Contactless Digital Data Transmission with Ethernet Interface


It is now a long established standard in the mobile communications arena for manufacturers to install active components directly into the antenna. More recently, producers of radar systems have been motivated to incorporate more and more into the antenna as the need for more technically sophisticated solutions becomes more and more ubiquitous. The benefit? A huge increase in system efficiency and enhancement to the integrity of the signal.

Dual Channel Ethernet Module

Dual Channel Ethernet Module Ethernet Subassembly, Rotor Side, Small Version

For radar rotary joints, this means that the traditional RF modules for the different frequency bands are being replaced by diverse media couplers, power current paths and signal transmission paths. The media couplers are used to create a cooling circuit with a liquid medium and, if required, for the ventilation and/or depressing of the RF line sections with dry air. The power current is primarily necessary for supplying the radar amplifiers, which often achieve an output rating of several 100 kW. In addition to this, antenna heating systems are also supplied with it. The electrical signals from and to the active antenna equipment are transmitted either optically via a multi channel fiber optic rotary joint, by a slip ring or by means of a contactless coupler.

The optical rotary joint has the disadvantage, however, that it requires the central inner bore of the overall system. This disadvantage is not shared by our new contactless signal transmission module. Depending on requirements, an inner bore of ran-domised diameter (keyword hollow shaft) can be realised.

The actual signal transmission between the stator and rotor unit occurs electromagnetically in the context of which the signal to be transmitted is digitally modulated. As now standard in all areas of the technology, Ethernet is also used as the standard interface for data transmission in the radar field. This is the reason that SPINNER has configured the newly developed module as a contactless Ethernet coupler. This coupler is called module, because it has its own bearing support. This module is freely scalable in its diameter. Through stacking, it can also be configured to create a multi channel design. The primary advantage of the contactless solution is naturally its wear-free operation. Another advantage compared with a contactbased design, however, is that the maximum data rate is not influenced by the size of the module. That’s why the Ethernet module also consistently supports Gigabit Ethernet regardless of the dimensions. The intelligent electronics recognise the Ethernet standard of the connected devices automatically, and adjust themselves accordingly. It is therefore unimportant as to whether a device is connected with 10 Base-T (10 Mbit/s) or Fast Ethernet (100 Mbit/s) or Gigabit Ethernet (1 Gbit/s), the transmission works without requiring intervention of the user. The subassemblies on the stator and rotor side require an external power supply of a nominal 24 VDC, or optionally 12 VDC.

Ethernet Table 

A wide range of diagnostics functions are integrated in the electronics as well as a sophisticated functional surveillance system. During initial operation in factory, this information is evaluated in order to ascertain and ensure the quality. Prior to delivery, every module is subjected to a “Burn In”. The subsequent evaluation of the diagnostics information and a test of the LAN interface according to RFC2544 are required for approval for delivery. This means a high degree of reliability is guaranteed throughout the entire lifetime of the Ethernet module.

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