Research On The Control Of Antenna Radar Cross Section

Stealth technique is playing an important role in the modern warfare because the battlefield survivability of the combat platform is greatly affected by its stealth performances. The stealth technique will be applied more and more widely in the future integrated electronic warfare. Antennas are the necessary components on radio equipments such as radars, communication systems and so on. The radio equipments work only if the electromagnetic waves are well transmitted and received by the antennas in the complex battlefield environment. Antennas become one of the most important targets due to their special operating characteristics. One of the most urgent problems in the stealth technique is how to make the antenna invisible to the enemies while maintaining good working performance. Being associated with national research projects, this dissertation focuses on the antenna scattering theory and antenna radar cross section (RCS) control techniques. The antenna RCS control techniques on the ultra wide band (UWB) antenna, circular polarization antenna, monopole antenna and antenna array are studied. The author's major contributions are outlined as follows:1. The far field expressions of the antenna radiation field are derived and applied on the derivation of the far field expressions of the linear and circular polarization antennas. Expression of the incoming traveling-wave amplitude received by the linear and circular polarization antennas is derived based on the reciprocity theorem. According to the theoretical formulas of the antenna scattering, the scattered field expressions of the linear and circular polarization antennas are also derived. This is the theory foundation of the study on the linear and circular polarization antennas in the following sections.2. Based on the sequence of antenna design and RCS control, a novel method for antenna RCS control is proposed, which designs the antennas according to the radiation and scattering requirements and then compensates the loss of the radiation performance. In the conventional methods a design margin of radiation performance should be made in order to reckon in the deterioration of radiation performance resulted from the RCS reduction. Generally it is difficult to precisely predict the loss of the radiation performance, so it is a big challenge to determine the design margin. However this problem is totally avoided by the novel method proposed by the author.3. According to the new method, a UWB antenna with low RCS level is designed. The radiation and scattering characteristics of the proposed antenna are analyzed. Compared with the reference antenna, the scattering mechanism of the UWB antenna is studied by applying the parameter analysis. At last, the validity of the new method is proved by simulations and measurements.4. Based on the study on the radiation and scattering mechanism of the circular polarization antenna, a novel circular polarization microstrip antenna with low RCS level is designed. The radiation mechanism of the proposed antenna is studied by applying the parameter analysis. And the time and frequency domain characteristics are studied and compared with those of the reference antenna. At last, the radiation and scattering characteristics of the proposed antenna are proved by simulations and measurements.5. According to the frequency of the incoming wave the antenna scattering can be separated into the in-band scattering and out-band scattering. According to the scattering mechanism the antenna scattering can be separated into the antenna mode scattering and structural mode scattering. Based on the two standards above, the antenna scattering can be classified in four related parts: in-band antenna mode scattering, in-band structural mode scattering, out-band antenna mode scattering and out-band structural mode scattering. By the analysis on the difference between the four parts, a novel method for antenna in-band structural mode RCS control is proposed.6. According to the new method, band pass frequency selective surface (FSS) is applied in the monopole antenna in-band RCS control. A monopole antenna with low in-band RCS is designed and its radiation and scattering characteristics are studied. The validity of the new method is proved by simulated and measured results.7. Based on the research on the circular polarization antenna RCS control technique, the low RCS circular polarization antenna proposed in chapter 4 is used in the design of circular polarization array. The radiation and scattering characteristics of the proposed array are studied. The structural mode scattering and frequency domain scattering characteristics are analyzed and compared with thoses of the reference antenna. At last the performances of the proposed array are proved by simulations and measurements.