Category: FDCS On-wafer measurements
Symptoms / Solutions:
For an on-wafer setup, the maximum smith chart coverage that can be achieved by the tuner is affected by the insertion loss between the tuner and the DUT reference plane. In most cases, the insertion loss comes from the on-wafer probe and the cable between the on-wafer probe and tuner as shown in the following figure.
Figure 1: Common on-wafer setup with load tuner
The gamma at the DUT reference plane can be expressed as:
(1)
where Γtuner is the gamma presented by the tuner itself, S11, S12,S21 and S22 are the S-parameter of the probe & cable.
From (1), to improve the smith chart coverage, it is recommended to use low insertion loss probe and cable.
Additional Information:
To preview the gamma at the DUT reference plane with different insertion loss and tuner gamma, RF Calculator in the Utilities can be used as shown in Figure 2.
Figure 2: VSWR/Loss utility
Keywords: On-wafer, tuner, coverage, maximum gamma
Last date modified: 2017/05/02
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