Active Components Downconversion mixer for VLIF receivers taps

T growing market of portable wireless communication systems, such as wireless (cordless and cellular) phones, wireless local area network (WLAN) and the global positioning system (GPS) has increased the need for low-cost and high-performance receivers. The zero intermediate frequency (ZIF) receiver is often used to avoid the image-frequency, but this architecture suffers from the flicker noise (also called 1/f noise). Because of the problems mentioned above, another architecture that trades off between the ZIF and flicker noise has been developed. It lowers the intermediate frequency (IF) to very low IF or VLIF. Consequently, such low-frequency signals can be easily processed by today’s digital signal processors (DSPs). Thus, VLIF receivers are getting more and more popular in wireless applications[1]. Since the RF mixer is a building block of the wireless system, it demands stringent dynamic range, which determines the performance of the receiver[2]. The dynamic range is determined by the noise floor and the linearity. For the VLIF applications, the flicker noise limits the noise floor of the mixer. To meet the above requirements, a micromixer was proposed by Gilbert, which achieves the high linearity and is widely used in wireless communication systems[3]. However, the second-order intermodulation products generated in double balanced configuration are more difficult to remove by the IF filter than the third-order products generated in VLIF design[4]. To address these problems, a novel downconversion mixer configuration is presented.