Antenna Compliance Design; Designing An External Passive Patch Antenna - Sierra Wireless AirPrime XS1110 Product Technical Specification

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Rev 4.0 Jul.20

Antenna Compliance Design

The GNSS antenna is the receiving part of the device that acquires weak GNSS

signals from the sky. A common solution is to use a ceramic patch antenna

because of its small form factor and low cost.

A passive antenna is a standalone component without a signal amplifier such as

an LNA. Patch antennas and chip antennas are the most commonly used passive

antennas with GNSS modules. When using an external passive antenna, ensure

that it is correctly fine-tuned to ensure best possible signal strength.

1. In general, a 50

patch antenna will work well with the GNSS module. The

antenna can be connected to the antenna IN pin with a 50

trace.

2. Keep the patch antenna far away from noise sources such as the switch

power supply, high speed digital logic signal, and radar wave guide.

3. The 50

trace should be kept as short as possible to reduce the chance of

picking up noise from the air and PCB. A simple direct-line trace is recom-

mended.

4. If needed, a matching circuit can be placed between the patch antenna and

the module. The matching circuit design could vary depending on the patch

antenna.

5. For 50

matching, refer to the following figure.

Figure 5-3: PCB trace design for antenna impedance matching

6. It is not necessary for the antenna design to use an active antenna. The

module design includes an external LNA that provides enough signal gain.

Sierra Wireless recommends the usage of a passive antenna that achieves

the best signal performance.

7. Use a shorter trace to improve the path losses, noise factor, and sensitivity.

General Rules for Circuit Design

impedance

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