GPS antenna requirements

To reach optimized Global Positioning System (GPS) sensitivity, a high-efficiency antenna and external Low-Noise Amplifier (LNA) are needed. GPS front-end, antenna, and the characteristic impedance of the GPS transmission line must be 50 Ω to minimize mismatch losses.

A GPS signal is broadcast by satellites with Right Hand Circular Polarization (RHCP). If the orientation of the device in actual use can be pre-defined, selecting an RHCP antenna that has a directive radiation pattern with maximum gain towards the sky may be advantageous. Due to multipath propagation, the angle of arrival may vary significantly in some environments.

Polarization may differ when the signal reaches the device. Therefore, a linearly polarized terminal GPS antenna with a relatively low maximum gain typically offers adequate antenna performance. Antenna efficiency should be as high as possible, but a minimum of 50 %. The GPS antenna and front-end requirements are summarized in the following table.

Table 1. GPS antenna and front-end requirements
Parameter Requirement Note
50 Ω impedance, antenna VSWR <2:1 Recommendation
<3:1 Absolute requirement
50 Ω impedance, antenna Return Loss (RL) >9.5 dB Recommendation
>6.0 dB Absolute requirement
Efficiency >50 % Recommendation
LTE TX rejection >30 dB Absolute requirement between the ANT and GPS pins and a recommendation between the LTE antenna and external GPS LNA input. Note the impact of both the antenna and layout.
LNA gain >15 dB Recommendation
Maximum LNA Noise Factor (NF) 1.0 dB Recommendation
Maximum LNA filter module NF 1.5 dB Recommendation

A dedicated GPS antenna or combined LTE and GPS antenna can be chosen.

In both cases, the LTE TX attenuation requirement in the GPS input must be met. Examples of GPS antennas are listed in the following table.

Table 2. GPS antenna examples
Vendor Product Part number Note
Abracon 1575MHz GPS Ceramic Chip Antenna ACAG0301-1575-T Miniature ceramic chip antenna (SMD) with linear polarization
Pulse GPS L1 Band & GLONASS Ceramic Patch Antenna - Ceramic patch RHCP antenna, manual soldering
Ignion TRIO mXTEND FR01-S4-210 SMT chip antenna component. Can be tuned to cover LTE and GPS with adjusted matching network.