EMC ’ 04 / Sendai PW ( Parallel Wired ) cell using pyramid ferrite absorber as a microwave absorber

PW cell is used to test radiated electromagnetic field immunity for small equipment up to frequency of several GHz. As the carbon absorbers as a microwave absorber are conventionally used for PW cell, the inside measurement space is limited to small sized EUT. For the tests in this report, we tried to use a pyramid ferrite absorber, which has been developed recently, instead of a carbon absorber, in order to make the measurement space larger. First, we measured the return losses in the frequency range of 1 MHz – 6 GHz and then found that the return losses by the pyramid ferrite absorber were improved in the range of 40 – 500 MHz, comparing with those by the carbon absorber. Next, we measured the electric field uniformity inside the PW cell respectively at 100, 800 MHz and 2.4 GHz by both absorbing materials, and then found that the uniformity at 100 MHz by the pyramid ferrite absorber was improved similarly as the return loss and that the equivalent uniformity values were obtained by both materials at other frequency points. From the above results, by setting the pyramid ferrite absorber in the PW cell instead of the carbon absorber, it is clarified that the improvement of the reflection coefficients and uniformity as well as the enlargement of the inside measurement space are achieved.