Research On Calibration Technology Of Direction Finding With Interferometer

Direction finding (DF) is the measurement of angle of arrival (AOA) of radiationsignal. Almost all of the electronic warfare (EW) and signals intelligence (SIGINT)systems need to have the capability of measuring direction of enemy’s signal source. Asa well developed system in direction finding, Interferometer has the features of stronganti-jamming performance, high precision, low time-consuming and wide frequencycoverage, which derive the signal AOA by measuring the phase of RF signal receivedby two antennas and comparing the difference between the two phases.In the age of the radar modulation parameters changing rapidly and on a large scale,the stability and accuracy of AOA measurement is vitally important. In order to improvethe accuracy of AOA measurements, this paper focuses on the calibration technology ofinterferometer direction-finding system, including the calibration of the antenna phasecenter and channel phase mismatch, and provides a theoretical basis fordirection-finding system design and implementation.This essay mainly involves following several aspects:First of all, the composition of interferometer direction-finding system and theprinciple of direction-finding are introduced. The causes of “mirror ambiguity” and“phase ambiguity” and main defuzzification methods are researched. In particular,several ways of solving the problem of phase ambiguity, including combination of longbaseline and short baseline, remainder theorem of bi-baseline system and combinationof time difference and phase difference, are discussed in detail and emulated bycomputer.Secondly, AOA measurement accuracy is discussed. On the basis of analyzingvarious factors that cause angle measurement error, the article mainly study the effect ofantenna phase center offset and channel mismatch on accuracy, paving the way forsubsequent calibration techniques.Finally, several methods of detecting antenna phase center offset and calibratingchannel mismatch are proposed and verified by simulation. The experimental resultsshow that the calibration of the interferometer direction-finding system effectivelyensure the accuracy of AOA measurement.