Abstract
A new type of low pass filter with ulttra-wide rejection band and compact size by using a cross coupled topology (CCT) is proposed. The topology and circuit model are adopted to design the on-chip low pass filters through parameter extracting and electromagnetic optimization. One of the designed CCT low pass filters with 1-dB cutoff frequency f(c) of 2.2 GHz demonstrates the stopband rejection of 30dB up to 20 fc i.e. 45 GHz and rejection of 20dB up to 52 f(c) i.e. 110GHz. The measured passband insertion loss is less than 2.2 dB. The size of the low pass filter is only 350 mu m by 280 mu m or 0.0089 lambda g x 0.0071 lambda g (lambda g is the guide wavelength on silicon at cutoff frequency). With the size chip area, a tunable CCT LPF is introduced to further improve the stopband rejection and rolloff.