The voltage threshold for triggering a Voltage-Controlled Oscillator (VCO) in Phase-Shift Keying (PSK) modulation can vary depending on the specific design and implementation of the modulation scheme, as well as the characteristics of the VCO being used.
In PSK modulation, the VCO is often used to generate the carrier signal, and the phase of the carrier signal is shifted based on the data being modulated. The exact voltage threshold for triggering the VCO would depend on factors such as the modulation index, the desired phase shifts, the frequency range of the VCO, and the specific circuitry used in the implementation.
Generally, the voltage threshold for triggering a VCO in PSK modulation would be set based on the specific requirements of the communication system. It would typically be determined through experimentation, simulation, or calculations that take into account the desired modulation characteristics and the VCO's frequency and control voltage characteristics.
If you are working on a specific PSK modulation implementation, it's best to consult the datasheet or documentation for the VCO being used and perform any necessary calculations or simulations to determine the appropriate voltage threshold for your particular application.