Design And Research Of Boardband Transmitter Used In 5G Channel Measurement System

The measurement of the channel parameters of the new generation mobile communication system,a multi-channel broadband channel measurement system is required.At present,most of the existing foreign measurement equipment is built of the combination of discrete instruments with superior performance,which has certain practical effects but the cost is high.At the same time,domestic relevant research and measuring has been carried out,but it started late and still needs further development and improvement.In response to this actual demand,A500 MHz?19 GHz broadband transmitter used in a 5G channel measurement system has been designed and studied.The main works completed in this thesis are:1.Determined the system architecture of the broadband transmitter.According to the technical index requirements of the measurement system for the transmitter module,it is determined to adopt the direct up-conversion combined with superheterodyne,together with three external filters as the transmitter architecture.It has the advantages of simple structure,easy realization and low cost.2.Completed the design,implementation and test of the broadband transmitter.It mainly includes the gain budget of the transmission link,chip selection and performance evaluation,electrical schematic design,PCB layout design and drawing,shielding cavity design,programming of the bottom driver program of the programmable chip,and the design of the control interface of the transmitter host computer.The technical indicators of each sub-module of the transmitter and the whole machine were tested,and the test results meet the system design requirements.3.Solved the key technical problems in broadband transmitters such as carrier leakage,IQ imbalance and spurious frequency interference.Using the mode search algorithm to reduce the power value of carrier leakage;establish a transmission model,use a blind calibration algorithm based on signal statistical characteristics to obtain unbalanced parameters,and predistort the baseband IQ signal at the digital end of the transmitter module to offset the original transmitter.Some IQ imbalance characteristics;reasonable planning of the frequency combination used by the transmitter while introducing an appropriate external cavity filter,greatly reducing the interference of spurious frequencies.The working frequency band of the broadband transmitter designed in this thesis is500 MHz?19 GHz,the sideband suppression of the full-band transmit signal is better than-30 d B,and the transmit power can be adjusted programmatically between-40 d Bm?+20 d Bm.The carrier suppression algorithm and IQ imbalance calibration algorithm proposed in this thesis and the frequency planning method also have relatively good practical effects,which fully meet the needs of the measurement system.