The Increased Need for Receiver Protection and the Importance of Auto-Tune Filters™
Electronic warfare is the invisible battle of detecting and disrupting radar and radio transmissions on which the modern military depends. There is an increased need for receiver protection as Global Positioning System (GPS) units, radar systems, and communications networks are targeted with high-powered signals that overwhelm the receivers, ultimately decapitating their key functions.
As we create more and more networks, we must also ensure interference protection for each individual network. Metamagnetics’ Auto-Tune Filter™ provides a broadband, fast-response, simple solution that protects receivers from electromagnetic interference (EMI) and ensures that signals-of-interest are detected. EMI could be intentional as well as unintentional in some cases.
How Does Radio Frequency (RF) Interference Occur?
RF receivers detect signals that are beamed through the air at various frequencies and power levels. The receiver collects signals over a desired frequency range and passes it into electronics that process the signals. RF interference occurs when a high-powered signal hits a receiver—these signals can either hinder the signal processing function of the receiver or physically destroy the components in that receiver by burning them out. The act of sending out a high-powered signal could be intentional, such as an electronic attack or unintentional, such as a being close to a transmitter.
GPS units can also be affected by RF interference. Today, GPS receivers can be found in most cell phones, cars, and aboard every Army, Navy, and Air Force platform for navigation purposes. These receivers compute the location by detecting timing signals that are beamed down by a constellation of satellites located in the medium Earth orbit. Due to the great distance between the satellites and the surface of Earth, GPS signals are very weak by the time they reach ground-based GPS receivers and are highly susceptible to being undetectable, jammed, and/or interfered with. Furthermore, these signals can scatter in urban areas by bouncing off buildings and other structures, which causes a staggered arrival time at a receiver and inaccurate position data.
The Problems with Existing RF Filter Technology
Time Lag
The problem with employing traditional tunable RF filters is that they have a search-and-respond approach, making the process time consuming. Sophisticated software is required to reduce the power of the detected offending signal. This causes a lag from when the signal hits to when the system reacts, and in that window the system can be compromised.
Catch-All Protection Method
Many countermeasures to RF interference are able to prevent harmful signals from damaging your system at the cost of hindering desired signals necessary to communication efforts. These catch-all protection measures basically turn off the input to the receiver until the threat is gone.
Limited to One Tone per Device
Typical RF filters are only able to mitigate one tone per device, thereby limiting the user to determine how many, which frequency, and what direction the interference is coming from. This rigidity leaves systems designers to attempt to predict the number of signals their devices will encounter in the field.
Auto-Tune Filters™: The Next-Generation RF Filter to Mitigate RF Interference
Auto-Tune Filters™ are completely passive devices, requiring no electricity to perform their function. Composed of inert materials, this device can survive the toughest environmental conditions in land, sea, air, and space applications. Here are some of the features that make Auto-Tune Filters™ a more viable solution than pin-diode limiters and tunable filters:
- Automatically adapt to filter interference above a preset power level without attenuating desired below threshold signals
- Fast response time and excellent selectivity
- Multi-octave bandwidths with high linearity
- Completely passive and suitable for phased array applications
- Less than 50 nanoseconds to attenuate a high-power signal to half its original power level
- Adaptable across multiple platforms for land, sea, or air solutions
- No limitation on number of signals that can be attenuated in band, including intermods
Metamagnetics currently offers fully packaged devices for S-, C- and X-band, with each device covering its entire band respectively. Threshold levels of limiting can be tailored to your application.
Read more about our Auto-Tune Filters™ for adaptive mitigation of GPS jamming threats in our white paper.
