We present the design of two 22 GHz tunable bandpass filters based on variable capacitors (in Niobium MEMS technology) realized as short sections of superconductive lines with properties similar to microstrips. The air gap between the top electrode (the microbridge) and the bottom electrode of the thin film Niobium (Nb) microstrips can be varied by ~30% through the electrostatic force generated by a DC bias voltage. Electromagnetic simulation of the two filters predicts a tuning range of ~11% and ~14% of the central filter frequency. One goal of this development is to demonstrate the application of Nb microbridges for variable filters at 22 GHz in view of a transfer to several hundreds of GHz. All steps of the low temperature (<150°C) fabrication procedure are compatible with the fabrication of Nb-Al/AlOx-Nb SIS tunnel diodes, used in heterodyne high frequency mixers operated at 4 K. This fabrication procedure sets limits to the dimensions of the microbridges.