The Design of High Intermediate Frequency Fast Automatic Gain Control Circuit Based on Digital-analog Mixed Technology

This paper proposed a design method of high intermediate frequency (IF) fast automatic gain control (AGC) circuit based on digital-analog mixed technology to satisfy the demands of high data transfer rate and rapid response speed of receivers in modern wireless communication systems. In this method, a digital open-looped structure was adopted for coarse tuning of post-stage variable gain amplifier (VGA) to ensure the fast convergence speed of AGC. Then an analog closed-looped structure was deployed for fine tuning of VGA so as to obtain an accurate and stable output signal of AGC. To validate the proposed method, an AGC circuit with operating frequency of 305±60 MHz was designed and fabricated. Experimental results show that the AGC circuit has an extreme fast convergence speed and its response time is just within 1 μs. The power dynamic range of input signal is 34 dB when a -11.6 dBm output signal is maintained. The power flatness of the circuit is also quite well by the way. The proposed method provides a design platform to implement a high IF fast AGC circuit flexibly and reproducibly.