Anechoic chambers




An anechoic chamber is a RF shielded room whose walls and ceiling have been covered with Radiation Absorbent Material (RAM)* that scatters or absorbs so much of the incident energy that it can simulate free space. An anechoic chamber is simulating an Open Area Test Site (OATS), without interference from environmental electromagnetic field pollution.  Its origins can be traced to efforts to build aircrafts which absorbed or scattered radar signals during the Second World War. Recent innovations such as the use of ferrite tiles, have greatly enhanced the performance of these anechoic chambers.

The anechoic chamber is typically used to house the equipment for performing measurements of antenna radiation patterns, electromagnetic compatibility (EMC) and radar cross section (RCS) measurements. Testing can be conducted on full-scale objects including various electronic devices, vehicles, aircraft, spacecraft, or on scale models where the wavelength of the measuring radiation is scaled in direct proportion to the target size.  The internal appearance of anechoic chambers is sometimes similar to that of an acoustic anechoic chamber, however, the interior surfaces of the RF anechoic chamber are covered with radiation absorbent material (RAM)* instead of acoustically absorbent material.
 
*The more common name for RAM is microwave absorbers.
 
To satisfy each unique customer requirement Comtest Engineering can provide turnkey solutions for the following EMC test facilities:

•    3m semi anechoic chamber
•    5m semi anechoic chamber
•    10m semi anechoic chamber
•    Compact full anechoic chamber
•    CISPR-25 semi anechoic chamber
•    Mil STD semi anechoic chamber
•    Hybrid & Microwave absorbers
 

Reverberation chambers




A reverberation chamber is a specialized EMC test chamber generating very high field strength using modest amplifier power. The reflections between the RF shielded walls are optimized to add up to maximum of as many standing waves as practically possible. The chamber is mainly used for testing electrical immunity. The RF shielding is established by constructing the reverberation chamber from a 2 mm pan-type ZMA-140 galvanized or 3mm aluminum panel system. RF shielded doors and cabling access to the reverberation chamber are specially shielded for RF signals. This ensures that unwanted electrical noise from the outside world does not affect the test results and electrical immunity testing can be made without disturbing the surroundings. 

EMC testing in a reverberation chamber
When performing electrical or electromagnetic testing (EMC testing) the reverberation chamber is mode-stirred or mode-tuned by means of a stirrer. A stirrer system is a (large) structure of aluminum plates that is stepwise turned during testing. The objective is to maximize the standing wave pattern in the usable test volume. These EMC tests are statistically evaluated and the “worst case” data are used for the final evaluation of the test result. Electrical emission tests or specialized EMC testing in accordance to military, aerospace or automotive EMC test standards can be made in the reverberation chamber.

Multi functional EMC test facility
The reverberation chamber creates a multi functional EMC test facility for commercial, military and automotive testing. Comtest reverberation chambers comply with the following standards: IEC 61000-4-21prt 4-21, EUROCAE/ED-14F, MIL-STD 461F, RTCA/DO-160 as well as various automotive standards. The reverberation chamber can also be used for immunity and shielding effectiveness tests as well as for measuring total radiated power. Another application for the reverberation chamber is simulating complex multipath environments like computer rooms and other electrically congested areas.

Advantage of a reverberation chamber
The main advantage of testing in a reverberating chamber over the traditional semi anechoic chamber tests is that less power input is required to achieve the same field levels which make expensive amplifiers obsolete.

Reverberation chamber solutions
Comtest Engineering can supply the following reverberation chamber solutions:
- Reverberation chamber model 1716-0080 (LUF 80MHz)
- Reverberation chamber model 1716-0200 (LUF 200MHz)
- Reverberation chamber model 1716-0400 (LUF 400MHz)
- Reverberation chamber model 1716-1000 (LUF 1GHz)
 

RF shielded rooms & doors




RF shielded rooms
Since sophisticated electronics permeate modern life controlled electromagnetic environments such as RF shielded rooms become essential. RF shielded rooms and RF shielded doors are an integral component in modern EMC test facilities. Communication and data centers, calibration and EMC test laboratories as well as many other related test facilities all require electromagnetic shielding.

RF shielded doors
The Comtest RF shielded doors are designed for high performance shielded enclosures. The shielding characteristics are achieved using a double knife edge, matching quadruple beryllium copper finger contact strip. Comtest RF shielded doors are equipped with a unique parallel closing mechanism and patented locking and latching system. All Comtest shielded doors are available in manual, semi- and full automatic operation. Our standard range of swing and sliding doors consists of many different models and can be designed with a 50mm low threshold. In EMC applications both ferrites and absorbers can be affixed to the standard door leaf.

Comtest Engineering can provide the following RF shielded rooms:
  -  RF shielded rooms
  -  Tempest shielded rooms
  -  MRI rooms
  -  RF shielded rooms for Radio Astronomy
  -  RF shielded rooms accessoires
  -  RF shielded doors