Research On CPW Air Bridge And Its Application In Discontinuities

Coplanar waveguide (Coplanar Waveguide, CPW) is a kind of microwave transmission line, which iswide band, low dispersion, and transfer quasi-TEM mode. It plays an important role in monolithicmicrowave integrated circuit (MMIC) and microwave integrated circuit (MIC). CPW can be used as aconnected device in amplifier, frequency multiplier, mixer, and so on, in microwave elements and circuits.Many discontinuities, such as open-ended, short-ended, step, taper, gap, bend, tee junctions, crossing etc. arepreset in CPW. On the basis of these discontinuities’ characteristic, many microwave devices are formed andwidely used in MMICs and MICs.However, slot-mode and other mode are present in CPW bend, T-junction, and crossing, and theslot-mode may lead the performance of the transmission line get worse. Then air bridges are introduced tocontrol the slot-mode, and the magnitude of transmission coefficient, reflection coefficient are carried out.Firstly, research on CPW with capacitive airbridge (class A) and inductive airbridge (class B) are taken tofind out the airbridge’s influence on the transmission. And find out that transmission’s character withairbridge A is worse than that with airbridge B during low frequencies, and airbridges’ geometry, locationand number are also have effect on transmission characteristic. Then airbridges are located in bend, teejunction, and crossing to improve the characteristic of the CPW discontinuities, and the result is satisfying.