Philips

About: Philips is a company organization based out in Vantaa, Finland. It is known for research contribution in the topics: Signal & Layer (electronics). The organization has 68260 authors who have published 99663 publications receiving 1882329 citations. The organization is also known as: Koninklijke Philips Electronics N.V. & Royal Philips Electronics.

A 2.4-GHz 0.18-/spl mu/m CMOS self-biased cascode power amplifier

Abstract: A two-stage self-biased cascode power amplifier in 0.18-/spl mu/m CMOS process for Class-1 Bluetooth application is presented. The power amplifier provides 23-dBm output power with a power-added efficiency (PAE) of 42% at 2.4 GHz. It has a small signal gain of 38 dB and a large signal gain of 31 dB at saturation. This is the highest gain reported for a two-stage design in CMOS at the 0.8-2.4-GHz frequency range. A novel self-biasing and bootstrapping technique is presented that relaxes the restriction due to hot carrier degradation in power amplifiers and alleviates the need to use thick-oxide transistors that have poor RF performance compared with the standard transistors available in the same process. The power amplifier shows no performance degradation after ten days of continuous operation under maximum output power at 2.4-V supply. It is demonstrated that a sliding bias technique can be used to both significantly improve the PAE at mid-power range and linearize the power amplifier. By using the sliding bias technique, the PAE at 16 dBm is increased from 6% to 19%, and the gain variation over the entire power range is reduced from 7 to 0.6 dB.

Neurite dispersion: a new marker of multiple sclerosis spinal cord pathology?

Abstract: Objective Conventional magnetic resonance imaging (MRI) of the multiple sclerosis spinal cord is limited by low specificity regarding the underlying pathological processes, and new MRI metrics assessing microscopic damage are required. We aim to show for the first time that neurite orientation dispersion (i.e., variability in axon/dendrite orientations) is a new biomarker that uncovers previously undetected layers of complexity of multiple sclerosis spinal cord pathology. Also, we validate against histology a clinically viable MRI technique for dispersion measurement (neurite orientation dispersion and density imaging,NODDI), to demonstrate the strong potential of the new marker. Methods We related quantitative metrics from histology and MRI in four post mortem spinal cord specimens (two controls; two progressive multiple sclerosis cases). The samples were scanned at high field, obtaining maps of neurite density and orientation dispersion from NODDI and routine diffusion tensor imaging (DTI) indices. Histological procedures provided markers of astrocyte, microglia, myelin and neurofilament density, as well as neurite dispersion. Results We report from both NODDI and histology a trend toward lower neurite dispersion in demyelinated lesions, indicative of reduced neurite architecture complexity. Also, we provide unequivocal evidence that NODDI-derived dispersion matches its histological counterpart (P < 0.001), while DTI metrics are less specific and influenced by several biophysical substrates. Interpretation Neurite orientation dispersion detects a previously undescribed and potentially relevant layer of microstructural complexity of multiple sclerosis spinal cord pathology. Clinically feasible techniques such as NODDI may play a key role in clinical trial and practice settings, as they provide histologically meaningful dispersion indices.

Short distance attenuation measurements at 900 MHz and 1.8 GHz using low antenna heights for microcells

Abstract: Short-distance, low-antenna-height signal attenuation measurements are presented in connection with their use in the design of future microcell cellular radio networks. Measurements presented are based on the propagation along busy city streets in a direction radial to a fixed antenna site. Antenna heights between 5 m and 20 m were chosen for the fixed site, while 1.5 m was chosen for the mobile vehicle. The signal strength was then measured out to a distance of 1 km in a line-of-sight path from the fixed site at both 870.15 MHz and 1.8 GHz. The measurements show that extrapolation of the M. Hata (1980) and Y. Okumura et al. (1968) formulas into the low-antenna-height, short-distance area is not valid and can lead to inaccuracies. The results show that at short distances from the antenna the signal attenuation slope is very much less than that predicted by extrapolating the results of Hata and Okumura et al. >

Frequency-dependent electrical response of holes in poly(p- phenylene vinylene)

Abstract: Transport of holes in poly$(p$-phenylene vinylene) has been studied as a function of frequency, temperature, dc bias, and polymer thickness. For such a low mobility material we demonstrate that the specific frequency dependence of the response reflects the wide distribution in transit times of the injected carriers due to dispersive transport. The dc mobility is shown to correspond to the average of this dispersion and follows the empirical $\mathrm{ln}({\ensuremath{\mu}}_{\mathrm{dc}})\ensuremath{\propto}\sqrt{E}$ law.