Design Method for Q-Enhanced Reconfigurable Bandpass Filters With High Selectivity, Large Bandwidth Variable Range, and Large Dynamic Range

A design method of generating multiple transmission zeros (TZs) is proposed by introducing feeding-forward transconductance amplifiers for the cascaded Q-enhanced reconfigurable bandpass filters (BPFs) in this article. With the proposed method, it can generate two TZs at the upper and lower stopbands for every two Q-enhancement resonant units, significantly improving the stopband suppression. Furthermore, by controlling the feeding-forward amplifiers, the position of the zero and the depth of the TZs can be flexibly controlled. Meanwhile, to improve the power consumption, linearity, and noise figure (NF), the guideline of distribution of the transmission poles (TPs) generated by the Q-enhancement units is discussed in detail. To demonstrate the proposed method, a reconfigurable on-chip Q-enhanced BPF was designed and measured based on a 55-nm CMOS process with a core area of $1.36\times 0.62$ mm. Multiple TZs were clearly observed in the filter and achieved a stopband suppression of more than 50 dBc up to 15 GHz. The bandwidth of the proposed filter can be tuned with a range covering from 0.2 to 1 GHz at a center frequency of 1.8 GHz, while the center frequency can be tuned from 1.68 to 1.94 GHz with a constant bandwidth of 600 MHz. The input 1-dB compression point (IP1dB) is better than -1 dBm for all tuning states, and the NF varies from 12.7 to 20.3 dB. The dynamic range (DR) can reach more than 165 dB and the total power consumption is less than 180 mW.