How does a stub filter work page 4

Reflection Coefficient Measurement

7) The test set up is now changed as per Figure 15 with the Stub Filter removed and the T junction output terminated into 50Ω. The purpose of this measurement is to establish the attenuation of the RF Bridge, prove that the Reflection Coefficient has been calculated properly and to give an intermediate stage that proves the test set up is working properly.

Figure 15

[Set up for measuring Reflection Coefficient - Forward Voltage]

The peak to peak voltage displayed on the oscilloscope input from the RF Bridge is recorded as forward voltage.

The test set up is changed as per Figure 16 by reversing the RF Bridge.

Figure 16

[Set up for measuring Reflection Coefficient - Reflected Voltage]

The peak to peak voltage displayed on the oscilloscope input from the RF Bridge is recorded as reflected voltage and a simple calculation performed.

Reflection Coefficient = Forward Voltage / Reflected Voltage

The results should be in the region of -0.333.

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