Investigations on Air Bridges Used for MMICs in CPW Technique

Two principle types of air bridge realizations are distinguished. The different electrical behaviour of both types is pointed out. Measurements indicate significant losses and phase shifting. A variety of modifications of each type is built on GaAs substrate. Some hints for improved monolithic microwave integrated circuit (MMIC) design are offered. The air bridge T-junction is introduced as a new component. A travelling-wave amplifier (TWA) fabricated in coplanar waveguide (CPW) technique is presented as a design example using a minimum number of air bridges.