A BW-Extended Fourth-Order Gain-Boosted N-Path Filter Employing a Switched g_m-C Network

This article reports a bandwidth (BW)-extended gain-boosted N-path filter with a switched g(m)-C network, in which a 4th-order response is achieved with the subtraction method by shifting the baseband (BB) admittance with poly-phase g(m) cells in the BB. It features not only in-band RF gain and high-Q bandpass response but also other valuable properties, such as a wide passband BW and a high linearity. In addition, a class-A/-B amplifier is employed to provide the RF gain, in which the linearity is optimized with a tunable bias voltage. Fabricated in a 65-nm CMOS process, our proposed filter measures a 10.7-12.7-dB voltage gain and a 5.3-6.2-dB noise figure (NF) over a 0.5-1.5-GHz RF range. With g(m)-linearity optimization, our filter centered at 1 GHz exhibits an out-of-band input-referred 3rd-order intercept point (OB-IIP3) of 18.2 dBm and a passband BW of 50 MHz. The ultimate stopband rejection of the filter is > 50 dB. The power consumption is 11.1-15.9 mW, and the die area is 0.083 mm(2).