The voltage threshold for triggering a Voltage-Controlled Oscillator (VCO) in Frequency Division Multiplexing (FDM) can vary depending on the specific design and application. In FDM, multiple signals are transmitted simultaneously over a shared communication channel by allocating specific frequency bands to each signal. VCOs are often used in FDM systems to generate carrier signals at different frequencies.
The voltage threshold for triggering a VCO in an FDM system generally depends on factors such as the desired frequency range, the tuning sensitivity of the VCO, the modulation scheme being used, and the noise tolerance of the system. The voltage-controlled oscillator's input voltage will affect its output frequency, and the threshold voltage at which the VCO starts oscillating will depend on its design parameters.
In many cases, the VCO might have a specified control voltage range within which it operates. This range might be defined by minimum and maximum control voltages. The VCO would typically start oscillating when the control voltage crosses a certain threshold within this range.
For a more specific answer, you would need to refer to the datasheet or technical documentation of the particular VCO you're using in your FDM system. It's worth noting that VCO characteristics can vary widely between different manufacturers and models, so the voltage threshold for triggering the VCO can differ from one device to another.