| As a device to receive and transmit signals in wireless communication,the antenna plays an important role in the RF front-end.Also,the filters,duplexers and amplifiers are indispensable parts for the RF front-end.However,the research of a single RF front-end component has developed decades.It has been becoming a limitation,such as the insertion loss,out-of-band suppression and frequency selectivity of the filter,the combing efficiency of the power amplifiers,or the size of the antenna.Then how to further reduce the loss and size of RF front-end is a problem.In order to solve this problems,the multi-functional antenna is proposed in this paper.Based on the “extra” potential performance of an antenna,multi-functional antennas integrated with filtering response or power combining are proposed in this paper.Two dual-band antenna units with high isolation based on the filtering elements,two power combining antennas based on the multiple feeding ports are designed in this paper.Without extra feeding network,the filtering performance or power combing capability can be achieved by these proposed antennas.Miniaturization and low-loss can be realized in RF front-end.The details of this paper are as follows:(1)In the design of multi-functional antenna with filter response,a dual-band dual-polarized base station antenna array with a small frequency ratio is designed.This design operates at two commonly used bands,790-862 MHz and 880-960 MHz.Due to the two bands are close,mutual coupling will be very strong when the two arrays are placed together,resulting in serious degradation of isolation and radiation performance.The common method in the industry is to design two antenna arrays separately.In this way,the distance between two arrays must be large enough to realize the required isolation,which will lead to high cost in base-station erection.In this paper,a decoupling mechanism based on filtering antenna is proposed.Without additional duplexer,high isolation between two arrays at close bands is achieved in a small ground size.Compared with the similar antenna designed by the company KATHREIN,the size is reduced by more than 50%.Based on the decoupling mechanism of filtering antenna,another dual-band dual-polarized antenna unit is designed for the 4G LTE band(2.5-2.7 GHz)and 5G band(3.3-3.8 GHz).Compared with the last dual-band antenna,this antenna is with better out-of-band suppression and more compact size.This dual-band dual-polarized antenna unit can achieve isolation of-27 dB in the whole operating frequency band without using extra filtering circuit.(2)In the design of multi-functional antenna with power combining,patch antennas fed by arbitrary port number and feeding position are studied firstly.This multi-port antenna can directly be connected to multiple amplifiers,without additional power combiner,to achieve power combining.The traditional method of power combining is to use the power combiner to realize the combining of multiple amplifiers in parallel,which will introduce additional line losses.The proposed multi-port antenna with arbitrary feeding port number and feeding position is useful in particular application scenarios.Especially for the integrated design of antenna in package,difficult wiring problem can be reduced by the proposed multi-port antenna when the number and positions of chip pins are fixed.Next,a four-port patch antenna with six polarization states is designed based on the power combining mechanism of the multi-port antenna.By calculating and analyzing the S-parameters of the four-port antenna,the antenna can achieve the same impedance matching bandwidth under six polarization states without additional feeding network.In this design,four power amplifiers with 90-degree phase difference are designed and connected directly to the four ports of the proposed antenna.The measured results show good performance in the antenna gain,axis ratio,and radiation pattern.According to the results,power combining capability of multi-port antenna is verified. |
PDF Full Text Request