AMiBA PROJECT WEEKLY MEETING MINUTES

Date: 21/September/2000

Attendants: B. Martin, H. Wang + 3 students, T.H. Chu, M.T. Chen, M. Kesteven, M. Sinclair, H.C. Lu, Eugene Hwang , Ray Wei, H.C.Li, P. Shaw, J. Wang

Issues and Description	Action by	Output
MMIC- W- Band InP HEMT LNA
1. Regarding the Sub Hamonic Mixer’s chip test at ATNF, they got some results about "conversion loss" and "return loss". Huei would like to know is there any progress on the measuring of the "isolation property". Mal says the test work is still ongoing, he hopes they could work out something in the next week. 2. Regarding the JPL's stuff, Todd Gaier sent a formal request to the JPL's headquarter to request to loan us two modules of InP LNA MMIC. Huei says that s bad news from Todd, the JPL’s head quarter rejected his request to loan the amplifiers to us. However they told Todd that they will approve it if NASA approved it. So Todd will send a request to NASA, but we don’t know the chance is. But Todd told him that it is no change to put the InP HEMT MMIC on JPL's mask, so Huei will finish the design by early November. 3. As for the 0.1um GaAs HEMT design work is still ongoing, all the chips will be sent to CIC for reviewing by this coming Saturday, and CIC/Taida is still negotiating the contract with TRW. 4. As to the export license application for the InP HEMT of TRW, Huei says Joyce told him that the review process is still ongoing at the State Department He is expecting to get a final decision on that issue by early November. 5. Waveguide filter – Mal says that they have been doing some experiments with particular type of sorts there, due to the cut off rate is not sufficient, they need to do some small work on that in a couple of weeks more. He will send some of data to Huei to take a look. 6. As for purchasing the 4 units of 82~106 GHz amplifiers from NRAO, we sent a letter to NRAO for export license application. Once the internal purchasing procedure was completed we will release that order to NRAO. Paul says that the internal purchasing process is ongoing. 7. Mal sys that their lab will get ready to test the rest of 6 units of w-band InP LNA in a week or two. 8. Prof. Chu says the local distributot of Specek told him the amplifiers as we ordered should be delivered by the end of this month, he will keep on watching it.	M. Sinclair H. Wang H. Wang H. Wang M. Sinclair P. Shaw M. Sinclair T.H. Chu	ongoing ongoing ongoing ongoing ongoing ongoing ongoing ongoing
Lag Correlator Hybrid
1. For the 17 lag correlator, Jeff starts the discussion with Gramic about making these tree divider structure that they sent a email about, and we talked about two weeks ago . They like the idea, but suggested that we should make the structure with print resistors on synthetic substrate alumina, and that was discussing on making the entire part on alumina mixer at all instead of using hybrid. The alumina has a advantage of very good loss tangent. So they are discussing it. If it works out the entire lag correlator would be shrink by 3 inches dimention, and that will be very nice if we could achieve that. So that is the discussion they are having. Warwick says that the high dielectric constant is an advantage making things smaller, but the problem is the distortion with the wide bandwidth. He agrees the use of print resistor will be the only way we are able to do it for the 20GHz wide band correlator. And for the other substrates, similar to alumina but having lower dielectric constant, may be not common and a little bit expensive, but might be an option. Warwick agrees to collect some information about the specs of substrates, and send them to Jeff to look. 2. Warwick said he is still waiting for the HBT Gilbert Cell multiplier wafers have been shipped next week from TRW, so they he hope doing the wafer testing probably a couple weeks of time. Then they will get some information on how well the HBT Gilbert Cells would. 3. Ray Wei says he has simplified the circuit and also completed the simulation for the IC circuit. There are some problem about the frequency mismatch between master PLL and slave VCO, so is trying to solve these problems. After that he will start to design the degital part. 4. As to the simulation on the Gilbert Cells Multiplier, Huei says that he got some comments by email on that simulation result from Jeff and Warwick. He has more questions needed to discuss with Paul Roberts.	J. Peterson W.Warwick R. Wei H. Wang	Ongoing Ongoing ongoing ongoing
Receiver
1. Mingtang says he is starting the purchasing process for the cold heads and some key components. 2. Yugene says he only got a sheet of specs from the Atlantic Microwave Company about the OMT, they only guarantee the band width of 94~96 GHz. Bob suggests Yugene that he should talk to NRAO people about the OMT while he visiting there by next week, and Bob will follow up that also.	M.T.Cheng Y. Hwang	ongoing ongoing
LO/IF
1. Eugene says due to the optical delay line configuration is not clear to him, so he only finish the diagram for LO noise source. He needs some inputs, e.g. the total delays, tracking requirements. 2. Eugene says that the purchasing process for the instruments and components are still ongoing. 3.As to the IF, Prof. Chu says he is making the equalizer for the cable which base on George's design, he is also starting to design the layout fro the amplifier, that amplifier is base on the HP 20GHz wide band.	Y. Hwang Y.. Hwang T.H. Chu	Ongoing Ongoing ongoing
30 cm antenna
Michael says he spoke to G. James, James is still working on the calculations for the small antennas, and need a little while to work out the number we need, he thinks.	M.Kesteven	ongoing
Platform/mount
1. Base line - Bob says that we should set up the limit for base line ASAP. Warwick says he did few calculation based on the 20m value being around in the past week ; for 1.2m dishes, it seems to him is still within the range of setting the correlator, so probably ok in this concern. Bob says he will propose this the base line we move forward with 20m is the limit, and we start figure out the delays and what is the application on the delay tracking on IF from there. 2. Bob proposes another configuration for platform and mount, he suggests having 3 hexagonal mounts with 2.5m wide platform. There are some discussions about this issue as below: Warwick - we need to make the decision on how many antennas we need to have 19 or 21 ? It does cause increase the size of correlator by that a quarter, from 19 to 21, but it is not significant. He think the major cost is coming from the modulate and de-modulate, and the delay line itself is not such a large components cost. So initially, we will build a compact antenna without any delay line on the platform, and then the photonic IF system and delay line system can be sort out in the second part. Michael - he like the three platform suggestion, and he thinks we should concentrate on the CMB platform as the first stage. This simplfies the development path- one platrform, no delay lines and delay tracking machinery. During the first year of CMB shakedown/observations we develop the SZ platform along with the delay tracking machinery. And he also thinks that it could be save some cost if we directly built a 2.5m platform for prototype. Jeff - he thinks this idea is interesting, he also think 21 antennas doesn't change the correlator significantly.	B. Martin	ongoing
Site acquisition
Bob says he talked with John Barnes of the Mauna Lao Observatory last week. John is the Station Chief of the MAO opeation in Hilo. It sounds very promising that our needs may mesh with what they look for in the use of the site. Bob says he is planning to visit Hilo in November, to take a look at the application process that we need to do. He hopes we could test the prototype over there by next year.	B. Martin	ongoing
Prototype Specification and Project Book
1. Ravi and Michael will be join the today's science meeting to discuss some observational technique relative issues with science team in order to get some outstanding issues resolved more efficiently. 2. As to the specification drafted by Michael, Bob hopes to put it out anybody else in the court next week.	B. Martin B. Martin	ongoing Next week
Travelling
Yugene / Sep. 23 ~ Oct. 6; Bob / Oct.9 ~ Oct. 26
Next Meeting
8:30pm EDT, 8:30am Taiwan, 10:30 Australia, 5:30pm Tucson/Thursday/28 September 2000