Research On Antenna Technology And Theory In The Application Of MIMO Communication

Compared to mainstream telecommunication standards, future telecommunication systems can provide wider intelligent experience. In different frequency bands, wireless communication service can be offered by the future telecommunication systems. Broad band communication can be connected to Inernet elsewhere(including satellite and stratosphere communication). Besides, location and time fixing, data collection and remote control can also be realized.However, considered as the most important link, the performance of MIMO antennas technology can decide the communication quality of the whole system. Nowadays, MIMO antennas technology has become one direction of the most popular researches in the mobile communication. But, high isolation, wide band and compact structure are hardly being realized at the same time.In general, miniaraturization, broadband and multi-frequency are difficult to be achieved by handheld mobile terminal unit antenna, simultaneously. In communiaciton application, mutual coupling and high correlation is also easily caused by the nonorthgonal properties of MIMO antenans system’s radiation field. The application of MIMO antennas technology is limited due to the disadvantage. Even if diversity technology is used, the increased volume of mobile terminal may be deleterious to the integration of mobile phone antenna and RF front-end. In the dissertation, the planar meandered monopole and PIFA with miniaturalized and broadband feature is applied as element antenna. These unit antennas are used to be integrated with hybrid structure in the design. Base on 2×2 MIMO mobile terminal antennas system design, the mode diversity theory and technology is studied in detail. The design has many advantages, such as high isolation, compact structure and wide frequency-band.The main contents of this dissertation can be summarized as following four parts:1. In the dissertation, the theory and implementation of conventional diversity methods for mobile communication MIMO antennas system is introduced. In strong coupling environment, mode diversity method based on electric and magnetic multipole moment theory is applied to solve the high correlation of mobile terminal MIMO antennas system. Besides, technology route of mode diversity in engineering realization is programmed. At last, these relevant specifications are proposed for our programme, according to the mobile communication standards.2. Mobile terminal unit antenna is also studied in the dissertation. Just as low frequency, wideband and multi-frequency, the miniaturization is required in mobile terminal equipment. In the dissertation, a new type of PIFA with slotted ground structure is proposed. With the use of probe-fed, the antenna has many virtues, such as simple construction, high tolerance degree, and can be integrated conveniently. So, antenna consistency is assured. Besides, lumped element, slotted ground and meandered strip are applied for miniaturization. With dual-shorted points design, a better handheld antenna performance is realized at GSM850/900, DCS/PCS, UMTS, LTE2300/2500, WLAN 802.11 and Wi-MAX.3. Hybrid feeding network used for MIMO antennas system is also miniaturized in the dissertation. This hybrid feeding network has two characteristics:(1). Correlation must be reduced by two orthogonal modes in the network.(2). The isolation must be lowered as much as possible. Certainly, the volume should be compact. The meandered strip and parallel coupling line inverter are firstly integrated in the design. At last, test prototype is manufactured. By measurement, dual frequency operation and wide band is verified, and there is a perfect isolated effect between the ports.4. In the dissertation, the integration of antenna front-ends is manufactured and designed. For poor matching effect of low frequency band in difference mode port, matching network and impedance transformer are proposed. Based on these methods, the matching performance is improved at some level. But, for wideband work in low frequency operation, mode diversity technology should be riched and perfected in engineering application. Based on the improved mode diversity theory, matched angles are filtered. At the same time, the feasibility for design of non-180 phase shift hybrid ring is adequately verified. After manufacturing and testing, thoroughly improved bandwidth of difference mode port is acquired.