In Amplitude-Shift Keying (ASK) modulation, a voltage-controlled oscillator (VCO) is used to generate a carrier signal whose frequency varies based on the amplitude of the input signal. The VCO typically operates within a specific frequency range and is controlled by a control voltage.
The voltage threshold for triggering a VCO in ASK modulation depends on various factors, including the specific design of the VCO circuit, the modulation scheme being used, and the desired performance characteristics of the system. There is no fixed or standard voltage threshold that applies universally to all ASK modulations.
In general, the control voltage applied to the VCO should be adjusted to produce the desired carrier frequency when the input signal's amplitude is at its maximum (high) level. This typically involves designing the circuit such that the control voltage corresponds to the carrier frequency that is suitable for the application.
If you're working on a specific ASK modulation system, it's important to consult the datasheets or specifications for the VCO component you're using, as well as any application notes provided by the manufacturer. Additionally, the threshold voltage may also be determined through experimentation and testing to achieve the desired modulation performance.