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[Technical article / FAQ, rfforum Editorial Team]
GNSS patches often pass return-loss gates and still miss TTFF or sky-view metrics outdoors. The ground plane, keep-out, and nearby metals set multipath and axial ratio more than the ceramic part number on the BOM.
1. What actually moves the sky view
- Ground-plane diameter / board edge clearance shifts resonance and pattern; a coupon with a generous plane is not the handset or tracker board you ship
- Keep-out is three-dimensional: a shield can, battery, or LCD under/near the patch pulls RHCP purity and raises multipath lobes
- Perfect S11 on a fixture does not prove axial ratio or multipath rejection on the product stack
2. Freeze list before you lock the antenna
- Plane size and keep-out on the *product* board, not only the vendor evaluation board
- Enclosure / glass / metal bezel note next to every S11 and open-sky TTFF claim
- Whether you measure axial ratio or only RHCP gain at zenith — AR often fails first near the horizon
- Cable / connector dress if the patch sits next to a harness (same traveler discipline as small monopoles)
3. Habit
Archive plane size, keep-out, and enclosure with every GNSS "sensitivity" number. A ceramic patch that looked fine on the EVB can fail field multipath without any S11 change.
Discussion: on your last GNSS miss, did the fix land in ground-plane / keep-out, enclosure metals, or a different patch — and do you require an open-sky or chamber AR note next to S11?
— rfforum 编辑部 / Editorial Team
GNSS patches often pass return-loss gates and still miss TTFF or sky-view metrics outdoors. The ground plane, keep-out, and nearby metals set multipath and axial ratio more than the ceramic part number on the BOM.
1. What actually moves the sky view
- Ground-plane diameter / board edge clearance shifts resonance and pattern; a coupon with a generous plane is not the handset or tracker board you ship
- Keep-out is three-dimensional: a shield can, battery, or LCD under/near the patch pulls RHCP purity and raises multipath lobes
- Perfect S11 on a fixture does not prove axial ratio or multipath rejection on the product stack
2. Freeze list before you lock the antenna
- Plane size and keep-out on the *product* board, not only the vendor evaluation board
- Enclosure / glass / metal bezel note next to every S11 and open-sky TTFF claim
- Whether you measure axial ratio or only RHCP gain at zenith — AR often fails first near the horizon
- Cable / connector dress if the patch sits next to a harness (same traveler discipline as small monopoles)
3. Habit
Archive plane size, keep-out, and enclosure with every GNSS "sensitivity" number. A ceramic patch that looked fine on the EVB can fail field multipath without any S11 change.
Discussion: on your last GNSS miss, did the fix land in ground-plane / keep-out, enclosure metals, or a different patch — and do you require an open-sky or chamber AR note next to S11?
— rfforum 编辑部 / Editorial Team
