A 6th-order Chebyshev active-RC complex filter employing feedforward compensation operational transconductance amplifiers achieving +39.1dBm IIP3

A 6th order Chebyshev active-RC complex filter for high linearity global navigation satellite (GNSS) receiver is proposed in this paper. The filter is synthesized from a 6th order leapfrog low pass filter where the frequency non-ideality compensation technique for integrator is used. High linearity demands a robust and stable IIP3 through the pass band. Meanwhile, the 35dB rejection spec at 1.5 times bandwidth requires at least 6th order which degrades the linearity performance. A gain enhanced, current-reusing, feedforward compensation (FFC) OTA is designed to improve the linearity performance. The complex filter is centered at 15.48MHz with a bandwidth of 20.46MHz. It has 0dB gain and less than 1dB ripple. It draws 21.7mA from 1.8V supply, meanwhile it achieve more than +32dBm IIP3 through the pass band and a maximum IIP3 of +39.1dBm which are relatively high performance in 0.18µm CMOS process compared to other papers.