Design of an Optimal Layout Polyphase Filter for Millimeter-Wave Quadrature LO Generation

The analysis and design of a two-stage passive RC polyphase filter for millimeter-wave quadrature local oscillator generation is presented. The layout parasitics, which significantly deteriorate the filter performance at millimeter-wave frequencies, are identified with the help of impedance variation and transfer function analysis. To alleviate this parasitic degradation, a new optimal layout structure along with parasitic-compensation technique is proposed, which results in a 15-dB improvement in image rejection ratio, as compared with a conventional layout. Using the proposed techniques, more than 35 dB of image rejection over a bandwidth of 7 GHz is demonstrated in an outphasing transmitter at 60 GHz in 40-nm CMOS.