Ultra-wideband Automatic Gain Controller Chip Design

Thanks to the development of semi-conductor fabrication technology, the integration and working frequency of radio-frequency integrated circuits have been increased continuously. The high integration of IC will permit one chip with more functions. And the high carrier frequency makes higher speed wireless communication possible, which also has some merits good for sensing and imaging. Due to its own physical characteristic, high frequency carrier communication is sensitive to transmission route, which may make the quantization of receiver difficult. An automatic gain controller can alleviate the problem. However, high specifications on gain and bandwidth are not easy to realize in modern CMOS technology, because its low intrinsic transistor gain. Bi-CMOS fabrication technology combines the benefits of bipolar and CMOS transistors, which is good for high gain high bandwidth RFIC design. In recent years, the Bi-CMOS technology based on SiGe has been in vast use.This paper is mainly focused on the design of the automatic gain controller, which is suitable for high speed wireless communication, especially high-carrier frequency high bandwidth signal transmission. The sensitivity of gain to temperature in the signal main path, as well as the extra delay in the loop makes the design process complicated. Considering these problems, this paper gives a few solutions. Through building behavioral models, the loop stability and fast settling process are guaranteed. Temperature feed-back and common mode voltage feed-forward make the chip suitable for multiple PVT conditions. Utilizing 0.13μm SiGe Bi-CMOS process, this paper simulate a 2.5V automatic gain controller with max gain 40 d B, gain dynamic range 60 dB and 3-d B bandwidth 20 GHz. Post-simulation shows the settling time of this AGC is smaller than 0.4us, demonstrating the validity of the design. This design is also fabricated for tests.