RHCP Antennas vs. Linear-Polarized: GPS Insights from Measured Data

In MIOT’s ongoing GNSS hardware programs—including asset trackers, industrial sensing nodes, fleet/telematics devices, and smart IoT terminals—we have conducted extensive testing on antenna polarization, board placement, and overall RF performance. The choice of antenna has a significant impact on cold-start acquisition, signal stability, and positioning accuracy.

Linear Polarization vs. 25×25 mm Ceramic RHCP 

Linear-Polarized GPS Antenna

Linear-polarized antennas are compact and cost-efficient, but the polarization mismatch against GPS satellites (which transmit RHCP signals) results in:

• 3–6 dB polarization loss

• Cold-start TTFF around 50–60 seconds

• Lower signal strength (C/N₀), more unstable tracking

• Weaker performance in vehicles, city canyon, and indoor, near-window environments

• Higher sensitivity to multi-path reflections

This option is typically used for ultra-low-cost tracking but does not meet MIOT’s industrial-grade accuracy requirements.

25×25 mm Ceramic RHCP GPS Antenna

A 25×25 mm ceramic patch antenna provides a strong match to satellite RHCP polarization. MIOT’s tests show:

• Cold-start TTFF: 30–35 seconds

• 4–8 dB higher C/N₀ signal strength

• Much faster position convergence

• Better multi-path resistance

• More consistent accuracy across field scenarios

• Suitable for industrial, automotive, and high-performance IoT devices

This is MIOT’s recommended antenna option for all performance-sensitive GNSS applications.

Recommended GPS Antenna Scheme for Current Projects

Based on MIOT’s experience and customer requirements, we recommend the following approach for devices requiring stable GNSS performance:

✔ Recommended Option (MIOT Standard)

25×25 mm Ceramic RHCP antenna + GNSS LNA + well-isolated ground plane

• Delivers the highest GPS signal integrity

• Ensures robust performance in North American fleet and industrial environments

• Supports multi-GNSS (GPS / GLONASS / Galileo / BeiDou) without redesign

• Matches MIOT’s modular RF designs for future scalability

✔ Optional Compact Solution

18×18 mm or 20×20 mm Ceramic RHCP patch: For smaller enclosures, while keeping much better performance than linear antennas.

✘ Not Recommended for MIOT Industrial Devices

Wire/linear GNSS antenna, unless size or cost constraints dominate. Performance loss is significant and may not meet customer accuracy targets.

Hardware Layout and Antenna Placement Guidelines

To maximize GPS performance, MIOT’s RF and PCB teams follow several key principles:

Ground Plane Requirements

• Minimum recommended ground plane for 25×25 mm patch: 35×35 mm or larger

• Larger ground planes improve C/N₀ and tracking stability

• Keep the antenna centered on the ground plane when possible

Antenna Placement

• Position the patch at the top of the enclosure, facing the sky

• Avoid placement near: (1)High-speed digital lines; (2) Switching power regulators; (3) LTE/5G antennas; (4) Metal shielding cans

• Maintain at least 10–15 mm clearance from other antennas (LTE/WiFi/BLE)

  
  

RF Routing

• Use a 50 Ω controlled impedance trace from antenna → LNA → GNSS module

• Keep the GNSS feedline as short as possible (< 30 mm recommended)

• Avoid sharp bends; if needed, use 45° bends or arc traces

• Do not route under noise-heavy components such as DC-DC converters

Power & Noise Isolation

• GNSS LNA and module require clean, low-noise power

• Add: (1) π-filter at supply input; (2) Separate LDO from noisy 3.3 V rails; (3) Ground stitching vias around RF zone

Enclosure Considerations

• Plastic housing preferred

• If a metal housing is required: (1)Provide an RF window or a non-metal area above the antenna; (2) Avoid placing screws or standoffs directly over the patch

Conclusion

MIOT’s testing confirms that GNSS performance is driven primarily by antenna choice and RF design. Ceramic RHCP patch antennas—especially 25×25 mm—significantly outperform linear antennas in TTFF, signal strength, and positioning stability. For industrial and automotive IoT devices, MIOT recommends ceramic RHCP antennas with a proper ground plane and RF layout to ensure reliable, accurate, and scalable GNSS performance.