Design Of A Reconfigurable Mixer For Multi-mode Multi-standard Receivers

With the rapid development of the wireless communication technology, various wireless communication standards for different applications emerge in endlessly. Its applications have been expanded to the fields of cellular mobile communication standards, global navigation satellite system(GNSS), wireless local area network(WLAN), wireless sensor network(WSN), etc. It is necessary to design a transceiver, which is compatible with multiple communication standards. Mixer is one of the key modules in the receiver, it becomes very meaningful to research its reconfigurable performance when it is used in a multi-mode multi-standard receiver.A reconfigurable wideband passive mixer for direct conversion multi-mode multi-standard receivers is presented in this thesis. It is consist of three parts:transconductor stage, switch stage and transimpedance amplifiers stage. Different from the traditional current-commutating passive mixers, the transconductor stage in this design is variable, and the transimpedance amplifiers stage is a second-order low-pass transimpedance amplifiers based on Tow-Thomas biquad topology, working as a current mode filter with tunable bandwidth. The mixer is controlled by a 4-bit control word to realize the flexible gain and variable intermediate frequency bandwidth. Other characteristics such as power consumption, noises figure, and linearity are also reconfigurable according to different communication standards.The mixer is implemented in 0.18μm CMOS process, the whole layout of the mixer occupies an area of approximately 760μm×600μm including pads. Post-simulation results can satisfy the design requirements. On-wafer measurements show that, with the radio frequency ranges from 700 MHz to 2.6 GHz, it provides four voltage conversion gains (8/14/20/26dB) and three -3 dB intermediate frequency bandwidth(5/7.5/10MHz). Under the maximum gain, the double-sideband NF of the mixer is 9.1dB; and under the minimum gain, it has good linearity, and IIP3 is about 8.5dBm. It drains a current of 4.9mA from a 1.8 V supply in two low gain modes and 7.8mA in two high gain modes.