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# Study Of Fast Measurement And Calibration Techniques For Phased Array Antennas

Posted on:2011-07-06Degree:DoctorType:Dissertation
Country:ChinaCandidate:J P ShangFull Text:PDF
GTID:1118360305964255Subject:Electromagnetic field and microwave technology
Abstract/Summary:PDF Full Text Request
Measurement of phased array antennas'radiation characteristics is a complex technical subject. In modern phased array antennas area, how to identify the amplitude and phase of element excitation rapidly and accurately and diagnose element faults are of great significance to the phased array antennas'manufacture and verification. Recently with the widespread application of phased array antennas, it has put forward new demands on measurement. To meet this requirement, a fast measurement method of phased array antennas called phase-shifted measurement method is introduced in this paper. The basic idea is that with the phased array antennas and probe both fixed, we measure the received signal's amplitude and phase of phased array antenna corresponding to different phase states, then use mathematical algorithms to process the experiment data. Therefore we can determine channel excitation in any phase state, and further, we can recover all the patterns according to one of the measurement result. At the same time, element fault can be identified, which is the greatest virtue compared with other measurement methods. The main achievements are as follows.1. Through the intensive study of basic theories of using fixed probe to measure the characteristics of phased array antennas in the middle distance, a mathematical expression is established. The expression contacts the amplitude and phased of the fixed probe signal with the complex amplitude of each channel excitation wave of phased array antennas under condition of different match. Through the analysis of the solution to the expression, we find the rank of the expression's coefficient matrix under different control steps is not full rank. And it is necessary to solve its generalized inverse matrix in the process of solving. It causes multi valuedness of the solution to channel excitation characteristics. Some priori information of the phase shifters of phased array antennas and the constant amplitude characteristics (or very tiny changes) as the phase state changes is utilized to eliminate multi valuedness of the solution, evaluate the real excitation and identify and diagnosis the channel faults.2. The main work of the measurement method is to determine the array pattern of each radiating element and the excitation amplitude of each channel. Since the array pattern of elements is used in the process of solving each channel excitation and the recovery of whole pattern. The accuracy of the array pattern of each element will directly affect the accuracy of measurement. The array pattern of elements in the phased array antennas made up of dipole antennas is studied in the paper. And a method to determine the array pattern of elements that meet certain accuracy is put forward.3. To obtain the excitation of each channel, the linear equations established by the excitation of channels and received probe signal of phased array antennas in different phase states must be solved. Solving the generalized inverse matrix remains an unanswered question in different measurement control steps of large phased array antennas composed of many elements. But for some special matrix form, we can use rapid algorithm to obtain its inverse matrix. The conforming rules of establish experimental steps is made based on the characteristics of phase-shift method. The control steps of the unit control, the circular phase-shift control and the Walsh function control, and the optimized phase-control is studied base on the principle of minimum error and measure numbers. The adaptation range, measurement error and corresponding fast algorithm are also studied. The whole process of the fast measurement of phased array antennas model made up of dipoles is simulated by computer on the basis of theory study. The results showed the correctness and efficiency of the method.4. The phase-shift measurement is characterized by its rapid recovery of the amplitude and phase of element excitation in different phase state. However, due to the singularity of the measurement equation, can be solved only by introducing additional equations. This cause much inconvenience and recovery error. Hence the combination of phase-shift measurement method and encoding matrix method as an improvement to made the measurement equation full rank. The method can reduce the measurement numbers and improve the measurement precision with any other priori knowledge.5. With the experience in antenna measurements research based on the theory study, the equipment composing of fast measurement system of phased array antennas is proposed. We have discussed the optimal configuration of probe, and analyzed the equipment error, the method error, mathematical algorithms error and the pattern's recover error of this measurement method. Some requirement of system and environment is also proposed.Based on its advantage, the fast measurement method of phased array antennas can greatly reduce the test time. And the requirements of environmental are low. It will be used widely and play important role in the study and manufacture of phased array antennas in future.
Keywords/Search Tags:phased array antennas, fast measurement, distribution-phase, phase-shift measurement method, circle phase-shift control, optimized phase-control, calibration, faults diagnose, encoding algorithm
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