Linearity of PIN Diode Switch in Both ON-state and OFF-state

This paper focuses on the linearity behaviour of the PIN diode, a highly desirable component for RF switches and limiters. The non-linear behaviour of the PIN diode generates intermodulation in both its ON-state and OFF-state, with the OFF-state typically exhibiting worse behaviour. Despite its importance, the effect of the impedance seen by the PIN diode in determining its linearity behaviour is often overlooked. This paper investigates the effect of impedance on the third input intercept point (IIP3) of the PIN diode in both ON-state and OFF-state, using theoretical and experimental methods. To optimize the impedance seen by the PIN diode, a wideband impedance transformer is developed using a quarter-wavelength transmission line. The experimental results demonstrate a significant improvement of up to 9 dB in IIP3 measurements, with the highest measured IIP3 in both ON-state and OFF-state reaching 87 dBm.