The paper reports on the coupled nonlinear/electromagnetic design of active LTCC transmitters including integrated antennas, based on neural models of the entire passive circuit layout. EM tools [1], [2] are used to train multiple neural network models of both the linear subnetwork and the antenna. A separate artificial neural network (harmonic neural network HNN) is used in the neighbourhood of each harmonic of interest in order to overcome the bandwidth problem. Special ANN are used to model the radiated field, allowing the design goals to be formulated in terms of far-field specifications, and suitable figures of merit encompassing radiation and nonlinear performance are introduced. The transmitter analysis and optimization is then carried out by connecting the nonlinear devices to the EM-derived multiport network.