Com-Power broadband AHA-118 Active Horn antennas have an integrated preamplifier to amplify low level signals immediately at the antenna output during electromagnetic interference testing. With this arrangement the maximum signal is boosted prior to being fed to the typically lengthy cable bridging the test area and control room. Most high frequency (above 1 GHz) EMC testing on DUT (device under test) are performed at 1-to-3-meter distance on an open area test site (OATS) or absorber lined shielded enclosure (ALSE). As the test distance increases the signals become more difficult to see above the noise floor of typical spectrum analyzer or receiver. Reduction of the resolution bandwidths (RBW) will increase the instrument sensitivity, but regulatory tests typically specify fixed, RBW settings for the individual frequency ranges of the test. This necessitates the use of a high gain preamplifier in order to properly measure low level emissions. The typical gain of the integrated preamplifiers for AHA-118A is 40 dB.
The preamplifiers are integrated into small enclosures attached to the rear of the respective horn antennas. A very short U-shaped cable connects the antenna output to the preamplifier input. This cable can be removed if the antenna is used for transmitting applications such as radiated immunity/susceptibility testing. The flexibility of this cable also allows the user to install any necessary filters to the preamplifier input employed to facilitate measurements of radio equipment by attenuating the fundamental emission level.
The integrated preamplifier in the horn antenna has low noise, so it contributes very little to overall increase system noise floor. For example, the AHA-118A has noise figure less than 3.5 dB. This helps increase overall measurement system sensitivity without increasing the noise floor to make it easier to see the weaker signals to be seen on a spectrum analyzer or receiver. For better accuracy of measurement, the built preamplifier has minimum gain variation across the frequency range. Typically, the gain variation of an AHA-118A active horn antenna is +/- 3 dB.
The same preamplifier integrated into active horn antenna are also available in bench-top configurations; The model is PAM-118A.
The power to the preamplifier is supplied by an external AC/DC adapter. Battery-powered versions of each antenna is currently under development and will become available in the near future.
All Com-Power preamplifiers are supplied with calibration traceable to the International System of Units (SI) through NIST or the recognized National Metrology Institute. ISO 17025-accredited calibration is also available.