An adaptive data compression device for compressing data having variable frequency content, including a plurality of digital filters for analyzing the content of the data over a plurality of frequency regions, a memory, and a control logic circuit for generating a variable rate memory clock corresponding to the analyzed frequency content of the data in the frequency region and for clocking the data into the memory in response to the variable rate memory clock.
The method of the present invention minimizes the time required to display portion of a time sampled data file. A plurality of compressed data files are generated based on the time sampled data file. Each of the compressed data files is defined by a corresponding unique compression ratio such that each compressed data file contains fewer data points than the original time sampled data file. Each compressed data file characterizes the original time sampled data file. The compressed data files are stored in a data storage device for subsequent retrieval. A resolution factor is defined for each of the compressed data files. One of the compressed data files is then selected based on the resolution factor and the portion of the time sampled data file requested for display. The selected compressed data file is transferred from the data storage device to the display device.
A method and apparatus selects an appropriate sampling rate for an input signal based on a dynamic measurement of the bandwidth of the signal. In the preferred embodiment, the bandwidth of the input signal is determined by comparing the power of the entire input signal with the power of the input signal within a selected bandwidth. A discrete Fourier transform is used to perform the bandwidth analysis.
A CT scanner in which the amount of x-ray information acquired per unit time is substantially increased by using a continuous-on x-ray source and a sampled data system with the detector. An analog filter is used in the sampling system for band limiting the detector signal below the highest frequency of interest, but is a practically realizable filter and is therefore non-ideal. A digital filter is applied to the detector data after digitization to compensate for the characteristics of the analog filter, and to provide an overall filter characteristic more nearly like the ideal.
A low cost wireless multi-band communications device automatically adapts itself to a signal received from a particular system. On the basis of a bandwidth determination of the received signal, a sampling bandwidth and/or sampling time is selected and/or derived for down mixing the received signals. Improved noise immunity is provided via a band limiting of the sampling means. An adaptive filter is coupled to the output of the sampling means and is adjusted in to obtain a satisfactory level of adjacent channel interference rejection.
A method and apparatus for controlling the position of a disk drive transducer head relative to a target track are provided. An oversampled control output allows frequencies that are higher than the Nyquist frequency of the servo control system to be filtered. The system initiates a plurality of control outputs during a single sampling period, allowing the use of a single processor interrupt for each sampling period. The outputs initiated during a single sampling period may be of unequal length. In addition, the outputs may be proportioned so that the total control energy provided to the actuator is equal to the control energy that would be provided by control outputs initiated every one-half sampling period.
