Corresponding Person: Phone: , Fax: S.W. Chang 2008/03 ASIAA SMA Antenna Monitoring System of Submillimeter Array Su-Wei Chang ‡, Derek Kubo *, Paul Yamaguchi †, Brain Koge * ‡: Academia Sinica Institute of Astronomy & Astrophysics, Taipei, Taiwan, R.O.C. * : Academia Sinica, Institute for Astronomy & Astrophysics, Hilo, HI 96720, USA † : Smithsonian Submillimeter Array, Hilo, HI 96720, USA Introduction An antenna monitoring system (AMS) is developed for monitoring specific critical signals within the antenna of Submillimeter Array (SMA). This system is composed by a network of RF-switches which controlled by the National Instrument (NI) ethernet to TTL switch controller, and using HP 8563E spectrum analyzer to monitor all the signals. Figure 1 describes the proposed system setup in an antenna cabin which has the capability to monitor one of twenty signals using a spectrum analyzer. The monitored signals are as follows: a) Gunn 109MHz IF monitor (8 possible signals) b) 109/200 MHz monitor references for both LO1 and LO2 (2 signals) c) 200 MHz YIG PLL error monitor for YIG1 and YIG2 (2 signals) d) YIG1 and YIG2 monitor outputs (2 signals, 5.3 to 8.7 GHz) e) IF1 and IF2 post amplified and leveled monitor outputs (2 signals, 4 to 6 GHz) f) MRG LO1 and LO2 monitor reference (1 signal, 5.5 to 8.5 GHz) These test points permit monitoring of the signals without interruption through the use of built-in directional couplers allowing simultaneous measurement with observations. All switches will be TTL controlled and of 50 Ohm termination to prevent reflection of unmonitored signals. The switches will likely be located within the metal enclosure to minimize the number of physical penetrations and to reduce potential EMI leakage into the cabin. Fig. 1. Proposed Antenna Monitoring System Fig. 2. These pictures show the two switches located inside the IF/LO enclosure. Left photo – JFW switch (S3) connected to the low frequency signals, mid photo – Miteq switch (S4) connected to the high frequency signals, right photo – the connectors J7 to J12 mounted on the enclosure TTL controller Dow-Key Switch (S5) DC Power Supply Fig. 3. Left photo is the HP 8563E Spectrum Analyzer. Right photo shows the NI ethernet to TTL switch controller, the Dow-Key switch (S5) which is the final switch collected all the input signals and went to the spectrum analyzer, and the DC power supply to power all the switches and the TTL controller Remote Software Programming The first version of the remote software for the AMS system was programmed and tested. The Labview software is used to control the TTL controller and monitor the spectrum analyzer. There are 15 JPEG spectrum photos and one row data taken by the software automatically. This program resides on a PC which is physically located at the summit of Manua Kea. Fig. 4. The first version of the Labview remote program. Left photo – the front controlled panel, right photo – the monitoring spectrum results Fig. 5. The 15 spectrum photos and one row data taken by the Labview program Conclusion and Future Works The AMS system has been prototyped and tested in antenna 7 for development purposes. The program successfully control the RF switches and also display the desired signals of interest. The further progress is revised the program and integrated into the SMA Observation Center for the real operation purpose.