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A novel reconfigurable lowpass-polyphase biquad filter based on MFB structure is proposed in this paper. In this biquad, only one op-amp is adopted which improves the matching and reduces the power consumption. And its transmission function is synthesized by the complex signal flow graph. Then a 3rd order filter used in Zigbee transceiver is implemented to illustrate the technique, which is realized in 0.13 lm CMOS technology. To avoid the variation of resistance and capacitance, an onchip tuning scheme is integrated. The test results show that when in polyphase mode, it is centered at 2 MHz with 3 MHz bandwidth and the image rejection is about 23 dB with the voltage gain of 12 dB. When in lowpass mode, the cut-off frequency is 1.5 MHz, and the DC gain is 12 dB. The in-band 3rd order input intercept point (IIP3) is 9 dBm in polyphase mode and 13 dBm in lowpass mode. Attractively, the filter only consumes 2.3 mA with a 1.2 V power supply, and occupies an area of 0.26 mm 2 .

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A b s t r a c t This paperproposes a concept about Weather StationOn a Chip (WSOC). WSOC is defined as a system which includes sensors, a microcontroller, interface circuits for linking the microcontroller and snsors, and ASIC for power management. WSOC is used to monitor environmental weather parameters including temperature, humidity, barometric pressure, anemometer, and wind direction. Research and development of WSOC in our laboratory is briefly introduced.