Modeling of an inverted L antenna (ILA) on a small chassis is expressed in a form of an equivalent RLC circuit. The complete model of the ILA consists of three parts: antenna radiator (AR)'s RLC resonator, chassis radiator (CR)'s RLC resonators and an AR-CR coupler. AR and CR's RLC resonators are systematically defined. The interaction between the AR and the CR is analyzed in a straightforward manner by adjusting the turn ratio of a transformer in the AR-CR coupler.