QUICK CHECK (Cont'd)
It may be that the demodulated button signals are uneven, like this:
Synchronous demodulated signal.
Each period 100…125µs represents
the successive buttons A, B, C, D, A, B…
This demodulated signal indicates large
difference of power applied to the button
inputs.
Differences in signal level as shown here
exceed 1 dB.
The on-board button attenuators could be adjusted to compensate for the input power difference,
therefore equalize the signals, but...
Do not readjust the on-board attenuators before you are familiar with the BPM behaviour.
What if the display does not look as shown
Check that all DIP switches of the table-top test kit are set OFF (left position).
Check that all cables are properly connected.
Check that the RF source gives the required frequency and amplitude.
If you have more than one BPM module, try another one.
Getting familiar with the BPM
Vary the power from the RF source to simulate beam intensity variations.
Explore the range from 0 dBm down to -90 dBm.
Remember that the 4-way power splitter absorbs some power: adjust for it !
While the RF source output power is changed, observe the intensity dependence of X and Y
outputs on the voltmeters. If the BPM electronics gain has been set for 1 V/mm, each mV is
equivalent to 1 µm beam displacement.
Measure the rms noise at various signal levels.
Observe the noise spectrum with an FFT or baseband spectrum analyser, at various signal levels.
BERGOZ Instrumentation
Multiplexed
01630 Saint Genis Pouilly, France
Beam Position Monitor
Tel. +33-450.426.642
Fax +33-450.426.643
Page 5
User’s manual
BERGOZ Instrumentation - 01630 Saint Genis Pouilly, France - Tel.: +33-450.426.642 - Fax: +33-450.426.643
TVA-VAT-IVA-USt. Nº FR88414997130 - Sàrl. capital 152K - Siren 414 997 130 R.C.S. Bourg - APE 332B
