Drafting Standard Engineering Statement of Work Test Requirements
Draft engineering test requirements by binding parametric limits to specific fixture loss compensations, statistical sampling schemes, and clear failure remedies.
Fixture Insertion Loss
Meaning
Signal attenuation caused by the internal cables, connectors, and printed circuit traces within a test enclosure reduces the measured power of a device under test. This reduction, termed fixture insertion loss, must be quantified to prevent false rejection of wireless modules. It represents the difference between the power delivered to the fixture input and the power that reaches the test instrument.
Measurement Influence
Test receivers see a lower signal strength than what the transmitter actually emits when cables are long or poorly shielded. If fixture insertion loss is not accounted for, the device under test might be incorrectly graded as failing the minimum power threshold. This discrepancy is particularly problematic at millimetre-wave frequencies where trace attenuation is high.
Calibration Method
Vector network analyzers use specialized calibration kits to measure the precise attenuation of the internal signal paths. To compensate for fixture insertion loss, engineers record the s-parameters of the fixture cables and subtract these values from the final measurements. This process establishes a reference plane right at the RF interface of the device under test.
Standard techniques such as thru-reflect-line calibration allow the test executive to run mathematical de-embedding routines that run automatically during every test cycle. This ensures that the test instrument compensates for the losses in real time.
Engineering Consequence
Accounting for signal attenuation ensures that the calculated transmission power is accurate to within a fraction of a decibel. This precise calibration prevents the factory from shipping out-of-specification devices or rejecting perfectly good products. Yield optimization relies directly on this measurement accuracy across multiple test stations.