| With the rapid development in the field of wireless communications, miniaturization of the terminal equipment becomes a research trend of major companies. Besides that, a series of questions, such as the increasingly constrained band resources of modern communications, more and more communication data, miniaturization of communication equipment, band resources and commumcation rate, and so on, naturally make many scientists keen to study. As an element to receive and transmit signals for wireless communications equipment, antenna inevitably becomes the research focus of many scientists. Now antenna is developing in the direction of miniaturization, broadband and multi-antenna. Miniaturization is in order to meet the trend of miniaturization of the terminal equipment, broadband is helpful to better adapt to communication band of various systems and increase band resources, multi-antenna is in order to adapt to a big, fast, a wider range of transmission data in modern communication.This paper mainly designs two minor ultra-wideband microstrip antennae and a small ultra-wideband antenna, integrating several methods of ultra-wideband microstrip antenna technology. Then according to one of them design a Ultra-WideBand (UWB)-Multiple Input Multiple Output (MIMO) antenna.The first antenna is multi-minor ultra-wideband antenna. The antenna uses the E-type symmetrical structure as the prototype. On this basis, we constantly expand the electrical length of the antenna and use a variety of matching techniques to achieve ultra-wideband performance. By digging semicircular groove through the ground, we make the S11parameter of7.5GHZ-12.6GHZ band lower than-10dB, then beside the semicircle groove we add two1/4circular grooves to make the S11parameters of12.6GHZ-14.7GHZ band lower than-10dB(Antenna is symmetrical on both sides, on the left and right there are respectively two semicircular grooves, on both sides of two semicircle grooves there are also two1/4circular grooves),thus these form the final ultra-wideband antenna, the bandwidth of which covers3.2GHZ-3.8GHZ and 4.6GHZ-18GHZ. And the antenna has a relatively high peak gain, which is substantially above lOdBi. Then, on the basis of this antenna process improvement, simplifying the structure of the antenna, the antenna is more stable during the test, the improved antenna working bandwidth of3.2GHZ to18.7GHZ.The second antenna is based on a traditional circular microstrip patch antenna, then we combine with a rectangular patch and rounded sides intersect to form a symmetrical structure, thereby increasing the electrical length of the antenna to obtain the bandwidth of the low band. And then we correspondingly match on the ground to get the3.1GHZ-11.5GHZ ultra wideband antenna, which covers the3.1GHZ-10.8GHZ ultra-wideband band the Federal Communications Commission (FCC) formulates, also its size is smaller than the size of previous circular ultra-wideband microstrip patch antenna.Third paragraph antenna is an UWB-MIMO antenna with4ports on the basis of the second antenna. These4ports are located in the four directions of the antenna. Two adjacent antenna radiating elements is perpendicular and on both sides of the dielectric substrate, which can increase the isolation between two adjacent radiating elements. Then add a cross of copper metallic structure, each foot of which is located between two adjacent radiating elements. This makes it possible for isolations within the S21, S31, S41at work frequency3.1GHZ-11. GGHZ of each radiating elements of antenna all are less than15db, then meet the isolation requirement of the communication system. And the height of the cross is only1.3mm, the total height of the antenna is only1.9mm, so it can be implanted into handheld communication devices with no big effect on the size of the equipment. The UWB-MIMO antenna with small size, high isolation, peak gain of lOdBi, basic radiation efficiency above90%, good diversity gain, is a good choice for UWB-MIMO systems. |
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