In phase-shift keying (PSK) demodulation, a voltage-controlled oscillator (VCO) is often used to recover the phase information of the modulated signal. The voltage threshold for triggering a VCO in PSK demodulation typically depends on the specific demodulation scheme and the design of the demodulator circuit.
In PSK demodulation, the VCO generates a waveform whose frequency is proportional to the phase of the incoming modulated signal. The exact voltage threshold for triggering the VCO can vary based on factors such as the modulation index, the desired demodulation scheme (e.g., binary PSK, quadrature PSK), and the characteristics of the VCO and demodulator circuitry.
In binary PSK (BPSK) demodulation, where the phase of the carrier signal is shifted by 180 degrees to represent different binary symbols, the VCO threshold might be set to detect the zero phase shift point or the phase shift between the two binary symbols.
In quadrature PSK (QPSK) demodulation, where the phase of the carrier signal is shifted by multiples of 90 degrees, the VCO threshold might be set to detect transitions between the quadrature phases.
The specific voltage threshold for triggering the VCO would be determined through the demodulator's design and the characteristics of the received signal. Generally, the threshold would be set to detect phase transitions accurately while minimizing the risk of false triggering or noise-induced errors.
It's important to note that the exact voltage threshold can be part of the proprietary design of a specific demodulator circuit, and it might not have a standardized value across all implementations. If you are working on a specific PSK demodulator circuit, it's recommended to refer to the circuit's documentation or consult with the circuit's designer for precise details regarding the VCO triggering threshold.