Electronics components fall into two categories—lumped components and distributed components. Lumped components are smaller than the wavelength, where:

In these cases, the wavelength of the voltages and currents at which they are operating is significantly larger than the components themselves. Ohm's Law, in this case, is valid. For example, a 1/4 watt resistor is about 0.270 inches long and 0.090 inches in diameter.

RF components, on the other hand, are most often distributed elements, where the phase of a voltage or current changes significantly over the physical extent of the device. This is because the device dimensions are similar to, and in some cases even larger than, the wavelength. Standard circuit theory is therefore not always applicable to circuits that are working at a few MHz to above 1 GHz.

The usual models for lumped components are often not valid for RF devices. For example, a capacitor can behave like an inductor and an inductor can behave like a capacitor at high frequencies.

RF components exhibit parasitic effects, and have models different from those used in low frequencies. Connections between two nodes at high frequencies exhibit different behavior than those at low frequencies, and are modeled using capacitances and inductances. These connections behave as transmission lines when implemented on a printed circuit board (PCB). The board itself becomes part of the circuit, interfering with the normal circuit function. Consequently, low frequency circuit simulation EDA tools can become unreliable at higher frequencies.

Standard RF components include capacitors, inductors, toroids, ferrite beads, couplers, circulators, transmission lines or striplines, waveguides, and high frequency active devices such as transistors and diodes. More complex components, such as quadrature hybrids, mixers, filters, and attenuators, are built using these standard components.