Patch antenna radiation pattern shows where the antenna sends or receives RF energy. For many patch antennas, the strongest radiation is near broadside, which is perpendicular to the patch surface. That directional behavior is useful in GPS/GNSS, timing, and fixed wireless applications, but it also means placement and orientation can decide whether the device performs well.
Beamwidth is part of the same topic. It describes how wide the main coverage region is, usually measured between points where gain has dropped by a defined amount. For product selection, do not treat beamwidth as a separate buying metric. Read it together with the full radiation pattern, gain, polarization, ground plane, and installed device layout.
Quick Answer: What Is a Patch Antenna Radiation Pattern?
A patch antenna radiation pattern is a map of antenna gain in different directions. It shows the main lobe, side lobes, back radiation, and coverage angles. In a typical patch, the main lobe points away from the patch face.
In supplier conversations, beam pattern is often used as a simpler phrase for the same practical question: where does the antenna have useful coverage, and where does performance fall off?
Main Pattern Terms
| Term | Meaning | Why it matters |
|---|---|---|
| Main lobe | Direction of strongest radiation or reception | Shows where the antenna works best |
| Beamwidth | Angular width of the main lobe at a defined gain drop | Helps judge coverage angle |
| Side lobe | Smaller lobe away from main direction | Can affect interference or unwanted reception |
| Back lobe | Radiation behind the antenna | Relevant for ground plane and installation |
| Front-to-back ratio | Main direction compared with rear direction | Useful for directional control |
| Polarization pattern | RHCP, LHCP, linear, co-polar, cross-polar response | Critical for GNSS and multipath behavior |
Why Patch Antennas Are Directional
A patch antenna is normally built over a ground plane. The patch and ground plane form a resonant structure that tends to radiate strongest away from the patch surface. This broadside pattern is one reason patch antennas work well when the signal direction is known, such as a sky-facing GNSS antenna.
That same directionality can be a problem when the device orientation is random. If the antenna faces away from the signal or is blocked by metal, peak gain in the datasheet may not help.
Patch Antenna Beamwidth
Patch antenna beamwidth is the angular width of the main lobe. It is often expressed as half-power beamwidth, meaning the angle between the two directions where gain drops by 3 dB from the peak. When a datasheet shows a beam pattern, compare the useful coverage angles rather than only the peak direction.
Beamwidth can be widened or narrowed by antenna size, ground plane, substrate, array configuration, and surrounding structure. But for commercial GPS/GNSS and embedded devices, the useful question is not “How wide is the beamwidth?” It is “Does the installed pattern cover the angles my device needs?”
Reading a Radiation Pattern Datasheet
When reviewing a patch antenna radiation pattern, check:
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Frequency used for the plot. A pattern at one frequency does not prove performance across all bands.
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Test ground plane. The pattern may change when the antenna is installed on your PCB.
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Plane cuts. Look for multiple planes, not only one attractive view.
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Polarization. For GNSS, review RHCP gain and LHCP rejection where available.
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Scale and normalization. A normalized plot shows shape but not absolute gain.
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Installed data. If the supplier can test in your enclosure, that data is more useful than a free-space fixture.
GNSS Radiation Pattern Considerations
GNSS antennas receive satellite signals from a large portion of the sky. A useful GNSS patch antenna should have good RHCP response over practical elevation angles, not only a high number at zenith. Low-elevation satellites can help geometry, but they are also more exposed to multipath and obstruction.
For RTK, surveying, tracking device, and precision agriculture products, review the pattern items below. Keep the deeper polarization discussion on the RHCP vs LHCP patch antenna page so this article stays focused on pattern and beamwidth.
- RHCP gain pattern
- Axial ratio over angle
- Phase center behavior
- Ground plane size
- Enclosure and radome effects
- Cable and LNA details for active antennas
How Installation Changes the Pattern
The radiation pattern in a datasheet is not guaranteed inside your product. These installation factors can change it:
- Small or irregular ground plane
- Metal frame, battery, display, shield can, or mounting bracket
- Plastic enclosure thickness and dielectric loading
- Nearby cellular antennas and transmitters
- Coaxial cable routing near the patch
- Adhesive, radome, or weatherproof housing
If the device is used in an orientation that changes, test more than one position. A single upright lab result can hide real field problems. For ground-plane and enclosure validation steps, use the patch antenna design guide.
Common Mistakes
| Mistake | Why it is risky | Better approach |
|---|---|---|
| Choosing by peak gain only | Ignores coverage angle and pattern shape | Compare full pattern and average useful coverage |
| Treating beamwidth as separate from pattern | Beamwidth is only one pattern metric | Review main lobe, side lobes, back lobe, and polarization |
| Ignoring RHCP/LHCP data | GNSS depends on polarization quality | Ask for RHCP gain and axial ratio |
| Using datasheet pattern as final proof | Product enclosure changes performance | Test in the final assembly |
For the full topic hub, product paths, and application map, see the Patch Antennas guide.
FAQ
What is the radiation pattern of a patch antenna?
A patch antenna radiation pattern usually has a broadside main lobe, meaning strongest radiation or reception is perpendicular to the patch surface.
What is patch antenna beamwidth?
Patch antenna beamwidth is the angular width of the main lobe, often measured between points where gain has dropped by 3 dB from the peak.
Why does ground plane affect radiation pattern?
The ground plane is part of the antenna environment. Its size and shape affect current distribution, back radiation, and pattern stability.
Is wider beamwidth always better?
No. Wider beamwidth can improve coverage angle, but it may reduce peak gain or change rejection of unwanted directions. It depends on the application.
What radiation pattern should a GPS patch antenna have?
A GPS patch antenna should provide useful RHCP coverage toward the sky with acceptable gain, axial ratio, and multipath behavior in the installed device.
Conclusion
Patch antenna radiation pattern is one of the most important datasheet items because it shows where the antenna actually works. Beamwidth is useful, but only inside the full pattern story. For GPS/GNSS and embedded devices, check the installed pattern, not only the lab fixture plot.
View GPS / RHCP patch antenna options or contact our engineering team if you need radiation pattern data for your device layout.
