Antenna Balance vs Symmetry

Nov 18 2020 in News  

If you intend to use a hybrid antenna for final compliance measurements as per ANSI C63.4-2014, then the antenna must meet the symmetry requirements called out in Annex N of the document. But which condition should be used to determine compliance? Condition A or Condition B? And what frequency range is required for the symmetry test?

TDK has made available online an article that explores this topic: Antenna Back to Basics: Balance vs. Symmetry. The questions it discusses are: How are balance and symmetry the same? How are balance and symmetry different? How to measure and who requires them?

Antenna symmetry measurements are intended to determine whether received signals on both element sides are similar across the usable frequency range of the antenna. The measurement is used to determine if mechanical or electrical differences can affect the AF values. Balance is used to describe the measurement variation between the 0° and 180° positions, and symmetry is used to describe the antenna topology’s symmetrical design both physically and electrically.

The symmetry requirement for hybrid antennas was introduced formally with the release of ANSI C63.4-2014. A hybrid antenna is defined in ANSI C63.4 Annex N as an antenna that is constructed with the combination of both a broadband dipole antenna (biconical or bowtie) elements and log-periodic dipole array elements.

The terminology differences between symmetry and balance are much more straightforward and easier to answer than the question of which condition is used for determining symmetry and what range of frequencies are required.

TDK's HLP-2008A hybrid antenna enforces symmetry and meets CISPR 16-1-4 and ANSI C63.4 standards even under adverse conditions, such as vertical polarization combined with close proximity to a conducting ground plane.

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