This paper discusses the application of modern NF measurements and statistical analysis techniques to efficiently characterize the FF radiation pattern statistics of antennas and other EM emitters whose radiated EM fields vary erratically in a seemingly random manner.
During the last years, new algorithms, based on time filtering, spatial or modal filtering, have been designed for echo reduction techniques applied to antenna measurements. These algorithms have been used for different applications where the effect of the echoes is important, as far field system, VHF or UHF applications, automotive systems, small antennas, etc.
The source reconstruction or equivalent source method allows to represent each type of radiating device as nearfield equivalent source in form of equivalent electric and magnetic currents (EQC). The equivalent currents can be evaluated from measured data (near-field and far-field) through a post-processing step involving the solution of an integral equation.
A multi-probe array (MPA) spherical near-field antenna measurement system, comprised of OTS equipment, has been developed for testing UHF antennas mounted of an aircraft rotodome. The spherical probe radius is 5 meters, which accommodates a 24 ft. diameter rotodome.
—Experimental validation of numerical antenna models are performed to verify the model accuracy before their use in larger scale simulations. Model validation is usually performed by comparing to measurements of the antenna or device under test.
Wireless industry through 3G Partnership Project (3GPP), and CTIA The Wireless Association has been studying, validating, and standardizing the 2x2 MIMO Downlink OTA tests since 2009. Especially, CTIA has already provided the guidelines for the MIMO OTA tests in both the Spatial Multiplexing, and Transmit Diversity scenarios .
Performing on-chip antenna measurements at 60 GHz presents new challenges and magnifies legacy challenges. Testing on-chip antennas uses a micro-probe to interface the RF measurement system to the antenna under test (AUT). The small features of the antenna, the micro-probe, and the wavelength are among these challenges.
Accurate electromagnetic models of measured antennas are available from the expansion of the measured field using equivalent currents. The constructed model is importable in commercial Computational Electromagnetic (CEM) solvers in the form of a Huygens Box.
In antenna measurement, well-established procedures are consolidated to determine the associated measurement, uncertainty for a given antenna and measurements scenario. Similar criteria for establishing uncertainties in numerical modeling of the same antenna are still to be established.
Coupling a Chip Antenna to an Antenna Measurement System is typically achieved using a coplanar micro-probe. This micro-probe is attached to a probe positioner that is used to maneuver the micro-probe into position and land it on the chip. Through this process, the chip antenna is supported by a dielectric chuck.
Active Antenna System (AAS) technology is receiving increased attention as a component for upcoming 5G cellular networks. These networks will have flexible radiation patterns that are capable of adapting to changing conditions. In order to fully characterize ASS' in the 3D space, a new approach is required.
Measurement applications using a Compact Antenna Test Range (CATR) often require low cross-polarization or high polarization purity of the Quiet Zone (QZ). This requirement is often the main motivation for choosing the more complex and thus expensive compensated dual reflector system as opposed to the simpler and cheaper single reflector system.
Classical probe corrected Spherical Near Field (SNF) measurement assumes a |μ| = 1 probe -. This requirements is needed to fully compensate the effect of the probe during the NF/FF transformation . If the probe has an higher order mode content, a residual error will affect the measured pattern (probe modal truncation).
Computational Electromagnetics (CEM) solvers are important engineering tools for supporting the evaluation and optimization of antenna placement on larger complex platforms. Due to the conclusiveness and high reliability of actual measured data, antenna measurements are required for the final validation of most systems containing an antenna.
In classic probe-corrected spherical NF measurements, one of the main concerns is the probe , , . Standard NF-FF transformation software applies probe correction with the assumption that the probe pattern behaves with µ=±1 azimuthal dependence. In reality, any physically realizable probe is just an approximation to this ideal case.