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"Inventing For Tomorrow"
INTERFERENCE MITIGATION
identify, suppress, & protect
ABOUT
Interference Mitigation refers to the methods and techniques used to reduce or prevent interference caused by unwanted radio frequency (RF) or electromagnetic (EM) signals.
The interactive "Receiver (RX) Chain" block diagram below illustrates a simple, front-end, single-channel Interference Mitigation system, also known as an RF Signal Conditioner (Fully Integrated System), which highlights how our products work in tandem to generate a resilient communication link that can withstand various interference situations. **
Our interactive diagram offers a great opportunity to explore the various ARS product options and related literature, making it easier to identify the best solution. Kindly note that some links will lead to different product pages.
interactive RECEIVER (RX) Chain
Fully integrated RF SIGNAL conditioning system
Depending on user needs, either Notch Filter or Canceler can be used as the primary frequency selective suppression device.
** Our individual interference mitigation solutions are also fully compatible with non-ARS systems, ensuring effective performance across different applications and contexts.
THEORETICAL FOUNDATIONS
GENERAL NOTE
At ARS products, we believe that understanding the theoretical underpinnings of our technology is not only imperative for designing robust systems that maintain functionality and performance in various electromagnetic environments, but equally valuable for our customers to understand in order to make informed decisions about their purchases, particularly regarding scope, purpose, and function. While our team of experts help guide and tailor solutions based on the varying needs of our customers throughout the product development and manufacturing process, we are passionate about highlighting both the capabilities and potential limitations of RF systems from a theoretical standpoint.
introduction
The advent of digital receivers and tuners has brought us wider bandwidths, finer resolution (paired with demodulation) and faster acquisition. Although these scientific gains are built around the ever-improving Analog to Digital Converter (ADC), the engineers and architects implementing these new system designs need to fully work within the new parameters and pitfalls of the digital receiver.
One of the challenges is mitigating receiver overload conditions. Typically this occurs when trying receive a low level signal (Signal of Interest, SOI) in the presence of a high level signal (often referred to as the Interferer). Because the receivers' front end band width has widened, the high level signal may be spectrally distant from the SOI. The consequence of this high level signal is that the ADC digitally over-ranges and the receiver becomes "deaf".
EVOLUTION OF SOLUTIONS
Traditionally the solution was to increase (add) front end attenuation. This approach degrades receiver sensitivity, 1dB for each dB of attenuation. Since front end attenuation is undesirable, other techniques are warranted. Front end attenuation is usually reserved as a last resort.
The most desirable technique is to selectively reduce the high level signal while leaving the balance of the spectrum unaffected. This can be visualized as a notch filter being applied at the frequency of the Interferer.
The result will be only reducing the high level signals (interferers) while retaining the required sensitivity. This keeps the receiver in its desired "sweet" spot of operation. This selective spectrum management is referred to as "Signal Conditioning".
APPLICATION
With the basic premise of frequency selective signal reduction as the main goal for receiver system design, let's discuss the avenues available to us.
The techniques are centered around the ability to selectively attenuate high level signals, while leaving the Signals of Interest (SOI) unaffected. There are two classes of equipment for this application, the Frequency Programmable Notch Filters (FPNF) and Signal Cancelers. The Cancelers are further divided into Coherent and Reference-Less types.
A quick summary of primary parameters differentiating several ARS hardware types are listed in Table 1 (below).
The above numbers are typical for most applications in the 1 to 1200 MHz frequency range. Band widths are expressed as a percentage of the center frequency.
It is quickly recognized that each type caters to a unique environment and no one type fits all applications.
The amount of selective signal attenuation is referred to the notch depth for FPNF and canceling depth for the cancelers. The entry level is 20 dB minimum for all types and 40+ dB is available for all types. ARS has manufactured dual loop coherent cancelers that deliver 90+ dB of canceling.
ADDITIONAL CONSIDERATIONS
Before going into the classes of frequency selective reduction, let us discuss another condition. That is the transient condition, the event that occurs when the Interferer becomes present (active).
During this transition the receiver may become deaf while the mitigation equipment deals with applying a selective reduction device. This will take some time. This is particularly painful if the mitigation system uses the main receiver.
A device to deal with the transient case is the Non-Reflective Limiter (NRL). During the transient, the NRL proportionately attenuates the spectrum to keep the receiver out the over-range condition. Meanwhile the system is still receiving and deploying the appropriate selective reduction device. Once the selective reduction is in place, the NRL releases (no attenuation) and returns to high sensitivity reception.
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