The pass band filter has planar ring resonators arranged in pairs partly
side-by-side and partly one above the other and a housing cover for each
resonator. Each resonator includes a respective substrate provided with
upper and lower conductive layers of high temperature superconductor
material on respective opposite sides of the corresponding substrate, so
that each planar ring resonator is operable in an edge-current-free
TM010-oscillator mode. A respective coupling hole of radius r.sub.i is
provided in the lower conductive layer (3) of each resonator and the lower
conductive layers of both resonators in each pair face each other so that
both resonators are coupled. Each housing cover has a respective truncated
cone-shaped step ring (20) having a corresponding inner housing cover
radius (r.sub.G). The radius ratio r.sub.i /r.sub.a (r.sub.a is the radius
of the circular upper conductive layer) and the inner housing cover radius
for each resonator are selected so that resonance frequencies of undesired
oscillator modes of the resonators are shifted up to about 22% relative to
the resonance frequency of the edge-current-free TM010-oscillator mode.