HP 8753E manual Device Measurement

Device Measurement

Now the unknown is measured to obtain a value for the measured response, E&J, at each frequency (see Figure 6-41).

'~IA(~RF)

s i1M = E DF+ mA

Figure 6-41. Measured SI 1

pg658d

This is the one-port error model equation solved for S11A. Since the three errors and SLIM are now known for each test frequency, &IA can be computed as follows:

(SllM - J%F)

&lA =

J%F(S~IM - EDF) + ERF

For reflection measurements on two-port devices, the same technique can be applied, but the test device output port must be terminated in the system characteristic impedance. This termination should have as low a reflection coefficient as the load used to determine directivity. The additional reflection error caused by an improper termination at the test device’s output port is not incorporated into the one-port error model.

Two-PortError Model

The error model for measurement of the transmission coefficients (magnitude and phase) of a two-port device is derived in a similar manner. The potential sources of error are frequency response (tracking), source match, load match, and isolation (see Figure 6-42). These errors are effectively removed using the full two-port error model.

6-66 Application and Operation Concepts