Research On Broadband Microwave Successive Detection Logarithmic Video Amplifier

Successive-detection logarithmic video amplifier has been widely applied in many cases where the logarithmic transform is required, such as Radar and EW receivers. The research presented in this thesis is aimed at working out the design of a SDLVA which could deal with the signals within K and Ka bands with a quick response to pulse. Related theoretical analysis and experiments are given.In chapter one, background and reasons of the research are introduced, some of the domestic and oversea outcomes with the structure of this whole thesis are also presented.In chapter two, introduction of the transformation what a SDLVA can do to a signal and analysis of the way to fulfill logarithmic transformation are given, and then several characteristic parameters which need to be noticed during the design are analyzed. By dividing the module into several functioning parts, the methods and feasibility of accomplishing each part are discussed.In chapter three, the process of the design including the routing of micro-strip lines and PCB board lines, the chosen of device chips and design of power supply and so on are described in detail.Final testing results are given in chapter four. Tangential sensitivity of this designed module could reach about-57 dBm at some frequencies while it is only around-43 d Bm at some other frequencies. The output voltage signal behaves as logarithm of the input power until the input power arise to some degree, and these linear-logarithmic transition points differ a lot at different frequencies, at some frequencies this point is near-47 dBm, and it is about-30 dBm in the tested worst situation. The logarithmic error is basically within ±2dB, and the rise time during a pulse response is about 100 ns.At the end of this thesis, the direction and some possible methods of improvement are pointed out.