  Here we present the microwave characterization of microstrip resonators made
from aluminum and niobium inside a 3D microwave waveguide. In the low
temperature, low power limit internal quality factors of up to one million were
reached. We found a good agreement to models predicting conductive losses and
losses to two level systems for increasing temperature. The setup presented
here is appealing for testing materials and structures, as it is free of wire
bonds and offers a well controlled microwave environment. In combination with
transmon qubits, these resonators serve as a building block for a novel circuit
QED architecture inside a rectangular waveguide.
