A Broadband CPW-to-Microstrip Modes Coupling Technique

A broadband vertical transition from coplanar waveguide (CPW)-to-microstrip modes is presented. The transition has a double resonance and can be tuned for very wide-band operation. The CPW-to-microstrip modes coupling technique is useful for the vertical integration of multi-layer millimeter-wave circuits, packaging and antenna feeding networks. A vertical transition has been fabricated on 100 μm silicon substrate for operation at W-band frequencies and shows less than 0.3 dB of insertion loss and better than 12 dB of return loss from 75 to 110 GHz. A 94 GHz CPW-fed microstrip antenna showing a 10-dB bandwidth of about 30 % has been built using the same transition technique.