An RF choke works based on the principle of inductance.
In an RF choke, the coil of wire acts as an inductor. When an alternating current (AC) passes through it, an electromagnetic field is generated around the coil.
Due to the property of inductance, the RF choke opposes any change in the current flowing through it. At high frequencies (in the radio frequency range), the inductive reactance (XL = 2πfL, where f is the frequency and L is the inductance) becomes very high. This high inductive reactance restricts the flow of AC current, especially at the intended radio frequencies.
This property makes RF chokes useful in various applications. For instance, in power supply circuits of electronic devices, they help filter out high-frequency noise or RF interference, allowing only the desired direct current (DC) or low-frequency components to pass. In radio frequency circuits, they can be used to block or limit the flow of RF signals in specific paths or branches, control the resonant frequency in tuned circuits, or provide impedance matching to optimize the power transfer and performance of the circuit.
In summary, the RF choke's ability to present a high impedance to high-frequency AC currents while having a low impedance to DC or low-frequency currents is what makes it an essential component in many radio frequency and electronic circuits.