Design Of Ultra-Thin Broadband Antennas For Indoor Distributed System

With the promotion and popularity of the 4th generation communication system and the rapid growth of the number of users, customers put forward higher requirements for the mobile communication network coverage area and cover quality; it also proposes a bigger challenge for the communication suppliers at the same time. An indoor distribution system is a solution to improve the indoor mobile communication environment for indoor user groups. Indoor distributed antennas as the terminal equipment of the indoor distribution system, play a decisive role for indoor signal coverage, and also have a significant impact on the performance of the indoor distribution system. According to indoor distribution system construction requirements, the antenna should has characteristics of compact volume, broad bandwidth, low profile, and concealment, beautification functions. In this thesis, research for indoor distributed antenna has considerable necessity and practicability. This paper proposes three kinds of wide-band ultra-thin antennas for indoor distribution systems based on practical applications. The major contributions of this thesis are summarized as follows:1. An ultra-thin broadband omnidirectional antenna is proposed based on a plate dipole. Due to the utilization of the Hexagonal planar dipole substructure with patch loaded, the proposed antenna can cover all the indoor communication frequencies. Experimental results show that the VSWRs of the antenna are less than 1.5:1 over 0.7-2.8GHz. It has a stable, omnidirectional radiation pattern in its H-plane. The radiator size is3135′125′5mm and achieves small electrical dimensions of 0.337l ′0.313l ′0.0125l, making it electrically small suitable for ceiling or surface mounted indoor distributed antenna applications.2. An ultra-thin broadband omnidirectional antenna is presented taking the form of a wide slot configuration. The proposed antenna has wider bandwidth and thinner thickness than the first one. The fabricated antenna prototype has a measured impedance bandwidth of 129%, covering 0.69-3.1GHz with the VSWR less than 1.5.It has a stable, omnidirectional radiation pattern in its H-plane. The radiator size is 3Φ70*H2mm and achieves small electrical dimensions of 0.327l ′0.327l ′0.0046l. The advantages of the broadband, omnidirectional radiation feature and ultra-thin thickness make the proposed antenna a perfect candidate for ceiling or surface mounted indoor distributed antenna applications.3. A low profile broadband omnidirectional antenna is proposed. In order to reduce the height of the antenna, it consists of two antenna elements. One antenna element employs a PIFA structure to cover the 698-960 MHz frequency band, and the other antenna unit is a modified conical monopole to cover the 1.7-6GHz frequency band. The VSWR≤1.5 is achieved covering all frequency bands for 2G, 3G, 4G communications and WIMAX3500,WLAN5200/5800 systems. The omnidirectional radiation pattern is occurring at theta=30°. The measured results agree well with the simulated ones. Compared with the antennas in the references’, the proposed antenna height reduces greatly to 25 mm, making the proposed antenna a perfect candidate for indoor distributed antenna applications.