Research And Design Of Analog Baseband Circuits For UHF RFID Transmitters

Compared with other frequency bands, the ultra high frequency RFID (UHF RFID) has a greatdeal of research and application value based on the advantages of long read range, large informationstorage, small antenna size and so on. Based on the analysis of several kinds of commonly usedwireless transmitter architecture, direct up-conversion architecture is used in this paper. Accordingto the ISO/IEC18000-6C protocol, the requirements of analog baseband circuits are given, whichinclude the low-pass filter and the programmable gain amplifier.Firstly, some research on different types of low-pass filter is done in this paper. And inaccordance with the requirement of the UHF RFID transmitter, two kinds of adjustable differentiallow-pass filter are designed, which are realized by multiple feedback biquad structure andTow-Thomas biquad structure. The cut-off frequency of the low-pass filter is range from480kHz to1.68MHz which is controlled by MOS switch.Secondly, in accordance with the characteristics of basic programmable gain amplifier, a novelprogrammable gain amplifier is designed in this paper, which combines the high linearity of theclose-loop resistance feedback structure with the low power consumption of the open-loopcommon-source amplifier. It reaches a gain range of-12~24dB by1dB step with a gain error lessthan0.02dB. The performance of high gain accuracy, good linearity and low power consumptionmakes the design meet the system requirement.Thirdly, the layout of this design is implemented by SMIC0.18μm CMOS process, and the postsimulation is accomplished after extracting parasitic parameters. The results show that both thelow-pass filter and the programmable gain amplifier can achieve the system requirement.Finally, the tape-out of the Tow-Thomas low-pass filter is carried out and the chip test alsofinished. The test results show that the cut-off frequency of the low-pass filter is range from605kHzto2.15MHz, and the input referred1dB compression can reach-6.98dBm. The whole performancecan achieve the desired goal.