Microwave measurements determine the frequency of a signal between approximately 1 and 100 gigahertz, which is the microwave range on the electromagnetic spectrum. Microwave measurements have a broad range of applications that include wireless communication and broadcasting (radio, television, Internet and satellite), ovens, radar and scientific research.
Microwave frequencies are measured using frequency counters (electronic technique) or physical resonators (mechanical technique).
Frequency counters use a tuneable oscillating circuit to generate a frequency, usually by sending an electric signal through a quartz crystal. The frequency generated by the crystal acts as a reference, which is then tuned to match the microwave frequency being measured. This technique is also referred to as beat frequency detection.
Physical resonators, such as absorption wave meters, use a coil of wire attached to a circuit to measure frequency. Instead of tuning to the resonant frequency, the coil, which is usually attached to the outside of the instrument, is brought near the microwave frequency, generating a DC voltage that is represented to the technician on a galvanometer. Some mechanical frequency meters use silver plated tuneable pistons instead of a wire coil. The pistons are moved in and out of one another until the microwave frequency is matched, which is then displayed on a rotating scale on the surface of the device.