3.6 RF Components

3.6.1 Warfighter Needs

The successful pursuit of national objectives requires the continued superiority of our military-essential RF electronics. The widening variety of military missions challenges these systems to be increasingly flexible, timely, and precise on their application. The RF components' sub-thrust is meeting this modernization challenge by developing affordable electronics technology for information dominance and improved dexterity in national strategy and response actions.

Radar remains DoD's primary all-weather sensor to provide capabilities such as surveillance, situation awareness, self and area defense, targeting, terminal guidance, and battle damage assessment. In addition, a major complement to the hardkill capability of weapons is the softkill afforded by EW systems that can potentially handle a much larger attack force than hardkill weapons. Finally, the glue that holds all these capabilities together to form an effective warfighting force is the communications networks. These three areas rely heavily on and are enabled by RF technology, which represents the key to force multiplication (the ability of a minimal number of U.S. platforms and personnel to defeat a much larger enemy force) and the avoidance of technological surprise on the battlefield. The following Joint Warfighting Capability Objectives are supported: Information Superiority, Precision Force, Combat Identification, Electronic Combat, Joint Theater Missile Defense, Military Operations in Urban Terrain, Joint Countermine, and Joint Readiness and Logistics.

The availability of affordable, manufacturable RF electronic components that satisfy the performance, weight, size, interoperability, cooling, and maintainability requirements of military systems is vital for sustaining the competitive edge of U.S. forces over their adversaries. These warfighting capabilities require reductions in size, weight, volume, power consumption, and costs. Advanced high-performance and affordable RF solid-state, vacuum electronic, frequency control, and antenna technologies are currently being transitioned into a broad range of military systems, including the F-15/ALQ-135, LANTIRN, AMRAAM, MILSTAR, GEN-X, GBR, GPS Longbow, Patriot, SADARM, Scamp, Staff, and F-22 radar and EW arrays.

3.6.2 Overview

3.6.2.1 Goals and Timeframes. The RF components thrust involves the technology required to generate, control, radiate, receive, and process VHF, UHF, microwave, and millimeter-wave signals. The technologies under development are applicable to solid-state and vacuum electronic devices, low-noise signal and frequency control components, microwave power modules (MPMs), monolithic microwave integrated circuits (MMICs), transmit/receive (T/R) modules, advanced packaging and interconnect technology, and antennas. The five technology thrusts that compose the RF component subarea are solid-state electronics, vacuum electronics, signal and frequency control, antenna support, and multichip assemblies. The results of these efforts enable many of the goals in radar sensors (3.1); Weapons—ordnance (Chapter X); Electronic Combat—threat warning, self-protection, and mission support (Section 4.H); Information Systems Technology—seamless communications (Chapter III); and Space Platforms—space vehicles (Chapter VIII). The timeframes of the goals of the RF components area is presented in Table VII-7.

3.6.2.2 Major Technical Challenges. A particularly challenging technical obstacle confronting military systems is in producing affordable solid-state and vacuum power amplifiers for broadband microwave and millimeter wave applications that simultaneously achieve high output power, high efficiency, small volume, and acceptable linearity. Specifically, amplifiers meeting these objectives have instantaneous bandwidths extending over frequency ranges from 1 to 18 GHz, 18 to 40 GHz, 40 to 75 GHz, 75 to 110 GHz, and 110 to 140 GHz at costs ranging from one-fifth to one-tenth that which can be achieved using present design approaches and manufacturing capabilities. Another technical challenge is the achievement of two orders of magnitude improvement in frequency clock stability where size is critical and where stress due to shock and vibration are factors. A third major technical challenge is to develop RF solid-state components that reliably operate at junction temperatures greater than 300°C. Such components are needed for compact sensors that operate in extreme military environments. Another technical challenge is to develop highly integrated, low-power consumption RF electronics for advanced RF and digital applications. This includes devices, ICs, and high-density multichip assemblies. Specific needs are for a family of miniature digital receivers for use in radar and EW sensors. A final challenge is to develop reconfigurable, adaptive beamforming for affordable compact and shallow-depth phased array antennas used in C⁴I and radar applications.

3.6.2.3 Related Federal and Private Sector Efforts. Related efforts include metrology work with DOC/NIST and joint programs with NASA in solid-state and vacuum electronics.

3.6.3 S&T Investment Strategy

Four major thrusts are being undertaken in order to address the deficiencies noted in Section 3.6.2.2.

Solid-State RF Electronics. A generic technical obstacle associated with the front end of military systems is producing affordable and compact solid-state RF electronics with adequate sensitivity, bandwidth, and dynamic range for use in the frequency range extending from 0.1 to 140 GHz. One specific challenge is achieving high output power, high efficiency, and small volume with acceptable dynamic range, linearity, and low-power consumption. Similarly, there is need for increasingly capable and affordable small signal/low-noise components and integrated circuits for amplification and signal processing at the higher frequencies and over broader bandwidths; compact multifunction downconverters and related receiver components, at costs ranging from one-fifth to one-tenth that which can be achieved using present design approaches and manufacturing capabilities; and advanced devices that operate in severe environments (e.g., high temperatures). The following projects are being undertaken in order to address these deficiencies:

• Leverage development of novel semiconductor materials, device structures, and circuit designs to realize enabling RF electronics including 10-100-watt, low-cost, solid-state RF power sources and wide bandgap devices operating at temperatures above 250°C.

• Development of advanced design tools and high dynamic range, power, and multifunction processes to realize significant across-the-board cost reductions in design, fabrication, assembly, and testing.

• Continued effort at the interchip level to develop improved, more compact packaging and interconnect technology, and at the intrachip level to increase the level of RF IC integration.

Vacuum Electronics. This thrust involves the development of vacuum electronic devices and related components and materials technologies to meet DoD system insertion needs. The impact of this thrust is new capabilities, improved performance, survivability, and greater affordability of military electronic systems. These objectives will be achieved by exploiting scientific advances and technological opportunities and by channeling industrial activities into areas of importance to the national defense. The major challenge is finding ways to achieve higher power output, efficiency, and linearity over broad bandwidths extending from 1 to 18 GHz, 18 to 40 GHz, 40 to 75 GHz, 75 to 110 GHz, and 110 to 140 GHz at a cost that is 2x to 10x lower than can be achieved using present design approaches and manufacturing capabilities. The effort includes (1) integrating a solid-state driver with a vacuum power booster to produce compact power sources, (2) computational techniques extending from electromagnetic simulations to final product design and manufacturing, (3) high-performance millimeter-wave devices exploiting fast- and slow-wave technologies, and (4) vacuum microelectronics and supporting technologies (e.g. improved magnetics, dielectrics, electron emitters, and materials technology).

Signal and Frequency Control. The objectives of this thrust are to develop ultrastable, low-noise frequency sources, digital synthesizers, and clocks for radar, communications, navigation, and IFF systems. Such development will provide higher time and frequency accuracy with lower power consumption, ultra high stability in small volume and in severe environments, and lower noise close to the carrier, especially in vibrating environments. Examples of these improvements include:

• Two orders of magnitude reduction in vibration sensitivity of oscillators, stable oscillators, and microresonator filters in a size comparable to MMIC chips.

• High-accuracy clocks that are 10x smaller and 10x lower power consumption with 10x higher accuracy.

• New piezoelectric materials. Microcomputer-compensated, low-power clocks.

• Novel miniaturized resonators for highly integrated microwave circuit applications.

• Microresonators for ultra high stability.

• Miniaturized atomic frequency standards using optical pumping techniques.

• Microresonator arrays for uncooled IR and biological and chemical sensors.

3.6.3.1 Technology Demonstrations.

None.

3.6.3.2 Technology Development.

Millimeter-Wave Power Modules (DTO SE.26.01). The primary objective is the development of 18-40-GHz power modules technology and facilitating the transition and insertion of power modules into a wide range of radar, electronic warfare, and military communications systems. This DTO supports JWSTP Information Superiority DTOs A.10, High-Altitude Endurance Unmanned Aerial Vehicle ACTD; A.13, Satellite C³I/Navigation Signals Propagation Technology; and A.02, Robust Tactical/Mobile Networking.

Microwave SiC High-Power Amplifiers (DTO SE.27.01). The primary objective is to develop compact, lightweight, highly efficient L- through X-band microwave, solid-state transmitter building blocks from wide bandgap materials (e.g., advanced SiC-based field effect transistors (FETs) and static induction transistors (SITs)) that meet output power, power density, efficiency, linearity, operating voltage, and temperature to provide size, reliability, and life-cycle cost advantages over competing Si- and GaAs-based, solid-state amplifiers and tube-based RF transmitter systems. This DTO supports JWSTP Information Superiority DTO A.02, Robust Tactical/Mobile/Networking, and Joint Theater Missile Defense DTO D.04, Advanced X-Band Radar Demonstration.

Low-Power Radio Frequency Electronics (DTO SE.28.01). Affordable, low-power consumption RF electronics are being developed for military manportable communications and for airborne/space platforms that are volume and weight starved. This effort addresses development of devices and technology for power-efficient RF electronics including high-efficiency amplifiers and sources, ultrastable frequency control oscillators and clocks, miniaturized low-loss filters and microresonators, and enhanced thermal management technologies. This DTO supports JWSTP Information Superiority DTOs A.02, Robust Tactical/Mobile Networking, and A.13, Satellite C³I/Navigation Signals Propagation Technology; Precision Force DTOs B.03, Precision Signals Intelligence Targeting Systems ACTD, and B.05, Target Acquisition ATD; Combat Identification DTO C.01, Battlefield Combat Identification ATD; Joint Theater Missile Defense DTO D.04, Advanced X-Band Radar Demonstration; and Military Operations in Urban Terrain DTO E.01, Small Unit Operations TD.

3.6.3.3 Basic Research. Basic research in the RF component technology area is directed toward the synthesis of advanced semiconductor, superconductor, ceramic, piezoelectric, ferroelectric, ferromagnetic, and ferrite materials; the development of affordable processing sequences for them; and the realization of accurate predictive modeling and simulation algorithms and techniques. The successful completion of research tasks in these areas will enable development of high-performance, reliable, low-cost structures for RF devices and components used in DoD systems. Basic research efforts provide technology options for device and component designers and fabricators that may lead to the realization of improved or entirely new classes of devices and components. Specific device/component-related goals that motivate these efforts are achievement of improved device performance (e.g., higher frequency, higher temperature operation, higher efficiency, lower noise, reduced complexity, and ability to support small feature sizes), lower cost, higher yield, improved predictability of properties, and greater reliability.