Research And Design Of The Channel Select Filter In Analog Baseband Of The Multi-mode Multi-frequency Wireless Transceiver

Due to the development of the wireless communication technology, various kinds of wireless communication types and protocols are booming up. Consequently, people have the need to making their wireless terminal equipment available to adapt itself freely in Multi-mode Multi-frequency conditions and communicate each other without freely. In this paper, after the study of several communication protocols and a great many papers on wireless receivers, the relevant theory of filter is summarized carefully. Efficient work has been done in the filter circuit design, and a reconfigurable channel select filter is presented, which can adapt four main-stream communication standard (GSM, TD-SCDMA, WLAN, RFID) and alter among them optionally. This paper is organized as follows:Firstly, started from the classic analog filter design theory, this paper compares the two most employed techniques:Active-RC and Gm-C filter, followed with the analysis of their principles and problems, respectively. The transfer function, synthesis method and the influence of the non-ideal factors to the filter's amplitude and frequency is also introduced. The paper focuses on the specification of key targets of the CSF, such as cut-off frequency, noise performance, and linearity, from the consideration of GSM, TD-SCDMA, WLAN and RFID protocols, and the calculation results are given.Afterwards a novel 7th-order reconfigurable Chebyshev Active-RC low pass filter with tunable range from 300kHz to 10MHz is presented. This filter is formed with a 5th-order leapfrog filter base on LC-ladder cascaded by a 2nd-order Tow-Thomas filter. This architecture not only prevents the cut-off frequency affected by the component's variation but also guarantees good stability and reconfiguration. In order to trade off between the linearity and the noise performance, a pre-amplifier is included in the architecture.Thirdly, for the WLAN a/b/g mode requires the signal bandwidth as high as 10MHz, which means the operational amplifier (Op-Amp) of the filter should have an extraordinary high gain bandwidth (GBW). Therefore, this paper presents a considerable part to discuss the design procedure of a novel well-modified high-gain large-bandwidth Op-Amp and the calculation of the key modules. Instead of the conventional miller compensation method, this Op-Amp utilizes a zero to cancel the 2nd-pole to improve the GBW drastically and keeps the sufficient phase margin at the same time. The GBW of the OP is as high as 4GHz. What's more, it also benefits in a relative low power consumption and high gain. At the output node of the Op-Amp a unity gain buffer is used to testify the common-mode level and avoid the DC instability caused by the resistance mismatch when using the large resistance..Finally, the design is implemented in 0.13μm CMOS process. The post-simulation and test result are also given, which justify the design theory and method.