E.10 Measurement distance
37.5443GPPConformance testingRelease 16TSUniversal Terrestrial Radio Access (UTRA) and Evolved UTRA (E-UTRA)User Equipment (UE) Over The Air (OTA) performance
The uncertainty contribution from a finite measurement distance is estimated in three parts.
E.10.1 Offset of DUT phase centre from axis(es) of rotation
In all the measurements defined in this test procedure the DUT and phantom combination is rotated about the ear reference point of SAM phantom, which is also assumed to be the location of the phase centre in both angular directions of the measurements.
For some turntables this may be practically impossible in which case a measurement uncertainty contribution can arise because the phase centre will rotate on a non-zero radius about the centre of rotation, thereby giving a variable measurement distance. Data averaging process may lead to a partial self-cancel of this uncertainty.
The following formula is used to estimate this uncertainty contribution in stage 1:
Uphase_center_limits (dB) =
If a gain calibration is performed in Stage 2, the uncertainty contribution of calibration antenna’s displacement is estimated with the previous formula. Misalignment can be estimated with following formula,
Umisaligment (dB) = ,
where is the misalignment angle between the calibration antenna and the probe antenna. The contribution shall be added to displacement error:
Ucal (dB) =
For an efficiency calibration with an omnidirectional calibration antenna, the Ucal is calculated similarly as for gain calibration but the uncertainty may be divided by factor 2. This is due to correcting impact of data averaging in this type of calibration.
E.10.2 Mutual coupling
In measurement of radio performances of UMTS mobile phones in speech mode, the mutual coupling uncertainty for this frequency band is a 0.00dB value (see annex A-2 in [27]).
The 0.00dB value can be extended for the GSM, DCS and PCS band frequencies.
E.10.3 Phase curvature
This uncertainty originates from the finite far-field measurement distance, which causes phase curvature across the DUT. If the measurement distance is > 10λ, this error is assumed to be negligible. At 2 GHz λ is 0.15 m, thus 10λ is 1.5 m.