Digital signal

About: Digital signal is a research topic. Over the lifetime, 44213 publications have been published within this topic receiving 345279 citations.

Bootstrap method for writing servo tracks on a disk drive

Abstract: A method for defining and writing parallel and concentric magnetic signal tracks to a spinning disk surface of a magnetic data storage disk drive system using the components of the Head Disk Assembly (HDA) implemented by an appropriately programmed digital signal central processing unit (CPU) or micro code in an integrated circuit (IC) and a digital signal random access memory RAM is described wherein an initial magnetic signal track is written under least (minimum) energy equilibrium conditions with undulating boundaries and a meandering center line relative to axes of the spinning disk surface for one revolution of the surface. Then servoing to an edge of the just written track, a digitized position signal table is created in memory for storing digital position signals representing the amplitude of the signals read from n sampling points per disk revolution over a number of disk revolutions, where n is determined with reference to `Nyquist criteria`. A comparison/demand signal is derived by the CPU for input to the serve controller for each sampling point by first obtaining a target position signal comprising an average of the digitized position signals stored in the memory table and the just read digitized signal for that sampling point and by then comparing that target position signal to the just read digitizing position signals. The resulting current command signal energizing the actuator is normalized, and variation therein thereafter clamped in steps to bring the slider head to a quiet, least energy equilibrium or coast status relative to the spinning disk surface. A second memory table is generated and stores coast digital position signals for the n sampling points for a plurality of coast or least energy disk revolutions. Servo position then is initiated using averaged values in the second memory table such that any position error signal command to the actuator is a response to random noise or forces. Then preserving the least energy equilibrium state to the extent possible, a subsequent track of servo burst pattern is written onto and around the disk and the procedure repeated referencing the edge of the newly written track. A fiducial track concentric with the axes of the spinning disk is defined by each two iterations of the procedure after writing of the initial track. In this manner track densities in excess of 10,000 tracks per inch (track pitches<100 μin.) can be reliably achieved.

Spread spectrum adaptive power control communications system and method

Abstract: A system and method for adaptive-power control of a spread-spectrum transmitter of a mobile station operating in a cellular-communications network using spread-spectrum modulation. A mobile station transmits a first spread-spectrum signal. A base station has an automatic-gain-control circuit for generating an AGC-output signal, from a received signal. The received signal includes the first spread-spectrum signal and an interfering signal. The base station also has a correlator for despreading the AGC-output signal, a power-measurement circuit responsive to processing the received signal with the despread AGC-output signal for generating a received-power level, a comparator coupled to the power-measurement circuit for generating a comparison signal by comparing the received-power level to a threshold level, a transmitter for transmitting a second spread-spectrum signal, and an antenna. The mobile station has a variable-gain device responsive to the comparison signal for adjusting a transmitter-power level of the first spread-spectrum signal.

Personal communication device with hearing support and method for providing the same

Abstract: The present invention is related to a personal communication device arranged for providing hearing support. The personal communication device comprises an input for receiving an audio signal, programmable processing means and an output for outputting the processed signal. The programmable processing means is arranged for performing a filtering operation on a digital version of the audio signal in a first signal path based on parameter settings and for providing control logic for determining the parameter settings based on information on user preferences, on audiological information and on information on the listening situation, in which the personal communication device is used, obtained via sound environment analysis of the received audio signal and/or via sensing means of the personal communication device, so that the programmable processing means is operable as a hearing loss compensation module arranged for outputting a hearing loss compensated signal. The programmable processing means further has a second signal path in parallel with the first signal path, said second signal path comprising a module for transfer function calculation arranged for receiving the digital version of the audio signal and the parameter settings and for determining the filter coefficients of the filtering means based on the parameter settings and the digital version of the audio signal.

Method and apparatus for broadband transmission from a central office to a number of subscribers

Abstract: A method of transmitting broadband video services from a broadband digital signal source which includes forming the digital signal from said source into a plurality of channels of digital signals and modulating a plurality of carrier signals with respective channels of the digital signals. The resultant modulated channels are multiplexed to form a combined signal which is then used to modulate light from a laser light source. The modulated light signal is transmitted along a light fibre to a local distribution box where it is converted to electrical signals and broadcast to a number of subscriber set top terminals, Each set top terminal detects the modulated signal of a channel pre-assigned to that set top terminal. User control information is also received by that set top terminal and transmitted to the central office.

SignalLens: Focus+Context Applied to Electronic Time Series

Abstract: Electronic test and measurement systems are becoming increasingly sophisticated in order to match the increased complexity and ultra-high speed of the devices under test. A key feature in many such instruments is a vastly increased capacity for storage of digital signals. Storage of 109 time points or more is now possible. At the same time, the typical screens on such measurement devices are relatively small. Therefore, these instruments can only render an extremely small fraction of the complete signal at any time. SignalLens uses a Focus+Context approach to provide a means of navigating to and inspecting low-level signal details in the context of the entire signal trace. This approach provides a compact visualization suitable for embedding into the small displays typically provided by electronic measurement instruments. We further augment this display with computed tracks which display time-aligned computed properties of the signal. By combining and filtering these computed tracks it is possible to easily and quickly find computationally detected features in the data which are often obscured by the visual compression required to render the large data sets on a small screen. Further, these tracks can be viewed in the context of the entire signal trace as well as visible high-level signal features. Several examples using real-world electronic measurement data are presented, which demonstrate typical use cases and the effectiveness of the design.