THEQEETIC_AL!CQNSI12ERATIONS 9N LMll TIRCHNIQ1lESWhen the LMR (Line-Match-Reflect) technique is applied to microstrip-Test-Fixture based chip transistor measurements, a practical drawback arises. In fact, the MATCH Standard r M should be ideal (FM = ) or perfectly known [4,7], a requirement that is difficult to meet in the higher frequency band (20 to 40 GHz) using chip microstrip-mounting loads. To circumvent the difficulty, one option is to assume a non-ideal unknown Match. In this case, the exact value of rM is not relevant for the calibration process (provided it is small and equal at both ports), but an accurate value for the Reflect Standard r R (equal at both ports) has to be provided to the calibration algorithm. The error commited assuming an ideal microstrip short is usually less than the error committed assuming an ideal microstrip load [6]. A similar argument can be used in the waveguide measurement case.The calibration equations for the case of known-Reflect LMR are not referenced in the literature. Following the same notation as in [4], it can be shown that:
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