Understanding the fundamental material constants in microwave measurements

Microwave characterisation of dielectric materials is vital to implement the material in communication devices and circuits. The microwave characterisation parameters are the dielectric constant, loss tangent, Q0 times f0, temperature coefficient of frequency and temperature coefficient of permittivity. This paper examines the microwave characterisation data of four different dielectric materials. From several experiments on different dielectric materials, it has been concluded that the concept of using Q0 times f0 and temperature coefficient of frequency, as a material property will not reflect on material's fundamental behaviour. On the other hand, it has been interesting to note that the temperature coefficient of permittivity of a material is a constant irrespective of the measurement technique and hence it is a material parameter. The studies on temperature dependent permittivity will reveal the knack of a material to operate as a frequency stable circuit or device