AMiBA PROJECT WEEKLY MEETING MINUTES

Date: 2 November 2000

Participants: W. Wilson, M. Sinclair, M. Kesteven, B. Sault, M.T. Chen, C.H. Lu, Y.J. Hwang, P. Shaw

Issues and Description	Action by			Output
MMIC- W- Band InP HEMT LNA
1. Regarding the Sub Hamonic Mixer¡¦s chip test at ATNF, Huei asked Mal last week whether AT can make three more mixer isolation measurements. Mal says that they are planning to do at least two of those in late Dec. once they finish the installation of receiver. But on measurement has a lot of difficulties been doing, because of it requires a certain device, which we don¡¦t have. 2.Huei says that the first design for the InP HEMT MMIC is ready, and now is waiting for the wafer test data from JPL. Todd told him that he needs two weeks more to work out that test data. Fred says he will visit Pasadena in a week time. So Huei will inform Todd about Fred visit and ask him to arrange an appointment with the person in NASA who is responsible for the export license approval. 3.As for the 0.1um GaAs HEMT, Huei says the chip is ready shipped to TRW. There are some arguments on contract terms, and need to solve 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.Wave-guide filter ¡V Huei received some experiment data from Mal by fax, Mal will provide some drawings to Huei as well, and Huei will forward those data and drawings to Prof. Wu. This would be a good reference to Prof. Wu to develop his design in parallel. (Mal is modifying the existing design of 80 GHz to 85 GHz as we need.) As for the prototype receivers, Mal suggests Mingtang to investigate if he can find the required filters in the market. 6.Leo got a HPF quotation from Quinstar; the price is $1,000USD for each, but it would be $250USD each if we once order 40 units; specs are 80.5~105GHz, 84GHz at 3dB cut off, insertion loss 27db at 82 GHz. They need 60 days to deliver the first 4 units, and another 30days to deliver the remaining 36 filters. Mal says that it sounds a pretty good job on that design, and price also looks good. Leo will contact the supplier to confirm their specs could meet our requirement. George Grace provides some information of wave- guide filter to Leo. How to handle the thermal and expansion problems of wave-guide, Mal suggests that he would look carefully at any shaping the wave-guide in couple, and using the thermal stainless steel guide in straight section with thermal isolation only, and keep them straight. 7.Regarding the InP MMIC, Mal says that there are two things happening here now; they are currently testing some K-band amplifier added wafer run with the 3mm MMICs around, doing the cold measurement on amplifier to see the material behavior under cryogenics condition, and the noise temperature in cooler. He found some problems with the isolation of amplifier, a lot of gains on small chips. Several fixes they are trying at this moment, and basically he believes it is the coupling problem. He suspects we may have the same problem for W-band chips. 8.As far as the W-band chips concern, Mal says that the chips have been tested at room temperature, and currently there are 6 chips have been mounting on the amplifier body, they are constructed by this moment. And he hopes they would have several amplifiers tested by next week at room temperature. There is also the 3 mm amplifier design on move. 9.According to the contract terms, Specek should pay the delay penalty to Taida. Because of the deviation on the conversion loss with the specs is not much, and it can be compensated by other IF components. So Prof. will inform the above decision to Specek. 10.Regarding the NRAO W-band amplifiers, Mintang asked for some mechanical drawing, bias drawings and circuit drawing from NRAO, but without response. He will resend a request to NRAO today.	H. Wang M. Sinclair H.Wang H.Wang H. Wang H.C. Lu H.C. LU M. Sinclair M. Sinclair T.H. Chu M.T. Chen			Late Dec. ongoing ongoing ongoing Done ongoing ASAP ongoing ASAP ongoing
Lag Correlator Hybrid
1. Jeff says if we could use the alumina for the transmission line in the correlator, the area required for the whole correlator would be 5 times smaller. Currently some of his students are working on this study and doing some calculation. And it needs a couple of weeks more to know the answer. 2. Regarding the prototype mixer based lag correlator, Jeff will inform the update status by next week 3. Warwick says that they almost complete measurement on the HBT Gilbert Cell multiplier wafer, and the result looks like promising to use that multiplier up to 20GHz bandwidth. Warwick will put together all information and send over to everyone in the next few days. 4.The ACX Company has answered Warwick¡¦s enquiry about the correlator element fabrication by email, they also raised some questions to us. Warwick has answered ACX¡¦s questions, and Paul forwarded Warwick¡¦s response to ACX as well. 5. Warwick says he did few measurements on the narrow band prototype correlator and it seems going very well and it is working quite nicely at the 3 GHz bandwidth. And the next thing is to do the noise measurement. 6.Huei says that they finished the design work on the Gilbert Cells Multiplier, but there are some Problems unsolved. So he will talk to Paul Robert to find out solution.	J. Peterson J.Peterson W. Wilson P. Shaw W. Wilson H. Wang			ongoing next week soon done ongoing ASAP
Receiver
1. Mingtang is working on the Dewar layout; he is waiting for the mount layout, wish to know the supporting interface between receiver and mount. He is still working on the components in the deward. (Paul got one layout from J. Kingsley this morning. Kingsley says that he will send over the rest of file to Paul once he backs from Sweden in next week.) 2. Regarding the collaboration proposal on the development of NRAO OMT, Mingtang thinks that is a good idea, but still needs Fred¡¦s approval. Paul asks John to provide cost breakdown and detail time schedule to us accordingly. John agrees to do so; he will work out this information together with J. Kingsley. 3. Mingtang is working on the feed horn detail design; he has worked out some calculation and circulated it to everyone last week. Mintang sets up a priority for horn design ¡V 1.to fix the feed horn design first; 2.to decide whether we will use the multiple hole coupler or not; 3. to look at the OMT parts to see what kind of things would be putted in and then consider the physical design of phase shifter. Mingtang says that according the prototype dish specification - the F ratio is 4; it would be very difficult for us to design a 14 degree angle feed horn. And this problem should be clarified further with Bob. Mal says that according the production schedule, they should complete their own prototype feed horn by Feb. or March next year. Mingtang thinks it would be good for us if we could use the AT feed horn design on AMiBA. 4. Jeff says that he has made a design for feed horn year ago, and it is very easy to machine. He will send that design data to Mingtang to look at. 5. Regarding the ¡§circular & linear systems¡¨ issue, Mal, Michael and Jeff have been working on it. But for the prototype, we will use the linear one. 6. Jeff will send the window foam material information to Mingtang once he got it. Mal will send some window foam information to Mingtang as well.	M.T.Chen H.C. Lu J. Payne C.T. Mingtang J.Peterson J. Peterson M. Sinclair		ongoing ASAP ongoing Ongoing DONE ongoing
LO/IF
1.Eugene just generates a NRAO visit report today; he will circulate it to everyone to look at. We will put it on the ASIAA web site, and welcome everyone to take a look and to comment. 2.Eugene is working on ¡§the wideband LO noise effect calculation¡¨; he will send over to everyone to look at once finished. 3.Eugene says that the fabrication run in TRW for the 0.15£gm GaAs PHEMT process has been delivered to Taipei. This is his first iteration design on the Subharmonic Mixer. Eugene ask Mal whether AT is able to test that chip for us by Mid. Nov. Mal says that their lab is very busy now, and he thinks it would be not possible to do it for us until early next year. So Eugene will start to make simulation on chip and to finish the package design.		Y.J. Hwang Y.J. Hwang Y.J.Hwang		DONE DONE ongoing
Platform/Mount/Dishes
1.Jeff doesn¡¦t think the caesarian could work with the 30cm antenna due to its high ground pick up. He will do some quantitative analysis to demonstrate this case. 2.Regarding the height of ground shield for our antenna, Bob requests Michael to ask their expert to verify what size is good for us? 3.Mingtang says our new engineer assistant C.W.Lu fould a local expert in the field of Hexapod. The expert, Prof. Perng, leading a lab in the Department of Power mechanical Engineering of The Tsing-Hua University. Prof. Peng has more than 10 years research experience on Hexapod, and he is very interest in the AMiBA work. So Mingtang will invite him over to ASIAA to give a talk on what he knows and what he think about our mount. Mingtang will organize lunch talk for Prof. Peng on Nov.9.		J. Peterson M.Kesteven M.T. Chen		ASAP ongoing ongoing
Site acquisition
Bob says that he plans to visit Mauna Lao Observatory by the second week of November, to take a look on site and see what the possibility is and how we proceed.	B. Martine			Ongoing
Prototype Specification and Project Book
1. Ravi inputs a report on the topic of ¡§Confusion & AMiBA SZE Survey¡¨; you can also read it on the AMiBA web page. 2. As to the secondary mirror supporting structure, Jeff will collect some material information and send it over to everyone to look at.	J. Peterson			ASAP
Visitor
Darrel Emerson Nov. 9~13 / J. Payne Nov. 9~16/ B. Martin Nov. 2~13
Traveling
Next Meeting
8:30pm EDT, 8:30am Taiwan, 10:30 Australia, 5:30pm Tucson/Thursday/Nov. 9. 2000