| Nowadays, the airborne radar is an important part of avionics system in various types of aircraft. With continuous development of technology, this subsystem has become more and more crucial in the whole system of aircraft, and also occupies higher and higher cost. Airborne radar is the foundation of mission in every flight stage. Airborne radar holds important position in all of the two subsystems of avionics system. In common subsystem, it is used for communication, navigation and flight control support. In mission subsystem, it is used for detection, identification and fighting etc. The routine inspection and maintenance for equipments of airborne radar need the support of relevant test and measurement instruments. While the testing is made for airborne radar equipments, except for the common test items such as frequency, power and other functions as well as index testing, it is generally required to input test stimulations to the Device Under Test(DUT) to simulate its real space electromagnetic environment and then detect its work status. The traditional testing on avionic equipments is often realized via adopting universal instruments such as frequency meter, power meter, oscilloscope, and spectrum analyzer, and combining with customized test module to build testing platform or automatic testing system. With development of avionic technology and testing requirement, the real-time of universal instruments in testing response and their diversity in testing functions have been unable to meet the testing requirement of airborne radar system.Firstly, combined with some airborne radar test instrument and equipment projects which the author participates in during the studying, this dissertation describes the analysis and summary based on specific testing demand of avionic devices. Then, this dissertation takes overall demand of airborne radar equipments as research background to carry out classification on tested equipments, classifies it into Primary Surveillance Radar(PSR) and Secondary Surveillance Radar(SSR) according to their signal feature and working mode, subdivides the testing demand of those two kinds of DUT, summarizes commonality testing demand and difference testing demand, and then selects representative research directions to carry out work. Finally, this dissertation describes the research on fusion technology of test functions based on modularized, minimized, and intelligentized development trend of test instrument. The main contributions of this dissertation are as follows:1. Research on common features test of airborne radar signals. The frequency measurement is the commonality test demand of airborne radar equipments. The return signal simulation of PSR needs the support of accurate and quick frequency measurement value, and the simulation of interrogating and reply of SSR also needs the frequency value as test parameter to follow-up process. According to features of modulating signal transmitted by airborne radar devices, as well as narrow pulse width of signal modulation, and high requirement for measurement timeliness and accuracy, this dissertation proposes an instantaneous burst carrier frequency measurement scheme combined with timestamping counting method based on field programmable gated array. With the multiplication and phase shift of counting clock, multiple parallel counters run continuously, and the times of rising edge of measured frequency are counted simultaneously. The frequency is calculated using the least squares line fitting method of regression analysis from the count values of measured frequency and timestamping clock. The theoretical analysis, error mode, simulation, and detailed design implementation are presented. Compared with other measurement methods, the proposed method can effectively improve the accuracy of carrier frequency measurement and reduce the processing time. Currently, this measurement method has been successfully applied in many projects.2. Research on difference features test of PSR signals. This dissertation selects airborne radio altimeter as the subject to carry out research on returned signal simulation technology of PSR. Traditional radio altimeter test device can only implement the simply delayed and transmitted function. This dissertation carries out analysis and simulation on the testing under on-field environment through Zero Memory Nonlinearity(ZMNL) and Spherically Invariant Random Process(SIRP) algorithm to archive the simulation on many kinds of target reflection surface features. Then, this dissertation takes target reflector the sea surface as an example and carried out theoretical analysis, mathematical modeling and simulation on features of returned signals to provide a kind of radio altimeter testing method which can simulate electromagnetic environment in real complicated space. In addition, the engineering implementation and results are given in this dissertation.3. Research on difference features test of SSR signals. This dissertation selects airborne Air Traffic Control(ATC) equipment as subject to carries out research on working procedure and signal features of SSR. This dissertation proposes a kind of rapid demodulation method which can be used for decoding and processing of interrogation and reply. Key aspects of principle of stimulation signal generation, actual test procedure and its implementation are described in detail. The engineering implementation and test results are also given in the dissertation, and results show that the proposed test implementation can satisfy the requirement of DUT.4. Research on fusion technology of signal test functions. In consideration of modularized and reconfigurable development trend of airborne avionics system, this dissertation combines with the on-field and off-field test demand of new generation of airborne Line Replaceable Unit/Line Replaceable Module(LRU/LRM) to research the reconfigurable technology of test function and instrument. The reconfigurable principle and implementation model are described. This dissertation proposes a kind of improved on-chip reconfiguration and optimization algorithm, and carries out simulation and verification on the algorithm. Finally, this dissertation provides a kind of engineering implementation of module-level test functions reconfiguration. Test results prove its effectiveness and practicability, and which lays a good foundation for system-level global test function fusion.
|
PDF Full Text Request