A simple electric near field probe for microwave circuit diagnostics

An electric field probe applicable to the 1-20 GHz band has been developed, using miniaturized semirigid coaxial cable. It is shown that the probe is well suited for the diagnostic of the microwave circuits. The field probe has very small dimensions and it does not need to be connected to the operating circuit under test, therefore the circuits properties nearly are not disturbed by the probe. This simple, stable and cheap field probe is very useful for assisting the design of microwave circuits, antenna diagnostics and testing products in industry. As an example, the field distribution in a 2.4 GHz hybrid power amplifier is measured and the result is analyzed in this paper.