Digital Vector Modulation And Correction Techniques

In the signal simulation of electronic countermeasure domain, there are very strict requirements on the image reject ratio (IRR)and local-oscillate reject ratio (LRR) of up-converted signal.In the engineering application, the digital vector modulation technology is always used to implement the up-converter at a low cost way and broaden the instantaneous frequency of baseband signal simultaneously. But, in the up-converted structure which used this technology, the magnitude/phase error and DC bias are inevitable.These errors will decrease the IRR and LRR of output signal dramatically. In order to reach the requirements on IRR and LRR of up-converted signal in electronic countermeasure domain, it is necessary to do some research on digital vector modulation and its calibrating technology, compensating the magnitude/phase error and DC bias to acquire high spectral pure signal.In this thesis,the relationship between magnitude/phase error and IRR and the relationship between DC bias and LRR are discussed. The methods which using power measurement to obtain these errors and adopting pre-compensation to calibrate them are investigated when the input is a narrowband signal. Two different methods (the low-pass filtering and all-pass filtering) are discussed to calibrate these errors when the input is a wideband signal.When implementing this algorithm on hardware, the consumption of resources and the fastest working speed are depicted. When verifying this algorithm on the experimental bench, the programs of the generation of baseband signal, the implementation of calibrating algorithm and the control of instruments are described.The experimental results demonstrate that the bandwidth of baseband signal can be broadened to 200MHz and the IRR can be reached at least to 30dB.In the application of signal modulation, the calibrated system has the ability to simulate more authentic electromagnetic signals, consequently, it will improve the effectiveness of training equipments.