Modern vector network analyzers (VNA) can be calibrated for measuring scatt
ering parameters of waveguide circuits without the need for an expensive ki
t of standard waveguide components. It is possible to specify the quality o
f a low reflection load bu using a sliding matched lend of lower quality an
d, therefore use it as a standard circuit. Similarly, the VNA can be used a
s a transmitter/receiver for measuring geometrical parameters of a referenc
e circuit from which a standard open circuit can be specified.