High Performance Sensor Data with Rotary Interfaces

With the proliferation of high performance, real-time sensing applications, the bandwidth capabilities of the transmission lines that carry these signals are highlighted. Much of the advancement in sensing and imaging technologies has been accomplished in the digital conversion of sensor data. The aggregate data rate of sensor systems continues to increase due to the increase in the fidelity of individual sensors,as well as the increased use of multiple sensors to expand the versatility of sensor systems. Sensor fusion techniques that combine the output of a variety of sensors are expanding into a variety of applications adding additional bandwidth pressures on transmission lines.

In most sensor applications,data must be transferred to the processor along a transmission path in real time with sufficient bandwidth to maintain the signal integrity. Since the data transmission path is only as fast as its slowest element, it is important to analyze the bandwidth characteristics of each element of the path. In cases where these sensors must rotate, one of the areas of interest is how the data gets across the rotational interface —traditionally the job of a slip ring. There are a number of tools to increase the bandwidth of this rotational interface to avoid a data bottleneck.

Passive devices transmit signals without any signal processing and can be analyzed and specified using typical transmission line properties, e.g., signal attenuation and noise properties. The two passive components for transmitting high speed data to and from rotating platforms are slip rings and fiber optic rotary joints (FORJ). Active rotary transfer devices transmit signals using signal processing electronics to convert the signal into a form that can be transmitted across the interface and then,of course,convert them back to the original form. There is a whole family of components that use this active approach and vary the manner used to transmit the signal across the interface; however,since the transmission method is transparent to the user and the specification method is fairly universal,it is useful to consider these techniques as a single type of active component which will be referred to as a High Speed Data Link (HSDL)