LINEARLY POLARIZED CONICAL LOG-PERIODIC SPIRAL ANTENNA FOR MICROWAVE EMC EMI MEASUREMENT/

Theoretical values of site attenuation for broadband receiving antenna or the antenna factor of broadband antenna over the frequency range f rom 30 MHz to 1 GHz have been calculated or measured by some researche rs, For a frequency range over 1 GHz, wire antennas or horn antennas s hould be used. However, the theoretical site attenuation or antenna fa ctor over 1 GHz have never vet been calculated. A CLS (Conical Log-per iodic Spiral) antenna is generally used for EMC/EMI measurements in th e microwave band as a broadband wire antenna for the swept frequency m ethod. However this antenna has the defect that its use results in the loss of polarization information. So we proposed an improved CLS ante nna which has linear polarization. This new CI-S antenna has another w ire wound symmetrically to that of the standard CLS antenna. For this reason, we named it a double-wire CLS antenna. The double-wire CLS ant enna loses no polarization information. We calculated the height patte rn and the frequency characteristics of CSA (Classical Site Attenuatio n) for the double-wire CLS antenna when used for receiving, or used fo r both transmitting and receiving, as well as the antenna factor. More over, NSA (Normalized Site Attenuation) when the double-wire CLS anten na is used for receiving or used for both transmitting and receiving i n free space were calculated.