v1.0

GPS mode

A simple test to evaluate Global Positioning System (GPS) sensitivity is to measure the CN0 level in radiated mode.

The following table shows recommended test cases for radiated GPS signaling mode.

Table 1. RF performance tests for radiated GPS signaling mode
Mode Test item Test specification/ID Requirement Note
GPS RX Total Isotropic Sensitivity (TIS) No regulatory limit.

Based on end product requirements or targets.

Recommendation for good GPS performance

CN0 = GPS_sig_level-Ant_Eff-RX_NF_tot–Noise_floor (at 1 Hz)

CN0 = -140 dBm -1.5 dBi -2 dB –(-174 dBm) = 30.5 dB

CN0 = -140 dBm –1.5 dBi (+ 3 dBic) -2 dB –(-174 dBm) = 33.5 dB (RHCP)

Radiated noise coupling from, for example, Integrated Circuit (IC)s or LEDs may cause desensitization to the GPS receiver that is impossible to test in other than radiated signaling mode

To achieve good GPS performance, the efficiency of the GPS antenna should be a minimum of 1.5 dBi. Using a Right Hand Circular Polarization (RHCP) type of antenna can improve the antenna's efficiency theoretically by 3 dB in ideal Over-the-Air (OTA) conditions. The antenna gain RX_NF_tot includes any potentially radiated spurious from other parts of the design, such as LEDs or ICs.