Analysis of Radio Frequency Interference Cancellation Technology

Introduction: Powerful electronic jamming can be used to suppress enemy radar, thus protecting allied aircraft from entering enemy territory. But high-power interference will also interfere with our own airborne communication.

Burying Cow's Nose: Radio Frequency Electronic Jamming Suppresses Jamming Communication

What is radio frequency interference cancellation technology and how to eliminate interference?

When it comes to radio frequency interference cancellation, everyone will definitely think of EA- 18G radio frequency interference cancellation system (Incans) module. EA- 18G Growler uses powerful electronic jamming to suppress enemy radar, thus protecting allied aircraft from entering enemy territory. But high-power interference will also interfere with our own airborne communication. INCANS receives a sample of the interference signal, which forms a cancellation signal, and then combines it with the received signal of the receiving branch, thus canceling the interference signal of the receiving branch, leaving only the required received signal. The module circled in red in the figure below.

In 2004, the INCANS module was developed by Edo Company, and the first set was completed in 2005. The key technology of INCANS module is CIMS of EDO. CIMS is an active canceller, which can carry out long-distance voice communication while airborne jamming equipment radiates interference. In this module, ALQ-99 implements full-band interference suppression and adopts active interference cancellation technology to ensure its own VHF communication is smooth. This technology is also the first application.

In 2007, EDO Company was acquired by ITT Company and Exelis Company was established. The use of this module is shown in the following figure. Exelis claims that in the laboratory environment, the cancellation ratio of INCANS module can reach more than 60dB. Although the cancellation ratio is reduced in real environment, it can still reach the cancellation ratio of 40-50dB. For the system with instantaneous bandwidth of 2GHz, the cancellation ratio of 60dB at the center and 10dB at the edge can be obtained.

You can see the relevant parameters of this module in the product manual of Exelis Company as follows:

Size: 330.2mm long? Wide? 157.48mm？ Height 193.04 mm

Weight:11.577kg.

Modular design: 10 SRAS (workshop replaceable parts)

20 15 Harris buys Exelis company. Harris Company claims that its latest interference cancellation scheme can provide 100db or even higher real interference cancellation, as shown in the following figure. The latest generation of Harris interference canceller adopts advanced interference cancellation system (AIMS) and a standardized, open and extensible architecture, which can be quickly deployed on fixed stations, ground vehicles, airplanes and ships. In addition, AIMS can provide electromagnetic interference protection from one to multiple interference sources for multiple interfered receivers. AIMS can be applied to broadband or broadband signals with a wide spectrum range, from high frequency to above X-band.

The origin of RF interference cancellation technology can be traced back to 20 years ago.

Silent machines appeared in the 1930s. 1934, Paul.

Leug puts forward a method of eliminating noise by using acoustic inverse interference cancellation, that is, artificially introducing noise sources, adjusting them to be equal in amplitude and opposite in phase to the original noise sources, and superimposing cancellation to reduce noise. This technology was later widely used in aircraft cockpit noise.

At the end of 1960s, interference cancellation technology was gradually applied to communication anti-jamming. Rome Aviation Development Center (Rome)

Air development

RADC (Center for Interference Cancellation) first undertook this task, and proposed to adopt "active interference cancellation technology" to develop an open-loop interference cancellation system with automatic phase fine-tuning. The system frequency is 300 MHz.

At the carrier frequency, the adjacent channel interference is suppressed. At the end of 1960s, several experimental systems were developed, which proved that this technology was feasible. Since 1970s, it has been applied to various fields of military communication, such as air command, air traffic control, shore-based communication and airborne communication.

The initial development idea of radio frequency interference cancellation technology is to construct a radio frequency signal with the same amplitude and opposite phase as the interference signal, and synthesize it with the interference signal to form the cancellation effect of the interference signal. Because of its simple principle, the cancellation technology can be easily realized in various technical forms, and the orthogonal synthesis technology of interference signals is the initial technical realization form. The figure below shows the orthogonal synthetic RF interference cancellation system based on photon technology.

In recent years, with the development of digital technology, multi-delay signal synthesis technology based on adaptive filtering has appeared, that is, the weight of each synthesized signal is controlled by adaptive filtering algorithm, and finally the original signal is filtered, so as to achieve the purpose of interference cancellation.

Although the implementation methods are different, generally speaking, both methods obtain the desired signal by constructing the cancellation signal related to the original signal.

Foreign application

1, Harris Company

As can be seen from Google patents, most of the patents for interference cancellation were applied by Nucleonics Company of the United States, which is now Harris Company.

See the previous issue for others.

2. Zege abrams Company

Zeger-Abrams was founded in 1977, and has been devoted to the research of advanced signal processing technologies such as composite interference and co-frequency interference suppression. Related products mainly include:

A. frequency hopping adaptive interference canceller (HAIC)

Frequency range: 30 to 400 MHz

Transmit power: up to +35 dBm.

Coherent interference input: up to +22 dBm

Interference cancellation output power:? & lt-40 dBm

Insertion loss (expected signal): < 4.5 dB

Output increases broadband noise:? not have

Input third-order intercept point: +62 dBm

Frequency hopping stable transient peak:

Size: 3.7 inches x2. 1 inch x6.2 inches per module.

Weight:

B, anti-multipath system

Frequency range: 0.5- 18 GHz

Adaptive elimination of multipath interference can achieve accurate direction finding with ultra-low sidelobe antenna.

3. British Times Company

ERA has developed a variety of offset products, including miniaturized offset products and multi-channel offset products.

In 2006, the company designed and manufactured an 8-channel interference canceller in 150 ~ 175 MHz band for the US Coast Guard. When 8 channels work at the same time, the canceller can achieve a cancellation ratio of 40 dB. When the interference signal is separated from the useful signal by 250 Hz, the useful signal is only attenuated by 3 dB.

4.PSI company

PSI (Photonic System Company) was established in 1999, mainly engaged in the research of microwave photonic technology. With decades of experience in integrated optoelectronics, PSI brings first-class component and link solutions to customers in defense, communications, research and government departments.

In 20 12, with the support of SBIR project, PSI company carried out the research on "high-power interference canceller with optional self-generated reference", put forward a scheme to actively suppress high-power interference, and developed a high-power interference canceller (LASCAN? )。 The following figure shows the scheme adopted by PSI:

LASCAN developed by PSI? It can significantly reduce the unnecessary radio frequency interference when the system uses the electromagnetic spectrum. Such a system usually needs to be used in the face of high-power interference, which can improve the signal-to-noise ratio by about 100dB. When connected between the antenna and the system transmit and receive paths, LASSCAN? 60-70 has been displayed.

Eliminate large interference power (dB).

So far, Lasquin? The cancellation ability from HF(3 MHz) to X-band (12 GHz) has been verified, and signal cancellation up to W-band (100 GHz) can be realized in principle. ? LASSCAN can also eliminate all forms of co-channel interference.

The RF interference canceller developed by PSI can work at 50W power, and a hybrid IC version with lower power consumption and smaller size is developed, which is called INchip? .

PSI-76 1 1-00 1G INchip？ PSI-7600 50W Interference Canceller

5.POC company

Founded in 1985, POC (Physical Optics Company) is an advanced technology system integrator serving the military, national defense, security and commercial markets.

The company has developed a high-power tunable agile RF filter for RF interference cancellation, which works in the analog domain and can provide in-band attenuation exceeding 100 dB, and the incident power (VSWR) is very small.

6. cobham Antenna System Company

Radio frequency interference cancellation is one of the integrated communication environment (ICE) technologies developed by Cobham antenna system company, which is used to optimize the performance of multiple radios (jammers and walkie-talkie systems) running simultaneously on the same platform. Cobham developed a new radio frequency interference elimination technology, which greatly improved the sensitivity of the equipment.

A. Multi-station interference cancellation system -ICE 720 1

Frequency range: 30–512 MHz

Elimination ratio: 60dB (typical)

Power:

VSWR: 1.5

B. Communication via electronic warfare system -ICE 7720 1

Frequency range: 30–512 MHz

Elimination ratio: 60dB (typical)

Power:

VSWR: 1.5

7.ADRF company

ADRF Technology (ADRF) is the largest service provider in the world. ADRF's product suite includes distributed antenna systems, repeaters, small batteries, antennas and passive components.

On October 20 14, 14 10, ADRF introduced AXM2 100-9543-ICS, which is the company's patented interference cancellation system (ICS). To overcome the interference of various outdoor environments.

Product highlights:

? Patent Interference Cancellation System (ICS)? Provide stable coverage, and obtain system isolation up to-15dB within the cancellation window of ≤6 microseconds.

? The maximum gain is 95 dB and the maximum output power is 43 dBm.

Other parameters are as follows:

Reference: Shine Wong. Development and application of interference cancellation technology in electronic information system [J]. Telecommunication Technology, 2016,56 (12):1409-1416.