A microwave apparatus comprises a microwave source for providing a microwave signal, connectable to a load； control means configured in operation to vary over a frequency range a frequency of the microwave signal provided by the source； a microwave detector for performing microwave measurements, arranged to receive reflections from and/or transmissions to the load in operation and to perform a plurality of measurements, each measurement corresponding to a respective one of a plurality of different frequencies of the frequency range； and means for determining from the plurality of measurements a measure of reflection and/or a measure of transmission.
