High Speed Digitizer for Remote Sensing
Project Description
This SBIR Phase II proposal requests support for Alphacore, Inc. to design and characterize a 24 Gsps (gigasamples per second), wide input bandwidth (40 GHz), 6-bit (5.0 effective number of bits, ENOB), low-power (700 mW), and low-cost analog-to-digital converter (ADC) for use in a wide range of NASA's microwave sensor remote sensing applications. The ADC does not employ time-interleaving and provides a very wide spur free input bandwidth making it more suitable to NASA's remote sensing missions and a variety of radio astronomy applications than any other ADC available. In addition, the ADC will be radiation hard (>300krad) and thus suitable for use on-board space missions. A key innovation in Alphacore's approach to the ADC design is that we have considered how the ADC will be used in a system; a custom designed digital back-end implements digital data de-multiplexing and signal conditioning to allow seamless integration with commercially available, high-end, field programmable gate arrays (FPGA) that are the main building blocks of modern scientific spectrometers and interferometers. Alphacore's ADC provides these improvements at much lower power and lower cost than existing commercial ADCs that use off-chip components to provide these features. Alphacore's design takes advantage of the latest low-power, high-speed digital CMOS processes, resulting in ADC power consumption that is less than 1/8 of the power consumption of competitor ADCs. The proposed ADC employs an innovative topology with high-bandwidth front-end sampling circuit combined with an interpolated flash-type ADC and encoder circuitry that simplifies FPGA interfacing. All the needed clock signals are generated from a low-cost 100MHz crystal clock reference with a low-jitter (<200fs), radiation-tolerant on-chip PLL.
More »Anticipated Benefits
Some of the currently planned missions that benefit from Alphacore's ADC are listed below. The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a 2.7 meter airborne telescope that includes multiple spectrometers covering a broad range of wavelengths. Its Heterodyne Instrument requires 64 high-bandwidth ADCs, similar to the Alphacore ADC. Global Atmospheric Composition Mission (GACM) has passive and active remote sensing instruments in low Earth orbit (LEO) including a UV spectrometer, an IR spectrometer, and a scanning Microwave limb sounder (SMLS). Alphacore's ADC that has 24GSps sampling rate, 40Ghz bandwidth and is radiation hard meets the requirements of these instruments. Compact Adaptable Microwave Limb Sounder (CAMLS) is a collection of instruments, scalable for use in balloons, aircraft and eventually in space. It is a follow-on mission for GACM, and requires digital spectrometers to cover 40 GHz of bandwidth. Six high-bandwidth (and rad-hard) ADCs are needed. Alphacore's ADC is an excellent match to this application. Airborne Scanning Microwave Limb Sounder (A-SMLS) instrument requires seven high bandwidth ADCs for analysis over the spectral range from 225 to 234 GHz. Other NASA missions that can benefit from Alphacore's ADC are TSSM, CCAT, JUICE, MARVEL and VESPER.
In addition to NASA's remote sensing applications Alphacore's ADC is a perfect match to a wide range of radio astronomy applications. Alphacore received several letters of support form the international radio astronomy community to go with this application. The features that make it an exceptional match to the requirements of international large-scale radio astronomy experiments are: seamless interfacing to FPGAs, single core design instead of time-interleaved one, very high sampling rate and bandwidth, easy clocking with an on-chip PLL, low power dissipation and low cost. The ADC also has wide commercial applicability in networking (coherent receivers, network modules), communications (software-defined radio), test equipment (high-speed digital oscilloscopes), radar and electronic warfare (EW) devices. The radiation hardness makes it suitable for commercial and defense sector space applications.
Project Library
Primary U.S. Work Locations and Key Partners
| Organizations Performing Work | Role | Type | Location |
|---|---|---|---|
| Alphacore, Inc. | Lead Organization | Industry | Tempe, Arizona |
| Jet Propulsion Laboratory (JPL) | Supporting Organization | FFRDC/UARC | Pasadena, California |
Primary U.S. Work Locations
-
Arizona
-
California
