quarter wavelengths long the network can be made longer by simply adding more pairs of tunable and non tunable co planar waveguide sections by careful choice of the relative lengths of each tunable and non tunable section the cascaded network forms a tunable impedance matching network over a wide frequency band the slots in co planar waveguide sections 224 226 228 a and 228 b may also be bridged by a tunable layer similar to the tunable sections 212 214 and 216 but in that case the layer may be less tunable reduced tunability in regions 224 226 228 a and 228 b can be achieved by using a material that is less tunable and or by using wider slot gaps to reduce the bias field strength in these regions instead of using different types of materials in the strongly tunable and lesser tunable slot regions a tunable material can be deposited which may have varying tunability along the co planar waveguide length fig1 is a block diagram showing a matching network 10 constructed in accordance with this invention coupled to a tunable microwave device 232 the tunable microwave device 232 could be one of many devices which have varying input output characteristic impedances such as tunable phase shifters delay lines filters etc in the arrangement shown in fig1 the adjustable external dc voltage source is used to supply bias voltage to the matching network 10 and the tunable microwave device 232 in tandem as the.