Slip Ring for Antenna
Antenna is a converter that converts the guided waves propagating on the transmission line into electromagnetic waves propagating in an unbounded medium (usually free space), or vice versa. From the perspective of the receiving antenna, it converts electromagnetic waves from space into electrical signals and transmits them to the receiving device (such as radio, television, radar, etc.). From the perspective of the transmitting antenna, it converts the electrical signals generated by the transmitting device (such as radio stations, communication base stations, etc.) into electromagnetic waves and radiates them into space.
In many application scenarios, antennas need to rotate continuously to achieve full-range signal reception or transmission. If the transmission line connecting the antenna is directly fixed, it will be entangled or even damaged during rotation. Slip rings allow the transmission line to maintain continuous electrical connection when the antenna rotates, and can adapt to multi-degree-of-freedom movement to avoid damage to the equipment.
The Specific Role of Slip Rings in Antenna Systems
Transmitting Power
The slip ring provides power for the antenna's drive motor and signal amplifier. In satellite communication antennas, it transmits power from the ground power system to the continuously rotating antenna structure, driving the antenna to track satellite signals.
Transmitting Signals
The slip ring can be involved in the transmission of multiple types of signals, including RF signals and control signals. In the vehicle-mounted mobile communication antenna system, it transmits the satellite signal received by the antenna to the communication device in the vehicle. It also transmits its control signal to the antenna to adjust their angle and tracking signal.
Requirements On Slip Rings For Antenna Systems
Bit Error Rate
When transmitting various types of signals, the antenna system requires the slip ring to have a very small bit error rate. For example, when we use digital TV transmission standards such as DVB-T, the bit error rate of the slip ring should be stable below 1×10⁻⁶. In this way, even if its antenna system works continuously for a long time, the TV picture can be kept clear and stable.
01
Signal Attenuation
In high-frequency signal transmission, such as the C band (4GHz - 8GHz) and Ku band (12GHz - 18GHz) commonly used in satellite communications, the insertion loss of the slip ring to the signal should be controlled within 0.5dB. This can transmit the weak satellite signal received by the antenna to the subsequent signal processing equipment without loss.
02
Anti-interference Ability
There are a large number of electronic devices and wireless signal sources in urban environments. The slip ring should shield redundant electromagnetic signals with an efficiency of more than 60dB, which can significantly reduce the strength of external signals. Therefore, it can stably transmit communication signals between base stations and mobile terminals.
03
Temperature Adaptability
Antenna systems can be installed in a variety of environments, from cold polar regions to hot desert areas. Slip rings should work normally in the range of at least -40°C to 70°C. This is achieved by using more temperature-resistant metals, enhancing sealing structures, and optimizing heat dissipation designs.
04
Waterproof and Dustproof
For antenna systems installed outdoors, the slip ring must have a protection level of IP67 or above. In this case, when encountering heavy rain, the slip ring can completely prevent rain from invading the internal circuit and prevent poor electrical contact caused by water vapor erosion.
05
Rotation Performance
In some satellite tracking antenna systems, the slip ring needs to support the antenna to rotate 360° continuously at a speed of 10 to 60 revolutions per minute to help track satellites. During the rotation process, its friction torque should be controlled below 0.05N·m so that the rotation of the antenna can remain flexible and smooth.
06
Shock Resistance
Antenna systems sometimes need to be installed on mobile carriers, such as vehicles and ships. The slip ring should be able to withstand a certain degree of vibration and shock, and be tested according to the MIL-STD-810G military standard to withstand acceleration shocks of 5g to 20g without damaging the internal structure and electrical connections.
07
Communication Protocol
The slip ring should be compatible with various communication protocols used by the antenna system, including TCP/IP, RS-485, CAN bus, etc. Taking CAN bus as an example, it should have a transmission rate of 1Mbps to transmit real-time communication and control instructions between the internal components of the antenna system.
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