This paper describes the design of a balanced signal distribution system to feed an n by n set of mixers with local oscillator signals equal in frequency, phase and magnitude. This system is used in a planar n by n receiving/ transmitting array that measures and/or controls the direction of arrival of the received/transmitted signals. The design steps are clearly described. Optimization goals and variables are specified and the results of linear, electromagnetic and combined simulations are given and compared. The final product layout is shown and its performance is described. This paper is a typical example of a successful computer-aided design which saves time, effort and money before manufacturing a prototype. It introduces the active power divider as a zero-loss signal distribution device.