A reconfigurable 1/2/3-order Butterworth LP/CBP filter with noise canceller for sub-GHz applications

This paper presents a configurable 1/2/3 order Butterworth low pass(LP)/complex bandpass (CBP) filter for sub-GHz Applications in a 180-nm CMOS process. The filter employs operational transconductance amplifier (OTA) unit with feedforward capacitor instead of conventional two-stage amplifiers to broaden bandwidth while consuming no extra power. In order to achieve a good noise figure, extra noise cancellers have been carefully designed. The 3-dB bandwidth of the proposed filter can be 500k/1M/2M for LP mode and 1M/2M/8M for CBP mode. The filter consumes 0.8-4.6mA of current from a 1.7V power supply for different modes. A minimal 1dB compression point of 5dBm is also achieved while the noise figure of 27.53dB at 1MHz as a result of a good balance between linearity and noise.