LISA-U1 series - System Integration Manual
3G.G2-HW-10002-3
Preliminary
Design-In
Page 104 of 125
Figure 55: |S
11
| sample measurement of a wideband antenna
2.4.2
Antenna radiation
An indication of the antenna’s radiated power can be approximated by measuring the |S
21
| from a target antenna
to the measurement antenna, using a network analyzer with a wideband antenna. Measurements should be
done at a fixed distance and orientation, and results compared to measurements performed on a known good
antenna. Figure 56 through Figure 57 show measurement results. A wideband log periodic-like antenna was
used, and the comparison was done with a half lambda dipole tuned at 900 MHz frequency. The measurements
show both the |S
11
| and |S
21
| for the penta-band internal antenna and for the wideband antenna.
Figure 56: |S
11
| and |S
21
| comparison between a 900 MHz tuned half wavelength dipole (green/purple) and a penta-band internal
antenna (yellow/cyan)
The half lambda dipole tuned at 900 MHz is known and has good radiation performance (both for gain and
directivity). Then, by comparing the |S
21
| measurement with antenna under investigation for the frequency where
the half dipole is tuned (e.g. marker 3 in Figure 56) it is possible to make a judgment on the antenna under test:
if the performance is similar then the target antenna is good.
