ON-BOARD ATTENUATORS ADJUSTMENT (Cont’d)
Beam Position Monitor board
BUTA
BUTB
BUTC
BUTD
IF BPF
Level shift
AGC
IF BPF
RF BPF
Attenuators
Clock
adjust
Y gain
Σ
adj.
X gain
LO
Lock
Carrier phase
F-Key
Demod. phase
Demodulator
SBS-mode
fixed level gain
GaAs
switch
driver
GATE
(option)
Single
Button
Sampling
(option)
Mixer
LNA
IF
IC
To adjust the attenuators, use a screwdriver with a ceramic tip. A metal tip changes the signal !
Set all four on-board adjustable attenuators 1/4 of a turn clockwise. One turn is ca. 3
π
/2.
Set the RF source to the BPM operating frequency. Set power level such that -10 dBm is applied to
each button, taking the 4-way power splitter attenuation into account.
Adjust progressively A, B, C and D attenuators until the SDEMOD signal has minimum level
differences.
Note: The BPM module adjustment must be done by observing SDEMOD to minimize the button-
to-button power differences. It can not be done by simply adjusting X=0 and Y=0 : There is an
infinite number of A,B,C,D combinations satisfying X=0 and Y=0; i.e. A=1, B=2, C=1, D=2
yields X=A-B-C+D=0 and Y=A+B-C-D=0.
BUTTON SAMPLING
The BPM module has an on-board clock to drive the input multiplexer. The internal clock
frequency is adjustable by the “Clock adjust” potentiometer from 8 to 10 kHz.
Each button is thus sampled during 100 to 125 µs, and a complete scan is made in 400 to 500 µs.
The beginning of each scanning cycle is available as output signal SYNC rising edge (See
“Connector Pins Allocation”, this manual). SYNC frequency is 1/4 of sampling frequency.
The internal clock can be overridden by an external clock.
BERGOZ Instrumentation
Multiplexed
01630 Saint Genis Pouilly, France
Beam Position Monitor
Tel. +33-450.426.642
Fax +33-450.426.643
Page 7
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
Содержание MX-BPM
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