Abstract: A disk drive includes a head and a disk, spiral patterns are located on the disk, and the disk drive self-writes servo patterns on the disk using the spiral patterns as a reference for servoing the head. In an embodiment, the disk drive uses preliminary servo patterns to determine repeatable runout of the spiral patterns. In another embodiment, the disk drive reads each spiral pattern with multiple timing windows.

Abstract: A disk drive includes a head and a disk, spiral patterns are located on the disk, and the disk drive self-writes servo patterns on the disk using the spiral patterns as a reference for servoing the head. In an embodiment, the disk drive uses preliminary servo patterns to determine repeatable runout of the spiral patterns. In another embodiment, the disk drive reads each spiral pattern with multiple timing windows.

Abstract: Spread Aloha Multiple Access (SAMA) or other multiple access hubs provide feedback to each RTU on the frequency error in its transmission, so that each RTU can change its frequency output to the correct transmission frequency. At any time, and especially when a RTU has not transmitted for a time or is not transmitting, or during transmission, the hub requests that an RTU broadcast a pure tone of frequency. That pure tone produces a beat with the hub's detector. The hub filters the beat frequency and passes it to a comparator that produces a signal waveform. The period of the waveform is measured by the hub. The hub calculates the error in the RTU's carrier and sends a correction value for the RTU to use when transmitting. The hub measures slow drift in the carrier during continued transmission from a RTU and provides corrections to the RTU on the fly.

Abstract: A method of holographic recording in a photorefractive medium wherein stored holograms may be retrieved with maximum signal-to noise ratio (SNR) is disclosed. A plurality of servo blocks containing position feedback information is recorded in the crystal and made non-erasable by heating the crystal. The servo blocks are recorded at specific increments, either angular or frequency, depending whether wavelength or angular multiplexing is applied, and each servo block is defined by one of five patterns. Data pages are then recorded at positions or wavelengths enabling each data page to be subsequently reconstructed with servo patterns which provide position feedback information. The method of recording data pages and servo blocks is consistent with conventional practices. In addition, the recording system also includes components (e.g.