[mmaimcal]Fwd: ATF De-scoped downconverter [wbrundag at aoc.nrao.edu]

[Bryan Butler]

all,

FYI.  the engineers seem to think that interferometry is definitely being
descoped.  is this just for the formal test/acceptance/selection period,
or for the whole thing?  seems to me that if we want to do interferometry
after 2004jan01, then we'd better make sure that the electronics is
capable of supporting it...

	-bryan


On 2002.04.02 09:02 Bill Brundage wrote:
All,
	The proposal, likely to be approved at ALMA Week, to de-scope the Antenna Test
Facility by eliminating interferometry and spectral line tests means a highly
de-scoped downconverter.  I solicit comments on the draft primary specifications
for the de-scoped downconverter, given below.  Especially, is the interface to
the front end practical at this time?
...Bill Brundage

Date:  2002 April 02

DRAFT PRIMARY SPECIFICATIONS FOR ATF DE-SCOPED DOWNCONVERTER

------

Two inputs from Front End: Polarization 1 and Polarization 2

Polarization 1 from Band 3 (84-116 GHz):
	4-12 GHz nominal, no band-limiting filter,
	-33+/-3 dBm/GHz when Tant = 290K,
	[TBD] dBm/GHz minimum,
	[TBD] dBm/GHz maximum.

Polarization 1 from Band 6 (211-275 GHz):
	4-6 GHz nominal, no band-limiting filter,
	-33+/-3 dBm/GHz when Tant = 290K,
	[TBD] dBm/GHz minimum,
	[TBD] dBm/GHz maximum.

Polarization 1 from 50-ohm termination at 290K.

Polarization 2 from Band 3 (no Band 6):
	4-12 GHz nominal, no band-limiting filter,
	-33+/-3 dBm/GHz when Tant = 290K,
	[TBD] dBm/GHz minimum,
	[TBD] dBm/GHz maximum.

Polarization 2 from 50-ohm termination at 290K.

Source S22 magnitude of polarizations 1 and 2:
	<-20 dB to minimize spectral ripple from reflections.

------

Inputs from LORR

48 millisec period:
	RS422, 5 volt differential, positive edge, rise time < [TBD].
25 MHz:
	Sine wave at 0 dBm.

------

Total Power Detectors

	Polarization 1:
		Select 4-12 GHz bandpass filter for Band 3, or
		Select 4-8 GHz bandpass filter for Band 6 or Band 3.
	Polarization 2:
		Select 4-12 GHz bandpass filter for Band 3, or
		Select 4-8 GHz bandpass filter for Band 3.

-----

AMB (M&C for downconverter module)

	Monitor:
		Voltages,
		Temperatures.

	Control:
		Set step attenuator for total power detector 1,
		Set step attenuator for total power detector 2,
		Select bandpass filter for polarization 1,
		Select bandpass filter for polarization 2,
		Set SPDT switches to zero calibrate both total power 		detectors.

-----	

AMB-TP (M&C for total power detectors)

	Monitor:
		16 bit total power data for polarization-1 detector, 		every 2 millisec,
		16 bit total power data for polarization-2 detector, 		every 2 millisec,
		Various functions of 2 sigma-delta digitizers.

	Control:
		Various functions of 2 sigma-delta digitizers.


Notes:
	It may be possible to mount all microwave, analog and digital components into 1
doublewide module.
	EMI risk avoidance may require mounting all digital boards in a separate M&C
module.