Low cost K-band CPW rat-race mixer

A K-band single balanced Schottky-barrier diode (SBD) mixer, suitable for automotive collision-avoidance radar, has been designed and fabricated. We used a coplanar wave guide (CPW) as a transmission line element for a rat-race hybrid because of its low transmission loss. A new analyzed method to rat-race hybrid is introduced and testified by EM simulation. Lower LO power as better conversion loss is particularly considered in designing of mixer. When LO signal with the power of 9 dBm at 25 GHz is injected, a conversion loss of 5.2 dB is obtained. Also, the LO to RF and LO to IF isolation of 46.4 dB and 37.7dB are obtained, respectively.