u-blox LISA-C200 User Manual
Also see for FW75-C200: Application noteSystem integration manual
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Error! No text of specified style in document. - System Integration ManualCDMA-2X-11004-P1 Objective Specification Design-InPage 64 of 7974.2.2 Antenna radiationAn indication of the antenna’s radiated power can be approximated by measuring the |S21 | froma target antenna to the measurement antenna, using a network analyzer with a widebandantenna. Measurements should be done at a fixed distance and orientation, and results comparedto measurements performed on a known good antenna. Figure 17 through Figure 18 showmeasurement results. A wideband log periodic-like antenna was used, and the comparison wasdone with a half lambda dipole tuned at 900 MHz frequency. The measurements show both the|S11 | and |S 21| for the penta-band internal antenna and for the wideband antenna.Figure 17: |S11| and |S21| comparison between a 900 MHz tuned half wavelength dipole (green/purple) and a penta-bandinternal antenna (yellow/cyan)The half lambda dipole tuned at 900 MHz is known and has good radiation performance (both forgain and directivity). Then, by comparing the |S 21 | measurement with antenna under investigationfor the frequency where the half dipole is tuned (e.g. marker 3 in Figure 17) it is possible to make ajudgment on the antenna under test: if the performance is similar then the target antenna is good.Figure 18: |S11| and |S21| comparison between a 900 MHz tuned half wavelength dipole (green/purple) and a widebandcommercial antenna (yellow/cyan)Instead if |S 21| values for the tuned dipole are much better than the antenna under evaluation(like for marker 1/2 area of Figure 18, where dipole is 5 dB better), then it can be argued that theradiation of the target antenna (the wideband dipole in this case) is considerably less. |
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