Qh. Wang et al., FABRICATION AND MICROWAVE CHARACTERIZATION OF MULTILAYER CIRCUITS FORMMIC APPLICATIONS, IEE proceedings. Microwaves, antennas and propagation, 143(3), 1996, pp. 225-232
A technique to fabricate novel multilayer monolithic microwave integra
ted circuit (MMIC) structures using polyimide as insulating dielectric
layer is described. The polyimide layer formation, curing and dry etc
hing processes are investigated in an attempt to obtain high quality d
ielectric layers suitable for MMIC applications. By employing this tec
hnique, MMIC design and circuit routings become much easier and conven
tional microstrip transmission lines and lumped passive components can
be realised with effective use of the substrate material. In the pape
r it is shown that a V-shaped MMIC coplanar waveguide (CPW) transmissi
on lines with low characteristic impedance and edge offset broadside d
irectional couplers can easily be designed using the multilayer techni
que. This implementation can avoid the well known current crowding eff
ects on the conductor edges. Within the Ku and K band frequency range,
circuits have been characterised and show good performances. By using
the same technique, miniaturisation of a lumped-distributed CPW ring-
resonator bandpass filter can be achieved with built-in shunt capacito
rs. Two transmission poles and two transmission zeros could be impleme
nted by introducing two discontinuities. The measured results show a 3
dB bandwidth of 3.7 GHz at 13.7 GHz.