RFEHs developed for the utilization of low-power devices. From the modest single band to the complex multiband circuitry, the work reviews state of the art of required circuitry for RFEH that contains a receiving antenna, impedance matching circuit, and an AC-DC rectifier. Furthermore, the advantages and disadvantages associated with various circuit architectures are comprehensively discussed. Moreover, the reported receiving antenna, impedance matching circuit, and an AC-DC rectifier are also compared to draw conclusions towards their implementations in RFEHs for sensors and biomedical devices applications.

Sensitivity and spectrum of bacterial isolates in infectious otitis externa.

OBJECTIVE: To determine the spectrum and antibiotic sensitivity pattern of organisms from aural swabs taken from cases of infectious otitis externa. DESIGN: Descriptive study. PLACE AND DURATION OF STUDY: Department of ENT, Combined Military Hospital, Peshawar, from May 2002 to April 2003. SUBJECTS AND METHODS: One hundred and twenty-four patients, diagnosed clinically as infectious otitis externa without concomitant suppurative otitis media, perforated tympanic membrane or otomycosis, were selected for the study. Samples of pus from external auditory canal were taken on sterile cotton swabs and were cultured on blood agar and MacConkey Agar for 24 to 48 hours. Sensitivity was tested and interpreted by Kirby-Bauer disc diffusion method of grading zones of inhibition. RESULTS: One hundred and twenty four subjects were cultured. Sixteen samples showed no growth. One hundred and eight specimens yielded growth of bacteria. No specimen revealed multiple organisms. Staphylococcus aureus was found in 38%, and Pseudomonas aeruginosa was found in other 38%. Others included Proteus, Enterococci, Klebsiella, and E. coli. Majority of organisms were resistant to co-trimoxazole, amoxicillin and erythromycin, while 100% were sensitive to imipenem. Sensitivity to enoxacin was 96%, Ninety-two percent were sensitive to ciprofloxacin and ofloxacin. CONCLUSION: Pseudomonas aeruginosa and Staphylococcus aureus were the most common bacterial isolates. Both were sensitive to fluoroquinolones. The latter can be used empirically for treatment of acute infectious otitis externa.