Corrugated Feed Horn Assembly
Dual X/Ka-Band Corrugated Horn with OMT and Polarizer
Dual-band (X and Ka) corrugated feed horn with ortho-mode transducer (OMT) and quarter-wave-plate polarizer, illuminating the high-gain reflector with a near-ideal Gaussian pattern to maximise aperture efficiency.
Purpose
Convert between guided waves (rectangular/circular waveguide) at the transceiver and the radiated/received free-space waves at the dish focus, with low cross-polarization, symmetric pattern, and frequency-independent phase center.
Context
RF interface between L3-COM-EARTH-XBAND (X) and the L3-COM-ANT-HGA reflector. Provides dual-polarization handling for diversity reception. Dual-band capability future-proofs the Ark for Ka-band high-rate growth without replacing the entire feed.
Principles
- ▸Corrugated horns achieve symmetric E- and H-plane patterns with sidelobes <–30 dB and cross-pol <–35 dB across wide bandwidths
- ▸Hybrid HE11 mode propagates without dispersion in the corrugated section, producing a Gaussian-like illumination
- ▸Spline-profile corrugated horns can support dual-band X+Ka by exciting X-band via lateral waveguide ports and Ka-band on-axis
- ▸OMT (orthomode transducer) splits the two orthogonal polarizations to separate waveguide ports; isolation typically >35 dB
- ▸Quarter-wave plate polarizer converts between linear (waveguide TE10) and circular polarization (free space)
Typical implementations
- ▸Mars Reconnaissance Orbiter dual X/Ka feed (JPL design, flight-proven 2005–present)
- ▸JUNO X-band corrugated feed for Cassegrain Cassini-class HGA
- ▸Dual X/Ka feed horn published in IEEE 7696481 (Rotholz et al., for deep space telecom)
- ▸ESA BepiColombo MPO HGA dual-band feed
- ▸Frontiers 880606 dual-polarized horn covering 24–50 GHz with VSWR <2 and 40 dB isolation
Lunar considerations
- ▸Vacuum operation means no air dielectric losses, simplifying matching
- ▸Thermal cycling causes feed expansion (~25 µm over thermal range for Al horn) — designs must keep electrical length stable to <λ/100
- ▸Dust intrusion into the feed mouth is a concern — protective vacuum-compatible window (Kapton) or hermetic feedthrough preferred
- ▸Cassegrain configuration places feed at vertex of dish, minimising thermal soak from sunlit reflector
- ▸Long-term waveguide flange galvanic corrosion is avoided by using same material throughout and conductive coatings
Specifications
Functional
| primary function | Bidirectional dual-band, dual-polarization waveguide-to-free-space transition for HGA |
| inputs | Waveguide-fed X-band TX signal (5 W), Waveguide-fed Ka-band TX signal (Ka growth path), Received RF coupled from reflector focus |
| outputs | Radiated illumination pattern matched to reflector edge taper (~–12 dB at edge), Coupled receive signals delivered to OMT polarization ports, Linear or circular polarization selectable via polarizer |
| x band range ghz | 7.1, 8.5 |
| ka band range ghz | 25.5, 32.0 |
| edge taper db | -12 |
| cross polarization db | -35 |
| return loss db | -20 |
| polarization isolation db | 35 |
| axial ratio db max | 0.5 |
| phase center stability mm | 1.0 |
Physical
| mass kg | 4.0 |
| dimensions | 300 mm length × 200 mm aperture diameter |
| materials | Aluminum 6061-T6 horn body (precision-machined corrugations), Silver plating on internal surfaces for low RF loss, Invar mounting flange to match reflector backing structure CTE, Kapton vacuum window (optional, for dust mitigation) |
| operating temperature c | -180, 130 |
Operational
| power consumption w | 0 |
| thermal range c | -180, 130 |
| lifetime years | 100 |
| mtbf hours | passive |
Interfaces
Provides
- Illumination pattern matched to reflector geometry
- Received signal at WR-112/WR-137 waveguide port(s)
Requires
- 5 W X-band TX signal via WR-112 waveguide
- Mounting interface at reflector vertex (Cassegrain) or focus (prime-focus)
Cite this entry
Lunar Ark Codex. "Corrugated Feed Horn Assembly" (L3-COM-ANT-FEED). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-COM-ANT-FEED
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.