Comprehensive Electronic-Warfare System Testing on Military Airframes

What you'll learn:

Issues with EW systems on modern military airframes.
The importance of RF cable feeds.
The importance of fast, accurate testing.

The proliferation of sophisticated sensors and electronic weaponry on today’s battlefield has created numerous entry points for adversaries. From jamming communications and spoofing signals to launching cyberattacks, electronic warfare (EW) has become increasingly critical in modern defense strategies. Enemies continuously attempt to inject interference in EW systems to disrupt missions, making signal integrity a key element of 21st century warfare.

Weak signals from amplifiers and signal generators may prevent an EW system from operating effectively. Furthermore, kinks in the cable or damaged connectors will cause signal degradation, as can the environmental conditions in which EW operates. All this can lead to system—and potentially mission—failure.

Therefore, measuring these elements' performance is essential to the efficient performance of an EW system. Selecting the proper test solutions is necessary to ensure those measurements are accurate and reliable.

Electronic-Warfare Systems on Military Aircraft

An EW system on modern military airframes is configured with antennas around the extremities connected to the signal-processing systems at the aircraft core. RF cable feeds from antennas to core processing units require regular testing. Other RF elements of an EW system, such as amplifier transmission systems and signal generators, are essential as well.

EW amplifier transmission systems are crucial because they boost the signal strength to enhance communication or disrupt enemy communications. Signal strength is important, so that the systems transmit the jamming signals, deceptive signals, or other signals at the necessary frequency and bandwidth.

Consequently, EW amplifier transmission systems must be robust, reliable, and capable of operating in harsh and dynamic environments typically encountered in warfare, from saltwater exposure and vibrations to electromagnetic interference (EMI).

Effective EW amplifier transmission systems have the ability to operate across different frequencies to adapt to changing battlefield conditions and quickly conduct signal processing to achieve the desired jamming effects. They also optimize power usage to extend operational duration in the field and seamlessly integrate with different aircraft systems and configurations, depending on the mission.

Signal generators help EW systems operate effectively in complex EMI environments. Testing EW signal generators is necessary to ensure they generate the proper signals to jam enemy communications and radar systems, effectively neutralizing threats or creating tactical advantages. EW signal generators also aid in signal intelligence (SIGINT).

Amplifiers and signal generators are susceptible to the same environmental challenges as all EW system components. Their performance can be adversely affected by EMI, shock, vibration, and extreme temperatures.

For amplifiers, technicians need to use spectrum-analysis tools to conduct measurements, including output power, gain, signal quality, and impedance. To monitor signal generator performance, test solutions must accurately measure frequency range, signal amplitude, modulation types, and signal accuracy.

Proper integration of the amplifiers and signal generators within the entire EW system is also necessary to achieve specified performance. Their maintenance is part of a complete system approach that should include testing cable and antenna systems.

How RF Cable Feeds Impact EW System Effectiveness and Reliability

RF cable feeds in military airframes are critical components, too. They enable the effective operation of RF-based systems essential for mission success and aircraft survivability in combat and other operations.

Military aircraft use specialized RF cables that are designed to handle high-frequency signals efficiently while minimizing signal loss and interference. These cables are often shielded to protect against EMI and maintain signal integrity.

RF cables in military airframes use specific connectors and interfaces that are ruggedized, reliable, and suitable for use in high-vibration and harsh environmental conditions encountered during flight. Such connectors ensure secure connections and maintain signal integrity under operational stresses.

RF cables are routed strategically throughout the airframe to connect to EW systems, antennas, and other RF equipment, including amplifiers and signal generators. Routing must account for signal attenuation, impedance matching, and minimizing interference from other electronic systems within the aircraft, as well as natural conditions and nefarious acts. Regular testing must be done to maintain compatibility and interference-free operation.

Comprehensive Testing for Electronic-Warfare Systems: Ensuring Signal Integrity

Military technicians must verify insertion loss and return loss in an EW system. They do this using a cable and antenna analyzer that can conduct return loss and voltage standing wave ratio (VSWR).

Newer instruments (see figure) integrate advanced real-time spectrum analysis (RTSA) to quickly identify and address EMI and signal-integrity issues to maintain the security of EW systems, along with the cable and antenna analysis. These advanced solutions also have IQ capture and streaming to gather intricate signal data in real-time, allowing for exhaustive analysis and troubleshooting.

1. Cable and antenna analysis are integrated with spectrum analysis for comprehensive testing of EW systems.

While return loss can verify the health of an EW system, distance-to-fault (DTF) is the best technique to troubleshoot systems and locate problems. The most effective DTF measurement uses a fast Fourier transform (FFT) to convert frequency data to the time domain and display signal reflections with respect to distance. A standard trace math feature found in some analyzers can monitor small relative frequency changes over time.

To expedite analysis and locate issues in the EW system, some analyzers have a split screen display (see Fig. 2). It allows return loss and DTF to be on the same screen, so the position along the RF cable where the highest reflections are taking place can be pinpointed while also showing overall return loss. Identifying the issue through this feature speeds up the resolution of the fault.

2. A split screen shows DTF and TDR measurements simultaneously to better pinpoint causes of signal degradation.

The Importance of Fast, Accurate Tests

Given the mission-critical nature of EW systems, locating and rectifying an issue as fast as possible is paramount. When a return loss measurement identifies a cable and antenna path that does not meet specification, it is necessary to locate the cause of the reflection and repair it. A basic DTF measurement quickly locates the distance of the individual reflections from the input test port. For long cable runs, the more information known about the reflection cause, the quicker and easier the repair becomes.

That is why TDR measurements are important, as well. They show impedance against distance, with a normal 50-ohm line running across the center of the display. Different causes of reflections, such as open circuits, short circuits, kinks to the outer cable conductor and water ingress, will cause characteristic changes to the transmission line impedance. This aids in identifying the cause of the fault and accelerates the repair process.

A transmission measurement needs to be made on fixed transmission lines, including coaxial cables within aircraft wings and fuselage. A USB sensor can be integrated into an analyzer to conduct transmission measurements. Such a configuration allows technicians to make those measurements quickly and efficiently. Some instruments allow the measurement to be made simultaneously with reflection (Return Loss or VSWR) or DTF to facilitate system verification.

Compact Design, Comprehensive Testing

Much like the EW systems that they test, the instruments must be durable to produce the required consistently accurate results. Analyzers should be designed and tested to meet the MIL-PRF-28800F Section 4.5.6.3 Explosive Atmosphere requirements for safe usage on flight decks and in areas where high volatility may exist. Additionally, the solutions must be compact so they can be carried and used in the tight confines of the aircraft.

Conclusion

Testing aircraft EW systems and their components is a proactive approach to maintaining operational readiness. It involves comprehensive testing, dedicated solutions, and stringent maintenance schedules to mitigate risks and maximize mission success. Measuring signal performance of EW systems involves testing individual components, such as amplifier systems, signal generators, RF cables, and antennas, using solutions that integrate multiple instrument capability and can produce accurate and reliable results in harsh environments.