Tuning limits of shunt varactor diodes for maintaining high OIP3 in arbitrary circuits

For the first time, an analytical formula is presented for calculating the OIP
₃
of any arbitrary circuit with a single shunt varactor diode. Additionally, numerical calculation of the limits on varactor tuning range when a specific OIP
₃
is desired is discussed, and a commercial varactor is found to maintain 44% of its tuning range with a OIP
₃
> 37 dBm.