Research On Electronically Steerable Antennas Based On Sub-wavelength Phase Modulation Structure Material

With development of radar and wireless communication technology, it is difficult for beam-fixed antennas to satisfy requirement of many new functions, especially for the beam steering function. Electronically steerable antennas are very attractive for remote transmission, anti-interference and detecting and tracking areas since it can achieve real-time beam steering and high gain. Traditional method to steer antenna beam is to use mechanical system, which has the disadvantages of low scanning speed, and frequently maintenance. Phase array antenna has the ability of realizing real-time scanning, but the use of many transceiver modules makes the whole antenna very expensive, blocking its wide application. Recently, sub-wavelength electromagnetic structure material(SESM) has caused much attention due to its unique phase modulation characteristic, and it may provide a low cost way to design electronically steerable antennas.In this dissertation, we mainly focus on the physical mechanism of SESM on electromagnetic phase modulation and its application in the electronically steerable antennas. Here we designed two kinds of SESM, which are based on frequency selective surface(FSS) and transmit-array, respectively. In addition, an amplifying SESM is studied to achieve high power output, and polarization modulation element is also integrated into the design of electronically steerable antennas for simultaneously controlling the polarization state and beam direction. The main works are illustrated as following three points.1. In order to reduce the cost of the traditional phased array, a kind of multilayer FSS-based material has been proposed to realize transmission phase tuning range over 360 deg by controlling the varactors loaded in its unit cell. When applying this material over a traditional horn antenna, the antenna composite can achieve continual beam scanning with a range of ±30° in both E- and H- plane.2. In order to construct highly integrated antennas for radar and wireless communication system, we have proposed an ultrathin phase modulation material using transmit-array. The proposed transmit-array is made of three parts: transmitter(Tx) cell, phase shifter with 360° of tuning range and receiver(Rx) cell, and it has small physical profile which is about 1/8 wavelength. When applying this transmit-array over a horn antenna, it can assist the horn antenna to achieve two-dimension beam scanning with a large angle range of ±60°.3. In order to further extend the antenna function, we have integrated polarization modulation element into the design of the transmit-array element, which not only can tune the polarization state, but also can control the transmission phase. In addition, an amplifying SESM has been proposed by inserting an amplifier into the transmit-array element. It can achieve high gain output and also compensate the high loss of the material, which paves the way for the application of this kind of SESM into the high power antenna system.