Antenna Stabilization Unit V1
Airborne Two-Axis Gimbal for INS-Based Antenna LOS Stabilization, Strip Map, Spot and GMTI Surveillance Missions
The Antenna Stabilization Unit (ASU) is an airborne two-axis gimbal system designed and supplied by System Controls for positioning and stabilizing RF antenna payloads on aircraft platforms. Using onboard INS data and a TMS-based DSP system for closed loop position, motor control and monitoring, the ASU maintains antenna Line of Sight towards the target of interest against aircraft yaw, roll and pitch, delivering position accuracy better than 1 milliradian.
What is ASU?
The Antenna Stabilization Unit (ASU) is an airborne two-axis gimbal system designed to position and stabilize an RF front end and antenna payload on an aircraft platform, maintaining antenna Line of Sight towards the designated target area against the continuous yaw, roll and pitch motions of the aircraft during flight. The ASU uses onboard INS data fed to a TMS-based DSP Antenna Control Unit to perform closed loop position control, motor control and monitoring, keeping the antenna aligned in azimuth and elevation regardless of aircraft heading and attitude changes. The complete system consists of the antenna, Antenna Control Unit (ACU) and a host computer. The host computer issues mode selection commands and relevant command data to the ACU.
| Parameter | Specification |
|---|---|
| Azimuth and Elevation Drive | |
| Number of Axes | Two (Elevation over Azimuth - orthogonal to each other) |
| Modes of Operation | Mode A: Strip Map, Mode B: Spot Mode, Mode C: Ground Moving Target Indication (GMTI) |
| Maximum Velocity Azimuth | 18 deg/second |
| Maximum Velocity Elevation | 18 deg/second |
| Minimum Velocity Azimuth | 6 deg/second |
| Minimum Velocity Elevation | 6 deg/second |
| System Requirements | |
| Maximum Roll Angle | Plus or minus 18 deg |
| Maximum Rate of Change of Roll Angle | 18 deg/sec |
| Maximum Pitch Angle | Plus or minus 10 deg |
| Maximum Rate of Change of Pitch Angle | 10 deg/sec |
| Maximum Rate of Change of Heading | 10 deg/sec |
| Maximum Yaw Angle | Plus or minus 10 deg |
| Yaw Rate | 10 deg/sec |
| Position Accuracy (Azimuth and Elevation) | Less than 1 milliradian |
| Orthogonality Between Two Axis | Less than 2 milliradian |
| General Specification | |
| Host Communication | MIL-1553B and RS422 |
| Weight | Less than 24 plus or minus 2 kg (excludes antenna) |
| Payload | Antenna disc 700x215x10mm, weight 6.0 kg |
| Fitment | Mounted on stiff back up plate of the gimbal; phase array on front side, strip line power divider and RF front end on backside |
| Supply Voltage | 28V |
| Protection | EMI/EMC conforming to MIL-STD-461E |
| Power Peak | Less than 100W |
| Power Average | Less than 50W |
| Environment Specification | |
| Temperature Storage | -40C to +70C |
| Temperature Operating | -40C to +55C |
| Thermal Shocks | -40C to +70C as a sudden change |
| High Altitude | 30,000 ft (Version 2: 35,000 ft) at -40C |
| Relative Humidity | 85% to 95% |
| Operating Limits | |
| Limits of Travel (Dead Stop) Azimuth | -50 deg to +230 deg |
| Limits of Travel (Dead Stop) Elevation | -15 deg to +65 deg |
| Electrical Limits Azimuth | -47 deg to +228 deg |
| Electrical Limits Elevation | -12 deg to +67 deg |
| Software Limits Azimuth | -45 deg to +225 deg |
| Software Limits Elevation | -10 deg to +65 deg |
| Maximum Speed | 3 RPM |
| Operational Speed | 1 RPM |
INS-Based Autonomous Antenna LOS Stabilization
The ASU uses onboard INS data fed to a TMS-based DSP Antenna Control Unit to maintain antenna Line of Sight towards the designated area of interest against continuous aircraft yaw, roll and pitch motions. This INS-based autonomous stabilization eliminates the need for external attitude reference inputs, enabling the system to maintain precise antenna alignment independently throughout the surveillance mission regardless of aircraft manoeuvres.
Sub-Milliradian Position Accuracy
The ASU delivers position accuracy better than 1 milliradian on both azimuth and elevation axes with orthogonality between axes better than 2 milliradians. This sub-milliradian precision, maintained against the full envelope of aircraft roll, pitch and yaw motions, ensures that the antenna beam is directed accurately and stably towards the target area throughout the mission.
Three Operational Modes Including GMTI
Mode A Strip map provides continuous wide area ground imaging along the flight path. Mode B Spot mode focuses the antenna on a specific area of interest for detailed surveillance. Mode C Ground Moving Target Indication (GMTI) detects and tracks moving ground targets from the airborne platform, making the ASU directly suitable for battlefield surveillance, border monitoring and maritime patrol missions requiring real-time moving target data.
Three-Layer Travel Protection Architecture
Three independent layers of travel protection are provided: software operational limits (azimuth -45° to +225°, elevation -10° to +65°), electrical limit switches (slightly wider limits) and mechanical dead stops as final protection. This layered architecture ensures the system is protected against runaway motion, software failure and electrical fault conditions across all operational and fault scenarios.
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The ASU maintains antenna Line of Sight towards a target by compensating for aircraft yaw and roll using onboard INS data and TMS-based DSP closed loop control. It supports strip map, spot mode and GMTI surveillance missions from airborne platforms.
Less than 1 milliradian on both azimuth and elevation with orthogonality between axes less than 2 milliradians, using TMS-based DSP closed loop position control via onboard INS data.
Three modes: Mode A Strip map for wide area imaging, Mode B Spot mode for focused surveillance and Mode C Ground Moving Target Indication for moving ground target detection and tracking.
30,000 ft at -40°C. Operating temperature is -40°C to +55°C with thermal shock tolerance from -40°C to +70°C as a sudden change.
Roll up to ±18° at 18°/sec, pitch up to ±10° at 10°/sec and yaw up to ±10° at 10°/sec, maintaining antenna alignment against all heading and attitude changes.
MIL-1553B and RS422 for host communication and command interface, directly compatible with airborne defence avionics platforms.
MIL-STD-461E, with power peak less than 100W and average less than 50W on a 28V DC supply.
Azimuth software limits: -45° to +225°. Elevation software limits: -10° to +65°. Three protection layers: software limits, electrical limit switches and mechanical dead stops.
