Some simple measuring techniques using a crystal doubler

The methods described rely on the use of a crystal both to generate a second harmonic and to detect the signal to be measured. The wanted signal is distinguished by a low-frequency modulation, produced mechanically or by a ferrite phase-shifter operating in the waveguide supporting the second-harmonic wave. The theory of the methods is developed, and experimental results in support of the conclusions are presented. It is shown that reasonably accurate measurements of v.s.w.r. and the relative permittivity of dielectrics can be achieved with simple easily-constructed apparatus.