OPTION 008 RF PROFILES AND COMPLEX SWEEP
Annex-B-9
Tutorial examples for RF offset and profiles
Example 1: RF offset - compensating for a combiner
Problem:
An application requires the addition of two RF signals with a combiner as shown in Fig. B-8. The
combiner has 6 dB insertion loss and it is desirable for the signal generators to display the signal
level after the combiner.
Fig. B-8 Two signal generator testing with a resistive combiner
Solution:
Use the RF offset facility. Set the RF output level (for example to +6 dBm). Then set
Offset 1
(see Fig. B-3) to -6 dB and enable the offset. The signal generators provide outputs of +6 dBm to
compensate for the signal loss of the combiner whilst now displaying the signal level after the
combiner (in the example 0 dBm) as required.
Note that the maximum displayed RF level will now be limited to +7 dBm since this represents
+13 dBm at the RF output connector (unless the overrange facility is enabled).
If the save setting facility is used (Fig. B-3) the generator can be set so that every time it is
switched on a -6 dB offset is applied.
Example 2: RF offset and profiles - compensating for an amplifier
Problem:
The signal generator is being used with an external amplifier having a nominal gain of 28 dB. The
generator is being used over the frequency range 100 MHz to 500 MHz. Amplifier frequency
response and cable losses result in the overall gain of the amplifier system varying between 25 dB
and 31 dB. The signal generator is required to display the power at the output of the amplifier.
Solution:
Use both RF offset and RF profile. First use the RF offset facility to enter an offset value of 28 dB
(i.e. the mid-point of 25 and 31 dB). Connect a power meter to the amplifier as shown in Fig. B-9
after making sure that the amplifier output is at a level which will not damage the power meter.