Fpga-based Microwave Ultra-wideband Frequency Source Control Technology

Microwave signal generator technology experienced from analog to digital analog mixed development process. Currently, the Microwave source which has high performance and complex function is more and more depend on digital control technology. Direct digital frequency synthesis technology (DDS) often requires fast, complex and flexible control in order to exert its merits. The use of programmable logic device (FPGA/CPLD) to control the microwave frequency synthesizer can achieve the complex and flexible working patterns. While on the microwave power controlling field, we can use FPGA and DAC to control voltage-variable attenuator to actualize the flexible control of microwave signal voltage between the whole frequency ranges.This thesis puts forward a scheme of the 2-18GHz ultra wideband frequency source control system, which adopts man-machine interface based on virtual instrument technology on personal computer and programmable logic circuit based on FPGA to realize the control requirement. The PCI local bus is used as the communication interface between PC and control circuit. The control speed is enhanced by realization of high speed and specific logic on FPGA.The results show that this scheme has realized the control of microwave source to work in single or sweeping frequency patterns. The output signal reaches the target requirements within the range of 2-18GHz. The frequency switch and sweep are realized. So the feasibility has been verified. The use of programmable logic device to control the microwave frequency synthesizer is propitious to improve the control speed, degree integration and stability of entire system.For the goal to obtain excellent flatness and minimum tuning step of the output voltage of broad band frequency source, a great many research and experiments have been done on several aspects such as the 0.25dB small step microwave signal power control between 2-7.5GHz. The microwave power controlling is achieved by electronic attenuator which come true with MMIC chip, so that the controller's size is small but the stabilization and precision is increased; moreover, the small step control was satisfied. Because of needing tremendous testing, the automatic testing software is written and the test results are analyzed. Through the process above, we can realize precision and small step voltage control in the whole frequency band by lookup the table of software. Finally, the feasibility of microwave signal voltage control between the whole frequency range by FPGA+DAC+electronic attenuator has been verified.