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Introduction
7
1.0 Introduction
ETS-Lindgren Model 3127 Resonant Loop Antennas are magnetic dipole
antennas designed to meet the Cellular Telecommunication and Internet
Association’s (CTIA)) +/- 0.1 dB symmetry requirement for ripple test
measurements at the labeled center frequency. These omni-directional antennas
have a magnetic dipole pattern approaching that of a half wave resonant electric
dipole. The pattern produced has the same peak and null orientation as that of a
sleeve dipole oriented along the same axis, but with the directions of the electric
and magnetic fields reversed. That is, the electric field vector along the azimuth
is perpendicular to the axis and the magnetic field vector is parallel to the axis.
The loop design allows the antenna to be end-fed to avoid cable and feed-point
interactions that interfere with the symmetry of the antenna. Integral quarter-
wave chokes and/or ferrite loading (depending on frequency range) also help to
reduce cable interaction. This design also provides exceptional symmetry to
meet the CTIA criteria for ripple test antennas.
All Model 3127 antennas are designed with better than +/- 0.1 dB symmetry (0.2
dB peak-to-null) in at least a +/- 5 MHz band around the labeled center
frequency. VSWR is less than 5:1 at the resonant frequency, which is slightly
higher than the labeled symmetry frequency. For reference purposes, gain and
symmetry values are provided for a 200-300 MHz band, depending on model,
centered about the labeled frequency. The loops have nominal 50 ohm
impedance, a maximum continuous transmit power of one watt, and are
equipped with a female SMA connector.
The loops are calibrated using an A2LA accredited process with a typical
measurement uncertainty on the order of +/- 1.0 dB at the center frequency.
During the calibration process, the dipoles are also certified to meet ± 0.1 dB
symmetry required for use in the ripple test specified in the CTIA’s Over-The-Air
Performance Test Plan, in a +/- 5 MHz band around the labeled center
frequency. Maximum ripple, VSWR, and approximate gain values are provided
with each calibration. Note that the gain values provided with this calibration are
for diagnostic reference purposes only. For accurate gain values to perform
range calibration, the Model 3126 Precision Reference Sleeve Dipoles are
recommended. Individual calibration data is included with each dipole.
