A High Performance Automatic Level Control Circuit Design

Power control of signal source is an important issue. Automatic level control (ALC) technology is widely used to this issue. In the present paper, the principle of the ALC technology is analyzed deeply. According to its characteristic, a high performance dual slop logarithm amplifier is designed. Microwave attenuator is one of the most important components in the ALC loop, In this paper, the relations between microwave attenuator characteristics and PIN diode spaces for a multi-stage attenuator are analyzed theoretically. According to theoretical results, a high performance wide dynamic range, broadband microwave attenuator whose band extends from 10 MHz to 26.5 GHz has been designed. In order to make it maintain good linearity in the whole power adjusting process, an exponential drive circuit has also been designed. After the design has been applied in microwave vector network analyzer for experiment, the results show that the dynamic range of the ALC can reach about 50 dB, and the linearity is within +/- 0.05 dB.