Written By Eric Oseassen
Next generation RF/Microwave components are expanding into the millimeter frequency domain. This includes applications in 5G telecom, automotive radar spanning 77GHz to 81GHz, and biomedical spectroscopy which can be in the terahertz region.
Vector network analyzers are following components into this higher frequency, but off the shelf coaxial, SOLT (short, open, load, through) standards are often not readily available and may not offer the optimal calibration performance or form factor. An alternative calibration technique is to use THRU/REFLECT/LINE, commonly referred to as TRL.
Metrologists may debate the terminology of TRL (Thru, Reflect, Line) as opposed to LRL (Line, Reflect, Line) but in general practice the implementation is largely interchangeable. There is extensive documentation discussing the theoretical foundations and validity of TRL/LRL techniques; I have included some in the reference section.
One aspect that I have found somewhat lacking are detailed, solved examples of the TRL/LRL implementation. In the following paper I will detail the actual technique of calculating the LINE segments of a TRL /LRL calibration kit.