A Novel Reduced-Size Rat-Race Broadside Coupler and Its Application for CMOS Distributed Sub-Harmonic Mixer

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A broadband distributed sub-harmonic resistive field effect transistor mixer with a novel modified rat-race broadside coupler using a 0.13-<formula formulatype="inline"><tex>$\mu{\rm m}$</tex></formula> CMOS foundry process is presented in this letter. Using the broadside coupler, a reduced-size rat-race is fabricated with a compact size of 110<formula formulatype="inline"><tex>$\, \times \,$</tex></formula>80 <formula formulatype="inline"><tex>$\mu {\rm m} ^{2}$</tex></formula>. From the measurement results, the mixer achieved a conversion loss of 12 dB from 32 to 70 GHz of RF frequency. The passive sub-harmonic mixer has zero power consumption. With the modified rat-race broadside coupler, the mixer achieves a good LO-IF isolation of better than 30 dB and a compact core chip size of 0.55<formula formulatype="inline"> <tex>$\, \times \,$</tex></formula>0.4 <formula formulatype="inline"><tex>${\rm mm}^{2}$</tex></formula>. </para>