The next generation of Electronic Warfare (EW) systems requires significant enhancements in a wide range of technologies, synergistically integrated, to remain relevant against evolving future threats. Threat systems are becoming more adaptable, networked, agile in time, and have capabilities across the spectrum.
EW systems must evolve with these threats to maintain effectiveness in all the warfighting domains: land, air, sea, space and cyberspace. The electromagnetic spectrum (EMS), an emerging sixth domain, is a battle space that offers opportunities for high tech dominance. It also presents an opportunity for low budget bad actors to operate effectively. We must be able to counter any adverse use of the spectrum.
Therefore our ability to maneuver in the EMS with systems that have an extremely wide operating frequency range, adjustable high efficient power, and fully arbitrary waveforms for radar, communications or EW is a must.
Enabling EW technologies for current and future threats must provide the ability to be RF-agile, adaptable, and for many missions high power. The system must have the ability to maneuver within the spectrum, monitor it and deliver a precise waveform where and when it is needed.
Key attributes include wide operating bandwidths, rapid switching, directive electronically scanned beams, full polarization diversity, and adaptive waveforms for superior spectrum maneuverability and manipulation. Raytheon has developed many unique Active Electronically Scanned Arrays (AESAs).
The AESA presented here is unique in that it is designed for EW application. The MFIRES software defined receiver/exciter also described here has the capability to deliver any EW technique within the EW mission space. Core technological advances are not limited to the RF sub-systems but are also needed for power generation and thermal management. Advances in efficient prime power generation and power handling are needed to deliver sufficient power for future secure standoff ranges.ADVANCED TECH NOLOGY EW SYSTEMS REQUIRED
There are many applications of EW. One motivating mission is shown in Figure 1. An initial phase of an air battle is the ability to achieve air superiority by degrading an enemy's Integrated Air Defense System (IADS). This is accomplished by breaking the kill chain of the enemy's IADS. An IADS system is composed of many radar systems each designed for a specific function and related communication systems for command and control. Each type of radar, (early warning, target acquisition, ground control intercept, or fire control), operates at a different frequency band with unique waveforms.
The total frequency band can range from UHF to X Band. Therefore, an effective EW system must have a significantly wider operating frequency bandwidth than any one radar requires. The RF communications networks need to be addressed in addition to the radars. This adds a significant waveform flexibility requirement to the EW system.
The US military has suggested that the EMS is a critical warfighting domain . The US Navy has initiated the Electromagnetic Maneuver Warfare (EMW) concept . EMW must be enabled by Advanced Technologies that are capable of RF-agility over a very wide bandwidth, adaptable waveforms, and for many missions high power. Technologies are under development that will provide all the key elements
required to enable EMW. The most important technology development is the AESA. An EW AESA is very different from any existing radar or communication AESA. Radar arrays have much lower frequency bandwidth requirements.
They usually only need to be single polarization: vertical or horizontal. And do not require 100% transmit duty cycle. The duty cycle reduces the average power output and therefore reduces the prime power and thermal management requirement. Communication systems do require dual polarization; however, the array usually requires less power output. The transmit and receive functions can also be separated into two antennas; one for transmit and one for receive. The wide bandwith and dual polarization requirement of an EW system stresses aperture design as well as the mechanical and thermal density of the T/R module elements.One of the key enabling technologies is the development of the GaN power amplifier for it's high power and efficiency. The dual polarization is essential because the EW system must match the polarization of whatever system it is encountering. Having dual orthogonal radiating elements enables a system to become polarization selectable.
The other key technology is the receiver/exciter. This is the heart and brains of the system. With the tremendous flexibility and adaptability required, the receiver/exciter must be programmable and have enormous throughput. The function of the receiver/exciter is to complement the RF front end with the ability to receive, to process and to transmit any signal of interest (SOI). The receiver/exciter must be capable of processing waveforms for Electronic Support (ES), Electronic Protection (EP), Electronic Attack (EA), & Communications Waveforms. Frequency selection, bandwidth adaptation, detection and demodulation are required. In addition to all the processing capabilities customers usually require that the processor be a Modular Open Scalable Architecture (MOSA). The IADS mission is just one of many EW missions, but it adequately depicts the rationale for the enhanced technology requirements of EW over traditional radar and communications systems. “FIRST FLIGHT” SYSTEM DESCRIPTION
A photograph of the "First Flight" Pod is shown in Figure 2 being mounted on a Gulfstream-III aircraft, under contract with Calspan Aerospace. The pod is securely seated on a low profile carrier that is wheeled in place under the MAU-40 mounting pylon under the G-III. The interface cables are connected; then the pod is raised in place and securely mounted to the pylon. The installation is quick and uncomplicated. There are four electrical cables that provide the electrical interface: the signals contain RF, digital control, data, and voltages. "First Flight" Pod being loaded onto the Gulfstream-III test bed.The pod is an aluminum structure with a wideband radome in the front and rear of the pod. Both radomes are identical. The equipment internal to the pod includes the AESA (located in the forward radome), the array power supply (APS, located just behind the AESA), a submerged Ram Air Turban- Generator (RAT-G), a liquid cooling system (LCS), and an instrumentation system.
The AESA meets all of the requirements mentioned above for EW missions. This array is uniquely capable of operating full power continuous wave (CW) (100% duty cycle) for transmit. It is also capable of pulsed operation, switching very rapidly between transmit and receive at any duty cycle. The AESA is very wide band with active transmit-receive (T/R) modules in tile configuration that contain efficient highpower GaN amplifiers in the transmit path, and low-noise amplifiers in the receive path.
Both paths contain phase shifters and gain control elements. The wideband array enables the spectrum agility and access needed for Spectrum Maneuver Warfare. The array is mounted on the front of the pod. The dual-polarized aperture elements enable the system polarization to be selectable. The array contains a digital controller that communicates with the MFIRES software defined receiver/exciter unit (SDREU) and sends digital signals to each module setting up the parameters that control the AESA beam (beam pointing angle, polarization, frequency, etc.)
The MFIRES SDREU, shown in Figure 3, is located in the cabin. This configuration was most convenient for the First Flight system. However, future demonstrations would likely locate the MFIRES SDREU in the pod. Both the timing and control and the RF signal are generated in the MFIRES SDREU and sent to the array. The RF system is under the control of the System Director operating one of the system workstations.
The System Director workstation receives the navigation (NAV) data; computes the desired beam pointing angle; and sends it to the AESA digital controller directly. The beam steering information is applied to all the AESA modules when the MFIRES SDREU triggers a beam change. The timing and synchronization between the AESA and MFIRES SDREU is very critical; and is a key requirement for the successful operation of the EW RF system - they must operate as one.
Figure 4 shows the First Flight operations center in the GIII cabin; where there are 4 operator seats. The functions of the 4 seats are System Operator, Pod Operator, Test Director, and RF signal monitor. The pod operator is responsible for bringing up the power generation system after the G-III enters the test range. The pod operator also has control of the liquid cooling system and the instrumentation system. Fig. 4. View of G-III Cabin showing the 4 seats with computer monitors.
The instrumentation system provides feedback status of all the pod systems. The feedback provided for the servo operation of the doors and the conditions of the power generation system is critical for assurance that the system is working correctly and all is safe. When the pod operator is satisfied the system is ready for RF radiation, the System Operator brings up the RF system. The system operator controls the RF system which includes the AESA, the APS, and the MFIRES SDREU. It is the system operator that selects the EW techniques to be generated. The test director is responsible for conducting the test and has a display of the target and aircraft location overlaying the test range and the location of the emitters. He is responsible for monitoring the flight path and communicating with the aircraft operators and ground systems to determine when radiation begins and the different techniques are to be generated. The engineer in the RF signal monitor seat is responsible for making sure the RF wave forms intended are being generated and sent to the AESA in the pod.
Figure 5 shows the system Functional Block Diagram describing the connectivity between all of the subsystems discussed above. The Pod Operator work station connects to the Speed Control Servo system via the Ethernet which controls the door actuators and the power generation system. The door control system adjusts the flow of the airstream to maintain proper RAT-G speed and power generator output to the Generator Control Unit (GCU). The GCU controls and limits the DC voltage to the APS. The APS converts the input power to all the different voltages and currents required by the AESA. The Speed Control System also responds to the instantaneous power input required by the APS/AESA. The System Operator work station communicates and controls the MFIRES unit and the AESA via Ethernet connections; the MFIRES in turn controls the AESA beam state triggering through the cabin to pod interface. relationship between the subsystems. Pod hardware is located above the “Pod to Cabin Cabling.” Cabin hardiware is located below.
The MFIRES SDREU operates over the full AESA operating bandwidth. It contains multi-channel up and down converter cards, a general purpose computer, and signal processing (SP) cards. The ADCs and DACs in the SPs are high dynamic range and sample rate. Therefore the SP cards operate via Direct Digital Synthesis (DDS). The SP cards derive their signal processing power form the programmable FPGAs and DSPs. The architecture of the MFIRES SDREU is modular so that the number of receiver/exciter processing channels is configurable for the application. This multichannel processor enables passive detection and tracking of signals of interest (SOIs). It processes the data, selects the frequencies, and provides the match filtering. The system then generates the desired wave form that is sent to the AESA and is radiated to the target. Since the AESA is electronically steerable, the transmit energy is focused on target with maximum Effective Isotropic Radiated Power (EIRP).
The Instrumentation unit collects the data from each subsystem in the pod and sends it back to the pod operator work station via the Ethernet. The instrumentation unit is shown in Figure 6; it provides a wealth of data. Status of the power generation, door control system, APS, and LCS are displayed and monitored by the Pod Operator. Figure 6 also shows one of the instrumentation displays. Vendor supplied software collects and logs instrumentation data for post flight analysis. FLIGHT TEST
The "First Flight" advanced jammer pod design and development was intense, rapid and involved many different Raytheon organizations. The completion of the integration and test commenced on October 7, 2014 with the successful Airworthiness flight that included mechanical checks, aircraft handling and vibration monitoring (see Figure 6). With a completely successful Airworthiness test, the final pod, cabin equipment, and aircraft integration testing was completed. On October 9, 2014 the ground based Electromagnetic Interference/Electromagnetic Compatibility (EMI/EMI) and Environmental Health and Safety (EHS) system checks were successfully completed at the edge of a remote runway at our operational airport.
Then on October 16, 2014, the Gulfstream III test bed roared to life as it sped down the runway on its way to the test range. The mission was to demonstrate successful system integration, array transmit power, jamming techniques and jammer management. This "First Flight," as it is now so named, was 100% successful. High-G Productions was contracted to photograph the "First Flight" mission. Figure 7 is one of the photographs taken of the First Flight mission. Power Measurements.
The first test was to measure the system EIRP. The flight path is shown in Figure 8. Raytheon's Mobile Range (RMR), an RF power measurement system, was located at the edge of a remote runway at our operational airport (approximately point B on Figure
. The system radiated RF power as the G-III flew from point A to point B. With the range from G-III to RMR taken into account, the pointing angle, beamshape loss, and the RMR dB budget, it was determined that the expected EIRP was being generated. Electronic Attack (EA) Demonstration and Flight Test
against the first emitter
The G-III then proceeded to the flight path shown in Figure 9. The view shed area that an aircraft flying at 20 Kft can be seen by this emitter is somewhat limited because the surrounding terrain. The G-III therefore needed to fly within a tighter region. When other restrictions to the allowed flight path are taken into account the flight pattern shown in Figure 9 is the result. The emitter is located just below the center of the flight path. The system was in CW transmit mode only for this test. More than a half dozen techniques were transmitted. The best techniques, created completely white PPI displays. EA Demonstration and Flight Test against the second
The second emitter was better located and provides a much larger view shed area. The flight path for this test is shown in Figure 10. Both transmit and receive modes were utilized for this test. The system was transmitting most of the time and proved to be very effective. The second emitter can perform with the operator choosing any one of a number of selectable frequency pairs. The initial flight test operated in receive only mode to verify that the First Flight system was acquiring and tracking the emitter waveform.
The next test was the desired EA technique during which the test director selected (via radio to the control center) the frequency pair. The emitter operator would announce the effect then the next frequency pair was requested until all frequency pairs were completed. Every frequency pair resulted in the announcement that the PPI displays were completely "white." A white display means that the screen is full of targets and the operator cannot find the real target (i.e., the GIII).
The final test instructed the emitter operator to manually change frequency pairs at will as fast or slow as desired. Again the PPI displays were called out to be white. The system was rapidly detecting the emitter pulses at the new frequency and tracking them. This test was repeated by adding noise to the transmitted waveform. There was no change in the outcome; the display was white in every case…. SUMMARY
First Flight was enormously successful. All of the planned EW missions were completed. Effective jamming of two different emitter systems from the G-III shows the maturity of the system in a relevant airborne environment. The pod generated and controlled its own prime power from the air stream under varying electrical loads. The test demonstrated performance from an end-to-end integrated system.
The AESA utilized Raytheon’s Gallium Nitride (GaN) technology in a high power, high gain, agile beam antenna. Both Transmit/Receive jamming and transmit only jamming was demonstrated through a single aperture. And most importantly, synchronized timing and rapid switching between the MFIRES SDREU and the AESA was demonstrated. The AESA beam was dynamically steered and controlled in-flight. The First Flight pod successfully demonstrated the submerged RAT-G that exclusively provides the prime power to the complete RF jamming system within the pod. And rapid reprogramability was demonstrated with the Polarization Diversity flight test.Future testing is anticipated to demonstrate the ability to conduct both EA and Communications EA since the RF system is designed to meet EW requirements for both radar and communication systems. The First Flight system is capable of Comm, and radar EW, enabling EA/Multifunction convergence.