Low Profile Active Retrodirective Array Based On Phase Conjugation

As electronical information technology is developing rapidly,the demands of accuracy for locating and recognizing the target by the radar are rising steeply,whose performance has a great influence on the outcome of an electronic warfare.Retrodirective array(RDA)is able to reradiate beams back pointing at the direction of received microwave without foreseeing the information in order to implement reverse beam scanning.This unique function could enhance radar cross section(RSC)of the object so that the object judgement of hostile radar is well interfered.Indeed,passive RDA needs to achieve a balance between wideband and wide reverse scanning angle because of its fixed phase conjugate network,while a non-planar RDA is hardly laid on the surface of the object.To solve the mentioned problems,two kinds of planar and low-profile RDA combined with active modules,which is used to adjust RCS for this RDA,are proposed in this thesis.They both operate at X band(8-12GHz)and more details are given in following parts:1.A wideband RDA formed by magnetoelectric dipoles are designed based on Van Atta Array.Artificial magnetic conductor(AMC)is attached around the antenna unit to achieve a lower profile and a low coupling between the array elements,also implement a wider scanning angle of.At the same time,four groups of low noise amplifier(LNA)and voltage control attenuator(VCA)are added to phase conjugate network of Van Atta array to obtain a flexible control of the backscattering field.The application of unidirectional amplifier introduces benefits to solve the phase issue of Van Atta Array caused by the frequency variation and thus obtain both wideband and wide reverse scanning angle with a fixed phase conjugate network.2.This one-dimensional RDA is constructed by R-KR lens.Two layers of rotationally symmetric R-KR lens and one layer of feeding network constitute the whole RDA with only high and covering reverse scanning angle.A circulator and mentioned active module are loaded at feeding port to adjust the assembled energy from the incident microwave when an arbitrary microwave is received and focused by lens.To be specific,if a gain is provided by the active module,the assembled energy is amplified and reradiated back.On the contrary,if an attenuation is provided,the energy is consumed almost completely so that little microwave is reradiated.Therefore,this method acts as a selective transponder for an arbitrary incident microwave.