about me
My humble beginnings
As a child I was always fascinated with radio communications and wondered such things worked. We lived near a small library in the Columbia City portion of Seattle and I quickly went through their collection of books pertaining to radio and TV. And to the dismay of my parents I was also into disassembling things to figure out how they worked. Most of my possessions, including my most valued electric train set was never the same again and I still carry some vivid memories of revelations from my experiences at 7 or 8 years old.
As with most people I knew, I started working part-time jobs from the 9th grade and continued through college where I majored in electrical engineering at UW. My first engineering job was at Boeing Aerospace in Kent Space Center. I had no idea what I was getting into and was assigned the task to design an RF circuit board to down-convert and digitize a radio signal from a JTIDS terminal. It was scary as this was my first exposure to surface mount components and microstrip/stripline designs but fortunately I had a good mentor (GWF). The engineering process of going from paper design to circuit boards, chassis and racks, then delivering and integrating at a Naval facility in San Diego was intense and at the same time appealing to me. Like putting together a giant jigsaw puzzle with pieces that you are inventing along the way.
After Boeing I ended up moving onto TRW in Redondo Beach, California, courtesy of someone I used to work with at Baskin & Robins (on MLK Jr Way So - still there!), while in high school. It really is who you know. TRW was a great place to work and I also found Los Angeles to be a fun place to live while in my 20s and 30s. I worked with a group of modem engineers and we specialized in the development of high data rate satellite ground station receivers. These experiences at Boeing and TRW (now Northrop Grumman) were my formative years as an engineer and played an important part of who I am today.
Fast forward to halfway through my career, I made a switch to work in astronomy and live in the small town of Hilo, Hawaii. Going from industry to a research organization was a difficult transition for me but I've found that most academic organizations are of the accommodating sort. I've definitely learned a lot of new things pertaining to astronomy and astronomical techniques that are not a normal part of communications. And like most things in life, the more I learn the more I know what I don't know. A big THANKS to the people that have and continue to share their knowledge with me, you know who you are. I consider myself quite lucky to be doing something that I yearned to do as a child.
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 for others to scrutinize. From here, trades and compromises are made until we arrive at an architecture that is realizable within the constraints of the project. It’s analogous to design by committee and is rarely a smooth process that's full of ambiguity and personalities. 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. And more often than not, I end up doing the mechanical design and assembly which can often be an integral part of the units thermal and electrical performance. My aim is for clean and simple designs that are both functional and aesthetically satisfying to myself and the final end user. I don't consider myself an artist but this is one of my few creative outlets that I spend a lot time thinking through carefully with an eye toward craftsmanship.
current projects
GLT LO Photonics Transmitter
2019 - This photonics transmitter unit was designed and tested in Hilo and integrated into the system at Thule AB in June. The unit provides optical transmission of 3 signals consisting of 100 MHz maser reference, 15.75 GHz pilot tone, and 18 to 31.5 GHz LO over a wavelength of 1557.2 nm from the maser house to the telescope receiver cabin over a signal fiber. This unit works in conjunction with the photonics receiver unit. The 100 MHz and LO consist of ultra low phase noise references to satisfy VLBI requirements. The 15.75 GHz pilot tone is received in the receiver cabin and retransmitted back to this unit over the same fiber at 1561.1 nm for round trip amplitude and phase measurement. A big thanks to Ryan for his craftsmanship assembly work. (D. Kubo, R. Chilson)
GLT LO Photonics Receiver
2017 - 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 both technical and staffing problems. In order to keep with the tight project schedule I assembled a partially functional prototype transmitter (see Gallery of Work below) for testing of this receiver. With the exception of the round-trip phase monitoring portion, 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
2017 - Though never a fan of the Just-In-Time (JIT) paradigm in the 90s, here is an example of it. Due to a shortage in our technical staff I ended up designing and ordering the hardware for the fiber system in parallel with working on the LO subsystem. After ordering the fusion equipment, I 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 & test the LO subsystem and to complete fiber installations and tests with the terminal equipment. First light for the telescope was obtained a month later in December 2017. (D. Kubo, P. Oshiro, J. Wang, S.H. Chang, ICP)
GLT IF Processor
2017 - 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. Kudos to Ryan for the beautiful craftsmanship. (R. Chilson, D. Kubo)
GLT Backend Reference
2017 - 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. Kudos again to Ryan for the beautiful work. (R. Chilson, D. Kubo)
GLT Hardware System Block
2019 - Consistent with my system design approach, 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 mm-wave 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-0Q, 17th revision. (D. Kubo, C.C. Han, M. Inoue, S. Matsushita, K. Asada)
recent projects
YTLA System Architecture
2016 - As part of an effort to repurpose the AMiBA telescope from a wide-band analog correlator to a digital correlator with higher spectral resolution, I was tasked to develop a microwave design architecture that can digitize any 2 GHz portion of the 2-18 GHz intermediate frequency (IF) band. I was initially struggling with the engineering 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. First light of the full dual polarization system was obtained in April 2018. Major kudos to Ranjani for working on the software and commissioning work. (D. Kubo, C.T. Li, H. Jiang)
YTLA I/Q Down Converter
2016 - 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. This assembly down converts any 4 GHz portion of the 2-18 GHz IF by tuning the LO and maintains decent amplitude balance and quadrature. Residual amplitude and phase correction is performed in the digital domain to maintain >/= 20 dB sideband rejection. The YTLA has completed its commissioning phase and has started early science as of April 2018. Kudos to John for the technical craftsmanship he put into the final production design. (D. Kubo, J. Kuroda, S. Ho, R. Srinivasan, J.C. Cheng, C.T. Li)
YTLA Noise + Tone Calibration Plate
2016 - 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 than meets the eye of the casual observer. (D. Kubo)
YTLA Clock Distribution
2015 - 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
2013 - 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. Kudos again to Ryan for the beautiful assembly work and to Ranjani for the software. (D. Kubo, R. Chilson, J. Kuroda, R. Srinivasan)
ALMA LORTM
2011 - 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. This design turned out to be more complicationed than anticipated, click link below to find out more. (D. Kubo, R. Srinivasan, C.C. Han)