Investigation On The Low-RCS Conformal Microstrip Antenna

The antennas are not only an important part of airborne on the aircrafts,, but also the majorcontributor to the overall electromagnetic scattering characteristics of the aircrafts. For the stealthaircraft, the conformal design of the antenna for RF integrated and shape stealth is one of theimportant technologies. However, the electromagnetic scattering mechanism of the antenna especiallyfor that of the average scatterer is much more complex. Therefore, it is important to deal with thereduction method of electromagnetic scattering of the antenna.The works in this thesis are presented as follows:1The method for reducing the RCS of microstrip patch antenna with impedance-loadingand slot-cutting technique is investigated based on the analysis of surface current patterns. Theresult showed that the surface current of the dominant mode on patch antenna is changed by thetechnique of loading resistors on the edge of patch, by cutting slots on the patch surface, thehigher-order mode current on the patch surface is suppressed.Using these two techniques,theRCS of the antennas can be reduced in and out of the operation frequences band.A planar and aconformal antenna with the virtue of excellent radiation performance and low-RCS are designedrespectively and compared with the traditional microstrip antenna.2The effects of the arrangement element on the RCS of the conformal array are studied.The problem of RCS reduction methods are decomposed to two sub-problem,which are thepattern item of scattered and the structure item of scattered.which are verified correctly throughthe simulation results. The pattern items of scattered have connection with terminal matched andthe type of polarization of incident wave. The reduction of the structure item of scattered isimplemented by changing the angle between the incident wave and the front and also by thefront modification.3The issue that how to achieve the mutual invisible of the antennas is further studiedwhen the two antennas close together on the same platform. The induced surface current of thenon-working antenna can approximately impressed by loading impedance at the port of antenna.Then，the electrically invisible state of the non-working antenna is obtained. By this method, theinterference of non-working antenna to the radiated pattern of working antenna can be removed.