Silicon-based PIN SPST RF switches for improved linearity

Analysis of PIN diode's geometric effects on the performance of RF switches is presented with measured data. The impact of periphery-to-area ratio (P/A) is investigated in terms of forward bias resistance and linearity. Theoretical analysis shows the smaller periphery-to-area ratio of PIN diode can reduce not only the forward biased resistance, but also the power handling capability. In addition, positive bias to the PIN diode's cathode terminal can reduce the effects of Psub-Nwell parasitic diodes, leading to enhanced linearity. Fabricated in a standard 0.18-μm SiGe BiCMOS technology, the 50 μm
²
PIN Single-pole-single-throw (SPST) RF switch MMIC can achieve an insertion loss of less than 0.69 dB from 2 to 18 GHz with the measured P
_1dB
of 16 dBm.