Abstract: Techniques are disclosed for systems and methods to provide automatic and substantially continuous calibration for compasses mounted to moving structures. A compass calibration system may include a logic device configured to receive one or more sensor signals and determine a corrected magnetic field based, at least in part, on a measured local magnetic field. The logic device may be configured to receive the measured local magnetic field comprising a series of magnetic measurements associated with a mobile structure; determine a valid portion of a toroidal shape of the series of magnetic measurements that is available for further processing; and determine the corrected magnetic field based, at least in part, on calibration parameters derived from at least the valid portion of the toroidal shape.

Abstract: Various techniques are provided to maintain drive belts at substantially constant tension over a wide range of conditions. In one embodiment, a system includes a housing, a bracket secured to the housing, first and second pulleys, and a belt engaged in tension with the first and second pulleys. The first and second pulleys are suspended from the housing through the bracket to reduce effects of thermal expansion of the housing on the belt tension. Other systems and related methods are also provided.

Abstract: Various techniques are provided to securely pair devices using default connection information. In one example, a method includes storing, on a first device, a connection list comprising a plurality of connection entries. The first device selects a default connection entry in the connection list. A secure default connection is established between the first device and a second device using the default connection entry. Defined connection information is received at the first device from the second device over the secure default connection. The defined connection information is stored in a defined connection entry of the connection list. A secure defined connection between the first device and the second device is established using the defined connection entry.

Abstract: A radar or sonar system amplifies the signal received by an antenna of the radar system or a transducer of the sonar system is amplified and then subject to linear demodulation by a linear receiver. There may be an anti-aliasing filter and an analog-to-digital converter between the amplifier and the linear receiver. The system may also have a digital signal processor with a network stack running in the processor. That processor may also have a network interface media access controller, where the system operates at different ranges, the modulator may produce pulses of two pulse patterns differing in pulse duration and inter-pulse spacing, those pulse patterns are introduced and used to form two radar images with the two images being derived from data acquired in a duration not more than twenty times larger than the larger inter-pulse spacing, or for a radar system, larger than one half of the antenna resolution time. One or more look-up tables may be used to control the amplifier.