The VCO is a voltage controlled oscillator and is an important part of the RF circuit. The RF circuit mostly uses modulation and demodulation, so it relies heavily on the local oscillator frequency. Modern communication technology requires new technologies such as multiplexing and frequency hopping. The use of voltage to control the capacitance of the capacitor in the oscillating circuit and thus the resonant frequency of the oscillating circuit has become one of the means to realize these technologies.
