Multi-band/Multi-Mode RF Front-end Receiver for Basestation Applications

Abstract

In the last couple of years, mobile telephony has truly become global, with more than 4 billion users worldwide nowadays (compared to less than 1bn ten years ago). This has represented a boost not just for the mobile phones industry, but also for that of wireless infrastructure. Larger-scale production and increased competition have transformed the manufacturing costs into an important issue for the producers of basestation equipment. The current state-of-the-art front-end circuits for basestations have extremely high dynamic range, but are narrowband and predominantly implemented in GaAs. One way to minimize costs is to use wideband low-noise amplifiers and mixers that cover all the mobile standards. Another way is to implement the aforementioned circuits in less expensive processes, such as SiGe. And finally, significant cost reduction can also be achieved if some of the constituent blocks (such as low noise amplifiers and mixers) are integrated on the same chip. The two criteria that describe the dynamic range of a basestation receiver are the (output) 3rd order intercept point, (O)IP3, and the noise figure (NF). To achieve the demanding linearity specifications (OIP3 above 30dBm), special linearization techniques (such as out-of-band harmonic cancellation) are employed in the design of the first stage, a low noise amplifier. Since the linearity of the following stages is even more important for the overall OIP3, a current-commuting NMOS mixer followed by a trans-impedance amplifier has been selected on account of their excellent linearity. Our down-converter achieves an output 3rd order intercept point higher than 37dBm over a bandwidth from 0.7GHz-3.5GHz (performance unmatched by any of the front-ends available on the market), and has a gain of 18.5dB and a noise figure of 3dB at 2GHz.