A new radio-frequency (RF) radiated immunity/susceptibility test method using four-septum TEM cell is proposed. A rotating-EM field can be generated inside the cell by feeding four-different RF DSB-SC signals to four septa arranged in the cell. Since a polarization plane of the rotating-EM field rotates in a low speed, the immunity/susceptibility test for the EM field with various polarizations can be conducted more easily. In this paper, a technique for generating the rotating-EM field in the cell is investigated. The basic characteristics of the cell and the rotating-EM field by using the technique are clarified. To verify the validity of this test method, a RF radiated susceptibility of a printed circuit board is measured. The measured results are verified by comparing with the theoretical results based on modified telegrapher's equations.

The four-septum transverse electromagnetic (TEM) cell is like the traditional TEM cell but has four plate-like septa in the internal space. A slowly rotating field can be easily generated in the four-septum TEM cell, thus radiated immunity/susceptibility characteristics of an EUT under arbitrary specific polarizations can be measured without rearranging the test setup. A design approach for the four-septum TEM cell is discussed in this paper. The characteristics of the cell are analyzed based on the telegrapher's equation and decomposition of the transmission mode into four independent modes. Then a design approach is given based on the analytical results. A prototype of the four-septum TEM cell based on the design is constructed and the characteristics of the prototype cell are experimentally evaluated. The validity and effectiveness of the design approach are confirmed.

A new generation method of rotating electromagnetic fields (rotating-EM fields) for radio frequency (RF) radiated immunity/susceptibility test and its basic characteristics are described. Two different double-side-band suppressed-carrier (DSB-SC) signals are required for generating the slowly rotating-EM field for the immunity/susceptibility test. These DSB-SC signals are generated by a DSB-SC-signal generator based on the new concept which consists of voltage-variable attenuators, bi-phase switches, a direct-digital synthesizer and a micro processor. Using the DSB-SC-signal generator, the DSB-SC signal of arbitrary RF frequency can be generated more easily than the conventional system. In this paper, the principle of the DSB-SC signal generator and the basic characteristics of the DSB-SC signals generated by the generator are clarified. The measured basic characteristics of the rotating-EM field generated using the new concept are shown and it is confirmed that the field can be applied for the RF immunity/susceptibility test. In addition, the susceptibility test of an equipment under test is made as an example, the validity of our proposed system is established.