Requirements for Accurate Design of Matching Circuits at 5 GHz

Abstract

There are many factors which make the design of matching circuits much more challenging at the 5 GHz frequency range than at lower frequencies. The starting point of the design is the measurement of the antenna input impedance at the correct reference plane, which must be determined using submillimeter accuracy. The measurement result also depends on the availability of a nearby ground reference, which is not always guaranteed. At higher frequencies, the effect of the layout (i.e., transmission lines between the matching components and parasitic reactances to the ground) becomes larger and must be taken into account in the design. Realistic and accurate component models of inductors and capacitors need to be used, capturing the effects of component losses and parasitic reactances. Finally, a proper measurement-based matching circuit design flow is not possible if the matching circuit layout interacts with the electromagnetic operation of the antenna.