VSWR Test Circuit And Performance Study

With the development of radio communication system. More and more RF signals are used in the circuit design. Good impedance matching plays a key role in the normal work of the circuit. Bad impedance matching can reduce the system efficiency, and even burn out RF devices if the reflected signal power is too large. Real-time monitoring the VSWR of transmission line or circuit and alarm when the VSWR is too large can provide a good protection.This thesis studies VSWR test circuit design and its performance. Futher more, made the material object to do the test and verify the feasibility of this method. The beginning of the thesis introduces the pattern of the existing VSWR test methods. On the basis of these methods, make the design of VSWR test method and prove its correctness.Then analyzed and considered the overall layout of the circuit and briefly introduces the key point of each part in design. After that, VSWR test circuit is divided into five parts on the basis of the functional areas as logarithmic amplifier module, operational amplifier module, AD module, FPGA module and upper desktop module. The principle and parameters of each module are particular introduced, and then introduces the error in the test results due to the non ideal of the devices. In order to make the test results more accurate, this thesis studies how to eliminate the error. After that, this thesis introduced the software part of the FPGA and PC program, respectively introduces the method to realize data conversion and control. According to the previous introduce, a material object is made to verify the feasibility of this scheme.A simulation testing method of the material object is introduced at the end of this thesis. By use two signal generators to produce two RF signals to simulate the input signal and reflect signal to built the test platform of the VSWR test circuit. PC can communicate via a serial port with the circuit board, thereby we can observe the real-time VSWR value and the change curve through the PC screen. At the same time, the alarm threshold can be modified through the PC. This thesis also introduces the problems that faced in debugging process, and put forward the solution to the problems. Finally, analyzed the result of the test pattern on the basis of the circuit debugging success and put forward the VSWR test circuit and the development direction of improvements.