Anechoic Chambers
Electromagnetic compatibility (EMC) or anechoic chamber is highly specialized testing equipment used to test electronic devices against regulatory standards regarding radiated and directed radio frequency (RF) emissions and the immunity.
EMC or the anechoic chambers are designed to create the enclosure with an extremely high level of protection attenuation against electromagnetic interference.
The word ‘anechoic’ means ‘without an echo.’ An anechoic chamber is a box, room, or enclosure designed to absorb the reflections of sound or electromagnetic waves completely.
The main feature of an anechoic chamber is that it is designed to absorb the reflections of waves within the room rather than making them bounces off the walls, which could cause echoes. If designed and assembled correctly, these rooms also do a great job of keeping waves out of the room, especially as they protect from outside interference. This combination means that the person or detector hears exclusively direct sounds without reverberating, simulating being inside an infinitely large room.
How does it work?
RF shield technology
The room will always be a shielded room or Faraday cage, which means that it is an isolated RF environment that is not affected by external interference and therefore does not disturb the external environment itself. Shielding specifications are typically specified from 10 kHz to 18 GHz and sometimes to the 40 GHz with acceptance testing methods described in the IEEE 299 or EN 50147-1, and the user will typically specify the levels of shielding attenuation required.
It is a mysterious metal box near radio frequencies, which effectively provides electric and magnetic field protection up to 100 dB over a wide range of frequencies. As a result, it is suitable for testing emissions because there are no ambient signals or noise from outside that can penetrate it, which makes it much easier to measure emissions from only the equipment under test. At that time, it is also suitable for immunity testing because no signals generated inside the enclosure can escape outside, which may cause harmful interference to equipment or personnel nearby.
One of the main applications of a radio frequency chamber is to measure the emissions of a product to determine if it will meets the limits specified in specified industry standards. RF anechoic compartments also use radioactive emission testing, radio immunity testing, radio transmitter testing, antenna testing, and the specific absorption rate testing.
Remember that there are different types of the shielding materials and configurations for anechoic chambers, and each has additional protection performance levels. If your application requires maximum shielding efficacy, you may want to consider double electrically insulated shielding material. This shielding has two layers of the metal (one on the inner surface and one on the outer surface), usually connected at the room’s main grounding point. If anything needs to be installed inside or outside a room, the set screws should be short enough to penetrate only the first layer of shielding and not go through the second layer.
Other components of the protected room are the door, the quality and size of which will significantly affect the overall cost and performance of the shielded room, as well as RF filtering for electrical cables, data cables, and other cables that must be present in the room.
Jet blast reflector
A jet blast deflector (JBD) or blast fencing is a safety device that redirects high-powered exhaust from the jet engine to prevent damage and injury. The structure must be very strong enough to withstand heat and high-velocity air currents, as well as the dust and debris carried by the turbulent air. A jet explosion can be dangerous to people, equipment, vehicles, and other aircraft without deflection.
The complexity of jet blast deflectors ranges from fixed concrete, metal, or fiberglass fences to heavy-duty panels that are raised and lowered by the hydraulic arms and are effectively cooled. Blowout deflectors can be used as protection against helicopters and fixed-wing aircraft. At airports and jet engine service centers, jet-blast deflectors can be combined with sound-blocking walls to form a geosphere where a jet engine can be tested safely and more quietly at full thrust.
Very
The exhaust of a high-powered jet engine can cause injury and damage. A jet explosion has been known to uproot trees, smash windows, overturn cars and trucks, flatten shoddy structures and injure people. Other aircraft in the blast, especially lightweight aircraft, were blasted and damaged by aircraft exhaust. Hurricane-force airflows moving at up to 100 knots (190 km/h; 120 mph) were measured behind the largest jet-powered aircraft at more than 200 feet (60 m). Two Boeing 777 General Electric GE90 engines combine to create nearly 200,000 pound-feet (900,000 Newtons) of thrust, a force high enough to kill people. To prevent these problems, jet-blast deflectors redirect the air stream in a non-hazardous direction, often upwards.
Airports
Jet-blast deflectors began appearing at airports in the 1950s. Airports in the 1960s used jet deflectors 6 to 8 feet (1.8 to 2.4 m) in height, but airports in the 1990s required deflectors that were twice the height and up to 35 feet (11 m) of jets such as the McDonnell Douglas DC-10 and MD-11, whose engines are mounted in the tail above the fuselage. Airports often place their deflectors at the beginning of the runways, especially when roads or structures are adjacent. Airports in dense urban areas often have deviations between taxiways and airport boundaries. Jet blast deflectors usually direct the exhaust gases upward. However, a low-pressure area can form behind the blast fence, causing surrounding air and debris to be drawn upwards with the jet exhaust and hot toxic gases to spread behind the blast fence. Jet blast deflectors are designed to counter this problem by using multiple plates at different angles and slotted plate surfaces.
Aircraft carriers
Aircraft carriers use jet-blast deflectors at the stern of aircraft slings and are positioned to protect other aircraft from exhaust blast damage. Blast-jet deflectors are heavy-duty materials raised and lowered by hydraulic cylinders or linear actuators. The jet blast reflector is located in a flush position and acts as part of the plane’s surface until the aircraft to be launched rolls over on its way to the catapult. When the jet is clear of the deflector, the heavy plate is raised into position to redirect the hot jet blast. Once the deflector is raised, another aircraft can be put into place behind it, and flight deck personnel can perform final standby duties without the risk of hot, violent exhaust gases. These systems were installed on aircraft carriers in the late 1940s and early 1950s, as jet-powered aircraft began to appear in the Navy.
