Isolation Method Research For Strongly-Coupled Antennas

Coupling is a parameter closely related with radiation performance in multi-antenna system, and it is one of the bottlenecks of appliance of multi-antenna system. Isolation is one of the most important steps during the designing of multi-antenna system too. According to higher and higher request for miniaturization of electronic systems, coupling among antennas increases sharply with smaller distance among antennas in multi-antenna system. So that it has become a main source of system noise, which paralyzes system features. Minimizing coupling, improving isolation is a premise for appliance of multi-antenna system under the situation of small dimension.To resolve the seriously influence to radiation performance from previous isolation methods, two new decoupling methods are proposed in this paper: isolation method with reverse-phase coupling and isolation method with reverse-phase signal, both of which realize high isolation by introducing additional reverse-phase signal to offset original coupling among antennas. Reverse-phase coupling method introduces reverse-phase coupling by resonance inverter, while reverse-signal method uses micro-strip to extract a signal with the same amplitude of coupling from radiation antenna and carry it for one half wavelength to invert the phase. In the futher, both of these two methods hardly affect the radiation structure and feed of antennas, and they make little influence to radiation performance of antennas. Certainly, these two methods extend the application for low requirement of antenna unit. The experiments results show that these two methods are useful to increase the isolation between the compacted antennas, and the antenna element keep it's good radiation performance. Meanwhile, the methods of polarization isolation are summarized in this paper, and its application is extanded under new situations. On the basis of the proposed isolation methods for dual-antenna structure, this paper discovers requirements and realization for quad-antenna structure and multi-antenna structure, and tries to increase the isolation of quad-antenna by designing an quad-antenna system with former new methods, so as to minimize size of multi-antenna structure in electronic and communicate systems.