Military wireless systems require sturdier defenses.

• Author: Ilsemann, Fred
• Position: Industry Viewpoint - Minimizing radio frequency interference

Radio frequency interference is pervasive in the wireless age. Cell phone customers undoubtedly have encountered some level of RH at one time or another.

For military users of wireless systems, failure to safeguard against unwanted RFI-particularly when it comes to sensitive defense systems-can have serious consequences.

While some RFI is innocuous, it can become a real threat when it interferes with systems used by military forces, such as remotely controlled weapons.

Because virtually every wireless device is subject to RFI, it is important that the source and strength of this interference be determined before it affects a component or system. The goal is to prevent RFI signals (both continuous emissions as well as short duration transient events) from interfering with any component or system that depends on radio frequency signals for operation or is susceptible to damage when exposed to high RF power levels.

Consider, for example, a communications satellite during assembly, testing or preparations for launch. Prior to launch, the satellite is subjected to a variety of quality-control tests and procedures. If unwanted RFI signals are allowed to interfere with any of the processes, they could contribute to ultimate failure of the satellite.

Electronic warfare systems or components undergoing tests at a range also could be affected by unwanted RH. If this interference doesn't cause direct harm (sometimes rendering a component or entire system useless), it could prevent accurate validation and calibration during the testing and evaluation phases. When RFI incidents such as these occur, it can be difficult or impossible to determine the cause of the failure or the reason for otherwise substandard performance.

It should be noted that RFI is not a new phenomenon. There are established technologies that are employed to deal with its detection. Among them are spectrum-analysis instruments that typically analyze a discrete, narrow band of frequencies that are usually present concurrently with other frequencies. Tuning to a discrete frequency implies prior knowledge of the RFI. Therefore, the spectrum analyzer is usually programmed to cover a range of frequencies by design, the spectrum analyzer scans (using a fixed RF bandwidth) over the frequency range of interest. The scanning reduces the probability of intercept. As the frequency range increases, the degradation can be significant, resulting in unreliable RFI detection.

To circumvent this...