R&S ZVA8 - Page 413

R&S ZVA Repairs
1177.5333.02 3.105 E-11
Bridge Directivity
The following is assumed:
 The generator and receiver sections of the reflectometer associated with the bridge unit are
OK.
 Perform a sweep from 300 kHz to 8 GHz, measure Ratio bx/ax Source Portx
 Screw the SHORT from a N-calibration kit to the port connector, save measured values (Data ->
Mem).
 Screw the OPEN from the calibration kit to the port connector, save measured values (More Mem :
Data -> Mem3).
 Screw the MATCH from the calibration kit to the port connector.
 Select User Def Math : linMag(Data) / ((linMag(Mem2) + linMag(Mem3)) / 2 : Math = User Def
 The trace gives the directivity.
Frequency range
Directivity
300 kHz to 50 MHz
< -10 dB
50 MHz to 8 GHz
< -16 dB
If the measured values are greater than the values stated in the table, the bridge unit must be replaced.
Bridge unit: Port Matching
It is assumed that there is a functioning reflectometer in the instrument.
 Loosen cables W514 (GEN -> Bridge unit), W515 (Bridge unit -> MEAS) and W518 (Bridge unit ->
REF) at both ends and unscrew at the bridge unit.
N.B.: When loosening, support the cable with a 7mm spanner
 Terminate the bridge unit input and bridge unit outputs with 3 SMA terminations.
 Connect N test cable to a functioning instrument port and perform a 1-port calibration at the end of
the cable.
 Connect the end of the test cable to the port of the bridge unit under test and display the Sxx
magnitude on the screen.
Frequency range
Sxx dB
300 kHz to 8 GHz
-18 dB
If the values in the table are exceeded, the board must be replaced.