A.2.3 Laptop Ground Plane Phantom

37.5443GPPConformance testingRelease 16TSUniversal Terrestrial Radio Access (UTRA) and Evolved UTRA (E-UTRA)User Equipment (UE) Over The Air (OTA) performance

Laptop ground plane phantom is used for radiated performance measurements in case of plug-in DUT like USB dongles. The objective of the laptop ground plane phantom is to reproduce the effects of the ground plane for the antenna of the DUT while avoiding the variation of the measurements introduced by a real laptop.

The laptop ground plane phantom, as showed in Figure A.2.3-1, is composed by the following parts:

– A rectangular plane covered by a conductive film on the upper side with thickness of 4mm to emulate the keyboard and main body of the laptop;

– A rectangular plane covered by the same conductive film on the upper side with thickness of 4mm to emulate the screen of laptop;

– The conductive film on the two planes is connected. The angle between the two planes is 110 degrees. The material is FR-4 copper-clad sheet and the length and width of these two planes are 345mm and 238mm respectively;

– A horizontal USB connector placed along the short end of the plane; the location of the port is at the right back corner, the distance between the central axis of the USB connector and the rear edge of plane is 45mm, the ground of the USB connector is welded on the conductive film of the plane. The detailed description of the structure is presented in Figure A.2.3-2;

– A USB cable crossing the ground plane and connecting the USB connector to a real functional laptop; the USB cable should be equipped with a shielded metal film, and the portion of the cable that is hung in the air shall be covered with absorbing material or treated with quarter wave chokes. The part of the USB cable lying on the plane is covered by a conductive adhesive strip used for fixing the cable on the plane and for guarantying at the same time the superficial continuity of the conductive plane. The shielded conductive film of this part of the USB cable is connected to the conductive film of the plane and the covered strip to well ground the antenna. The length of the USB cable should be no more than 3 meters.

Figure A.2.3-1: The laptop ground plane phantom, the DUT and the real functional laptop

Figure A.2.3-2: The structure and dimension of the laptop ground phantom

The real functional laptop is laid on the floor of the anechoic chamber, supplies power to the DUT and controls the state of the DUT. Both the USB cable and the real functional laptop are properly setup in order to have a negligible impact on the measurements: the real functional laptop is fully wrapped up with anechoic absorbers.