| Nowadays,the development and change of wireless communication are getting faster and faster,especially the mature 5G wireless communication technology has been widely used in all aspects of Internet technology and people’s life.As the communication transmission system needs to take the transceiver receiver system as the main structure,so the receiver performance index is more and more demanding.On the other hand,because the wireless communication needs to transmit more information,the market demand for the frequency band of the receiver becomes wider and wider,thus the broadband receiver comes into being.It has the characteristics of wide bandwidth,high data transmission and high sensitivity that the traditional wireless communication technology does not have.In this paper,according to the requirements of RF circuit broadband transmission,combined with the circuit and wireless communication system transceiver front-end knowledge,designed a frequency range of 6～26GHz broadband receiving front-end circuit.Specific work is as follows:First of all,this paper introduces the theoretical knowledge of broadband receiving front-end in detail,analyzes and compares the performance of various receiver systems,and determines the superheterodyne structure with single frequency conversion.As the receiving range of the receiver is about 20 GHz,covering a wide range of frequency bands,so according to the frequency band is divided into 6～12GHz,12～18GHz,18～26GHz three frequency bands,using the switch to control the three filter banks for frequency band selection,to determine the overall structure layout of the broadband receiver.Then,according to the system gain,noise factor,image suppression and other performance indicators,reasonable device selection,RF input port amplifier using low noise amplifier,it has a low noise factor of 2.5d B.The switch is SP4 T switch,which has the characteristics of high isolation and low plug loss.Filter A tunable image suppression filter is selected to achieve full frequency coverage.The mixer uses a passive image suppression mixer with I/Q output to further improve image suppression and out-of-band suppression.The circuit simulation is carried into ADS simulation software according to the selected devices,mainly including link budget simulation,channel selectivity simulation,gain simulation,image suppression simulation and out-of-band suppression simulation,so as to analyze the system’s gain,noise factor,image suppression,out-ofband suppression and other performance indicators.Finally,the circuit structure and schematic diagram of the broadband receiver are designed according to the simulation results,and the PCB board is made according to the designed schematic diagram.The PCB board is processed and formed,and the hardware test platform is built to complete the circuit hardware test.The whole receiver can complete the full coverage of 6～26GHz frequency band through the three-channel selection,realizing the broadband reception with low complexity,high gain and low noise coefficient.The test results show that the system gain is greater than 50 d B and the noise coefficient is lower than 6d B. |
