TCDk is a property which all circuit materials possess and it is how much the Dk of the material will change, with a change in temperature. Ignoring this property can cause RF performance variations when a circuit is deployed in an environment where significant temperature changes are common. The default test method for determining TCDk is typically done as a raw-material test and this video gives an outline of how to perform TCDk testing in circuit form. The circuit form testing for TCDk is considered a real-world test as opposed to the raw-material test method, which is typically intended for material characterization. Watch this video from John Coonrod covering this topic: