Technological developments in the super minimal electronic device industry have led to miniaturization of expensive devices such as semi-conductors and memory chips. These devices are illegally used as hidden devices containing industrial information including top secret data. The methods used to hide these illegal devices are often skillful and ingenious, so that detection is becoming increasingly difficult. In order to detect the hidden device easily, the development of a wireless non-linear junction detector (NLJD) is needed. In this thesis, a hidden device detection method was proposed and a multiband circular polarization patch array antenna was designed for non-linear junction detector (NLJD) system application. In Chapter 2, the characteristic of non-linear device was presented. In Chapter 3 and In Chapter 4, a single radiator and array antennas were presented. To realize a good axial ratio of the circular polarization patch antenna, the inclined slots, two rectangular grooves, and the truncated ground are newly considered for the conventional antenna. A good axial ratio with 1.5 dB lower than that of the conventional one was obtained by having asymmetric gap distance between ground planes of the CPW feeding structure. The common ground plane of the linear array has the optimum trapezoidal slot array to reduce the mutual coupling without increasing the distance between the radiators. The higher gain of about 1 dBi was realized by using the novel common ground structure. The measured return loss, gain, and axial ratio of the proposed single radiator as well as the proposed array antennas showed a good agreement with the simulated results. The conclusion of this thesis was summarized in chapter 5.