UDC Up/Down Converter for 12meter
aug16
A udc device takes 1 to 12 GHz rf input (one for
each pol). It mixes the signal up to around 22.5 GHz and then back
down to an IF that can be from 500 to 2.5 GHz. There are multiple
frequency band outputs (for various backends).
We will have 2 UDC'S connected to the 12 meter
telescope. 1 for sband and 1 for xband.
A udc consists of 2 chassis's:
- mixer chassis
- LUFF slsm3-11250 synth to generate fixed 22500 MHz
- LUFF TLSD5750-8250 .1 MHz synth resolution. .4 MHz
resolution after x4. Programmable synth to select rf,if1.
- attenuator, if distribution chassis.
The table below shows the output bands
available :
freq Range
GHz
|
use
|
2.0 - 2.5
|
vlbi
|
1.5 - 2.0
|
vlbi |
1.0 - 1.5
|
vlbi |
.5 to 1.0
|
vlbi |
.5 to 1.0
|
Ao iflo
|
1.0 to 2.0
|
Ao iflo |
History
- 09nov21: added pads in front of udc synth chassis
inputs: polA 15 db, polB 20d
- the sun was saturating the udc synth box
Controlling the udc
web page to control udc
|
udc12m.naic.edu
|
web page to config ethernet
to serial devices
|
ip addresses of
device
|
ipAddresses
|
|
|
udc1
(aug16)
|
synth chassis
|
192.168.100.228
|
atten chassis
|
192.168.100.227
|
udc2
aug(16)
|
synth chassis |
192.168.110.105 (udc2-105)
|
| atten chassis |
192.168.110.106 (udc2-106)
|
attenuator range
|
0 to 15.5 db (in .5
db steps ?)
|
lo1 range
|
5750 to 8250 MHz
|
Lo Equation:
|
Lo1= ( 22500
+ (rfFreq - If1Cfr))/4.
or
Lo1=5625 + (rfFreq - IfFreq)/4. In MHz
|
|
|
|
|
|
|
Notes:
- The LO1 lower limit of 5750 means you can't mix 2270 (the
center of 12m sband) to an IF1 above 1770 MHz.
- In the udc the upconvert (to around 22.5 GHz) and the down
convert (to if1) are both high side lo's, so the if1 band is not
flipped.
Attenuators
The attenuators are connected to an
arduino micro controller via an spi interface. The host
computer talks to the arduino via ethernet.
There are 12 programmable attenuators. 2 (polA,polB) for each of the
6 udc bands.
Synthesizers
There are 2 synthesizers:
- LUFF slsm3-11250 synth is used to generate fixed 22500
MHz lo for the downconvert,.
- It is connected to arduino via an spi (?) interface. The
host can then talk to it using ethernet to the arduino.
- The synth is configured via 4 24 bit latch registers.
- An Analog devices windows gui program lets you see
what these latch values should be for a given output freq (we
use 11250).
- Luis's memo to talk to the
synth via the arduino (.pdf)
- The default setup is loading into the synth when the arduino
boots up.
- the udcctrl program does not talk to this synthesizer.
- LUFF TLSD5750-8250 is the programmable synthesizer used to
determine the Rf and 1st IF
- It has .1 MHz synth resolution. .4 MHz resolution after x4
multiplier.
- it is on the 485 bus in the synth chassis (as well as the
ardiuno).
- Commands that start with SYN enable the arduino, commands
that start with > are used by the tlsd synth.
- luff serial
rs-232 interface to model tlsd & tls2 freq synth (.pdf)
- The udcctrl program will talk to this synthesizer.
Schematics:
UDC
schematic (.pdf)
211119 - linearity test.
On 19nov21 felix did a linearity test on
the udc synth chassis.
the setup was:
- signal generator: N5183B ->40dbattenuation (2
20dbpads)-> udc_syn input -> udc_syn output ->fieldfox
(fc=1500MHz,span-1GHz,rbw=5MHz,point=401,#avg 40).
- the output amplitude of the signal generator was then stepped.
The plots show the response of the udc_synth
chassis (.ps) (.pdf)
- Top: output vs input power
- black: polA
- red:polB
- green: linear fit to input power --60 to -40 dbm.
- the output power turns over around -34 dbm.
- bottom: Linear fit - output power
- a linear fit was done to the input range -60dbm to -40dbm
- the plot show linearfit - measured values.
- the 1db compression occurs at -34 dbm
- You see compression starting around -45 dbm (we probably
need a few points between -40 and -45dbm input to nail down
the start of compression.
- PolA goes into compresses a little faster than polB.
processing: x101/211119/udcsaturation.pro\
More info:
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