The many faces of integrated avionics.
There are still many obstacles to the realization of all the benefits of such an architecture, but there are also many smaller-scale implementations which could provide specific, if more limited, gains. Each of these approaches has its place in the EW business arena. For example, the morelimited integration activities are well suited for the avionics upgrade market. Operational improvements can be achieved while minimizing Group A and nonrecurring design costs. The more robust integration approaches require new system designs or technologies and are better suited for the new markets, including advanced platforms and comprehensive avionics upgrades.
This article addresses the potential benefits, issues and activities associated with various integrated avionics concepts. It will also highlight additional issues which must be addressed to continue the evolution toward the most robust concepts. Note that although the term "avionics" will be used throughout this article, the concepts described are equally applicable to both surface and land-based platforms.
THE PROMISE OF
Less weight, lower cost, improved mission performance and simpler support - how could you ask for more? The integration of traditionally disparate EW (or EW and non-EW) systems can lead to these results. Shared or common hardware provides the most straightforward example.
Shared hardware - such as a shared aperture, receiver or processor - is a single element used for multiple functions (versus replicating similar elements in each functional string). Common hardware, on the other hand, is identical hardware which is replicated in multiple functional strings. Elimination of a functionally equivalent asset through shared hardware translates directly to a reduction in cost, weight, volume and failure rate. Although a volume savings may not be realized in an upgrade to existing equipment, space may be freed to incorporate some enhanced capability. Common hardware elements will reduce weight only if redundancy is required and a single redundant element can serve more than one functional string. Common designs, however, even at the sub-assembly level, reduce cost due to the reduction of design requirements and increase in production quantity. Logistics support will also be reduced with common hardware.
A more common example of integrated avionics than shared or common hardware is the synergism of multiple functions. Synergism can improve a variety of contributors to situation awareness, including identification, location and determination of intent. Providing a greater volume of information in a reduced reaction time contributes to improved flight path or tactics planning. Survivability also improves; increased knowledge of the threat and threat time line allows a more effective selection of the optimal response. Directional countermeasures can also be employed.
Hardware savings also can be achieved through integrated sensor performance improvements. Gains achieved through integration allow a reduction in the required performance of an individual subsystem, while maintaining the required level of mission performance. This reduction in subsystem requirements translates into reduced hardware. An uncued flare dispenser, for example, will require significantly more capacity than one which is cued from a missile warning system which provides a time-to-impact estimate.
THE MANY FACES OF
Integrated avionics implies the interfacing or combining of separate avionics functions; this combination can include information only or physical hardware. There are five genres of integrated avionics: data integration, integrated control, integrated processing, hardware integration and weapon system integration. Although all are applicable to the ultimate weapon system integration, upgrades to existing avionics rely most heavily on data, control and processing integration.
Data integration, also known as data fusion, is the simplest form of integration. Individual subsystems continue to operate independently, but their outputs are combined to provide an enhanced estimate of the situation. Potential improvements include identification of spoofing, multimode or ambiguous emitters; friend/foe determination; threat location; and lethality assessment. Data integration can also provide a simpler, yet more comprehensive, display to the air crew.
This approach is practical for existing avionics because no mods are required to the existing systems. The only real drawback of this approach is overselling it - trying to make something out of nothing.
The next logical step from data integration is integrated control. This concept embodies the control of a subsystem or function based on inputs from an external source. For example, a system performing data integration for enhanced threat assessment is positioned to provide integrated control to one or more countermeasures subsystems to optimize the system response. Response management options include (1) prioritization based on range, angle, terrain and altitude; (2) cuing a dispenser or directional countermeasure; (3) selection of aspect-dependent countermeasures; and (4) other on- board/off-board coordination.
There are numerous initiatives across the services to develop and apply integrated data and control solutions to existing avionics. The Navy Integrated Defensive Avionics Program (IDAP) is tying together the RWR, missile warning radar, on-board ECM, expendables dispenser and towed decoy. Originally intended to upgrade the A-6, the integrated suite is slated for live-fire drone testing.
The Navy's Electronic Warfare Advanced Technology (EWAT) program is an advanced development effort that is going beyond IDAP. The EWAT program is performing the risk reduction necessary to integrate advanced missile and laser warning sensors/algorithms with countermeasure response processing. The first phase of integrated EW efforts was the development and demonstration of the Countermeasure Response Optimization (CRO) software, hosted on the AN/ALE-47 dispenser's processor. The CRO software provides strategy and response determination for expendable countermeasures, towed decoys, IR and RF jammers and air crew advisory.
A second phase has been initiated to integrate missile warning, laser warning and CRO software onto a single processor module. The EWAT program plans to demonstrate the integrated software hosted on an Advanced AYK- 14 processor module.
The Air Force Wright Laboratory is similarly in advanced development with the Advanced Defensive Avionics Response Strategy (ADARS) program to develop new techniques for improved defensive situation awareness, EW sensor management and response strategies. Laboratory demonstrations of the transportable ADARS software with representative avionics equipments are planned for mid-1994 and late 1995. There are many additional integrated data and control efforts on going within the various SPOs and international program activities.
Integrated control can also be implemented in die absence of data integration to provide optimized countermeasures, reduced system response time and enhanced detection range. Efforts in this area have focused on cuing countermeasures responses, specifically missile approach warning systems (MAWS) cuing off-board dispensers or directed IR countermeasures. The Army's Advanced Tactical IR Countermeasures (ATIRCM) program cues an expendables dispenser or directional IR jammer to the threat missile by a passive MAWS. The USAF Air Warfare Center has sponsored numerous live-fire tests of MAWS-cued expendable dispensers. Although these tests focused on die capabilities of die various active and passive MAWS, the dispenser integration is obviously transitionable to the field with the MAWS.
Wright Laboratory is developing an integrated control scheme to create effective countermeasures against an air-to-air anti radiation missile with minimum impact upon radar operation. Feasibility of effective anti-arm performance via coordinated ECM generator and radar waveform operation was demonstrated in the lab last year. A follow-on program to demonstrate performance of an integrated radar and EW system against a threat simulator is currently in source selection.
Integrated control for enhanced sensor performance has seen little activity. Coordinated search schedules and blanking schemes between the RNM, jammer and radar can reduce threat detection time lines. Sensor cuing, between RWR and power-managed jammer or to a MAWS, will reduce response time or extend detection range by modifying dwell times, revisit times or thresholds. Implementing control architectures such as these, however, requires low-latency interfaces and/or significant software and concept of operation modifications to existing systems.
Although these are not insurmountable obstacles, as evidenced by the ARM countermeasures initiative, there are limited programs in this arena for existing avionics. New system designs, such as the RAH-66 and F-22, however, offer the opportunity for these integration concepts to be incorporated into the functional flow, interfaces and software design from the outset.
Integrated processing embodies the first integration activity which addresses the merging of functional elements. The EW community has primarily been a follower on the Pave Pillar, Common Signal Processor (CSP), Advanced Avionics Architecture ([A.syp.3]) and JIAWG path. The cost, supportability and fault-tolerance benefits of integrated processing are well known, have been embraced on new developments including the Comanche and F-22 and will continue in future system developments.
Wright Laboratory is taking integrated processing one step further by applying it to existing avionics systems. The EW Processing Elements (EWPE) program is developing a modular, multi-processor, open-architecture, 64-bit processor and processor architecture that are not only Ada-programmable, but can run code from existing avionics systems. This eliminates the significant recoding costs associated with retrofitting an advanced processing architecture to an existing avionics system.
The characteristics of integrated processing and hardware integration are somewhat overlapped. Each uses shared or common hardware to implement multiple functions. Hardware integration, however, is outside the realm of the software development environment. It is further categorized as mechanical, electro-optical (EO) or RF hardware integration.
Mechanical integration is typified by integration of diverse functions within a common mechanical carrier. Westinghouse and Raytheon are under contract to study various missile warning system integrations with the ALQ-131 and ALQ- 1 84 pods, respectively. Each company will integrate two selected systems (one active and one passive) into pods for laboratory testing. The podded configuration provides the user with an operational flexibility that an internal MAWS installation does not. Westinghouse has also integrated a chaff/flare dispenser in the ALQ-131, lengthening the pod with a sectional insert.
The USAF Air Warfare Center at Eglin is independently performing a similar integration of the ALQ-131 and a Loral AAR-47 for live-fire evaluations, but with a "scabbed on" countermeasures dispenser.
Electro-optical systems have not seen widespread use in EW and correspondingly have seen limited hardware integration activities. The Navy has undertaken the integration of laser and missile warning into a single sensor package on the EWAT program. The development of miniaturized laser warning receiver technology has enabled integration with a UV MAWS, potentially sharing the aperture, sensor electronics, power supply and interface, in addition to a common processor. On corporate funds, Westinghouse has developed and flight tested an Advanced Distributed Aperture Infrared System (ADAIRS). This approach provides multiple IR staring array modules to provide all-aspect coverage, supporting targeting, navigation and missile warning.
The thrust toward RF integration has been ongoing. While its exact beginning is rather subjective, it is rooted in the development of multimode radar, EW and communications systems. The task of integrating EW RF hardware into multifunction EW systems has been addressed by programs such as INEWS. Receive and transmit functions for radar warning, precision location and active RF countermeasures are being combined into a single integrated RF architecture. The result is not only reduced weight, but improved coordination of countermeasures.
The F-22 and Comanche are implementing integrated RF designs in their EW suites. The Army is also developing an integrated RF suite initially targeted for upgrades to existing platforms. The Advanced Tactical Radar Jammer (ATRJ), currently in the ADM test phase, requires significant RF integration to provide robust countermeasures and precision DF capabilities in a modular design and within the limited weight budget of helicopter ASE. An EMD go-ahead for ATRJ is anticipated next year.
Less all-encompassing is the use of a towed decoy to enhance countermeasure effectiveness against the monopulse threat. Through integration with the on-board ECM assets, the decoy payload is reduced to a transceiver, TWT and power supply. This combination provides the robustness of all available on-board techniques transmitted from a physically separated source.
The boldest step in RF integration is the development of the architecture and technologies for integration of all RF avionics functions into an integrated sensor system. Given the challenges to provide greater RF capability and reduced radar cross section within cost limitations, integration must begin with the aperture. The Navy is currently leading Phase 3 of the Airborne Shared Aperture Program to develop a wideband active aperture capable of supporting radar, ESM, ECM and datalink functions. Westinghouse and Texas Instruments each developed proof-of-concept modules and arrays in Phase 2 of the program and are currently defining requirements for array fabrication and integrated system testing during the Phase 3 dem/val program. An operational array will be developed and integrated with available avionics subsystems to perform ground and flight-test demonstrations of the multifunction wideband array. Prototype modules are currently in development in anticipation of a down-select for array development and testing in the dem/val program.
With shared-aperture and common-processor developments underway, the challenge of integrating the RF sensor/transmission hardware in between is being undertaken on the Pave Pace program under the leadership of the USAF Wright Laboratories. The objective of this effort is to meet the requirements of current and emerging systems with reduced weight, volume and cost. The current program will design and simulate an optimized open architecture for the Integrated Sensor Suite of radar, EW and CNI prior to detailed design. Key challenges include IF bandpass diversity, detection and sampling diversity, opposing low-observable requirements, signal distribution, EMC and sensor management.
Completed trades have shown that while RF integration frequently reduces weight, volume and cost and enables enhanced capabilities (e.g., extended RF coverage, additional receiver channels, etc.), some challenges dictate that hardware elements be function-specific. In every case, the benefits of integration must be weighed against the difficulty, and subsequently the cost, of the effort. The follow-on to the current Pave Pace program is planned to design and develop the ISS architecture and modules and demonstrate end-to-end multisensor system functionality.
The final class of integrated avionics is weapon system integration. This approach incorporates any or all of the previously identified integration approaches. The key to weapon system integration is that the development of the avionics functions must be concurrent with that of the platform itself. Only then can the requirements and design of the avionics functions and the platform itself be balanced to provide a truly optimized weapon system design. The F-22 and Comanche programs are already following this course. The Advanced Integrated Electronic Warfare Suite (AIEWS) for the next-generation surface combatant will also have this opportunity.
STEPPING STONES TO THE
NEXT GENERATION AND
The numerous ongoing and upcoming integrated avionics programs will undoubtedly shed considerably more light on issues that need to be resolved. Several issues are already apparent at this early stage.
One of the most significant is resource management, from the highest level of mode management to the lowest level of timing and control. An architecture must be developed which allows evaluation of inputs from all sources, but at the same time can shortcut the process for decisions requiring immediate action. The hardware architecture for integrated control has the similar problem of providing control signals to a larger set of hardware in the integrated system, yet still providing for rapid, synchronized control with low overhead.
Response-management alternatives must be carefully assessed prior to relying on a largely intuitive rule base. It is far easier to identify the benefits of integrated decision-making (cuing a response based on a lethality assessment, for example) than to identify all the potential flaws or drawbacks of such an action. The initial design evaluations and subsequent testing must be sufficiently robust to evaluate the trade-offs.
The addition of an integrated capability may also throw into doubt the existing performance evaluations of avionics systems. Unlike an independent, autonomous addition, incorporation of an integrated capability may affect the performance of seemingly unrelated systems. The capability to test integrated systems must keep pace with the system development. We are just beginning to see die emergence of laboratory simulators which provide a coordinated, multispectral stimulus to an integrated system. Operational testing facilities are also currently lacking in providing the density and spectral diversity against which the integrated system has been designed.
New technology developments will also be required to support advanced hardware integration concepts. As the bandwidth requirements for integrated avionics increase, for example, it is desirable to provide that coverage with wider-bandwidth antennas. For low-observable platforms, wideband low-observable radomes and radiating elements will be required. Continued expansion of the bandwidth and functionality of active apertures requires miniature, wideband, low-loss circulators, higher-efficiency wideband power amplifiers and miniature, very low-loss filter banks (or programmable filters). The cost of wideband active apertures must continue to be reduced.
The receiver/detector technologies required include high dynamic range, wideband components and wideband A/D converters. Multifunction signal and waveform generators will benefit from low spurious and phase noise direct digital synthesizers. Critical technology developments for extending EO avionics integration include multiband, high-efficiency windows and low-cost multiband focal plane arrays.
The one technology which could revolutionize RF integrated systems is A/D (and D/A) converter technology. When the A/D gets to the point of unambiguously capturing die total bandwidth of die integrated system, all die RF hardware is replaced with very high-speed computers. Beamforming, filtering and detection can be performed simultaneously and independently by as many functions as there are computer resources to support them. Although this development is still a long way off for the total bandwidth of today's integrated systems, A/D efforts are progressing into the gigahertz range. Digital IF assets for integrated avionics are not far off.
In addition to the technical challenges, EW (and radar, EO, CNI, etc.) engineers face a cultural adjustment. Optimizing integrated avionics designs will require ingenuity and trade-offs between avionics disciplines - but there are no resident experts. EW designers need to develop an understanding of the needs and operation of the non-EW functions to identify and defend the optimal weapon system trade-offs which require something other than business as usual in the non-EW designs. Because of the inherent diversity of electronic warfare, EW designers are well suited to emerge in the lead roles in this new field. We must grow to meet the challenge.
The goal of integrated avionics is to maximize capability within a constrained volume/weight/cost envelope, where capability is measured in terms of functionality, performance, reliability, availability and supportability. A wide variety of integrated avionics solutions are being developed, based on the variety of constraining envelopes governing each activity. Many solutions are targeting cost-effective upgrades to existing systems. More advanced concepts are targeting a balanced avionics design for new platforms.
Although federated system upgrades will dominate for the near future, the EW community must begin to develop the multi-avionics expertise required for integrated weapon system initiatives.
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|Author:||Watts, T.; Milton, Curtis|
|Publication:||Journal of Electronic Defense|
|Article Type:||Cover Story|
|Date:||Sep 1, 1993|
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