Intermodulation and harmonic distortion in frequency reconfigurable slot antenna pairs

Due to the nonlinear nature of solid state devices, reconfigurable antennas with PIN diodes are capable of producing spurious frequency products through intermodulation and harmonic generation. These undesirable signals might act as an interference source to other electronic systems. In this paper, we investigate intermodulation and harmonic generation in frequency reconfigurable MIMO slot antennas. Our study has shown that intermodulation is more pronounced in the transmitting scenario than the receiving case. It is also found that an 'off' diode needs to be appropriately reverse biased to avoid RF leakage and harmonic generation when the RF power is high. In addition, the effect of mutual coupling on intermodulation and harmonic generation has been studied experimentally. Our results show that the level of intermodulation could be lowered by reducing the mutual coupling between the antenna ports. Lastly, we demonstrate that a particular spurious frequency product may be suppressed by inserting harmonic traps at the antenna level.