Motorola

About: Motorola is a company organization based out in Schaumburg, Illinois, United States. It is known for research contribution in the topics: Signal & Communications system. The organization has 27298 authors who have published 38274 publications receiving 968710 citations. The organization is also known as: Motorola, Inc. & Galvin Manufacturing Corporation.

Microwave Effects on the Nervous System

Abstract: Studies have evaluated the electroencephalography (EEG) of humans and laboratory animals during and after Radiofrequency (RF) exposures. Effects of RF exposure on the blood-brain barrier (BBB) have been generally accepted for exposures that are thermalizing. Low level exposures that report alterations of the BBB remain controversial. Exposure to high levels of RF energy can damage the structure and function of the nervous system. Much research has focused on the neurochemistry of the brain and the reported effects of RF exposure. Research with isolated brain tissue has provided new results that do not seem to rely on thermal mechanisms. Studies of individuals who are reported to be sensitive to electric and magnetic fields are discussed. In this review of the literature, it is difficult to draw conclusions concerning hazards to human health. The many exposure parameters such as frequency, orientation, modulation, power density, and duration of exposure make direct comparison of many experiments difficult. At high exposure power densities, thermal effects are prevalent and can lead to adverse consequences. At lower levels of exposure biological effects may still occur but thermal mechanisms are not ruled out. It is concluded that the diverse methods and experimental designs as well as lack of replication of many seemingly important studies prevents formation of definite conclusions concerning hazardous nervous system health effects from RF exposure. The only firm conclusion that may be drawn is the potential for hazardous thermal consequences of high power RF exposure.

MMSE analysis of certain large isometric random precoded systems

Abstract: Linear precoding consists in multiplying by an N/spl times/K matrix a K-dimensional vector obtained by serial-to-parallel conversion of a symbol sequence to be transmitted. In this paper, new tools, borrowed from the so-called free probability theory, are introduced for the purpose of analyzing the performance of minimum mean-square error (MMSE) receivers for certain large random isometric precoded systems on fading channels. The isometric condition represents the case of precoding matrices with orthonormal columns. It is shown in this contribution that the signal-to-interference-plus-noise ratio (SINR) at the equalizer output converges almost surely to a deterministic value depending on the probability distribution of the channel coefficients when N/spl rarr/+/spl infin/ and K/N/spl rarr//spl alpha//spl les/1. These asymptotic results are used to analyze the impact of orthogonal spreading as well as to optimally balance the redundancy introduced between linear precoding versus classical convolutional coding, while preserving a simple MMSE equalization scheme at the receiver.

Cyclic-prefix CDMA: an improved transmission method for broadband DS-CDMA cellular systems

Abstract: This paper describes a novel type of single-carrier DS-CDMA system that combines the use of OFDM-style cyclic prefixes with frequency-domain equalization, for use on the forward link of broadband CDMA cellular systems. The proposed method is referred to as CP-CDMA. The combination of cyclic prefixes and MMSE frequency-domain equalization solves many of the performance and complexity problems that arise in CDMA receivers when techniques such as multi-level modulation and full code usage are employed. Simulation results are presented for a 20 MHz system with multi-level modulation and these results are compared to the performance of a conventional CDMA system with either a RAKE receiver or a time-domain equalizer. Results indicate that CP-CDMA provides significantly improved performance, yet has lower complexity than the time-domain equalized system.

Maximum power tracker

Abstract: A buck regulator or impedance converter is disclosed for operating a current limited power supply such as a photovoltaic array at or near its maximum power point. The maximum power point for such a supply is achieved at the compliance voltage which is an almost constant voltage. Means are provided for sensing the voltage at the input of the regulator and for using this sensed voltage to control a logic circuit which, in turn, controls the duty cycle of a switching transistor. The output from the switching transistor is coupled to an LC filter and from there to the load. The logic circuitry, responsive to the sensed voltage, controls the duty cycle of the switching transistor in such a manner as to maintain the input voltage approximately constant and thus to maintain the power supply at or near its peak power operating point.

Handwritten character recognition using multi-resolution models

Abstract: A storage medium ( 72 ) having stored thereon a set of instructions, which when loaded into a microprocessor ( 74 ), causes the microprocessor ( 74 ) to extract strokes from a plurality of characters ( 76 ), derive a pre-defined number of stroke models based on the strokes extracted from the plurality of character ( 78 ) and represent the plurality of characters as sequences of stroke models ( 80 ).