Design And Implementation Of Local Oscillator And Control System On Short-wave Receiver Front-end Circuit

Short-wave communication as a technology widely used, has spread over all areas of civil and military. With the technological advances in all aspects, modern short-wave communication advances in high-speed, broadband, strong anti-interference ability, intelligence, networking and so on, using new technology to transform short-wave communications equipment is important. In particular, put forward the concept of software radio, changed the structure of short-wave transceiver. The purpose of this paper is to build software-based short-wave radio communications common hardware platform. The paper first introduced the topic of the research background and significance, then gave the short-wave receiver front-end design diagram. Research in this article included local oscillator and control system.Combined with high frequency front end design requirements, compare the local oscillator design several options to determine the program of direct frequency synthesis to design the local oscillator. The basic principles and characteristics of the output signal of direct digital frequency synthesis is analyzed in theory, and used VERILOG hardware describe language designed DDS various modules and top-level design under the QUARTUS environment, uses timing simulation tools complete its simulation, simulation results agree with the design requirements. Design Results was loaded into the programmable logic device, using instruments such as oscilloscopes and spectrum analyzer tested and recorded the corresponding results。Short-wave high-frequency front-end pre-filter section divided shortwave bands into eight bands, the same structure for each band, varactor diodes are used in electric tuner, it can change the resonant frequency by the means of changing the varactor diode reverse voltage across the resonant circuit to change the capacitance. Designed a micro-controller hardware under the requirement of the the RF front-end control system, designed a software with a simple user interface, to manage the task of the front-end receiver circuit channel, electric tuner, local oscillator output signal frequency changes. Design a circuit board, complete hardware and software debugging and the performance meet the design requirements.