Effect of impedance loading at higher harmonics on passive intermodulation in antennas

The goal of this work was to find out how the reflected PIM products are affected by different loading conditions at the 2nd and 3rd harmonics of excitation. The assembly, consisting of a GSM900 antenna and a microstrip feeding line with different impedance loads provided at 2nd and 3rd harmonics, was prototyped and measured with respect to PIM performance. As the PIM source, an SMA connector was used at the input of the antenna. Such a connector is very typical in patch antenna feeds and appears to be problematic in PIM sense.