This appendix expands on the JASA Functional Reference Model (Figure D-1) to explain what is intended by the functional blocks. In this figure, not all connections to the Command and Control/Information (C2I) network and the precision timing and navigation network are shown. Physical implementation is not addressed in this document, but rather the functions and the functional flow. This generic architecture is intended to comprise all aspects of an airborne SIGINT architecture that will meet the needs of manned aircraft as well as the needs of Unmanned Aerial Vehicles (UAVs). The goals of the JASA are to maximize interoperability; minimize duplication of development; be flexible, readily adaptable to new requirements, preferably through software reconfigurability; be evolvable to leverage technology and standards; allow the functionality to be optimized for mission and platform; have provisions for retaining required legacy systems; and to support multiple platform operations such as geolocation using similar or dissimilar platforms.
The coverage provided by the JASA, in frequency, simultaneous processing channels, and in the mix and type of signals, is intended to be scalable to meet the requirements of the missions and the restrictions of the platforms. Implementations of the JASA will use Government Off-the-Shelf (GOTS) and Commercial Items (CI) hardware and software, and standards based upon commercial hardware and software to the maximum extent possible.
RF Distribution
This block must be heavily tailored to the platform because it is the interface with the platform's specific antennas. Included in this block are such functions as antenna selection; band selection; antenna steering; interference cancellation for on-board emitters; blanking for high powered transmitters; RF processing for beamforming, cochannel, and within-band interference reduction; and sources for equalization, calibration, and built in test (BIT). Not all of these functions will necessarily be included in all paths or in the implementations on all platforms; rather, they will be included as needed and appropriate. The functional components here need to support the dynamic range, coherency, and phase/amplitude matching requirements for ALL processing (direction finding (DF), time Difference of arrival (TDOA), Differential Doppler (DD), pulse code modulation (PCM), etc.).
While RF Distribution will largely be a platform-specific implementation, many components can and should be common across airborne platforms.
This functional block may also include block downconverters and/or preamplifiers, possibly collocated with the antennas, for SHF and EHF paths. Antenna selection may incorporate a combination of non-blocking and blocking access.
Low Band and High Band Tuners
At the top level, the same functional description applies for both high band and low band tuners. However, signal densities and properties, propagation factors, and semiconductor physics necessitate different basic implementations.
The tuners will provide preselection of a portion of the RF spectrum and convert it to one of the standard intermediate frequency (IF) center frequencies. This allows the addition or replacement of tuners and/or preprocessors/digitizers without needing to replace the entire "receiver". Standard IF bandwidths corresponding to the standard IFs have also been identified. The tuner's technical specifications need to reflect the requirements to allow DF, TDOA, and DD, cochannel interference reduction (CCIR), etc. The IF from the high band tuners may feed through the IF Distribution back into the RF Distribution function to allow further selection and processing by the low band tuners and assets for narrowband signals. The IF from the low band tuners may feed into the high band IF Distribution function to allow further selection and processing for wideband signals. Actual implementation must provide seamless processing of all required signals.
The frequency coverage and number of channels will be a function of the platform and mission requirements. The tuners may provide pre-Detected (Pre-D) output at either IF or near baseband.
Set-On Receivers
The architecture incorporates provisions for a pool of set-on receivers to enhance collection if the platform's operational mission requires this. These receivers would be included when system constraints prohibit contiguous coverage, when additional throughput is required, or to provide additional coverage of specified signals. The set-on receiver outputs may be digital audio, digital IF (filtered), or analog (Pre-D or Post-D). The numbers, types, frequency range, modulations, and outputs of these receivers will be determined by mission requirements.
IF Distribution
The architecture allows for multiple IF's to exist in the system, for which standards are specified in this document. The IF Distribution accepts the various inputs from the tuners and receivers and routes them to the outputs specified via the C2I bus. The IF switches and distribution elements must support the dynamic range, phase noise, linearity, bandwidth, isolation and other functional specifications required of their collective applications.
IF Digitizer
The IF digitizer accepts the output of the tuners and IF Distribution, and performs the analog to digital (A/D) conversion. It may include such functions as downconversion and signal conditioning. This digital output is connected to the data flow network. The digitizers may be comprised of multiple speed, bandwidth and dynamic range converters (reflecting the different processing bandwidth/dynamic range trade-offs required for different signals). Data shall accept and pass a precision time stamp and system clock.
Subband Tuners/Digitizers
The subband tuners/digitizers accept the output of the high band tuners and IF Distribution. This module will support such tasks as: automatic and manual search with DF (antenna/array dependent); spectral analysis; signal characterization; sample incoming IF energy; and measure phase shift of IF energy. These functions must provide high performance (e.g., sensitivity, dynamic range, interference cancellation) and allow reprogrammability (scan plans, signal parameters, etc.). Signal data will be provided to the data flow network. This functional block must accept time synchronization and system clock, and tag the digitized data as required.
Special Preprocessing
This function provides for special preprocessors to accept IF or baseband analog input and support functions which are either not implementable in the digital domain, or optimized by analog preprocessing. Such functions may include wideband ELINT processing and multichannel processing. The output will be signals in digital format, which may take several forms, such as digitized IF, digitized audio, or pulse descriptor words.
The architecture allows for variations of special preprocessors to coexist in the system. The variations will be optimized to provide specific mission functions. The processors will have common interfaces for timing, to include both coherency and absolute time, and for command and control. The output of the processors will be interfaced to the data flow network and, if applicable, to the multimedia network.
Recorders
The wideband digital recorders provide a capability for such functions as recording preprocessed data and autonomous unmanned operations. Technological limitations may require the usage of non-digital media.
Ancillary Functions
The ancillary functions include such things as pre-mission programming, mission management, off-line playback, maintenance, training, and transcription.
Data Flow Network
The data flow network provides the transport and distribution functions for real-time exchange of digital data between Front End Processing and General Processing and among Front End Processing functions. The data flow network shall have a low deterministic end-to-end latency and must be non-blocking.
Multimedia Network
The multimedia network provides for the near real-time distribution of processed sensor data (e.g., digital audio, panoramic display data). The multimedia network provides distribution to processing elements, recorders, reporting elements, databases, and to/from the operator workstations. It shall be expandable to support distribution of imagery to support correlation and cross-cueing.
Command and Control Information (C2I) bus
The command and control information bus provides distributed commands to all architectural elements and provides synchronized control in concert with a precision system clock. It provides a transport/distribution pathway for ancillary information and processed data. It allows top level reconstruction of system configuration during mission and post mission processing. This shall be expandable to imagery to support such functions as correlation and cross-cueing.
Digital Signal Processing
The digital signal processing (DSP) function takes the digital data off the data flow network and performs such functions as: digital drop receivers (set-on receiver), subband tuners, channelizers, FFTs, detection, single target copy and DF, cochannel copy and DF, search, delay memory, snapshot memory, spectral display generation, pulse processing, signal analysis and processing, signal parameterization and tracking, modulation type classification, SEI, demodulation, beamforming, recording, decoding, audio analysis and processing, equalization, correlation, fusion, geolocation, TDOA, single sensor cochannel interference reduction (list is not all inclusive).
A variety of DSP implementations (including RISC's, FPGA's, etc, as well as dedicated DSP) will exist due to platform and mission requirements. Components of the DSP will use GOTS, CI, and standards based upon commercial hardware and software to the maximum extent possible.
Commercial BIT/BITE shall be used as well as systems engineering approaches to test and maintenance.
System Processing and Control
The system processing and control will support such functions as the following: system initialization and downloading of application programs; system status assessment including fault isolation; system report generation and dissemination; system configuration and resource management, based on mission priorities, degradation and tasking; control of input/ output data links, communications or LAN to include data compression and encryption/ decryption of data; data fusion; navigation processing; time conditioning; conflict resolution; periodic system recalibration; database management functions such as access, updating, downloading, and searching.
Databases
Database structure will allow for collection, storage and retrieval of both static and dynamic data. Databases can include nationally generated data, locally generated data, mapping data, DF calibration data, or any data required to successfully accomplish the mission. Databases may reside at platform specific support sites or can be transmitted via communications link from the support site to the platform directly. These databases shall also include necessary entries to support the emerging national databases, command and control, reporting, and other similar functions that are necessary to support Warfighters at all levels. The databases will be scalable to support a given operation, to meet the constraints of the platform, and to fit the payload functionality. Synchronization and normalization among distributed databases must be maintained.
Encrypted Storage
The encrypted storage provides the capability to store classified algorithms, data, etc., necessary to support the mission while allowing the aircraft to be unclassified when unkeyed.
When properly keyed for a mission, the SIGINT system is capable of full operation at a system high level.
Operator Workstations
The operator workstation, which may be collocated on the aircraft or remoted, provides the human machine interface (HMI) between operator and system. These functions include control of search; DF; precision location tasking; monitoring audio and performing gist/ transcription functions; control of ancillary processing; and report generation and review/release. Standard HMI will be used to minimize training and development cost and to maximize joint operational potential.
Servers
The servers support operator functions in the collection, analysis, reporting, mission planning, and post mission analysis.
Audio Recorders
Recorders are functionally shown on both the data flow network and on the multimedia network. The recorders provide digital recording capability compatible with existing national recording formats. They also provide real-time recording and playback functionality and support a multiplicity of storage mediums (e.g. hard disk, magnetic tape, and optical drives) and existing audio/SRI data transfer protocols.
Command & Data Link/Bridge
The command data link/bridge must allow for control of the SIGINT payload and the distribution and transportation of data and status. This may be via an internal bridge to collocated processors and operator workstations or external communications pathways (e.g., CDL) to ground/surface processing sites and other reconnaissance system, both ground and airborne.
Navigation and Timing
The JASA components will interface with the platform's navigation/timing system (GPS/INS) to accurately distribute precision platform time and navigation data internally. The platform time will be tightly synchronized to United States Naval Observatory - Coordinated Universal Time (USNO-UTC), and will include a common precision frequency reference (based on a precision frequency reference such as a rubidium or cesium reference). Accuracy, precision, latency and distribution requirements will be set to meet SIGINT processing requirements.
Reach Back/Reach Forward/Reach Between
The Reach Back/Reach Forward function provides a mechanism for the system to connect to the community for such purposes as: passing of selected signals (new modulations, etc.); passing of database updates; downloading of activity files; uploading of parameters; mission tasking, etc., and passing of COMSEC keys. When the Reach Back/Reach Forward connectivity is used between two systems, it is known as Reach Between.
Reporting
Both operator generated reporting and operator directed automatic reporting are included in the architecture. The reporting functionalities provided connectivity to existing/ required dissemination systems, utilizing the approved standards compatible with the reporting vehicles and databases.
Multilevel Reporting Guards
The architecture will support a system high operational environment in both self-contained airborne and remoted airborne configurations. The architecture will allow for multilevel reporting over appropriately secured transmission systems. The data link(s) for any remoted operations will be secured by COMSEC key for appropriate level of operations.