High Speed Test Interface Module Using MEMS Technology

With the transient frequency of available CMOS technologies exceeding hundreds of gigahertz and the increasing complexity of Integrated Circuit (IC) designs, it is now apparent that the architecture of current testers needs to be greatly improved to keep up with the formidable challenges ahead. Test requirements for modern integrated circuits are becoming more stringent, complex and costly. These requirements include an increasing number of test channels, higher test-speeds and enhanced measurement accuracy and resolution. In a conventional test configuration, the signal path from Automatic Test Equipment (ATE) to the Device-Under-Test (DUT) includes long traces of wires. At frequencies above a few gigahertz, testing integrated circuits becomes a challenging task. The effects on transmission lines become critical requiring impedance matching to minimize signal reflection. AC resistance due to the skin effect and electromagnetic coupling caused by radiation can also become important factors affecting the test results. In the design of a Device Interface Board (DIB), the greater the physical separation of the DUT and the ATE pin electronics, the greater the distortion and signal degradation. In this work, a new Test Interface Module (TIM) based on MEMS technology is proposed to reduce the distance between the tester and device-under-test by orders of magnitude. The proposed solution increases the bandwidth of test channels and reduces the undesired effects of transmission lines on the test results. The MEMS test interface includes a fixed socket and a removable socket. The removable socket incorporates MEMS contact springs to provide temporary with the DUT pads and the fixed socket contains a bed of micro-pins to establish electrical connections with the ATE pin electronics. The MEMS based contact springs have been modified to implement a high-density wafer level test probes for Through Silicon Vias (TSVs) in three dimensional integrated circuits (3D-IC). Prototypes have been fabricated using Silicon On Insulator SOI wafer. Experimental results indicate that the proposed architectures can operate up to 50 GHz without much loss or distortion. The MEMS probes can also maintain a good elastic performance without any damage or deformation in the test phase

Superconducting RF Technology R&D for Future Accelerator Applications

Superconducting rf technology (SRF) is evolving rapidly as are its applications. While there is active exploitation of what one may term the current state-of-the-practice, there is also rapid progress expanding in several dimensions the accessible and useful parameter space. While state-of-the-art performance sometimes outpaces thorough understanding, the improving scientific understanding from active SRF research is clarifying routes to obtain optimum performance from present materials and opening avenues beyond the standard bulk niobium. The improving technical basis understanding is enabling process engineering to both improve performance confidence and reliability and also unit implementation costs. Increasing confidence in the technology enables the engineering of new creative application designs. We attempt to survey this landscape to highlight the potential for future accelerator applications.Comment: Submitted to Reviews of Accelerator Science and Technolog

An ultra-fast digital diffuse optical spectroscopic imaging system for neoadjuvant chemotherapy monitoring

Up to 20% of breast cancer patients who undergo presurgical (neoadjuvant) chemotherapy have no response to treatment. Standard-of-care imaging modalities, including MRI, CT, mammography, and ultrasound, measure anatomical features and tumor size that reveal response only after months of treatment. Recently, non-invasive, near-infrared optical markers have shown promise in indicating the efficacy of treatment at the outset of the chemotherapy treatment. For example, frequency domain Diffuse Optical Spectroscopic Imaging (DOSI) can be used to characterize the optical scattering and absorption properties of thick tissue, including breast tumors. These parameters can then be used to calculate tissue concentrations of chromophores, including oxyhemoglobin, deoxyhemoglobin, water, and lipids. Tumors differ in hemoglobin concentration, as compared with healthy background tissue, and changes in hemoglobin concentration during neoadjuvant chemotherapy have been shown to correlate with efficacy of treatment. Using DOSI early in treatment to measure chromophore concentrations may be a powerful tool for guiding neoadjuvant chemotherapy treatment. Previous frequency-domain DOSI systems have been limited by large device footprints, complex electronics, high costs, and slow acquisition speeds, all of which complicate access to patients in the clinical setting. In this work a new digital DOSI (dDOSI) system has been developed, which is relatively inexpensive and compact, allowing for use at the bedside, while providing unprecedented measurement speeds. The system builds on, and significantly advances, previous dDOSI setups developed by our group and, for the first time, utilizes hardware-integrated custom board-level direct digital synthesizers (DDS) and analog to digital converters (ADC) to generate and directly measure signals utilizing undersampling techniques. The dDOSI system takes high-speed optical measurements by utilizing wavelength multiplexing while sweeping through hundreds of modulation frequencies in tens of milliseconds. The new dDOSI system is fast, inexpensive, and compact without compromising accuracy and precision

Coherent Receiver Arrays for Astronomy and Remote Sensing

Monolithic Millimeter-wave Integrated Circuits (MMICs) provide a level of integration that makes possible the construction of large focal plane arrays of radio-frequency detectors—effectively the first “Radio Cameras”—and these will revolutionize radio-frequency observations with single dishes, interferometers, spectrometers, and spacecraft over the next two decades. The key technological advances have been made at the Jet Propulsion Laboratory (JPL) in collaboration with the Northrop Grumman Corporation (NGC). Although dramatic progress has been made in the last decade in several important areas, including (i) packaging that enables large coherent detector arrays, (ii) extending the performance of amplifiers to much higher frequencies, and (iii) reducing room-temperature noise at high frequencies, funding to develop MMIC performance at cryo-temperatures and at frequencies below 150GHz has dropped nearly to zero over the last five years. This has severely hampered the advance of the field. Moreover, because of the high visibility of < 150GHz cryogenic detectors in astrophysics and cosmology, lack of progress in this area has probably had a disproportionate impact on perceptions of the potential of coherent detectors in general. One of the prime objectives of the Keck Institute for Space Studies (KISS) is to select crucial areas of technological development in their embryonic stages, when relatively modest funding can have a highly significant impact by catalyzing collaborations between key institutions world-wide, supporting in-depth studies of the current state and potential of emerging technologies, and prototyping development of key components—all potentially leading to strong agency follow-on funding. The KISS large program “Coherent Instrumentation for Cosmic Microwave Background Observations” was initiated in order to investigate the scientific potential and technical feasibility of these “Radio Cameras.” This opens up the possibility of bringing support to this embryonic area of detector development at a critical phase during which KISS can catalyze and launch a coherent, coordinated, worldwide effort on the development of MMIC Arrays. A number of key questions, regarding (i) the importance and breadth of the scientific drivers, (ii) realistic limits on sensitivity, (iii) the potential of miniaturization into receiver “modules,” and (iv) digital signal processing, needed to be studied carefully before embarking on a major MMIC Array development effort led by Caltech/JPL/NGC and supported by KISS, in the hope of attracting adequate subsequent government funding. For this purpose a large study was undertaken under the sponsorship and aegis of KISS. The study began with a workshop in Pasadena on “MMIC Array Receivers and Spectrographs” (July 21–25, 2008)1, immediately after an international conference “CMB Component Separation and the Physics of Foregrounds” (July 14–18, 2008)2 that was organized in conjunction with the MMIC workshop. There was then an eight-month study period, culminating in a final “MMIC 2Workshop” (March 23–27, 2009).3 These workshops were very well attended, and brought together the major international groups and scientists in the field of coherent radio-frequency detector arrays. A notable aspect of the workshops is that they were well attended by young scientists—there are many graduate students and post-doctoral fellows coming into this area. The two workshops focused both on detailed discussions of key areas of interest and on the writing of this report. They were conducted in a spirit of full and impartial scrutiny of the pros and cons of MMICs, in order to make an objective assessment of their potential. It serves no useful purpose to pursue lines of technology development based on unrealistic and over-optimistic projections. This is crucially important for KISS, Caltech, and JPL which can only have real impact if they deliver on the promise of the technologies they develop. A broad range of opinions was evident at the start of the first workshop, but in the end a strong consensus was achieved on the most important questions that had emerged. This report reflects the workshop deliberations and that consensus. The key scientific drivers for the development of the MMIC technology are: (i) large angular-scale Bmode polarization observations of the cosmic microwave background—here MMICs are one of two key technologies under development at JPL, both of which are primary detectors on the recently-launched Planck mission; (ii) large-field spectroscopic surveys of the Galaxy and nearby galaxies at high spectral resolution, and of galaxy clusters at low resolution; (iii) wide-field imaging via deployment as focal plane arrays on interferometers; (iv) remote sensing of the atmosphere and Earth; and (v) wide-field imaging in planetary missions. These science drivers are discussed in the report. The most important single outcome of the workshops, and a sine qua non of this whole program, is that consensus was reached that it should be possible to reduce the noise of individual HEMTs or MMICs operating at cryogenic temperatures to less than three times the quantum limit at frequencies up to 150 GHz, by working closely with a foundry (in this case NGC) and providing rapid feedback on the performance of the devices they are fabricating, thus enabling tests of the effects of small changes in the design of these transistors. This kind of partnership has been very successful in the past, but can now be focused more intensively on cryogenic performance by carrying out tests of MMIC wafers, including tests on a cryogenic probe station. It was felt that a properly outfitted university laboratory dedicated to this testing and optimization would be an important element in this program, which would include MMIC designs, wafer runs, and a wide variety of tests of MMIC performance at cryogenic temperatures. This Study identified eight primary areas of technology development, including the one singled out above, which must be actively pursued in order to exploit the full potential of MMIC Arrays in a timely fashion: 1. Reduce the noise levels of individual transistors and MMICs to three times the quantum limit or lower at cryogenic temperatures at frequencies up to 150 GHz. 2. Integrate high-performing MMICs into the building blocks of large arrays without loss of performance. Currently factors of two in both noise and bandwidth are lost at this step. 3. Develop high performance, low mass, inexpensive feed arrays. 4. Develop robust interconnects and wiring that allow easy fabrication and integration of large arrays. 5. Develop mass production techniques suitable for arrays of differing sizes. 6. Reduce mass and power. (Requirements will differ widely with application. In the realm of planetary instruments, this is often the most important single requirement.) 7. Develop planar orthomode transducers with low crosstalk and broad bandwidth. 8. Develop high power and high efficiency MMIC amplifiers for LO chains, etc. Another important outcome of the two workshops was that a number of new collaborations were forged between leading groups worldwide with the object of focusing on the development of MMIC arrays