New processes for highly integrated planar microwave circuits-applications to active filters for telecommunication systems

The paper discusses the use of high integration processes and their applications for telecommunications at microwaves. For comparison, implementation techniques are detailed both in GaAs and Si technologies for active LC filters. A comparison in terms of size and cost is also made with the design of integrated negative resistance circuits. We present the BiCMOS SiGe HBT process (in which the transistor base is doped with germanium) for comparison with the GaAs process. Although earlier results seem to give advantage to SiGe and Si technologies in terms of size, cost and power consumption, there are several limitations in comparison to better-known processes, such as GaAs processes, at microwaves. In particular, there are differences in individual component performances, such as inductors or transmission lines. Moreover, the way of implementing the component on the chip is very different. Also, particular biasing methods and topologies may complicate the design. If all these differences and constraints have been overcome, our design examples show that engineers can take advantages of using these processes at microwaves. However, our results also show that GaAs technologies still provide many advantages, would it only be in terms of process maturity at these frequencies.