Why use an inductor?

Many consumer products communicate with each other through broadband networks, and the bandwidth of data communication is increasing. The integrity of RF signals has become a major concern in design. This article provides some examples of how to use different inductors for RF isolation in a series of circuits for data allocation from narrow band applications (such as portable devices) to broadband networks. The different types of inductors used in these applications were identified and discussed.

Essentially, an inductor is a low-pass filter. At high frequencies, inductors become high impedance components that can be used for RF isolation. High frequencies cannot pass through inductors, but allow direct current and very low frequency signals to pass through. Without this type of isolation, antenna efficiency will decrease, signal loss will occur, and RF noise will interfere with other parts of the circuit.

The peak impedance of the inductor occurs at the natural self resonant frequency. The size of the peak inductance is related to the quality factor (Q factor) of the inductance. Low loss inductors with high Q values have very high peak impedance, while loss inductors have lower peak impedance.

By changing the winding method of the coil or the materials used in the structure, multiple resonances can be adjusted to demonstrate high impedance over a wide bandwidth.