Design Methodology of N-Path Filters With Adjustable Frequency, Bandwidth, and Filter Shape

Abstract

Abstract-In this paper, an adaptive N-path filter design technique is presented. The filter designed by this method can be reconfigured to different shapes, e.g. Butterworth or Chebyshev with variable bandwidth, based on the user requirements. In addition, an analytical synthesis procedure is introduced to realize high-order bandpass filters based on N-path architecture with a prescribed set of specifications. A proof-of-concept bandpass filter is fabricated and measured in a 65-nm CMOS process. The filter can be reconfigured to realize different filter shapes by changing coupling capacitors. The bandwidth of the proposed filter is also tunable. The passband of the filter is tunable from 0.2 GHz to 1.2 GHz with a gain of 14.5-18 dB, a noise figure of 3.7-5.5 dB, and a total power consumption of 37.5-52.7 mW. The channel bandwidth can be varied from 20 MHz to 40 MHz and the filter out-of-band IIP3 (∆f =50 MHz) is 25 dBm.

Switching Capacitor Filter with Multiple Functions, Adjustable Bandwidth in the Range of 5 Hz–10 kHz

“…where C I is the sampling capacitance of the integrator and C F is the holding capacitance of the integrator. According to the above Equation ( 43), it can be seen that bandwidth can be adjusted by changing the ratio of clock frequency to capacitance without changing the original structure of the circuit [30]. The C F value in this article adopts programmable output, and its structure is shown in Figure 18.…”