Satellite Ground Station Antenna Product

Overview

A satellite ground station antenna collects the few picowatts that survive the path from orbit and concentrates them onto a receiver, while pointing a kilowatt-class uplink back along the same line. The mid-size class described here — a 3 to 13 m parabolic dish on an elevation-over-azimuth pedestal — serves LEO downlink stations, telemetry and command sites, and teleport gateways. Everything in the design follows from two numbers: gain, which grows with aperture area and surface accuracy, and G/T, the gain-to-noise-temperature ratio that fixes how weak a signal the station can close a link on.

Reflector and feed

The main dish is a paraboloid assembled from stretch-formed aluminum Reflector Panel sectors on a Backing Structure of radial trusses. Antenna gain collapses when surface error approaches a sixteenth of a wavelength, so a dish intended for Ka-band at 30 GHz (λ = 10 mm) must hold roughly 0.3 mm RMS across its whole face, through gravity sag at every elevation angle, solar thermal gradients, and wind. Each panel corner sits on a Panel Adjuster differential screw, set during alignment campaigns using photogrammetry against the design figure.

Most stations use Cassegrain geometry: a hyperbolic Subreflector on a Quadripod folds the focus back through the dish vertex to a Feed Horn mounted on the structure, where heavy electronics can ride without blocking the aperture. The corrugated horn illuminates the dish with a 10–12 dB edge taper — the standing compromise between spillover noise from the warm ground and full use of the aperture. Behind it, the Polarizer sets circular or dual-linear polarization, and the Diplexer isolates the transmit path from the receive port by 80 dB or more.

The single most important component for sensitivity is the Low-Noise Amplifier bolted directly to the feed: a HEMT amplifier with 30–60 K noise temperature placed before any lossy cable, because every 0.1 dB of loss ahead of it adds about 7 K of system noise. Everything downstream — the Downconverter, the IF Fiber Link to the control room — matters far less.

Pedestal and servo

The Pedestal Assembly is an elevation-over-azimuth positioner. Azimuth turns on a large Slew Bearing that doubles as the bull gear, driven by paired servo motors through Drive Gearbox reducers. The pair is deliberately fought against itself: the Drive Amplifier apply a counter-torque bias so the gear train is always preloaded and backlash never appears in the position loop. Elevation tilts the Elevation Structure cradle via a jack screw, with Counterweight nulling gravity torque.

The Antenna Control Unit closes position loops on high-resolution axis encoders and applies a systematic pointing model — encoder offsets, axis non-orthogonality, gravity sag, foundation tilt from the Inclinometer — that turns a mechanically imperfect structure into a 0.01°-class pointer. LEO work is demanding: a pass rises, crosses, and sets in ten minutes, with azimuth rates peaking near zenith, which is why az/el mounts keep a small keyhole overhead and fast stations add a third axis or accept the gap.

Tracking

Pointing knowledge comes in layers. Program track steers open-loop from orbital ephemerides (TLE or operator-supplied state vectors), good enough for wide beams. Step track perturbs pointing slightly and climbs the signal-strength gradient. The best stations use monopulse: the Monopulse Coupler extracts higher-order feed modes whose amplitude and phase encode the angular error in a single measurement, and the Tracking Receiver drives the error to zero continuously — no scanning, millidegree-class accuracy, immune to signal scintillation that fools step track.

Keeping it on air

Weather is the persistent enemy. The Anemometer triggers automatic stow toward zenith before sustained winds exceed the operational limit, where the Stow Lock pins the structure for survival conditions near 200 km/h. The De-icing System burns tens of kilowatts keeping ice off the panels, since an asymmetric ice load both distorts the surface and unbalances the elevation axis. Waveguide runs stay pressurized with dry air so condensation never forms inside, and the Lightning Protection ring keeps strikes out of the electronics. A Test Loop Translator lets operators verify the full transmit-receive chain between passes without touching a satellite.