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SATCOM Wideband digital channel analyzer


OBJECTIVE: Develop a low cost silicon-based wideband digital channelizer for the military Ka-band WGS terminal that down-converts, digitizes, and channelizes L-band (9502150 MHz) intermediate frequency (IF) into multiple channels of baseband signal. DESCRIPTION: Current military Ka-band WGS SATCOM terminal employs multiple digital receivers to process signal in different channels. For example, four digital receivers, each with a 125 Mhz bandwidth can be employed to process signal in a 500 MHz bandwidth. The multiple number of digital receivers increases Size Weight and Power (SWaP) and cost. Recent research [2][3][4] focuses on the superconductor based mixed signal data converter to achieve direct digitization starting from the Radio Frequency (RF) signal. However, because of the cooling requirements, such systems are expensive and bulky. There are also other all-digital approaches [5] available, by focusing primarily on the digital processing; however, they do not offer an integrated, low-cost solution. This SBIR is seeking an IF L-band (950-2150 MHz) digital channelizer that provides cost and SWaP advantages over the above implementations by leveraging low-cost silicon technology such as CMOS. The key technology being sought in this SBIR is the IF L-band digital channelizer to down-convert the entire IF L-band signal, digitize the signal in a 500 MHz bandwidth, and produce multiple signal streams in different channels. The L-band digital channelizer combines the down-conversion, digitization, and channelization functions together in a single module. The number of channels should be configurable (1, 2, 4, 8, 16, 32, 64) based on individual channel"s bandwidth, with a total bandwidth of 500 MHz. The proposed wideband digital channelizer should be a single compact unit using low cost silicon technology. The proposal should apply a holistic approach that utilizes signal processing techniques for the effective filtering and the digitization resolution improvement (number of bits) with the sample rate of 1 Giga sample per second (Gsps), which corresponds to a 500 MHz bandwidth. Such holistic approach may include sophisticated digital calibration to correct for circuit impairments such as device mismatches and image imbalance that currently limits the filtering performance and the wideband analog-to-digital conversion resolution to a single digit in low-cost silicon technology. The holistic approach should apply system optimization to the channelizer design that utilizes signal processing as well as circuit design considerations to increase the wideband digitizer resolution to>12b using the low-cost silicon technology. The power consumption of the proposed channelizer should be less than 1W, and should operate in the 950-2150 Mhz L-band. Impacts to the high bandwidth efficiency modulation are beyond the scope of this SBIR. The wideband digital channelizer shall be able to operate in the same vibration, temp, and radiation environment as the existing Ka-band WGS terminals. The theoretical analysis should takes into account of the atmospheric condition, the imperfectness in the RF front end, IF, and baseband implementations. The model and simulation should be at the bit-level and should produce precise performance estimation. The simulation source code should be readily applicable to the FPGA implementation. PHASE I: Investigate circuit, architecture, and processing algorithms to determine the feasibility of producing a L-band IF wideband digital channelizer with greater than 12b resolution at 1GSps sampling rate, and consuming less than 1W of power. The investigation should include the theoretical analysis, circuit and architectrue design, and model and simulation. PHASE II: Develop and demonstrate a prototype wideband digital channelizer hardware. The demonstrated channelizer should take the L-band IF output from an existing Ka-band WGS terminal, and produces multiple channels (1, 2, 4, 8, 16, 32, 64) of baseband digital signals. The baseband digital signals should then input into COTS demodulator device for baseband processing. QPSK modulation should be used for demonstration purpose. PHASE III: The digital channelizer can be integrated into Ka-band WGS terminal to process L-band signal into multiple channels. This should reduce the SWaP of the SATCOM terminal. Research can be used within commercial satellite communication systems to enable simultaneous tuning of multiple channels. REFERENCES: 1. L. Wang and D. Ferguson, WGS Air-Interface for AISR Missions, IEEE 2007 MILCOM. 2. D. Gupta, et. al., Digital Channelizing Radio Frequency Receiver, IEEE Transaction on Applied Superconductivity, vol. 17, No. 2, June 2007. 3. S. Sarwana, et. al., Multi-band digital-RF receiver, IEEE Transaction on Applied Superconductivity, Vol. 21, No. 3, Jan. 2011. 4. W. Littlefield, A reconfigurable, digital Multi-band SATCOM terminal: Closer than you think, White paper from Hypres. 5. H. Beljour, et. al., Proof of concept effort for demonstrating an all-digital satellite communications earth terminal, IEEE 2010 MILCOM.
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