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Many Octave, Ultra-Sensitive Low Frequency Receivers



TECHNOLOGY AREA(S): Battlespace, Electronics, Sensors

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with section 5.4.c.(8) of the solicitation. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.

OBJECTIVE: The objective is to demonstrate Ultra-Sensitive Low Frequency Receiver with a compact RF front end that delivers better than 26 bit dynamic range and 1 Hz frequency resolution for >3 simultaneous signals of interest anywhere across 100 Hz to 20 MHz. This front end should encompass from the analog RF antenna feed into a commercial of the shelf (COTS) standard digital processor using a standard digital interface.

DESCRIPTION: Communications over the visual horizon is critical to operational coordination. Low frequency signals are more able to propagate around the world without relay stations than those at high frequencies. Unfortunately, intentional signals must also compete with high interference (effective noise floors) due to that ability and their usefulness for voice communications between, for example, taxi cabs and their dispatchers. Thus monitoring the weak signals in the spectra below roughly 20 MHz requires receivers with extremely large dynamic range. Historically analog channelization into a slowly scanning, narrow band receiver provides some awareness for platforms large enough to carry resonant antennas. Recently, magnetic field sensors and other approaches to electrically small, ultra-wide band antennas have been demonstrated, as have oversampling analog to digital convertors (ADC), which allow a fully digital, direct reception approach. That allows unrestricted parallelization of digital extraction of specific signals following cueing by a search mode. Beyond the complexity of the digital signal processor (DSP), the hardest technical problem is now to provide adequate inherent dynamic range and stability/accuracy of the required high clock rate analog to digital converters.

COTS acoustic ADC can achieve as much as 24 bit dynamic range for 5 or 25 KHz wide base band signals. However, to stare at 20 MHz of instantaneous band width(IBW) this way you need 800 channels or more, a nightmare for coherent clock & local oscillator distribution, component matching, and digital reconstruction of wider signals. Scanning lowers channel count but necessarily lowers either frequency resolution or probability of signal intercept. Direct, wide band digital reception is essential to full spectrum awareness.

The Phase I proposals must define an architecture for the entire front-end system. A technical risks section should be included with a discussion of the origin, nature and severity of each perceived risk, and potential solutions thereof, before clarifying which risk(s) would be reduced/retired during the phase 1 effort. Hypotheses should be offered as to performance one could expect at the end of phase 1 and 2. While smaller and lighter systems are always desirable, an entire front end system (antenna feed through to COTS Si processors) that occupies one 19 inch, full height rack or less and delivers user defined, arbitrarily chosen portions of the band is desirable.

PHASE I: During the Phase I effort, the front end architecture should be further developed and the highest technical risk component identified in the Phase I proposal be actively worked. The base phase should conclude with an Initial Phase II plan and refinements of the residual risks estimates. The option, if awarded, should further reduce technical risk.

PHASE II: The Phase II effort should develop and demonstrate a compact RF front end prototype that delivers better than 26 bit dynamic range and 1 Hz frequency resolution for >3 simultaneous signals of interest having different power levels and signal modulation types and IBW anywhere across 100 Hz to 20 MHz. This front end should encompass from the analog RF antenna feed into a COTS standard digital processor using a standard digital interface format, e.g. Vita 49. The base effort should focus on the part(s) (e.g. ADC) that initially prevents a demonstration of over 26 bits difference in input power between pairs of large and small signals placed individually anywhere in the band. The first option, if awarded, should produce a demonstration of multiple signals similarly resolvable from a single data stream. The second option, if awarded, will most likely include a classified test of receiver readiness and functionality defined by the transition sponsor.

PHASE III DUAL USE APPLICATIONS: The Phase III will consist of any further required risk reduction and integration of this front-end prototype with the required back-end DSP subsystem of the transition partner’s choice. Private Sector Commercial Potential: The primary commercial interest will be in the audio-phial market where extremely accurate recording of live music is required. They will, however, require a different power range and less instantaneous band width than DoD.


  • Superconducting High-Resolution A/D Converter Based on Phase Modulationand Multichannel Timing Arbitration. Sergey V. Rylov and Raphael P. Robertazzi HYF'RES, Inc., 175 Clearbmk Road, Elmsford, NY 10523.

KEYWORDS: analog to digital converters; direct reception; over-the-horizon communications; ducting; atmospheric scattering; thermal noise limits; oversampling

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