Research And Design Of Active Balun Feed Differential Antenna

With the rapid development of modern electronic technology and wireless communication technology,the demands of radio frequency front-end and antenna are becoming higher and higher,such as reducing the cross polarization of the antenna,improving the anti-jamming capability of the antenna and increasing the bandwidth of the antenna.In order to enhance the anti-jamming capability of wireless communication system,differential antenna has become one of the research hotspots in the field of wireless communication.The advantage of the differential antenna is that it can directly use the differential signal of the radio frequency circuit to feed,and does not need balun to transform the signal.Among them,balun can achieve single-ended to differential signal conversion.In the choice of balun,the active balun is more and more popular with engineers because of its wide frequency band and small area,which can be integrated in the front-end circuit.This thesis mainly studies the active balun circuit and differential antenna,and analyzes the related problems of active balun fed differential antenna.The main contents of the work include:1.The active balun is simulated and measured.Four kinds of active balun circuits are designed,which are active balun of single stage inverters,active balun of cross cascade inverters,active balun of common-gate/common-source and differential pair structure source,and the first three sections are tested.The simulation results of four kinds of active balun meet the requirements of the presupposition index.The working bandwidth in the L band is greater than 500 MHz,the phase imbalance is less than 5 degrees,and the amplitude imbalance is less than 0.2dB.The first three active balun are tested and compared with the simulation results.According to the simulation and the measured results,the circuit design is analyzed and improved,which makes the designed balun test results coincide well with the simulation results.The measured bandwidth is 1GHz-1.6GHz,the relative bandwidth is 23%,the phase imbalance is less than 2 degrees,and the amplitude imbalance is less than 0.1dB.The designed common-gate/common-source active balun satisfies the requirements of broadband system,and meets the requirement of phase amplitude balance error.2.The simulation analysis and field measurement of active balun feed differential antenna.Two kinds of microstrip differential antennas are designed.The active balun feed differential antenna with common-gate/common-source is selected.The simulation results show that the working bandwidth is 600 MHz and cross polarization is lower than-35 dB,which meets the requirements of broadband and low cross polarization.The measured results show that the working bandwidth is 1GHz-1.6GHz(600MHz),and the relative bandwidth is 23%,which meets the design requirements.