About Me
My Background
When I was in elementary school my father bought a small crystal AM radio set which fascinated me. How was such a thing possible? We often spent time at the local library in Seattle where I devoured anything related to radio communications. As I got older, this fascination never faded and eventually I went to college to study electrical engineering. My first engineering job was at Boeing Aerospace in Kent Space Center where I worked under the tutelage of a great mentor whom I still attempt to emulate today. We developed an RF circuit board to I/Q down convert and digitize a radio transmission signal from a JTIDS terminal for an environment simulator. This was the beginning of what continues to be a fascinating journey into radio communications and now in radio astronomy.
My System Design Approach
For system designs, I generally concentrate my early efforts working closely with scientists/system engineers toward developing an initial architectural system block diagram. Crude as it may be at this stage, it’s my attempt at laying out hardware solutions to satisfy the project requirements. From here, trades and compromises are made until we arrive at an architecture that is realizable within the constraints of the project. It’s rarely a smooth process but if done correctly can make a huge difference on the outcome of a project.
Instrument Designs
For custom instruments, I typically use a combination of circuit board designs and connectorized RF and/or optical components and integrate into a standalone EMI chassis. My aim is for clean and simple designs that are both functional and aesthetically satisfying to myself and the final end user. I put a lot of care and detail into these designs as it is a representation of me as a designer. It doesn't always turn out as planned but I'd like to think that I'm getting better with time.
Current Projects
GLT Hardware System Block
I generated the initial system block diagram outlining the electronics architecture for the GLT project. This architecture was based on our existing receiver and backend digital hardware technologies and I developed the Local Oscillator (LO) and Intermediate Frequency (IF) portions in between. A large fraction of this effort involved the design of a system amenable to remote operations and monitoring of phase and amplitude signal stabilities associated to VLBI requirements. This diagram has evolved to include several other systems/subsystems including fiber optics, network and computing, calibration, holography and others. A Taipei colleague and I continue to maintain this drawing to reflect the “As Built Configuration” in Thule AB. We are currently on Rev-0L, 12th revision. (D. Kubo, C.C. Han, M. Inoue, S. Matsushita, K. Asada
GLT LO Photonics Receiver
This photonics receiver unit was designed, assembled and tested chiefly by a single individual (said unabashedly of myself) and works in conjunction with a suite of other units within the LO subsystem. Consistent with most development projects, I ran into my fair share of problems and in this case a supplier who couldn't deliver two secondary reference LOs for the Photonics Transmitter. In order to keep with the tight project schedule I assembled a partially functional prototype (see Gallery of Work below) for testing of this receiver. The entire LO subsystem has been deployed and tested at Thule AB in November of 2017 where the telescope currently resides. (D. Kubo, EAO machining)
GLT Fiber Optics System
Though never a fan of the Just-In-Time (JIT) paradigm in the 90s, here is an example of it. After identifying & ordering a custom fiber cable capable of operation to -65C, I wishfully waited for someone to take the reigns of this system while I worked on the LO hardware but it didn’t happen. I dropped everything to design & purchase dozens of associated hardware along with the fusion splicing equipment, borrowed a tech from YTLA and flew to San Jose for a 1-day training session a week prior to traveling to Thule AB in September for splicing. Major kudos to Jackie for pulling off the large procurements and to Peter for fusion splicing. I went to Thule in November to install the LO subsystem and to complete fiber installations and tests with the terminal equipment. First light for the telescope was obtained in December 2017. (D. Kubo, P. Oshiro, J. Wang, S.H. Chang, ICP)
GLT IF Processor
Developed the unit requirements for the IF Processor (down converter) and had a technical staff member carry through the detailed work of design, parts procurement, fabrication, assembly and test. Two + 1 spare units were deployed to Thule AB in November of 2017. (R. Chilson, D. Kubo)
GLT Backend Reference
As part of the LO subsystem, I defined the unit requirements and procured the long lead PLOs for the 2nd LOs (3.85, 8.15 GHz) and clock (2.048 GHz). A technical staff member performed the detailed work of design, parts procurement, fabrication, assembly and test. This unit + 1 spare has been deployed to Thule AB as of November 2017. (R. Chilson, D. Kubo)
SWARM Noise Source & Distribution
Designed a noise + tone injection system for calibration of the SWARM digital correlator. Modified the existing noise distribution system consisting of amplifiers & power dividers to expand the bandwidth from the original 4 to 6 GHz to the current 4 to 18 GHz. (D. Kubo, J. Kuroda, P. Yamaguchi)
Recent Projects
YTLA System Architecture
As part of an effort to repurpose the AMiBA telescope from a wide-band analog correlator to a digital correlator, I was tasked to develop a system architecture that can digitize any 2 GHz portion of the 2-18 GHz intermediate frequency (IF) band. I was initially struggling with the concept of using switched RF filter banks because of its high cost and reliability issues. Then it dawned on me to use an I/Q down converter similar to my first job at Boeing decades earlier. We hashed out the pros and cons over the next several months and here we are today digitizing any 4 GHz (LSB + USB) portion of the IF band. (D. Kubo, C.T. Li, H. Jiang)
YTLA I/Q Down Converter
Developed a prototype I/Q down converter and performed astronomical tests to validate this concept. Supervised the design, assembly and test of this production version shown in the above photo, quantity of 14 + 2 spares. The YTLA has completed its commissioning phase and has started early science as of April 2018. (D. Kubo, J. Kuroda, S. Ho, R. Srinivasan, J.C. Cheng, C.T. Li)
YTLA Noise + Tone Calibration Plate
Designed a noise + tone calibration system (covers 2 to 18 GHz) using left over components from the decommissioned analog correlator system. Channel to channel isolation is > 120 dB and was achieved using cascaded SPDT RF switches. As with most things engineering, there was a lot more that went into this design that meets the eye of a casual observer. (D. Kubo)
YTLA Clock Distribution
Designed and procured parts for for this unit which synthesizes a programmable clock frequency (we currently use 2.24 GHz). Outsourced the assembly and test to our main facility in Taipei. This unit is currently providing the clocks to 16 ROACH-2 chassis at Maunaloa where the YTLA telescope resides. (D. Kubo, C.C. Han)
SWARM Block Down Converter
Designed and closely oversaw the assembly and test of the first of two sets of BDCs that cover the 8 to 10 GHz portion of the IF spectrum. A second set of 10 to 12 GHz BDCs were leveraged from this design and was constructed, tested & integrated into the system by a technical staff member. (D. Kubo, R. Chilson, J. Kuroda, R. Srinivasan)
ALMA LORTM
Designed, assembled and tested this LO Reference Test Module (LORTM) to support the ALMA receiver integration and testing at EA-FEIC in Taichung, Taiwan. A software colleague and I provided onsite support to integrate this unit into their system. (D. Kubo, R. Srinivasan, C.C. Han)
Gallery of Work
GLT - Loading of heavy equipment into receiver cabin, Thule AB, 21-Nov-2017 2:06PM, looks like night but it's early afternoon
