Slots Based Ultro-wideband End-fire Antenna Design And Its Conformal Array Research

As the RF front-end of wireless communication system, antenna is critical for the performance of wireless communication systems. With the high development of wireless communication technique in recent years, the performance of antenna is required with higher standards, like wider working frequency band, higher gain and more compact size. According to FCC(Federal Communications Commission), the working frequency band for UWB communication is as wide as 3.1~10.6GHz. The gain of antenna for high resolution radar reaches 30 dBi or more. For wireless terminal device applications, six or more antennas need to be arranged in a limited room. Kinds of antenna miniaturization techniques need to be applied in this case.Some platforms for antenna mounting put a stringent aerodynamic requirements for antenna designs. The antenna must be designed well so that they can be conformally mounted to minimize windage. Different from traditional antenna, end-fire antenna can realize end-fire radiation with a lower profile which is preference for the conformal application. On the other hand, it is necessary for antenna designers to take the considerations of the specific mounting environment for end-fire antennas, including effects of metal surface and dielectric antenna radome which will be a challenge for antenna design. At the same time, traditional conformal array is mainly designed for omnidirectional beam coverage or the whole airspace coverage by the use of various Pattern synthesis methods of circle array. The research for end-fire conformal array is seldom reported publicly so far, but end-fire conformal array plays more and more important roles in the applications like ultrowide band passive direction-finding, phased array radar, anti-radiation missile and so on. Therefore, research on the relative theories and the design methods of conformally mounted wideband end-fire antennas and end-fire antenna array design has great significance.To solve the problems mentioned above, This paper designed a novel slots based ultrowide band end-fire antenna and the relevant conformal array. The designed antenna have a simple feeding structure, a low profile and is easy to be conformally mounted.The major research work and innovations are listed as following.First, the folded slot was proposed as the element of log periodic antenna to design a wide band end-fire antenna. Against the beam tilting phenomenon existing in thedesign, a essential analysis was carried out and a solution for this was proposed by extending the length of the ground in front of the slots.Second, because of the characteristic of bidirectional radiation for slots and the need for being mounted on the metal platform it, some techniques was proposed to make the slots unidirectional radiate. Here, we analyzed two different ways for this goal with comparison, that is, by metal reflector loading and metal cavity loading. By comparative research, we proposed cavity loading was a better solution. The influence of the key parameters of metal cavity on antenna performance was studied so that a guideline for the following design can be summarized.Third, a inverted structure was proposed and a dielectric cover was added on the radiation aperture of the antenna. By these means, the antenna can realize good impedance match and stable end-fire pattern in the whole frequency band(6~18GHz).The gain of the just end-fire direction can reach 4dBi or more.Fourth, a novel CPW-to-microstrip transition based on coupling structure was proposed to feed the antenna conveniently. The designed transition can realize low insertion loss and good impedance match.Fifth, this thesis researched the different radiation performance of the proposed antenna when it is used with metal platform and without metal platform. A theory analysis for electromagnetic wave propagation within the layered dielectric was carried out which can be used as the basic theory for analysis of the effects of the proposed antennas coming from the dielectric radome. The guideline for conformal array design can be obtained according to the research mentioned above.The proposed low profile slots based ultrowide band end-fire antenna which is just as low as 11.1mm is good for conformal applications and can realize stable end-fire radiation over the whole 6~18GHz. The gain at the just end-fire direction can reach4 dBi or more. Moreover, the analysis of the influence for the proposed antenna coming from the metal platform and the dielectric antenna rodome can be a good guideline for end-fire conformal array design. The research in this thesis provides a novel method for wide band end-fire antenna design and can find applications in ultrowide band passive direction-finding, ultrowide band conformal phased array radar, missile borne antenna and so on.