Antenna Measurement Equipment
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For test equipment, we will attempt to illuminate the test antenna with a plane wave. This will be approximated by
using a source antenna with no radiation pattern and characteristics, in such a way that the fields incident upon the test antenna
are approximately planar. More will be discussed about this in the next section.
The required equipment for antenna measurements include:
A block diagram of the above equipment is shown in Figure 1.
 Figure 1. Diagram of required antenna measurement equipment. These components will be briefly discussed. The Source Antenna should of course radiate well at the desired test frequency. It must have the desired polarization and a suitable beamwidth for the given antenna test range. Source antennas are often horn antennas, or a dipole antenna with a parabolic reflector. The Transmitting System should be capable of outputing a stable known power. The output frequency should also be tunable (selectable), and reasonably stable (stable means that the frequency you get from the transmitter is close to the frequency you want). The Receiving System simply needs to determine how much power is received from the test antenna. This can be done via a simple bolometer, which is a device for measuring the energy of incident electromagnetic waves. The receiving system can be more complex, with high quality amplifiers for low power measurements and more accurate detection devices. The Positioning System controls the orientation of the test antenna. Since we want to measure the radiation pattern of the test antenna as a function of angle (typically in spherical coordinates), we need to rotate the test antenna so that the source antenna illuminates the test antenna from different angles. The positioning system is used for this purpose. Once we have all the equipment we need (and an antenna we want to test), we'll need to place the equipment and perform the test in an antenna range, the subject of the next section.
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