Improved structure and method for isolation among multiple antennas in MIMO system based on PIFA antenna

Abstract

The invention relates to an improved structure and a method for isolation among multiple antennas in an MIMO system based on a PIFA antenna, which are used for improving isolation among multiple antennas in the MIMO system based on the PIFA. The structure is characterized by comprising a plurality of PIFA antennas, a plurality of 50-ohm transmission lines electrically connected with ground arms ofthe PIFA antennas respectively, an RLC series resonance circuit electrically connected with the second ends of the 50-ohm transmission lines together, and transmission lines electrically connected with feed ports of the PIFA antennas and having the electrical length of e1 + e2. Every two groups of e1 + e2 transmission lines are connected in parallel with an SIR transmission line at a node with anelectrical length of e1. The structure can be applied to improvement of the isolation degree of the omnidirectional PIFA antenna of the indoor and outdoor small base stations at present, is a systematic design method, can solve the problem of poor isolation degree among multiple antennas, is clear in design steps, is added with a decoupling network, does not influence standing wave and radiationcharacteristics of the originally designed antenna, and does not need to repeatedly change the layout of the antenna.

Description

Technical field: [0001] The invention relates to an improved structure and method for isolation between multiple antennas in a PIFA antenna-based MIMO system. Background technique: [0002] With the development of modern communication technology, the application of MIMO technology has penetrated into all common base stations and terminals, and a key index in MIMO technology is the isolation of antennas. When the isolation between antennas is insufficient, the communication capability of the MIMO system will be reduced. For MIMO communication systems in the industry, in general, the isolation requirement of the antenna is above 20dB, and the higher the better. [0003] Due to the constraints of aesthetics, wind resistance, and cost on current base stations and terminals, the volume requirements for equipment are becoming more and more stringent. At the same time, MIMO systems have higher and higher requirements for communication rates. 4*4 and 8 The coexistence of multiple a...

AI Technical Summary

Problems solved by technology

[0005] Because the volume of indoor and outdoor small and medium-sized base stations is between very small base stations or terminals and large outdoor base stations, the space left for antennas is relatively critical, and the distance between antennas can still be greater than the near field radiated by omnidirectional antennas, which is not as compact as mobile phones. It is not as rich as the macro station antenna. In order to meet the performance of the antenna, the isolation between the antennas of the MIMO system is often between 10~20dB. Many manufacturers often achieve the isolation requirement through reasonable layout of the antenna position or the use of cross-polarization schemes. , but in this case, the radiation characteristics of the antenna are often sacrificed. The former is to find the zero point of the antenna radiation and align the zero point position with the adjacent antenna to improve the isolation between the antennas, which leads to the deterioration of the omnidirectionality of the antenna radiation. The latter has a good effect on improving the isolation, but because the efficiency and coverage of the horizontally polarized antenna are not as good as the vertically polarized antenna, and the horizontally polarized antenna needs to occupy a large space in the low frequency band, it is a compromise consideration. Although the two methods improve the isolation between antennas, the deterioration of other indicators will also affect the performance of the MIMO system

[0006] At present, there are two preferred methods for omnidirectional antennas. First, parasitic radiation elements improve the coupling between antennas; this method is more effective for MIMO systems with a small number of antennas, but once the isolation between multiple antennas cannot meet the target , this method will be more cumbersome to design, because there are more and more complex situations in multi-antennas; second, cut off the coupling current on the ground; this method is also aimed at between two antennas, once The isolation index cannot be met between multiple antennas, and the design is often difficult

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