Basically one wants to maximize the power from the transmitter and to make sure all of it radiates from the antenna, with all power being sent off into the air. These terms are used to indicate and describe the efficiency, operation and general characteristics of the antenna and transmitter overall. I’m sure you have heard of coaxial cable impedance, SWR, reflected power, forward power, match and other such terms. A coaxial cable is used to connect the transmitter to the antenna and forms an important part of the transmission system. The antenna is the device that takes the RF signal from the transmitter and ‘launches’ this signal out and into the air. We will also stay at a basic level in describing some principles and take some liberties in the way we define and explain things – again, this paper is to help shed some light into the effects and expectations when using small antennas within a shielded test enclosure environment. To make things simpler to describe, we’ll generally describe the transmitter side of things, remember that the same effect takes place when receiving. We’ll call the device that creates the RF signal a ‘transmitter’ and the device that captures and utilizes the RF signal a ‘receiver’. One can delve deeply into the physics of antennas, but in our case we wish to simply understand how signals are radiated inside an RF shielded test enclosure. So, while we will be discussing the radiation from an antenna, understand that the same thing happens in reverse when an antenna is receiving. Boxes are closed so all signals between the enclosures have to pass through the step attenuator.įirst, we need to understand the process of an antenna radiating or transmitting an RF signal – and by reciprocity, an antenna functions the same electrically when receiving. Two JRE 1812 test enclosures interconnected with antennas and step attenuator. So, just what sort of signal loss can we expect in this configuration? We’ll take a look at a few different scenarios at various frequencies and with different antennas. In these cases, the device under test operates within the small confines of the RF shielded test enclosure and antennas are placed inside the enclosure to radiate or receive the RF test signal. Many times a shielded test enclosure is called upon when actual radiated RF signals must be used rather than connection through coaxial cables and connectors.
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