Research Of Wideband Signal-Summing Programmable Gain Amplifier

The broadcast communication was born in the 1920s, and it used to applying two kind of modulation methods including analog amplitude modulation (AM) and frequency modulation (FM). In the past century, the broadcast communication has become an integral part in people's life. However, the conventional AM broadcast communication has inherent shortcomings of poor transmission quality and single function, besides AM method is susceptible to interference. Although FM radio is superior to AM, it has some disadvantages, such as a wide frequency spectrum occupancy and limited radius range of radio services. However, digital broadcasting can effectively avoid these disadvantages. Digitization of Analog broadcasting is the best choice to overcome analog broadcasting's fatal weakness and has been an inevitable trend in the development of technology. Digital Radio Mondiale (DRM) and Digital Audio Broadcasting (DAB) are two most important criteria in the process of the digitization, which are designed to solve the shortcomings of AM and FM methods. Meanwhile, DRM has become most mature, open and non-proprietary digital broadcasting system standards. Research of DRM receiver is of great significance for enhancing the core competitiveness in the field of wireless communications chips.In the paper, the first stage IF programmable gain amplifier (PGA) is designed for DRM/DAB receiver's RF front-end chip. Based on signal-summing technology, the open-loop PGA was designed with CMOS technology for wide band and variable gain. Similar to Gilbert cell, the signal-summing circuit can change gain by changing the controlling voltage without changing the bandwidth. Referred to signal-summing technology, the PGA is designed for the goal of changing the gain by controlling switch.The PGA is designed with Cadence tools, and its layout is completed with SMIC 0.18-?m CMOS process. The simulation results meet the requirements of the design specifications and can be integrated into the DRM/DAB receiver chip after further optimization.