Slip rings for satellite communication antennas (SATCOM on the move)

SATCOM-on-the-move terminals track satellites from moving vehicles, ships or aircraft, so the antenna must rotate continuously in azimuth while passing Ka- or Ku-band transmit/receive signals and power. Radome height and weight are tightly constrained, so RF rotary joints and slip rings are often integrated into one compact assembly. RF performance must stay stable as the antenna turns.

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What the slip ring has to handle

RF rotary joint for Ku- or Ka-band transmit and L-band/IF receive
Low VSWR and insertion loss with minimal variation during rotation
Slip ring for power to motors, encoders, GPS and active RF components
Compact, low-profile integration to minimise radome height
Lightweight aluminium construction
Wide temperature range and IP65 sealing
Continuous 360 degree rotation in both directions

Typical figures

Frequency	Ka transmit 27.5-31 GHz; L-band receive DC-2.15 GHz; Ku downlink 10.7-12.75 GHz, uplink 13.75-14.5 GHz
Power	Up to 40 W transmit (Ka example)
Vswr	1.3:1 transmit, 1.5:1 receive (Ka example)
Insertion loss	0.5 dB transmit, 0.4 dB receive (Ka example)
Temperature	-40 C to +60 C
Ingress protection	IP65

Example figures from the published sources listed below. Your requirement may differ; an engineer will confirm against your duty cycle.

Recommended slip ring types

Capsule slip rings Through-bore slip rings Rugged and military slip rings High-speed slip rings

Standards to consider

MIL-STD-810 - environmental test methods for military terminals
MIL-STD-461 - EMC for military equipment
IEC 60529 - IP code

The complete system

A slip ring rarely works alone. For satellite communication antennas (SATCOM on the move) it is usually specified together with:

azimuth motor
elevation motor
servo drive
encoder
IMU
RF rotary joint

Specifying these together avoids mismatched connectors, cable routes and feedback interfaces, and gives you one point of contact for the whole axis.

Common problems to design out

RF variation during rotation
Moisture ingress in exposed terminals
Contact wear from continuous tracking
Excess height or weight limiting radome design

Frequently asked questions

What does a SATCOM-on-the-move antenna need from a slip ring?

Power for azimuth motors, encoders, GPS and active RF parts, combined with an RF rotary joint for the Ka or Ku signals. Integrated assemblies save height.

Which frequencies pass through SATCOM rotary joints?

A published Ka-band design transmits at 27.5-31 GHz with a separate receive channel from DC to 2.15 GHz (L-band). Ku-band joints cover roughly 10.7-12.75 GHz downlink and 13.75-14.5 GHz uplink.

Can DC power pass through an RF rotary joint?

Some dual-channel coaxial joints carry DC on their RF conductors to power active rotating components, such as an LNA. Larger loads use a slip ring.

Sources

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