Research And Implementation On The Measurement Of Radiation Efficiency Of Standard Antenna

The microwave chamber is a cavity that can shield external interference and can form a near-reflection free space environment.Usually,the full-wave chamber is used to measure the radio frequency of the wireless device.Modern microwave chambers are often equipped with multiple measuring probe antennas,and the electromagnetic path loss between each probe antenna and the measuring center of the chamber needs to be calibrated before the chamber is delivered.When calibrating a microwave chamber,we typically calibrate each probe in the chamber using omnidirectional standard antennas such as dipole antennas and loop antenna efficiency values.However,when the standard antenna is not an electrically small-sized antenna,obtaining its accurate efficiency value is a difficult matter,and the accuracy of the efficiency value of the antenna is closely related to the accuracy of the final chamber measurement.Therefore,this paper mainly carried out the following work.1.Study the test method for the radiation efficiency of the standard antenna,compare the advantages and disadvantages of the various methods,and finally select the reflection method(the improved Wheeler cap method)to measure the radiation efficiency of the standard antenna;2.Theoretical analysis shows that when a small antenna is placed in a closed cavity,the amplitude of the difference between the reflection coefficient of the antenna and the reflection coefficient of the antenna in free space changes with the volume change of the cavity;3.The simulation analyzes the electric field distribution of the cavity under different attitudes of the half-wave electric dipole in the cavity.The conclusion that the polarization direction of the antenna should be the same as the electric field direction of the cavity can correctly stimulate the cavity mode.Based on the above work,this paper achieved the following results.1.A special resonant cavity is designed,which can realize the measurement of the radiation efficiency of the cavity-variation reflection method of the non-electric smallsized standard antenna.And the radiation efficiency of a 1700 MHz to 1900 MHz sleeve dipole antenna is measured,then the information including the cavity resonance point is removed by a certain algorithm to obtain a more accurate efficiency value.The result of antenna radiation efficiency has a good consistency with the simulation value;2.Sweep reflection method and cavity-variation reflection method is compared.Compared with the reflection method of the variable cavity,the sweep reflection method improves the test speed while sacrificing a certain precision.The test plan has a complete theory,good test speed,accurate test results,and has the expansibility of a certain frequency band.The resonant cavity and its ramification can be used for accurate measurement of radiation efficiency of other non-electric small-sized antennas,and has good practical value and further research space.