Tunable integrated active filters at microwave frequencies using gallium arsenide MMIC technology

A clear need for miniaturised integrated tunable filters in the microwave frequency band has been established. Transconductor-C networks with transconductors realised using GaAs depletion mode MESFETs and Si-N capacitors both realised in foundry GaAs technology appear to be viable. Some ideas and concepts relevant to the development have been discussed including linearisation techniques for GaAs transconductors, a tuning procedure for integrator Q-factor and unity-gain frequency and the need for a linear voltage controlled resistance circuit to implement Q-tuning. Simulation verifies that a fully tuned symmetrical transconductor appears suitable for precision filtering at 1 GHz