| Since ancient times,intelligence(information),together with material and energy,has been one of the basic resources for human survival and development.It traces the history of human communication and has existed for thousands of years in various main means of communication such as characters,symbols,senses and Courier stations.As a basis for the development of electrical communications,the artificial telegraph device was invented in 1837 by American Moss.Today it is less than 170 years old.Following the history of communication development and advancing along with the development of technology and market,communication,which has only taken more than 100 years to develop,has undergone tremendous changes and achieved astonishing and brilliant results.Due to scientific progress,electronic products have become one of the indispensable parts of the whole industry.Any industry has been fully or partially refined and dehumanized.In order to meet the needs of the industry,the demand for electronic products has also increased rapidly.Through the Internet,people can watch movies or entertain themselves online.However,with the development of smart phones and the increase of functions,the requirements for precision of devices are increasingly expanded,and the size of devices is further compressed.Antenna is a prerequisite for the operation of all kinds of communication systems.As mentioned above,the distance between antennas is also compressed.As a transceiver of the communication system,the influence of antennas is needless to say.In addition,the combination of antenna and antenna is an important bottleneck that affects antenna performance and restricts antenna development.In order to ensure the performance of the antenna,in practice there should be half wavelength interval between the antenna and the antenna.If the wavelengths are too close together,one surface wave travels through the antenna element to the other,causing a change in the current distribution on the antenna.As a result,the emission efficiency of the antenna is reduced and the antenna performance is low.How to make antenna which can coexist with each other is a difficult problem to realize antenna miniaturization.(1)A decoupling structure based on field cancellation method was designed to solve the coupling problem between PIFA antenna and dipole antenna with small spacing in the shielding cavity.This decoupling structure can introduce an additional coupling field between the antennas and cancel with the original direct coupling field so as to reduce the mutual coupling.The structure can make the mutual coupling of the antenna resonant at 433 MHz less than-10 d B in the shielding cavity,and the mutual coupling of the antenna is still low when the beef mass changes.(2)A decoupling structure based on SRR ring with band-stop filtering is designed,which can inhibit the propagation of electromagnetic waves in the coupling path of PIFA antenna.At the same time,grooves were made on the ground and side walls to filter the coupling of ground current.The simulation shows that this structure has a good coupling inhibition effect in both free space and shielding cavity.When the antenna resonance is 433 MHz and 2.5kg beef is placed,the mutual coupling of the antennas is less than-10 d B.(3)a decoupling structure based on single negative material is designed.The equivalent permeability of this structure is positive while the dielectric constant is negative.When the electromagnetic wave is incident in the horizontal direction,the energy is suppressed because the propagation constant is a pure imaginary number.The simulation shows that the mutual coupling between the PIFA antennas is about-12 db when the four-layer single-negative material structure is added.When the beef mass increases from 2kg to 4kg,the resonant frequency of the antenna is somewhat offset,but still less than-10 d B at 433 MHz,and the mutual coupling of the antenna is always less than-10 d B.(4)in order to further reduce the influence of beef mass change on antenna performance,a decoupling structure based on cutting line was designed.The decoupling effect of this structure was not affected by the distance of the antenna.When beef mass increased from 1kg to 5kg,antenna resonance was always at 433 MHz and antenna mutual coupling was always less than-10 d B... |
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