Impact of warm-up on S11 measurements of LoRa antennas using one-port USB-based VNAs

The stability and accuracy of S11 measurements of an antenna can be significantly influenced by the warm-up process of the Vector Network Analyzer (VNA) used. In the present work, the S11 parameter of two LoRaWAN antennas, working in the range of 915 to 928 MHz, is measured using two different USB-based 1-port VNAs: a PocketVNA and an Anritsu unit. A step-by-step procedure of measurement is proposed in order to evaluate the effect of warm-up the instruments and metric errors are also calculated . It is experimentally shown that warm-up can reduce the variability and increase the accuracy of the measurements.