Introduction
Skylink has bought together the best technological solutions for each of the key system components: uplink receive; all weather airborne platform; downlink transmit and downlink receive.
Operating at altitudes of up to 30,000 feet the Skylink system requires a high gain receive antenna for the video uplink. A mechanically steered high gain antenna cannot be certified due to aerodynamic constraints, and is limited by only being able to focus on one uplink at any one time. Skylink has overcome these problems by using a state-of-the-art phased array antenna system (PAAS) originally developed for military radar systems by QinetiQ.
The Pilatus PC-12, operated by Lions Air is the ideal all weather airborne platform for Skylink. Certified to carry a range of antenna systems, the PC-12 has proven to be a reliable relay platform, not only for the Skylink system but also for VHF voice and telemetry.
Skylink can provide a variety of antennas for transmitting the downlink from the PC-12 and receiving the signal on the ground. Short downlink ranges can be covered using simple passive antennas (such as a monopole), but for longer ranges a GPS steered antenna is available. On the ground, a manually or automatically steered high gain antenna is deployed.
The PC-12s have been fitted with an additional DC generator capable of delivering 300Amps at +28V DC to allow the use of high power RF amplifiers.
The Pilatus PC-12, operated by Lions Air is the perfect relay platform for Skylink.
With a cruise altitude of 30,000 feet this aircraft can fly above weather and provides Skylink with an all weather capability.
The PC-12 also offers: 7.5 hour flying time so no refuelling issues; high travelling speed of 450 kph allows fast transfer from Zurich to the event; low cruising speeds to maintain tight geographical positioning above an event; operation from small airfields enabling aircraft and crew to be based close to the event; large freight hatch for installing relay equipment.
Ensuring the aircraft is optimally positioned throughout the event is achieved using either an agreed set of fix points and timings, or a moving map that provides the pilots with the current positions of the various uplinks.
The PC-12s are certified to fit up to two phased array uplink antennas so one aircraft can relay up to eight independent video links.
1. Additional generator supplying up to 300A at +28V DC.
2. Low profile, high gain phased array antenna for receiving the uplinks: one below the cockpit, one below the wings. Each antenna can receive up to 4 independent uplinks.
3. 12 UHF + VHF antennas accessible from an internal patch panel and suitable for relaying voice comms and telemetry.
4. Two larger radomes for housing a range of downlink transmitter antennas,including a 2-axis GPS steered 11dBi antenna for long ranges.
The Phased Array Antenna System (PAAS), developed by QinetiQ, consists of two separate units; The Antenna Head Unit (AHU) and the Beamformer Unit (BFU).
The Antenna Head Unit (AHU) is the multi-element array that is housed in a weatherproof radome and is fitted directly to the underside of the aircraft. The AHU is cabled to the Beamformer Unit (BFU) rack that is located inside the aircraft. One BFU synthesises one antenna beam, and multiple BFUs can be connected to a single AHU.
Once the operator has entered the uplink frequency on the touch screen display and hit the ´track´ button, the PAAS automatically acquires and tracks the uplink signal even in non line-of-sight conditions.
The PAAS is compatible with all analogue and digital video links, including high definition.
| Frequency | 2.4 to 2.6GHz |
| Antenna Gain | +18dBi from +45° to -45° reducing to +13dBi at ±70° |
| Beams | 4 independent beams per AHU; 2 axis electronic scan over ±70° Each beam has full antenna gain |
| Auto-Tracking | Signals tracked using energy seeking algorithms; no GPS positioning information required |
| AHU | 560 x 380 x 80mm; 2 to 5kg (depending on radome); +5V DC, 15W; -40° to +80°C |
| BFU | 4U 19¨ rack mountable unit; 8kg; +28V DC, 55W; -10° to +60°C |
Skylink´s preferred downlink transmit system is a mini 2-axis gimballed antenna. Housed in it´s own aeronautical composite radome, the antenna uses GPS to automatically track the downlink receive site.
| Frequency | 1.9 to 10GHz (in steps) |
| Antenna Gain | +11dBi (nominal) |
| System Components | 2-axis gimballed antenna; Aeronautical composite radome; Auto tracking and GPS control unit; GPS receiver; Serial and power cable |
| Antenna | 600 x 256 x 400mm; 6kg; +10 to +40V DC, 40W; -55° to +60°C |
| Auto-Tracking | Automatic adjustment for platform heading and reference; 2° step size |
Skylink´s preferred downlink receive system is a ground based 2-axis gimballed antenna. The antenna can operated in a manual or automatic tracking mode. In manual mode the operator has control of the dish via a joystick. In automatic mode the aircraft calculates the azimuth and elevation pointing requirements for the ground antenna.
| Antenna Options | 1. 1m dish in 160kph wind 2. 1.5m dish in 100kph wind 3. Larger antennas if in a radome |
| 2-axis gimballed motor | Fully weatherproof; 200Nm torque; 0.01° tracking resolution; -55° to +60°C |
| Air-to-Ground data link | Dedicated UHF link to UHF radio on ground (400 to 470MHz) or multiplexed onto the RF video link |
| Antenna Control Unit | 1U 19¨ rack mountable unit; +80 to +240V AC, 300W; up to 200m cable to antenna |
| Control modes on ACU | 1. Manual override (joystick) 2. Offset (user defined north) 3. Auto-Track UHF 4. Auto-Track RF Audio Channel |