Reference Centre
Return to the Antenna Application Notes
Overview
GNSS antenna selection plays a critical role in positioning accuracy, satellite acquisition speed and overall receiver performance. This guide explains GNSS antenna types, ground plane behaviour, active and passive antenna operation, antenna placement and practical integration techniques for embedded IoT and telemetry applications.
Global Navigation Satellite System (GNSS) receivers are widely used throughout modern IoT and embedded systems.
Applications include:
The GNSS antenna is one of the most important factors affecting:
A poorly selected or badly installed GNSS antenna can significantly reduce positioning performance even when using a high-quality GNSS receiver module.
This guide explains:
Expected Result
At the end of this guide the user will understand how to correctly select and integrate GNSS antennas for embedded wireless applications.
GNSS stands for:
Global Navigation Satellite System
GNSS refers to satellite positioning systems used to determine:
Modern GNSS receivers commonly support multiple constellations simultaneously.
| Constellation | Region | Operator |
|---|---|---|
| GPS | Global | United States |
| GLONASS | Global | Russia |
| Galileo | Global | European Union |
| BeiDou | Global | China |
| QZSS | Japan / Asia-Pacific | Japan |
| NavIC | India Region | India |
| SBAS | Regional Augmentation | Various |
Modern receivers commonly combine multiple GNSS constellations simultaneously.
Benefits include:
GNSS systems operate across several RF frequency bands.
| Band | Frequency | Typical Use |
|---|---|---|
| L1 / E1 | 1575.42 MHz | Primary civilian GNSS |
| L2 | 1227.60 MHz | Precision positioning |
| L5 / E5 | 1176.45 MHz | High precision applications |
| GLONASS G1 | 1602 MHz region | GLONASS positioning |
| BeiDou B1 | 1561 MHz region | BeiDou positioning |
Several antenna types are commonly used in embedded GNSS applications.
| Antenna Type | Typical Use |
|---|---|
| Ceramic Patch | High performance GNSS systems |
| Embedded PCB | Compact embedded products |
| External Active GNSS | Vehicle and outdoor systems |
| Low Profile GNSS | Discrete outdoor installations |
| Helical Antenna | Compact GNSS devices |
GNSS antennas are generally categorised as:
Passive antennas contain only the antenna element itself.
They do not include amplification circuitry.
Passive antennas are typically used where:
| Advantage | Benefit |
|---|---|
| Low cost | Reduced BOM cost |
| Simple integration | No antenna power required |
| Compact design | Suitable for embedded systems |
| Disadvantage | Impact |
|---|---|
| No amplification | Reduced weak signal performance |
| Cable losses more significant | Reduced receiver sensitivity |
| Less suitable for long cable runs | Lower signal margin |
Active antennas include an integrated:
The amplifier boosts weak satellite signals before cable losses occur.
Active antennas are commonly used in:
| Advantage | Benefit |
|---|---|
| Improved receiver sensitivity | Better weak signal performance |
| Compensates for cable losses | Improved installation flexibility |
| Better urban performance | Improved satellite acquisition |
| Disadvantage | Impact |
|---|---|
| Requires DC bias voltage | Additional integration requirements |
| Higher cost | Increased BOM |
| Possible amplifier overload | Reduced performance in interference environments |
Ceramic patch antennas are one of the most common GNSS antenna types.
They are widely used because they provide:
Patch antennas generally perform best when mounted above a suitable ground plane.
GNSS antennas are highly sensitive to ground plane behaviour.
A suitable ground plane improves:
Insufficient ground plane size may cause:
| Ground Plane Size | Typical Behaviour |
|---|---|
| Small ground plane | Reduced GNSS performance |
| Medium ground plane | Acceptable embedded operation |
| Large conductive ground plane | Improved efficiency and stability |
GNSS systems use:
Right Hand Circular Polarisation (RHCP)
GNSS antennas are therefore designed to support RHCP operation.
Correct polarisation improves:
GNSS satellite signals use:
Right Hand Circular Polarisation (RHCP)
GNSS antennas are therefore normally designed to receive RHCP signals.
When GNSS signals reflect from surfaces such as:
the reflected signal may partially convert into:
Left Hand Circular Polarisation (LHCP)
Because GNSS antennas are optimised for RHCP operation, many LHCP reflected signals are naturally attenuated by the antenna.
This helps reduce:
This differs from many cellular systems where reflected signals may still be received with similar polarisation characteristics, potentially creating constructive and destructive interference patterns.
As a result, GNSS RHCP antenna designs help improve positioning stability in difficult RF environments by reducing the impact of reflected LHCP signals.
Multipath occurs when GNSS signals reflect from nearby surfaces before reaching the antenna.
This can cause:
Common reflective surfaces include:
| Recommendation | Benefit |
|---|---|
| Use quality GNSS antennas | Improved signal discrimination |
| Install with clear sky visibility | Reduced reflections |
| Avoid nearby metal structures | Reduced RF distortion |
| Use larger ground planes | Improved pattern stability |
Correct antenna placement is critical for reliable positioning.
GNSS antennas should ideally be:
| Poor Placement | Possible Result |
|---|---|
| Inside metal enclosure | No GNSS reception |
| Under vehicle dashboard | Weak satellite visibility |
| Near LTE antenna | RF interference |
| Near switching regulators | Receiver noise issues |
Many embedded IoT systems combine:
within the same enclosure.
Poor RF isolation may cause:
| Recommendation | Purpose |
|---|---|
| Increase antenna separation | Reduce RF coupling |
| Use filtered GNSS antennas | Improve interference rejection |
| Use proper grounding | Reduce RF noise |
| Avoid parallel RF cable routing | Reduce coupling effects |
GNSS signals arriving from satellites are extremely weak.
Cable losses can therefore significantly affect receiver performance.
Long cable runs may:
| Recommendation | Benefit |
|---|---|
| Use shortest practical cable | Reduced attenuation |
| Use low loss RF cable | Improved receiver sensitivity |
| Use active antennas for long runs | Compensate for cable loss |
| Minimise connector count | Reduced insertion loss |
Vehicle installations introduce additional challenges:
Low profile active GNSS antennas are commonly used in:
GNSS performance is commonly assessed using:
| Metric | Description |
|---|---|
| Satellites in View | Total visible satellites |
| Satellites Used | Satellites contributing to fix |
| HDOP | Horizontal Dilution of Precision |
| PDOP | Position Dilution of Precision |
| C/N0 | Carrier to Noise Density Ratio |
| TTFF | Time To First Fix |
| Application | Typical GNSS Requirement |
|---|---|
| Asset tracking | Compact embedded antenna |
| Vehicle telemetry | Active roof-mounted antenna |
| Agriculture | High precision GNSS |
| Timing systems | Stable satellite visibility |
| Industrial IoT | Robust outdoor operation |
| Mistake | Consequence |
|---|---|
| Poor sky visibility | Weak positioning performance |
| Ignoring ground plane requirements | Reduced antenna efficiency |
| Long low-quality RF cables | Signal attenuation |
| Incorrect antenna polarisation | Reduced signal reception |
| Poor LTE isolation | GNSS interference issues |
| Mounting inside metal enclosure | Complete signal blockage |
| Step | Action |
|---|---|
| 1 | Identify GNSS performance requirements |
| 2 | Select active or passive antenna |
| 3 | Review ground plane requirements |
| 4 | Assess enclosure limitations |
| 5 | Determine cable length constraints |
| 6 | Optimise antenna placement |
| 7 | Verify LTE coexistence behaviour |
| 8 | Validate GNSS performance metrics |
| Step | Purpose |
|---|---|
| Select antenna type | Match application requirements |
| Review ground plane | Improve antenna efficiency |
| Optimise placement | Improve sky visibility |
| Reduce cable losses | Improve signal sensitivity |
| Validate GNSS metrics | Confirm positioning performance |
Reference Centre
Return to the Antenna Application Notes
Support
For further assistance, please contact the Siretta support team.