What is the operating frequency range for this RF/microwave diode?
Answer: This question cannot be answered without information about the intended purpose of the circuit in which the diode will be used as well as information about the acceptable performance specifications for it.
For example, a PIN diode is often used as a switching element. The insertion loss and isolation the diode produces are determined by diode parameters (capacitance and series resistance) and the signal frequency.
For a shunt PIN diode, the magnitude of the vector sum of the diode’s series resistance when the diode is forward biased and its inductive reactance determines the isolation the diode produces. The diode’s capacitive reactance when it is not conducting largely determines its insertion loss. Both of these diode properties are affected by the signal frequency. The questions “How much isolation is enough?” and “How much insertion loss is too much?” determine whether a given diode is suitable for use at a specific signal frequency.
A varactor diode is commonly used as the tuning element in a resonant circuit in a voltage controlled oscillator. Such circuits also contain inductances or their equivalents which, in concert with the varactor capacitance, determine resonant frequency. This constitutes a single-equation-with-two-unknowns situation, in which the value of the inductance is as important as the varactor’s capacitance. Again, the suitability for use of a specific diode at a given frequency is decided by more than the diode’s properties alone.