| The 5th generation wireless systems has been officially commercialized.5G frequency band includes Sub-6G frequency band and millimeter-wave frequency band.Due to the small coverage range and large loss of signal transmission,the millimeter-wave frequency band has a high density of base stations that need to be deployed,and it is extremely difficult for large-scale commercial use.Sub-6G,as the current main spectrum,can utilize part of the resources of the old base station to realize rapid deployment,which greatly reduces the cost,therefore,Sub-6G is bound to be an important position of 5G deployment in China for a long time in the future.However,this frequency band contains 2G,3G and 4G spectrum,so the electromagnetic environment of the channel is complex.As an important part of the wireless communication system,the RF front-end is the bottleneck restricting the development of wireless communication,therefore,it is urgent to study the RF transceiver front-end with anti-interference performance for 5G.In this paper,the RF subsystem of 5G-oriented verifiability C-band anti-interference 2×2 MIMO wireless communication system is mainly studied.In this study,three sets of Rf subsystems are developed,with the operating frequency of5000MHz~ 5300 MHz and a total of 15 channels,each with a bandwidth of20 MHz.Each RF subsystem mainly consists of two transceiver channels,a sensing channel and a control module,supplemented by power circuits and so on.The design of RF subsystem,the test and joint debugging of the whole machine with baseband subsystem are completed.To be specific,the following four areas of work are covered:(1)Three sets of RF subsystem of C-band communication system are developed,and four functional sub-modules of transmitting channel,receiving channel,local oscillator and power supply are carried on the transceiver board,at the same time,the design of transceiver board and the development of circuit board were completed.The test results show that,firstly,the output power of the transmission channel is greater than14 dBm and the gain flatness is no higher than 2dB;Secondly,the gain of the receiving channel is greater than 70 dB,and the output SNR is greater than 20 dB which meets the demodulation requirements of 16 QAM modulation signal;In addition,the phase noise of828 MHz of low local oscillator is better than-90dBc/Hz@10kHz and-100dBc/Hz@100kHz;Finally,the channel switching function is realized with high local oscillator 5770MHz~6050MHz,The phase noise is better than-80dBc/Hz@10kHz and-90dBc/Hz@100kHz.(2)In order to improve the anti-interference ability of the RF subsystem,a sensing channel is designed to convert the power of interference signals in 15 channels within5000MHz~5300MHz into binary RSSI data and feed it back to the baseband system,so as to provide support for the baseband system to select working channels according to the interference situation.(3)In order to realize the data interaction between the RF subsystem and the baseband subsystem,a control module is designed to receive and analyze the data from the baseband subsystem,and complete the functions of channel switching and power control on the transceiver board.(4)The power module is designed to provide power support for the whole RF subsystem.The metal shielding cavity design of the main control board and the transceiver board was completed,which effectively reduced the signal crosstalk between different modules and improved the heat dissipation performance of the circuit board. |
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