Reference Centre
Return to the Antenna Application Notes
Overview
Antenna selection is one of the most important factors affecting wireless performance in embedded IoT applications. This guide explains the advantages, disadvantages and practical considerations of embedded, PCB and external antenna solutions used in cellular, GNSS, WiFi, BLE and LPWAN systems.
For many embedded IoT products, the antenna is often considered late in the design process.
However, antenna selection has a direct impact on:
Even the best modem or wireless module will perform poorly if paired with an unsuitable antenna solution.
This guide explains:
Expected Result
At the end of this guide the user will understand how to select suitable antennas for embedded IoT and wireless communication systems.
The antenna is the interface between the wireless device and the RF environment.
A poor antenna choice can result in:
A well-selected antenna improves:
Modern embedded systems may support multiple wireless technologies simultaneously.
| Technology | Typical Application |
|---|---|
| 2G / GSM | Legacy telemetry |
| 3G / UMTS | Legacy packet data |
| LTE / 4G | Industrial connectivity |
| 5G NR | High speed applications |
| LTE-M | Low power IoT |
| NB-IoT | Deep indoor IoT |
| GNSS | Positioning |
| WiFi | Local networking |
| Bluetooth / BLE | Short range communication |
| LoRa | Long range LPWAN |
| Zigbee | Mesh networking |
There are three primary antenna approaches commonly used in embedded IoT devices.
| Antenna Type | Description |
|---|---|
| Ceramic Antenna | PCB mounted compact antenna element |
| PCB Antenna | Integrated or external PCB-based antenna |
| External Antenna | Remote mounted antenna connected via cable |
Each approach has advantages and disadvantages depending on the application.
Ceramic antennas are compact RF antenna elements designed for direct PCB integration.
They are commonly used where:
| Advantage | Benefit |
|---|---|
| Very compact | Suitable for small products |
| Low component cost | Reduced BOM cost |
| Internal integration | No external antenna required |
| Mechanically protected | Antenna enclosed within product |
| Disadvantage | Impact |
|---|---|
| Requires PCB tuning | Longer design cycle |
| Sensitive to enclosure changes | May require redesign |
| Ground plane dependent | Performance affected by layout |
| Requires RF expertise | Increased development complexity |
Ceramic antennas rely heavily on the PCB ground plane.
The effective antenna system includes:
As frequency increases, wavelength decreases and the required ground plane size is generally reduced.
Lower frequencies usually require larger PCB ground areas and more careful clearance around the antenna.
PCB antennas provide a pluggable antenna solution using small RF connectors and coaxial cables.
They are widely used in:
| Advantage | Benefit |
|---|---|
| Easy integration | Fast development |
| No PCB RF tuning | Reduced engineering complexity |
| Flexible positioning | Improved placement options |
| Replaceable | Easier optimisation |
| Disadvantage | Impact |
|---|---|
| Larger than ceramic antennas | Increased enclosure size |
| Cable losses | Reduced efficiency |
| Connector cost | Increased BOM |
| Internal mounting restrictions | Placement limitations |
PCB antennas should normally be:
Poor placement can significantly reduce performance.
External antennas provide the highest flexibility and often the best RF performance.
They are commonly used in:
| Type | Description |
|---|---|
| Adhesive Mount | Internal or window mounted |
| Direct Connect | Attached directly to device |
| Magnetic Mount | Vehicle or temporary mounting |
| Through Hole | Permanent enclosure mounting |
| Pole / Wall Mount | Outdoor fixed installation |
| Embedded | Internal enclosure antenna |
| Family | Mounting Style |
|---|---|
| ALPHA | Adhesive mount |
| DELTA | Direct connect |
| ECHO | Embedded |
| MIKE | Magnetic mount |
| OSCAR | Outdoor wall/pole |
| TANGO | Through-hole mount |
Antenna gain describes how effectively an antenna radiates or receives RF energy in a particular direction.
Gain is normally expressed in dBi.
Higher gain does not always mean better performance.
| Low Gain | High Gain |
|---|---|
| Wider radiation pattern | Narrower radiation pattern |
| Better for mobile use | Better for fixed installations |
| More tolerant to movement | Improved long-range performance |
| Better close coverage | Better distant coverage |
Omnidirectional antennas radiate in 360 degrees.
These are commonly used in:
Directional antennas focus RF energy in a specific direction.
These are commonly used in:
Yagi antennas are a common directional antenna type.
Modern LTE and 5G networks use many frequency bands.
Different regions and operators use different frequencies.
An antenna must support:
| Band | Frequency |
|---|---|
| Band 20 | 800 MHz |
| Band 8 | 900 MHz |
| Band 3 | 1800 MHz |
| Band 1 | 2100 MHz |
| Band 7 | 2600 MHz |
Many IoT devices require:
within the same enclosure.
This may require:
MIMO stands for Multiple Input Multiple Output.
MIMO uses multiple antennas to improve:
Modern LTE and 5G systems commonly use MIMO.
MIMO antennas require:
Poor placement reduces MIMO effectiveness.
Wireless systems are normally designed around 50 Ohm impedance.
Poor impedance matching causes:
VSWR stands for Voltage Standing Wave Ratio.
Lower VSWR values generally indicate better matching.
| VSWR Quality Scale | |||
| Poor | Fair | Good | Excellent |
| > 3.0 | 2.0 to 3.0 | 1.5 to 2.0 | < 1.5 |
| Min 1.0 | Max 5.0+ | ||
RF signals may be:
Incorrect polarisation alignment can reduce signal levels significantly.
Circular polarisation may be:
| Type | Description |
|---|---|
| RHCP | Right Hand Circular Polarisation |
| LHCP | Left Hand Circular Polarisation |
GNSS antennas commonly use circular polarisation.
Cable losses can significantly reduce antenna performance.
Higher frequency systems suffer greater cable attenuation.
Use:
When designing embedded wireless products, consider:
| Design Area | Consideration |
|---|---|
| PCB Layout | Ground plane and RF clearance |
| Enclosure | Metal and shielding effects |
| Cable Routing | RF isolation |
| Power Supply | Noise coupling |
| Battery Placement | Detuning risk |
| Antenna Position | Radiation efficiency |
| Mistake | Consequence |
|---|---|
| Choosing smallest antenna only | Reduced efficiency |
| Ignoring frequency coverage | Missing network bands |
| Ignoring enclosure effects | Detuned antenna |
| Using high gain everywhere | Poor local coverage |
| Poor cable selection | RF losses |
| Poor antenna placement | Weak signal |
| Ignoring MIMO spacing | Reduced LTE/5G performance |
| Type | Reason |
|---|---|
| Embedded PCB antenna | Compact and low profile |
| Type | Reason |
|---|---|
| External through-hole antenna | Improved coverage and flexibility |
| Type | Reason |
|---|---|
| Directional outdoor antenna | Improved long-range reception |
| Type | Reason |
|---|---|
| Magnetic mount antenna | Temporary mounting and mobility |
| Step | Action |
|---|---|
| 1 | Identify required technologies |
| 2 | Identify required frequency bands |
| 3 | Determine installation environment |
| 4 | Select mounting style |
| 5 | Review enclosure limitations |
| 6 | Select gain and radiation pattern |
| 7 | Verify impedance matching |
| 8 | Evaluate cable losses |
| 9 | Prototype and test |
| 10 | Validate final performance |
| Step | Action |
|---|---|
| 1 | Identify technologies |
| 2 | Review frequency bands |
| 3 | Select antenna type |
| 4 | Assess mounting constraints |
| 5 | Review gain requirements |
| 6 | Verify matching and VSWR |
| 7 | Optimise placement |
| 8 | Prototype and validate |
Reference Centre
Return to the Antenna Application Notes
Support
For further assistance, please contact the Siretta support team.