Gregorian cal control
DOWNSTAIRS TTL cal selector
multiplexor
FIBER OPTIC XMT/RCVR
UPSTAIRS receiver cal multiplexor
CAL diode configurations
Standard gregorian cal block diagram
Online (VxWorks) tcl procedures
Measurements:
07dec17: cal selection
fails 13nov17 through 05dec17.. stuck at hcal
Summary
All receivers have noise diodes that inject power into the receiver
for
calibration purposes. A TTL signal is used to turn the noise diodes
on and off. Some receivers have a high (more power) and a low cal
(less power).
The newer receivers also have more than one configuration for the
noise diodes
(correlated, uncorrelated, 90 deg phase shift, path reversed).
The TTL signal used to turn diodes on/off is generated downstairs
and is
sent to the DOWNSTAIRS TTL cal selector multiplexor. It then goes
upstairs
via the fiber optic link. Upstairs the cal signal is sent to the
receiver
of interest via the upstairs receiver cal multiplexor.
DOWNSTAIRS TTL cal selector
multiplexor: (top)
This device is in rack 5 in the receiver room. It
has 8 input ports and
one output that is sent to the fiber optic transmitter. The user
selects one
of the 8 input ports via the calport routine. The current ports are:
- 1 - ttl signal from correlator
- 2 - ttl signal from 25hz cal generator
- 6 - 50 ohm load, forces cal to be off (used with 25hz cal).
- 7 - use front panel bnc as input
- 8 - use manual switch on the front panel.
This multiplexor can be manipulated with the "if2" or calport
commands from vxWorks.
FIBER OPTIC XMT/RCVR: (top)
This transmiter/receiver has a wide bandwidth
(about 50mhz) for fast
switching times. There is a single level (on or off) that is sent
upstairs
(both polarization's are driven from the same signal).
UPSTAIRS
receiver cal multiplexor: (top)
The upstairs receiver cal multiplexor takes the
0/1 level from the fiber
optic receiver and sends it to one of the 16 receivers. The port for
the
current receiver is automatically setup by the ifsetup routine.
CAL diode
configurations: (top)
The new receivers have a high and low cal (the
difference is generated
via a directional coupler) and 4 different cal diode configurations.
If the
diodes are labeled d1,d2 (where d1 goes to Pol A in the straight
through case)
then the configurations and keywords are:
| keywords |
code used
in hdr |
settings |
diode config |
| lcal,hcal |
4,5 |
lo hi uncorrelated cals |
d1->polA
d2->polB |
| lxcal,hxcal |
2,3 |
lo hi uncorrelated cals
crossed over |
d1->polB
d2->polA |
| lcorcal,hcorcal |
0,1 |
lo hi correlated cals |
d1->polA
d1->polb |
| l90cal,h90cal |
6,7 |
lo hi correlaated cals
with 90 deg phase shift |
d2+90Deg->polA
d2->polB |
The configuration is seleted by the ifsetup routine using the
setcal routine.
Cal block diagram:
The figure shows the standard cal block diagram for the
gregorian dome (.pdf)
Online (VxWorks) tcl
procedures. (top)
cal25 on,off -
turn the 25hz cal on or off.
calport 1..8 -
select the downstairs ttl cal port.
setcal configKeyword - select the cal configuration
hi,low,corr,uncorr...
corcal
0,1 -
turn the correlator ttl cal level on or off.
home_~phil