In SATCOM systems, especially at Ka-band and beyond, small mechanical misalignments can have disproportionately large effects on performance. One of the most critical — and often underestimated — alignment factors is the subreflector.
So, why is subreflector alignment so sensitive at higher frequencies like Ka-band (26.5–40 GHz) and Q/V-band?
Why Subreflector Alignment Becomes Critical at Ka-Band+
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Shorter Wavelengths, Smaller Margins for Error
At Ka-band, wavelengths are under 1.2 cm. This means a few millimeters of misalignment can cause phase errors, beam deflection, and gain loss that are barely noticeable at lower bands (like C or X-band), but catastrophic at Ka.
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Phase Center Sensitivity
The beam phase front curvature is much tighter at higher frequencies. Subreflector position shifts (axial or lateral) can push the phase center off-axis, distorting the main beam.
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Increased Sidelobe Energy and Pattern Distortion
A poorly aligned subreflector increases energy in sidelobes, degrading EIRP and opening the door to interference or regulatory violations — particularly dangerous in crowded Ka-band satellite slots.
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Impedance Matching and Feed Illumination
Misalignment affects how the feedhorn illuminates the reflector. Over- or under-illumination leads to spillover, loss of G/T, and unnecessary thermal noise pickup.
Signs of Poor Subreflector Alignment
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Decreased on-axis gain
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Skewed or offset beam pattern
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Failing radiation pattern tests
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Cross-pol performance degradation
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Az/El pointing offsets that won’t calibrate out
Troubleshooting Tips
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Use mechanical gauges or laser tools to verify subreflector standoff distance and centering
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Inspect for loose bracket hardware or bent supports (especially after shipping or heavy winds)
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Perform holography or near-field tests if available
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Use high-resolution pattern data (or FieldFox with antenna measurement options) to quantify impact
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Compare against reference templates at known-good alignment
Parity Global’s Take
At Parity Global, we don’t begin RF commissioning until subreflector alignment is fully optimized. Period. There is no reason to proceed with antenna commissioning & calibration if the subreflector isn’t perfectly positioned. Misalignment at this stage undermines everything that follows.
We verify and adjust subreflector positioning during initial deployments, retrofit upgrades, and even during routine Operations & Maintenance (O&M) visits as part of our preventive maintenance RF checks. It’s a non-negotiable step in our mission assurance approach — especially critical at Ka-band and above, where tolerances are razor-thin.