Ultra-wideband Digital Automatic Level Control System

In recent years, with the development of microwave technology and the increased requirements of the frequency band from application market, ultra-wideband microwave frequency synthesizer has gotten more and more attention. As the key of the frequency synthesizer to achieve specifications of the power accuracy, power flatness, power resolution and amplitude modulation, ALC(Automatic Level Control) system has raised more concern. It can be said, the performance of ALC system directly determines the power specifications of the frequency synthesizer.A digital broadband ALC system is proposed and designed according to the high specification requirements of the ALC system by the present ultra-broadband frequency synthesizer. Then complete the hardware circuit and debug the system. Finally, the testing result has verified the feasibility of the program.First, this paper describes the development and current situation of ALC, and has a brief description of its typical application. Then summarize the mainstream traditional system structure of ALC and compare it with the digital ALC proposed by research topic on specifications. And fully explain the meaning of reaching digital ALC. Then the feasibility of the program has been verified by calculating the various indicators of the design. Later, a detailed description of the five important parts of the system including controller, attenuator, power amplifier and power detector is presented. The description includes devices sizing, circuits design and simulation of the five parts. Then complete software and hardware making. Achieve specifications of frequency band 60MHz~6GHz, input power dynamic range -20dBm~+10dBm, output power +10dBm and power flatness±1dB by debugging. And analyze the influence by the ALC system on phase noise and spurs. At last, summarize of the problems existing in the system, but also propose the suggestions for improvement.