It is now a long-established standard in the mobile communications arena for manufacturers to install active components directly into the antenna. Manufacturers of radar systems have, in recent years, been motivated to incorporate more and more of these components as the need – and demand – for more technically sophisticated solutions has become increasingly ubiquitous.
The result? A huge increase in system efficiency and enhancement to the overall integrity of the signal.
Out with the old
For radar rotary joints, this means that the traditional RF modules for 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, to ventilate and/or depress the RF line sections with dry air. The power current is primarily necessary to the supply of the radar amplifiers, which often achieve an output rating of several hundred kilowatts. In addition, antenna heating systems are also supplied.
The electrical signals to and from the active antenna equipment are transmitted either optically via a multichannel fibre-optic rotary joint, by a slip ring or by means of a contactless coupler.
The optical rotary joint, however, requires the central inner bore of the overall system, a disadvantage not shared by Spinner’s new contactless signal transmission module. Depending on requirements, an inner bore of randomised diameter (a hollow shaft) can be realised. The actual signal transmission between the stator and rotor unit occurs electromagnetically; in this context, the signal to be transmitted is digitally modulated.
The pros of contactless technology
As in all areas of modern-day technology, Ethernet is also used as the standard interface for data transmission in the radar field. This is why Spinner has chosen to configure the newly developed module as a contactless Ethernet coupler.
This module – so-called because it has its own bearing support – is freely scaleable in its diameter. Through stacking, it can also be configured to create a multichannel design, but the primary advantage of the contactless solution is naturally its wear-free operation.
Another advantage, compared with a contact-based design, is that the signal transmission module’s maximum data rate is not influenced by its size, which is why the Ethernet module also consistently supports Gigabit Ethernet regardless of the dimensions.
Intelligent, user-friendly design
The intelligent Ethernet subassembly electronics recognise the Ethernet standard of the connected devices automatically and adjust themselves accordingly. It is therefore unimportant whether a device is connected with 10BASE-T (10Mbit/s), Fast Ethernet (100Mbit/s) or Gigabit Ethernet (1Gbit/s) – the transmission works without requiring any user intervention. The subassemblies on
the stator and rotor side require an external power supply of a nominal 24VDC, or optionally 12VDC.
A wide range of diagnostic functions are integrated into the electronics, as well as a sophisticated surveillance system. During initial operation in the factory, this information is evaluated in order to ascertain and ensure quality. Prior to delivery, every module is subjected to a ‘burn in’.
The subsequent evaluation of the diagnostic information and testing of the LAN interface, which take place in line with RFC-2544 benchmarking methology, are required before approval for delivery is given. This means a high degree of reliability is guaranteed throughout the entire lifetime of the Ethernet module.
