Making repeatable RF and microwave VNA Measurements from R&D to at platform for weapon systems

Measurement repeatability has been one of the biggest challenges for supporting weapon systems across the development - sustainment lifecycle. Typically, the Prime Contractor of a system (like a radar) uses the highest performance test equipment that the project can afford giving them the ability to make the best product they can. In the case of a Vector Network Analyzer, the cost could $150K or more, depending on the frequency range. It also can weigh in excess of 60 pounds, be 10.5 inches tall and consume over 400 watts of power. While this might be acceptable on an engineer's work bench and even on a manufacturing floor. It would be less acceptable in a repair depot and potentially unacceptable in an Intermediate-Level test system and completely unacceptable to make the needed measurements on a flight line where size and weight is critical (Not to mention that the technician is now in a potentially explosive environment). When confronting all these differing test environments, it is not possible to use one common piece of test equipment. However, using different instruments for these measurements add a degree of uncertainty. While the slightly different measurement results may not be a problem as long as one is well within the guard band of the equipment being used. The farther one is away from ideal measurement conditions the more likely there will be a failure and a repair will be initiated. Repairing the failed component presents additional challenges. For the rest of this paper we will focus on a RF cable being used in a radar system as cable failures are one of the highest incident of repairs and is done at all stages of the life cycle. The specifications of this cable may be determined at the Prime Contractors R&D lab and this specification may follow, the cable, through each stage of support all the way to the platform. It might be tested by up to four different pieces of test equipment giving slightly differing measurement results. This paper will discuss how using different equipment will give varying results and how it might provide some insight to this high incident of failure. This paper will also discuss the key contributors to this difference and some possible ways to use different equipment but not affect the results, thus providing the same degree of accuracy and repeatability from the R&D lab all the way down to a technician making measurements on a radar system at the flight line. The results would mean fewer incidence of repair and vastly reduced maintenance cost.